This curious case of shark-on-shark abrasion, featured in the BBC's groundbreaking series Blue Planet II, was filmed with the help of a whale shark "fin cam". The camera was deployed by researchers with the Galapagos Whale Shark Project (GWSP), who use the tech in the hope of learning more about how whale sharks use – and interact with – their habitat. (The cameras are non-invasive and programmed to pop off on their own.)

Despite reaching nearly 20 metres in length, whale sharks manage to keep a low profile as they traverse the world's waters. We still don't know where they give birth, and many of their migration routes remain uncharted. 

"The Galapagos is a special place for whale-shark research," the GWSP team wrote on Facebook. "Unlike in other whale shark hotspots, we see here almost exclusively large, apparently pregnant females. Studying them is important for the conservation of this endangered species, and we are making progress."

The best explanation for the silkies' behaviour is that the sharks are using their giant kin like loofahs. Shark skin is covered in thousands of tooth-like scales known as dermal denticles, and these are extremely coarse when rubbed against the grain. Coming in for a "rub-a-dub-dub" could help the smaller sharks rid themselves of parasites and dead skin, much like how orcas use pebble-bottomed coves.

The behaviour has been seen in the area before: wildlife photographer Thomas P. Peschak had a similar encounter while on assignment for National Geographic Magazine. And elsewhere in the world, other fish have been known to hit the "shark spa" when in need of a good skin peel:

A post shared by Erick Higuera (@erick.higuera) on Aug 11, 2017 at 10:53am PDT

"It does not seem to bother the whale sharks at all," says the GWSP team. 

That's not too surprising: at an impressive ten centimetres (four inches) thick, the skin of whale sharks is some of the toughest in the animal kingdom. (Their denticles can easily graze human skin!)

Why would a bus-sized animal need such tough armour? Whale sharks are docile filter-feeders, and they do have some natural predators (namely killer whales and great whites). In the face of danger, the sharks will sometimes barrel roll towards a potential threat, keeping that thick top-surface skin in the line of fire:

Learn more about whale-shark skin in our previous coverage here!

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Top header image: Shutterstock

Fire and critters have also lately been in the news courtesy of a fascinating study published late last year in The Journal of Ethnobiology investigating the so-called "firehawks" of Australia's tropical savannahs. Its authors delved into a phenomenon long known to Aboriginal peoples: raptors plucking flaming or smouldering sticks from bushfires and dropping them in nearby grass, thus sparking a new burn.

To some people who've never experienced one where they live, or where they love to recreate, a big burn can seem a disastrous aberration – and, ala Bambi, nothing but trouble for the creatures caught in its path. The intriguing case of the firehawks (which we'll explore a bit more later) suggests a more complicated story. Most of the world's ecosystems have evolved with fire of one kind or another, and animals have an instinctive (and opportunistic) relationship with it.

Let's have a look at some of what we know about a fire's impact on animals: the bad, the good and the grey areas in between.

Fire in ecosystems: An old story

First though, setting the stage. A remarkable share of ecological landscapes evolved under the regular influence of flame, though what sort of fire, and how frequent, and from what ignition source, vary considerably. Many Mediterranean-zone and semiarid grasslands, shrublands and woodlands burn chronically: from the fynbos of South Africa's Cape region and the eucalypt woods of southeastern Australia to the cerrado savannahs of central Brazil and the California chaparral. But many other plant communities that wouldn't seem terribly flammable at first glance – cold subalpine woods, northern taiga, temperate rainforest – do indeed burn, even if the intervals between fires are sometimes on the order of several centuries, even a millennium.

Lightning conspires with annual dry seasons or periodic droughts to spark wildfires, but we – human beings – are just as important ignition sources in many parts of the world. We've been intentionally starting fires for thousands of years: to improve hunting or herding opportunities, to clear land for agriculture and manage crops. The exact fire regime of a region depends on a whole suite of factors, but generally speaking a place that burns frequently tends to experience low-intensity fires – there's not time in between burns to build up a lot of fuel, basically – while countryside that tends to ignite once every few centuries will nourish bigger, fiercer fires.

An inferno raging through a forest or brushland may look apocalyptic, and some individual animals will perish in it, but such a blaze can also help maintain and rejuvenate the resources local wildlife depends on – and open up crucial opportunities for other species specially disposed to capitalise on the post-fire landscape.

But what about those real-time effects of the leaping flame and billowing smoke? What about the critters that perish, and those that don't?

Mammals

It's often surprising how few medium-sized and large animals appear to die in wildfires. In the mighty conflagrations that roared across Yellowstone National Park in 1988 (and changed wildfire philosophy and policy in the USA), known large-mammal deaths were in the low hundreds: 240 elk, nine bison, four mule deer, a pair of moose – most of them apparently felled by smoke inhalation. Reports of Yellowstone's big beasts running from the big crown fires were scarce; the main reaction was basically indifference. Several radio-collared grizzly bears hung around actively burning areas during the '88 Yellowstone fires, and more than a dozen grizzlies moved right into burned-over zones after the flames subsided. "Bison, elk, and other ungulates grazed and rested within sight of flames, often 100 metres or less from burning trees," noted a United States Forest Service report on the ecosystem impacts of wildland fires.

One basic reason why bigger mammals often escape a fiery death? Well, because they're pretty good at galloping, loping, trotting, even plain sauntering away from flames. The hair of mammals also provides a bit of a buffer against the extreme heat, especially longer and denser fur. This means they can sometimes get away with slipping right across a fire front. (That sort of doubling-back, for example, allowed several woylies – little kangaroo cousins – to remain in their home ranges during a moderate-to-high-intensity burn in a eucalypt forest in southwestern Australia.)

This past December, the manager of the free-roaming American-bison herd in South Dakota's Custer State Park noticed the bovids' shaggy coats seemed to offer some protection during a fierce and fast-moving grassfire: outer guard hairs were burned off, but the "underfleece" beneath provided a shielding layer.

That prairie blaze – which blew up from 4,000 to 35,000 acres on a single night due to winds exceeding 40mph – caused burns severe enough that a number of bison (as well as elk, deer and a feral burro) had to be put down. It goes to show that a swift wildfire can sometimes outpace or outflank even the large and the mobile: whether it's mustangs in the American West or elephants in South Africa, big mammals do sometimes fall victim to flame and smoke.

"Large mammal mortality is most likely when fire fronts are wide and fast-moving, fires are actively crowning, and thick ground smoke occurs," the US Forest Service report explained.

After the Jasper Fire of 2000 – the largest to impact the Black Hills of South Dakota and Wyoming in modern times – researchers studying pumas in the range found one of their radio-collared cats, an adult female, dead in a mountain draw. They concluded that the puma, which had burned paws and singed whiskers but otherwise minimal external injuries, had asphyxiated, probably on a day when strong south winds had driven the fire front forward at some 15mph – fast enough, they reasoned, to trap the animal in the draw.

Smaller mammals such as rabbits and rodents may also run away ahead of the flame front, or retreat underground. Ventilation is vital, though: mice have been found suffocated post-fire in burrows with only a single entrance.

Some mammals are more vulnerable to fires than others. Koalas, for example, a bit ungainly on the ground and prone to shelter in the canopy, can get in trouble when a bushfire rages through their highly flammable (and fire-dependent) eucalypt woods. Fire can also hit woodrats hard, as those rodents hole up in aboveground nests of grass and other litter – super-combustible homes they're loathe to abandon even when flames start crackling.

Reptiles & amphibians

Like small mammals, reptiles and amphibians may either flee fires or successfully endure them ensconced underground or within crevices, rotten logs and other cool, moist hidey-holes. In 2001, wildfires in New Mexico burned the entire known range of the endangered Jemez Mountain salamander, yet the population survived due to the refuge offered by rock nooks and crannies. Timing's everything, though: snakes in the process of shedding their skin may be less adept at sheltering from a fire.

Birds

Adult birds are pretty well set up to simply fly away from conflagrations, though eggs and chicks are vulnerable: surface or understory fires may destroy nests laid on the ground or in shrubs, while canopy broods go unaffected. (How significant the loss of a nest to fire is can depend on the species: as the US Forest Service notes in its wildfire/ecosystem survey, wild turkeys often don't re-nest if their brood is lost after a few weeks of incubation, whereas another upland game bird, the northern bobwhite, may re-nest several times a season.) In many fire regimes, however, peak burning season occurs after peak nesting.

Flying birds, well equipped as they are to dodge flames, may – like those big mobile mammals – sometimes be overwhelmed. A 1999 fire in the South Florida Everglades didn't harm two large rookeries of wading birds – even as sawgrass marsh around them burned, the "tree islands" harbouring the rookeries were wet or moated enough to endure – but it did kill 50 white ibises that were likely trapped by heavy smoke while out foraging.

Now, what about those pyromaniacal Aussie raptors? Birds of prey in many parts of the world commonly hunt along and above the fire front, scavenging crispy leftovers and feasting on the small creatures driven ahead of the flames, as well as insects lofted high by the fire thermals. But recent research has investigated the possibility that certain Australian raptors intentionally spread flames to flush out (and fry) more snacks. A National Geographic article on the study quoted a passage from the 1964 life story of an indigenous man named Waipuldanya Phillip Roberts that helped inspire the investigation: "I have seen a hawk pick up a smouldering stick in its claws and drop it in a fresh patch of dry grass half a mile away, then wait with its mates for the mad exodus of scorched and frightened rodents and reptiles. When that area was burnt out, the process was repeated elsewhere."

The researchers delved into traditional knowledge and mythology on the subject and also documented contemporary observations bearing out the firehawk behaviour among three quintessential raptors of Australia's northern savannahs: the black kite, whistling kite and brown falcon. Not everyone's convinced the birds' spreading of fire is intentional – it's also been proposed they accidentally nab smoking sticks in their talons when making unsuccessful predatory strikes – but the research team is continuing its inquiry, and hopes to record the firehawks in action on film.

Invertebrates

It's difficult to summarise what we know about wildfire impacts on invertebrates. Many aboveground insects and arachnids likely perish during fires, although one study* showed both adult acridid grasshoppers and nymphs were quite capable of escaping a savannah fire in Côte d'Ivoire. In many cases, invertebrate numbers and diversity recover quickly in burned zones due to dispersal from neighbouring unburnt habitat (though a recent study on Florida tortoise beetles showed recolonisation can take a good while for some bugs).

Invertebrates that tunnel into the litter layer or soil probably hold up better in fires, though high-severity burns have been known to destroy even subsurface eggs of mites. (In that case, incidentally, mite populations in the burn area were initially lower than surrounding plots, but by a year and a half post-fire, the burn area supported substantially higher populations than elsewhere, a trend often seen for aboveground invertebrates as well.)

Certain kinds of insects, meanwhile, are actively attracted to fires. Charcoal beetles (Melanophila) sense the heat of wildfires as far as 130 kilometres away and "beeline" for them (if you will) to mate and lay eggs beneath the bark of fire-killed snags. Writing in Bay Nature about the 2013 Morgan Fire near San Francisco, Emily Moskal described firefighters' vivid experiences with hordes of these beetles:

To protect themselves against the darting insects, the firefighters wore bee veils. The beetles emerged from their mating stages in the burned or burning trees to swarm, rising with the smoke and sizzling crackle of extinguished embers. Firefighters recalled that everywhere skin was exposed, beetles scratched and prodded ... [Firefighter Dylan] Jorgensen described a feeling of relentless buzzing in his hair, firefighters "ripping their helmets off like feeling a bee in your shirt," and dancing and shaking to get the beetles off of them.

Other types of wood-boring beetles as well as horntails (or wood wasps) follow the scent of smoke to reproduce in burned forests. "Firebug" is a common shorthand for all of the insects for which wildfires are one big smoking magnet.

Indirectly dangerous 

Animals aren't just killed outright by voracious flames and choking smoke. There are also dangers only indirectly related to fire – which would include, for example, the predation inflicted upon those skittering mice and snakes and insects fleeing the fire front.

Creatures retreating from fire face other risks, too. In one instance, a slew of Cape grass lizards were squashed on a gravel road they were crossing to escape a fynbos blaze.

What's more, injury from flames may hamper an animal's ability to obtain food or avoid predators. In early October of last year, a closely monitored male puma in Southern California's Verdugo Mountains turned up dead not long after a 7,000-plus-acre wildfire in the area. While the cause of his death was unclear – a necropsy ultimately ended up finding traces of rat poison in his system – a National Park Service spokesperson told LAist, "We've seen other cases of mountain lions surviving wildfires, and coming away with burned paws that make it difficult for them to hunt and survive."

Fire & wildlife habitat

The real-time deaths and miraculous escapes are the most superficially dramatic wildfire impacts on wildlife, but more significant in the long-term are the habitat changes resulting from burns. As firebugs demonstrate, these changes create opportunities for many animals.

"Fire turns the kaleidoscope of habitat. The post-burn environment favours some species, discourages others, which is why you want lots of patch burns so you have a good churn of habitat," Stephen Pyne, one of the foremost wildfire scholars around (and a former wildland firefighter) told me via email.

Amid the bountiful sunlight and released nutrients of a charred forest or shrubland, grazing animals may prosper; browsers may get their day when early-successional shrubs colonise burns and reign for a few decades. Woodpeckers and other cavity-nesting birds flock to the snags that stud a burned forest. The "case-hardening" by which flames toughen wood means that a fire-killed snag and the downed log it ultimately produces – apartment complex for all kinds of creepy-crawlies – may offer longer-lasting habitat than other deadwood.

Fire's impact on habitat varies from fire regime to fire regime, of course. A grass fire creeping across savannah or prairie preserves that ecosystem by killing invading trees and shrubs: many animals of the pre-fire landscape therefore reoccupy it in short order, if not immediately. A huge stand-replacement crown fire in taiga or subalpine forest, by contrast, removes its defining conifers and paves the way for fundamentally different plant communities – brushfields, deciduous woods – that will eventually, maybe a century later, transition back to conifer domination. More specialised animals found in the pre-fire old growth may not reoccupy the site until that happens, but in the meantime, a host of other species will stake their claim.

In the fire-dependent Cape fynbos of South Africa, nectar-eating sugarbirds and orange-breasted sunbirds lose local habitat to fire – it may take some eight years for their preferred nectar-bearing shrubs to reestablish themselves – while insectivorous species such as the Cape rockjumper may prosper on the heels of flame. In the grasslands of southeastern Arizona, cotton rats declined after a fire temporarily reduced the green vegetation they eat, while cotton mice and kangaroo rats increased in the area, likely because of plentiful seeds (their preferred nosh) generated by the forbs colonising the burn-scape.

Roughly speaking, animals specially adapted to fire environments ("pyrophytes"), as well as generalist species, tend to be the short-term "winners" when the smoke clears, while those reliant on habitats or resources that are temporarily destroyed are the "losers". Woodland caribou lose out on winter lichen reserves for a time when their boreal woods burn; white-tailed deer and moose, meanwhile, do well on account of all the abundant post-fire shrubbery.

Beyond the short-term aftermath of burns, it's important to emphasise just how many animals depend on habitats maintained directly by fire. The Kirtland's warbler is a classic North American example. The songbird – restricted to a small breeding range in Ontario, Michigan and Wisconsin, and wintering ground in the Bahamas – nests only in young stands of jack pine: a "serotinuous" tree bearing a large proportion of cones that open only when unsealed by fire. Historically, wildfires perpetuated both jack pine in general and the youthful, scrubby pinewoods the warblers needed; fire suppression has reduced warbler habitat, and prescribed burns (and selective timber harvest) are helping to restore it.

The evolving fire-scape

Part of the crazy complexity of fire ecology is the human element. We're fire animals like none other: our mastery of fire, right up there in our top two or three all-time breakthroughs, didn't just transform our ways of life – it also transformed ecosystems all around the world. Fire is an age-old force on Earth, one we learned to make and manage; for millennia, other organisms have evolved under the rhythms of anthropogenic burning.

Those rhythms, though, have changed considerably across time, as hunter-gatherer burning gave way in many areas to agricultural burning, and, in modern times, as intentional burning gave way to fire suppression. Again, it's complicated, but generally, policies of suppressing fires have built up fuel loads in many flame-adapted ecosystems to the point where they're prone to high-intensity, high-severity burns – as opposed to the low-grade fires that, erupting frequently, once maintained them.

In landscapes subject to institutional fire suppression and not, there's the even greater influence of climate change, which from the American Southwest to the Russian taiga seems to be promoting larger, fiercer and more frequent conflagrations. Climate change is such a planetary-scale, whole-earth-system phenomenon that it's an epic challenge to predict how specifically it'll influence local fire regimes, though more and longer-lasting droughts, higher annual temperatures, receding permafrost, and diminished and faster-melting snowpacks certainly seem to set the stage for more burning. Assessing how wildlife can adapt to an evolving new pattern of wildfire is just one part of the high-stakes puzzle climate change presents.

Our burning behaviour and effects on global climate coincide, of course, with all the other ways we impact wildlife. California condors, for example, have dealt with wildfire in western North America for many millennia; countless nests must have gone up in flames. That's less of an issue when you've got lots of condors, but today, the potential loss of just one nestling – like the chick caught in the Thomas Fire – is a major cause for concern.

"If you have a species tied to a particular place, isolated in a refugia, it may suffer from a big burn that blasts over the site," Pyne said. "Apart from any immediate fatalities, the species won't have any place else to flee to until the original site recovers."

Hemming wildlife into small, isolated patches of habitat surrounded by human development or otherwise unfavourable landscapes makes animal populations more vulnerable to fires, as they may have less ability to seek refuge and food, and fewer source populations for recolonisation. In this way, fires may have contributed to the extinction of the heath hen of eastern North America (a bird dependent on fire to maintain its favoured open habitats) when they broke out in the last remaining stronghold of its hugely reduced range, the New England island of Martha's Vineyard.

Meanwhile, a nearly 50,000-acre wildfire last year in the Pinaleño Mountains of southeastern Arizona killed 217 of 252 known Mount Graham red squirrels, and destroyed many of the rodents' seed caches. Scientists are anxiously hoping enough squirrels survive this winter to give the endangered subspecies a fighting chance in the wild.

If your main takeaway from all of this is that it's tough to generalise about fire impacts on animals – well, you've got it. Flames burn up woodrat nests and yet refresh wildebeest pasture. They destroy the boreal owl's old-growth home while making a new snag-ridden one for some of its close kin. They serve up a smorgasbord for hunting kites and a nursery for charcoal beetles. They pay off for this puma with lots of wild room to roam while mortally threatening that puma living in a pocket refuge walled in by humanity. Wildfire is such a defining element of so many ecosystems around the world that it's impossible to imagine them – and their constituent creatures – without it.

(Hey, did you know there's a connection between California condors, fire and Johnny Cash? No? Check out Stephen Pyne's blogpost for the story, which dates from the country legend's wild years...)

* Gillon, Y., 1972. The effect of bushfire on the principal Acridid species of an Ivory Coast savanna. Proceedings of the Tall Timbers Fire Ecology Conference 11, 419-471.

Take a dive in the waters surrounding Pulau Hantu, a small island off the west coast of Singapore, and you may reemerge feeling unimpressed. Visibility around the island rarely tops three to four metres, and plentiful algae tints the water a vivid green. For macro photographers like Katherine Lu, however, Hantu is a hidden gem. The island harbours a little-known reef that's teeming with tiny marine life – and among its most remarkable inhabitants are the local sea slugs.

"Pulau Hantu means 'Ghost Island' in Malay," Lu told WetPixel. "For the regulars who dive there, it never ceases to amaze what we might find." 

You just need to know where to look...

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Top header image: Katherine Lu/WetPixel

“The Big House”, home to the University of Michigan’s American football team, is one of the world’s largest stadiums. Here’s what it looks like when packed to the brim with more than 100,000 rowdy spectators:

Now, imagine replacing those people with Bornean orangutans. It’s a funny sight, isn’t it? Thousands of red-haired apes jostling in the stands. Well, scientists just learned that at least 100,000 of these orangutans have disappeared over the past 16 years. And the worst part of this story is that all the remaining orangutans on the vast island of Borneo would only just about fill The Big House again one more time.

This finding is the result of our new study, published in the journal Current Biology, in which we investigated what has happened to orangutans in Borneo, the Southeast Asian island where most of them live.

We first gathered 16 years of survey data, collected both from researchers on the ground and from “aerial surveys” which used helicopters to identify orangutan nests high in the canopy. We then combined this with satellite images which indicated how the landscape has changed.

Our results show that the declines were steepest in areas that were deforested or transformed for industrial agriculture (often oil palm or paper pulp plantations), as orangutans struggle to live outside the forest.

Killing is at least as big a problem as deforestation

Worryingly, however, the largest number of orangutans were lost from areas where the forest remained intact or where only the tallest trees had been selectively logged. Here the species is in decline because it is hunted, just like any other edible animal on Borneo.

One analysis, based on interviews with 5,000 local people, found that few hunters would go out specifically to target an orangutan, and locals generally prefer deer and pigs. However, when an orangutan is encountered at the end of a long hunting day, a big orange primate sitting in a tree is a sitting duck or, more accurately, a sitting ape.

2 workers cruelly killed an endangered orangutan with 17 shots but alleged their murder as self-defence https://t.co/4y1SbdknAy pic.twitter.com/DJBjSHpBwh

— BastilleGlobal (@BastilleGlobal) February 6, 2018

Orangutans are also increasingly killed when their forest habitat is cut down and they are pushed into people’s gardens and into plantations. People who encounter them there are scared or angry and resort to killing them.

Orangutans are very slow breeders. Previous research has indicated that a population will probably go extinct even if only one reproductive female per 100 adults is removed per year. But killing rates have been identified as being as much as three to four times higher than this, which would explain the immense losses seen within Borneo’s forests.

All is not lost

There is a positive twist to the story: there are actually more orangutans than we had previously thought. Some populations, in parts of Malaysian Borneo and larger national parks in Indonesian Borneo, even appear to be relatively stable and make it seem unlikely that the species will go extinct just yet.

And the more we learn about orangutans, the more we find that they are a resilient species that can adapt to new challenges. For example, our colleague Marc Ancrenaz has discovered that orangutans can cover large distances by walking on the ground, and that they adapt their diet to new resources such as acacia or oil palm. If they are not hunted, these abilities may allow them to survive in the fragmented landscapes that now make up most of Borneo.

Prevention is more important than rescue

People working on the ground know that the orangutan can be saved. It requires persistence, good collaboration with governments, strong support from local people, and help from companies that manage the land. Once forests are maintained and protected, and killing is stopped, orangutan populations can be stabilised. It might even allow them to slowly bounce back and recolonise forest areas where orangutans have disappeared in the past.

We need to think outside of the box. For instance, a lot of effort and funding goes towards rescuing individual orangutans, who are then moved to a safer place where they can be rehabilitated. But while this may help individuals in desperate situations, it is a very expensive and ineffective way to deal with the overall conservation problem. To put things into perspective, we lost more than 100,000 orangutans in the past 16 years and saved perhaps 1,000 through rescues, translocations and rehabilitation in the same period.

If we really want to stop the decline, we must both protect forests and stop the killing within them. As most orangutans live outside protected areas, we need to get the communities and companies who manage their habitats on board. Here, there are many possibilities. For example, one oil palm plantation is now protecting 150 orangutans within its concession, showing that oil palm is not inevitably linked to the complete destruction of primate habitat.

On a larger scale, the Malaysian state of Sabah and the Indonesian province of Central Kalimantan, both in Borneo, intend to certify their entire production of palm oil as sustainable by the year 2025, which includes a zero-killing policy. At the same time, both countries are developing new long-term action plans for orangutan conservation.

We urge the governments of Indonesia and Malaysia to include firm strategies to stop the killing of orangutans. Because if we do not learn from past failures that stadium will eventually be empty, forever.

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Maria Voigt, Doctoral Researcher, Sustainability and Complexity in Ape Habitat, German Centre for Integrative Biodiversity Research; Erik Meijaard, Adjunct professor, Australian National University, and Serge Wich, Professor of Primate Biology, Liverpool John Moores University

This article was originally published on The Conversation. Read the original article.

[The following video contains profanity and may be considered NSFW.]

There's no question that the fishermen involved in this incident broke the law (holding a protected species for the purposes of photographing it is also illegal), but some commenters have stepped up in support of the men, claiming no damage was done because the animal was ultimately released. Others have strongly condemned the behaviour, calling for "justice to be served" for an endangered shark. We've seen these angry debates play out before on many occasions, and they tend to follow a now-familiar pattern: lines are drawn, invectives are hurled in both directions, and a bullying back-and-forth erupts over the morality of sport fishing.

This dialogue is tired, divisive and, in the end, accomplishes very little. So let's put personal opinions aside for a moment, and create something useful instead: a resource for anyone who wants to learn more about hammerhead sharks. What makes landing these fish so bad? And what can fishermen do to help? (Not a fisherman? Don't like sport fishing? Keep reading anyway! Knowing the facts is just as important for anyone who supports shark conservation. Maybe something in this article will prepare you for a productive conversation down the line – no pun intended).

The hypersensitive hammerhead

It might seem inconsistent that some sharks – but not all – are illegal to bring on land for the purposes of removing a fishing hook. Indeed, many anglers caught in the act of doing this actually believed they were behaving in the best interest of the animal. 

Great hammerheads like the one in the Singer Island video are listed as endangered by the IUCN, and that's often the first thing pointed out by opponents of this kind of fishing. However, there are actually other reasons behind the no-landing rule.

While many sharks can handle stress well, research has shown that hammerheads do not fall in this category. Marine biologist Dr Austin Gallagher, who has done extensive work on fishing stress in sharks along with colleagues at the University of Miami, explains that hammerheads go into a "downward spiral" when caught on the line. "And they really can't get out of it," he notes.

In potentially dangerous situations, humans get a surge of the hormone adrenaline as our bodies prime themselves to rumble or to run. This "fight or flight" response might seem inherently human, but we have our ancient ancestors to thank for it (and sharks have been on this planet almost 500 million years longer than we have).

"When a fish is caught, it also gets the 'fight or flight' response," notes Gallagher. A surge of hormones in the shark's brain triggers the release of sugar and energy to the rest of the body – a boost to help the shark operate in overdrive. 

"So now the animal is fighting, right? You have all this new, mobilised, beautiful energy to the muscles," he explains. "You need it because moving and escaping really fast is demanding. The whole point of a stress response is to be quick ... The reaction is immediate, but the trouble is, it's not designed to be prolonged."

Hammerheads are notoriously hard fighters, and there's a problem with that spirited survival instinct: they can fight themselves to complete exhaustion very easily. 

Built for speed not distance

Despite being one of the most agile sharks, hammerheads are quite bulky, which means it takes a lot of energy for them to hit top speed. What's more, their mouths are quite small in relation to their large bodies, which limits the amount of oxygenated water that can move over the gills. To keep their energy consumption in check, the sharks usually rely on quick bursts of speed when they need to get up and go.

"Hammerheads are [built] for speed not distance, and that's the problem," says Gallagher. "We're analysing drone footage now of hammerheads hunting, and what we're finding is that they really only have four to five seconds going full speed before they have to stop, chill out and replenish their cells."

But when their fight-or-flight response is triggered, hammerheads will battle their way to complete exhaustion. They reach a point when there isn't enough oxygen or energy left in the body to keep up: the blood becomes loaded with carbon dioxide and lactic acid floods the muscles. These potentially lethal effects are amplified when the fish are dragged ashore in this state.

"In these situations, you're bringing an animal that's already at a high risk of metabolic collapse out of the water where it can't breathe," notes Gallagher. "That adds another stressor to the animal." Without the support of water, the shark's organs can also be crushed under their own weight. 

"Now the shark is in full-blown survival mode – so it's still firing some of those muscles, trying to escape," adds Gallagher. "And at that point, it's very hard for some animals to come back." It's estimated that as many as 40 or 50 percent of hammerheads will die after release following 40 minutes on a fishing line. (A figure of 90 percent is sometimes cited, but this comes from research focusing on commercial fishing practices). 

Removing large hammerheads from an already declining population can have devastating effects: the biggest animals are also the ones that contribute most to the population. "These impressive animals are the ones that have been 'road tested'," says Gallagher. "Those are the genes you want in the gene pool!"

This is true whether or not you're fishing in an area where hammerheads have been been granted legal protections. Science is telling us that there are negative consequences to putting these animals under stress.  

Turning the tide 

The story of the deadly impacts on hammerhead sharks has been known for years, and yet the landings persist and many similar cases have gone unenforced by state agencies. But the point here is not to present all sport fishing in a negative light. In fact, most scientists support sustainable shark fishing, and many anglers already collaborate with them on conservation projects. 

"I know a lot of land-based anglers who are really passionate about these sharks, and passionate about their conservation," notes Gallagher.

In the end, it's going to be up to the sport-fishing community to turn the tide on harmful practices – so alienating it is completely counterproductive.

"Some of the folks who get caught doing this don't know about the science or aren't part of communities that are well informed," Gallagher adds. "We have to turn these unfortunate events into learning opportunities – not blame games – if we're going to conserve the future of these animals. And in many cases, fishermen handle these situations the right way."

What is the right way?

Pick smart bait. Hammerheads are especially attracted to stingray prey, and typically go for live bait (some anglers have been known to cut rays in half while still alive to evoke a hammerhead's natural hunting response). Use something else instead. Many published fishing forums contain lists of the best bait options. 

Keep an eye out. Hammerheads are easily recognised by their tall, narrow and pointed dorsal fins. If you see one in the shallows, choose to fish in a different spot.

Cut the line immediately if you've caught a hammerhead by mistake. Sharks have incredible healing abilities, and experts overwhelmingly agree that a hook will do less damage than prolonged stress on the line. This is true for boat-based fishing as well: "Hammerheads tend to bang their heads around the side of a boat," notes Gallagher, which means that promptly cutting the line could reduce the risk of injury. "It's in the animal's best interest to keep it in the water, and reduce the additive stressors that continue to pile up."

Forgo the photo. Cutting the line often means giving up the chance to measure or photograph a shark, but if we want to be able to interact with these incredible animals for years to come, that's a necessary sacrifice. "Anglers want to get those pictures, they want to see the shark and celebrate it, which I understand," says Gallagher. "But science is telling us that for certain species, that just isn't the best way to interact with them from a fishing perspective." 

Share accurate information. For those of us who don't fish, there are ways to help, too – whether you support the sport or not. Avoid out-of-context, misleading data, and don't ignore the efforts of many responsible fishermen. This sends important conversations underground.

Bookmark this article (and this one from shark scientist Dr David Shiffman). The idea that shark fishing and shark conservation are at war is misguided. If a video gets your hackles up, don't get sucked into an ugly blame game. Instead, share accurate information and highlight good examples of responsible fishing.

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Top header image: USFWS Headquarters/Flickr

The mama lion in the footage, part of a newly minted breakaway pride in the reserve, was showing telltale signs of recent birth – suckle marks and swollen mammary glands – when ranger Grant Rodewijk spotted her on a riverbank during a game drive with guests.

"We were all on the edge of our seats, thinking that we could be the first people at Londolozi to potentially view [her] cubs," he writes in a blog post about the experience.

The hunch proved correct: the group was perfectly positioned to watch as the big cat gently grabbed first one, then another cub by the scruff of the neck to carry them safely across the water. 

Rodewijk's excitement at the sighting is understandable: lionesses go out of their way to keep their newborns out of sight, so these brief glimpses were a truly rare treat.  

The last few months of pregnancy are a secretive affair for expectant mothers: they'll usually leave the pride to give birth in a sheltered, hidden spot, where the new arrivals are spirited away for the first four to six weeks of life. "Typically lionesses will move off on their own, give birth and only re-introduce their youngsters [to the rest of the pride] when their eyes open and they are more capable of fending for themselves," explains Londolozi ranger Amy Attenborough.

Whether it's threats from roving hyenas, leopards or even their own kind (in the form of murderous adult males), young lions are extremely vulnerable, so their mother remains in the den site with them for those formative weeks, leaving only occasionally to hunt.  

Rodewijk and his guests had stumbled on one of the rare instances when the babies are exposed: as lionesses are sometimes known to do, this particular mother was in the process of a relocation mission, moving her offspring from one den site to another. 

The right-place-right-time nature of the incredible sighting is something Rodewijk is keenly aware of: "Sadly, I know it will most likely be a long, long time before I am lucky enough to see something like this again, if ever…" 

We all know that individuals fight over potential love interests. Just think of Daniel Cleaver (Hugh Grant) and Mark Darcy (Colin Firth) scuffling – rather impotently – over Bridget Jones in a fountain. But you might be surprised to hear that the fierce rivalry continues behind the scenes – in the form of sperm competition. This is when the sperm of two or more males compete inside the reproductive tract of a female to fertilise the eggs, something that is widespread in the animal kingdom.

It is generally assumed that the sperm in a female's reproductive tract around the time of fertilisation will belong to one male. But DNA fingerprinting has revealed that even "monogamous" bird species that form exclusive pair bonds are not as exclusive as was once thought.

In fact, extra-pair young (those fathered by another male) are found in around 90% of bird species, and extra-pair copulations (matings with a different male) result typically in 11% of all young. (The percentage of extra-pair young can be as high as 76% in species such as the superb fairy wren.)

Fertilising an egg is often likened to winning a lottery – the more tickets you possess, the higher your chances of winning. Consequently, the more sperm a male manages to get to the egg, the greater his chances of fathering offspring. This has led to huge variation in copulatory behaviour and sperm morphology.

Here are five elaborate methods that have evolved to increase the chance that an individual male's sperm is the winner:

1. When big is best

The obvious way to increase the chance of fertilising an egg is to increase the number of sperm that are produced. Males have been found to make the most sperm in species where individuals are most promiscuous. For example, the testes of gorillas – a monogamous species – are 30 grams, whereas the testes of chimpanzees – a promiscuous species with multiple mates – are a whopping 120 grams. To put this in context, human testes are around 50 grams, and chimps are around two thirds our body size, making chimp testes, relatively speaking, almost four times the size of human ones.

2. Sperm 'trains'

In general, larger sperm (specifically, those that are longer) are more successful because they have a greater swimming velocity. So, sperm length is longer in more promiscuous species. One animal that has truly taken advantage of this is the wood mouse, where the sperm possess hooks to attach to each other.

This means they can form aggregations, or mobile "trains", of hundreds or thousands of sperm cells, greatly increasing sperm motility.

3. Kamikaze sperm

Around 20% of sperm are abnormal – possessing two heads, no heads or two tails, for example. These “kamikaze” sperm are incapable of fertilising eggs but it is thought that they might be able to prevent sperm from rival males reaching the egg, either by killing them with enzymes or simply by blocking them. Although there is little evidence of kamikaze sperm in non-humans, some snails possess abnormal sperm that contain enzymes capable of degrading sperm.

4. Preventative behaviour

Many males cement up the genital opening of the female with a copulatory plug, producing an obstacle to prevent other males from further copulations. For example, male European dwarf spiders produce a plug which starts as a liquid secreted by a specialised gland and then hardens to become an obstacle. What’s more, the longer the copulation, the larger the plug left behind. Smaller, fresher plugs are relatively easy for other males to remove. But males are unlikely to try to remove larger plugs, benefiting those that have invested more time in the female.

5. Brushes and whips

If females mate with multiple males, each suitor generally will father more offspring than the previous one. Therefore, males compete by trying to ensure their sperm is the one to fertilise the egg.

This has led to the evolution of some bizarre penises. The echidna (a spiny, egg-laying mammal), for example, has a four-headed penis – although only two heads ejaculate at once.

In some species, penises are specifically shaped to pack sperm tightly into the corners of the female reproductive tract, whereas others are armed with spines, brushes, barbs or hooks to scrape out the sperm of previous males, or stimulate the females to release sperm. The most elaborate are the penises of odonata, insects such as dragonflies. Some even possess whip-like flagella to remove rival sperm.

These removal methods are quite successful as even the human penis is able to remove 90% of sperm from a reproductive tract.

Many reptiles, rays and sharks actually possess two "penises". In sharks, these are known as claspers, and either one can be used to inseminate the female. These claspers not only possess small hooks to anchor them in place, but they are also linked to siphon sacs filled with seawater that spray the sperm into the female reproductive tract under pressure. It has even been theorised that one of the claspers could act as a "jet wash", cleaning out the sperm of previous males, although there is little evidence for this as shark matings are rarely observed.

Whatever the reason, it is clear that animals have evolved some extraordinary ways of ensuring that they win the competition for fertilisation.

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Top header image: Pixabay

Louise Gentle, Senior Lecturer in Behavioural Ecology, Nottingham Trent University

This article was originally published on The Conversation. Read the original article.

This Tasmanian tiger snake certainly has an interesting way of getting around @bangorfarm! #WildOz pic.twitter.com/Y0OPQtuboM

— Wildlife Land Trust (@wlt_au) February 14, 2018

The video was filmed recently in Tasmania by Matt Dunbabin, owner of local vineyard, the Bangor Vineyard Shed. In the days since he posted it to Facebook, the clip has been viewed over six million times. 

"I've never seen anything like it – the views or the snake," Dunbabin quipped during an interview with a local radio station. "He went quite some distance, and he was still going when I left him. It's a long fence; he could have gone a couple of kilometres if he really wanted to!"

Exactly what the roving reptile (Notechis scutatus) was doing on the wire remains a mystery at this point (herpetologists, get at us!) but we can at least eliminate some wonky hunches and give you our best guess.

Some have speculated that the snake climbed up the wire to avoid burning itself on the hot soil. This is unlikely for two reasons: metal is a great conductor, so that fence was probably hotter than the ground. What's more, these snakes are known to take cover during exceptional heat waves.

We're also calling bunk on claims that the snake was trying to "sneak up" on the vineyard's guests. Not only was this fence located behind Dunbabin's farm – far from any visitors – but that scaremongering hypothesis also doesn't line up with what we know about tiger-snake behaviour. The snakes do possess a highly toxic venom, but they're unlikely to approach or engage with humans of their own accord. 

"Like most snakes, tiger snakes are first cowards, then bluffers, and only become warriors as a last resort," says Tasmania Parks and Wildlife Service (TPWS). "If threatened, a tiger snake will flatten out its neck, raising its head to make itself appear as frightening as possible."

Our "wire-walking" friend here, however, appears completely relaxed. 

"Snakes are part of the landscape down here, and I was quite happy to see him," added Dunbabin. "It really was an amazing bit of animal behaviour."

Dunbabin's assumption that this snake was male is probably correct. While all tiger snakes tend to roam about, male members of the species are especially prone to wandering. That said, both males and females are known to climb in search of food. 

Tiger snakes mostly feed on small mammals – in fact, they play an important role in keeping invasive rodent numbers down – but when furry food isn't around, the snakes raid birds' nests. Perhaps some avian activity along the fence prompted the snake to investigate. 

We'll be updating this post after weighing in with the experts, so watch this space!

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Top header image: TassieEye/Flickr

World, meet the green spoon worm – Bonellia viridis – and prepare for a wild ride.

Named for the shape they take when their proboscis (the worm equivalent of a feeding straw) is contracted, spoon worms (class Echiura) are difficult to collect and hard to tell apart, so it's no surprise that many of them remain poorly understood. The details we have uncovered about some representatives of the group, however, are sublimely strange – and B. viridis takes the cake. 

For starters, only female members of the species exhibit that signature emerald colouration. And in the Bonella world, "wearing" green is an option reserved for the ecologically elite. 

Green spoon worms begin life colourless and adrift in a sexually undifferentiated larval state: whether they end up male or female depends on where they settle – and if that landing zone is located in "unclaimed" waters. 

"If the spoonworm larva lands on the seafloor it becomes female and begins to secrete a potent toxin called bonellin," writes deep-sea ecologist Dr Andrew Thaler over at Southern Fried Science. Bonellin is responsible for a female worm's green hue, but it also plays an important role in the survival of her genes.

"Should [another] larva come in contact with this toxin, it will be masculinized and sucked into the spoon worm's body through her feeding proboscis," explains Thaler.

Once inside, that freshly "made" male will receive a life sentence: sperm-bank duty, without parole. The female holds masculinised larvae in her genital sac to be used like an on-demand fertiliser factory.  

Formally known as "environmental sex determination", this mechanism has been confirmed only in this particular spoon-worm species, but it's possible that others employ it, too. "Entombed" males have been found in B. viridis's close kin, but we don't know if similar biochemical warfare is involved in their development as well. 

"It's such a unique phenomenon," says Kagoshima University researcher Dr Masaatsu Tanaka, who recently described a new spoon-worm species discovered in the Seto Inland Sea. "Whether other Bonellids [there are 80!] follow this method is a very interesting topic."

One such cousin, a similarly shaded spoon worm called Metabonellia haswelli, was recently encountered off the coast of Australia:

Diver PT Hirschfield found the lone worm under a rock near Victoria's Port Phillip Bay. The sighting was a first for the local resident, despite the fact that he's completed over 800 dives in the area. "It reminded me a lot of a balloon animal in the process of making itself," Hirschfield told Storyful.

Some commenters suggested that the oscillating "bulges" seen in the worm are signs of a recently consumed gluttonous meal. It's a reasonable guess, but spoon worms slurp down only tiny edible particles. The blobs you see are actually the animal's own flesh. 

They might look like Jello-stuffed sausage casings, but these worms have surprisingly well-developed muscles. In fact, they have three layers of muscle, which surround a fluid-filled body cavity. Together, both of these structures help spoon worms achieve motion in the ocean.

By contracting their muscles in a wave-like pattern, the invertebrates send their internal fluid towards one end of the body. As fluid bulges in the direction they want to go, the muscles relax, squeeze and repeat. (This is how your own body moves food down your throat, only the worms use the process to scoot themselves elegantly along.) 

You can see these contractions in action by taking a gander at the distantly related spoon worm Urechis unicinctus, a species found in coastal mudflats that's commonly referred to as the "fat innkeeper" or "penis fish".

[The common name doesn't lie – what follows is NSFW viewing, so proceed with caution.]

The choice of shallow habitat is one that's shared by most of the spoon worms that have been well studied over the years. But as we continue to explore the ocean's murky depths, these animals are turning up in some of our planet's most extreme environments.

"I think there are many undiscovered species, especially in the deep sea," says Tanaka. "Some have been documented at 10,000 metres!" Revealing the details of their lives, though – let alone their sex habits! – will be a slow process. 

"Even for already described species, there are many puzzles left behind by brief original descriptions, lost [specimens], misidentifications and more," says Tanaka. "Even worse, the scientists working on Echiura are few – maybe fewer than ten persons in the world. As a taxonomist of this group, however, I also enjoy this [challenging] situation and hope to solve these puzzles one by one."

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Top header image: The spoon worm Metabonellia haswelli. PT Hirschfield/YouTube screengrab

According to reports, around 30 sharks had swum into a creek that feeds the Krom River, a 109-kilometre waterway that meets the Indian Ocean through a system of estuaries. The impressive shark party sparked alarm among some local commenters online, but the presence of these predators in the river system is nothing out of the ordinary.

It's easy to jump to the conclusion that the sharks in the video are bull (or "Zambezi") sharks, which are known for their habit of swimming upstream to pup in shallow nursery areas. But these apex predators aren't the only shark species that can manage the transition from salt to "sweet" water. 

The aggregation in the video is actually made up of sharptooth houndsharks (also known as "gully" or "spotted gully" sharks). The telltale clues are those broad, sickle-shaped fins (the scientific name for the species, megalopterus, roughly translates to "large wing"). 

These animals pose very little threat to humans: despite their menacing common name, sharptooth houndsharks eat small crustaceans, fish and cephalopods. A diet comprised of coastal species means the sharks spend most of their time in the shallows, but they're not known for approaching human bathers, let alone acting aggressively towards them. 

Several hunches are floating around about why this group of sharks was spotted in the river. 

Some commenters postulated that the sharks may have become stuck in the waterway after a large swell pushed them into the river, but this scenario is unlikely. Not only have local tides been relatively consistent, but according to Everton, the sharks moved off without any trouble later that day.

Other reports suggest that an upwelling event (which brings cold, nutrient-rich water up from the deep sea) resulted in a sudden temperature drop in St Francis Bay. This could have sent the sharks upstream in search of warmth, but South African shark scientist Dr Alison Kock notes that other factors could also have played a part. 

"This [upwelling-related migration] has happened numerous times with a range of species," Kock said. She added, however, that other drivers, like food or reproduction, could not be ruled out. 

Houndsharks elsewhere in South Africa are known to group together in sandy estuaries during the summer months, and scientists have observed large numbers of pregnant females during such aggregations. This shiver of sharks, therefore, may have been mating or pupping. (This would explain the splashing and grouping behaviour seen in Everton's clip: as we've discussed before, shark sex can get rough.)

Local resident Sulise Leja Human-Wells, who lives near the mouth of the bay, has seen such aggregations here before. "The sharks are there every year," she wrote on Facebook. "I hope no one tries to catch them."  

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Top header image:Illustrations of the Zoology of South Africa/Wikimedia Commons

A recent two-in-one sighting photographed at South Africa's Marakele National Park illustrates the point in remarkable, grisly fashion. Snapped by field guide student Daniel Hitchings Tar at Marataba Safari Lodge, the images show a Mozambique spitting cobra gobbling down a black mamba as though it were a piece of serpentine spaghetti.

Battles involving two such venomous combatants are rarely seen, or successfully documented. While it's not unusual for snakes to eat other snakes (cobras are known for having a particular penchant for this), the behaviour is not witnessed often, especially when the snake being ingested is one of the world's deadliest.

Black mambas have a fearsome reputation, due in large part to their frightfully fast-acting venom. A bite to the chest or head and you could collapse into paralysis in half the time it takes to watch an episode of Game of Thrones (a terrifying thought indeed, partly because you won't get to finish said episode). Black mambas, however, are not the dark-mouthed harbingers of death they're so often portrayed to be. Like many snake species, they avoid confrontation, attacking only when threatened. "Although often labelled an aggressive snake, the black mamba is very shy and nervous, and quick to escape when it has the choice," Johan Marais of the African Snakebite Institute told Africa Geographic. "But if cornered or hurt, it will not hesitate to strike."

So, with such evasion skills and venomous weaponry on its side, how did this black mamba end up inside of a cobra's belly? The answer may have something to do with size, and a lot to do with the cobra's venom-resistant superpowers. "This particular cobra was older and larger than the mamba," Charlotte Arthun explains over on the Marabata blog. "While the mamba put up a fight, continually striking at the cobra, the cobra won the battle with its superior size and strength, eventually eating the mamba."

Many venomous snakes have immunity to their own particular blend of toxins, which serves as a kind of failsafe in case they accidentally bite themselves in the confusion of a hunt, or receive a dose of venom during a rowdy mating ritual. However, when it comes to a snake's ability to withstand the venom of a different species, results seem to vary from snake to snake. "Most cobras are snake specialists and are highly resistant to snake venom," explains Marais, who believes that the cobra would have won this battle even if the black mamba had matched its size. "Both snouted cobras and Cape cobras readily eat puff adders [a venomous snake found in the African savannah and grasslands]," he added as further evidence.

So it's possible this individual took a few shots of mamba venom, but came off unharmed courtesy of some pretty neat evolutionary immunity. In instances where snakes have shown some resistance to the toxins of their slithery relatives, the tolerance usually applies only to species that share the same habitat (a Mozambique spitting cobra may not be able to shake off the venom of an eastern brown snake quite so easily, for example).

It's not only cobras that have shown powers of venom resistance. The ability to tolerate the effects of chemical weaponry is a trait shared by a fairly exclusive sect of hardy creatures. While opossums may lack good looks (no offence guys, but amiright?), they can boast about the venom-neutralising molecules in their blood. Egyptian mongooses gleefully hunt and eat venomous snakes thanks to cell mutations that block lethal neurotoxins. Skunks, hedgehogs, pigs and ground squirrels, meanwhile, have all shown some resistance to venom. But the poster animal for this toxin-defying guild is of course the internet's favourite (and nastiest) mustelid: the honey badger. The two-toned critters are equipped not only with molecular defences against cobra neurotoxins but also with physical armour: their thick, loose skin is tough for snakes to pierce through.

Interestingly, venom resistance is a lot more common in predators that regularly dine on venomous animals than it is among target prey species. (Aside from the unassuming woodrat – which can take a hit from a western diamondback rattlesnake and still make it home in time for dinner – most prey creatures targeted by toxin-wielding predators are not able to survive envenomation, and must use other defences to stave off an attack instead.)

For predators that can tolerate a dose of toxins, the reward is a more diverse buffet of potential prey: venomous scorpions and snakes are risky quarry for most, but the venom-resistant can tuck right in. And such meals can be very hearty. "Snakes are limbless, small-boned, little bags of meat," evolutionary biologist Danielle Drabeck told Jason Bittel in an article for Smithsonian Magazine back in 2016. "Even venomous snakes only have one pointy-end."

Our ancestors' transition out of the water and onto the land was a pivotal moment in evolution. No longer buoyed by water, early tetrapods (animals with four limbs) had to overcome gravity in order to move their bodies. Exactly how those early pioneers first evolved the fundamental capacity to walk has fascinated scientists for many years.

Fossil discoveries can tell us how and when vertebrates evolved the physical features needed to move onto land. But new research published in the journal Cell suggests that the neural circuitry needed to walk probably existed long before actual legs evolved. Because land-based animals and fish share the same circuitry today, their last common ancestor – an ancient fish which existed 420 million years ago – probably also had that circuitry and used it to move around beneath the water.

We already have a reasonably good idea of when fish evolved into land-based tetrapods because the fossil record documents the sequence of changes to their bodies. One of the most iconic specimens is Tiktaalik, a "transitional" fossil dating to around 375 million years ago.

Tiktaalik is special, because though it retains many fish-like characteristics, it also possesses wrist bones, suggesting that it could support itself on its front limbs. Fossils from rocks older than Tiktaalik lack these wrist bones, and are generally more fish-like. Fossils from younger rocks include more tetrapod-like species, with distinct digits and limbs.

But the new research from New York University in the United States suggests that fish needed more than just legs to learn how to walk, and in fact evolved the neural circuitry involved much earlier on. The researchers reached this conclusion by studying little skates, fish that move along the ocean floor by moving their hind fins in a left-right pattern, much as we would move our legs when walking.

The researchers found that the neural circuits little skates use for their alternating fin motion are the same as those mice and other four-legged animals use for limb movement. What's more, this circuitry is produced by similar genes.

Mind before matter

Because it is unlikely that the same circuitry evolved twice, this implies that the same genes and neural pathways found in tetrapods and skates were present in their last common ancestor, some 420 million years ago. This is long before the earliest fossil evidence for tetrapods, meaning that the circuits involved in walking first evolved millions of years before legs or feet first appeared.

Skates aren't the only walking fish that still exist today. In fact, it's fish that are less adapted for life out of water that move in a manner most like walking, where one limb is placed in front of the other. Blind cavefish fall into this group, using their fins to walk on the riverbed and to climb waterfalls. Lungfish, which move somewhat haphazardly on land, also seem to use their fins in an alternating pattern to propel themselves along the sediment surface when in water.

Scientists have also been observing how modern fish move over land, without the buoyancy aid provided by water. Obvious choices for such studies are fish that are capable of moving around on land, and regularly do so in nature. Mudskippers, for instance, move by using their forelimbs like crutches to propel themselves forward. Lungfish, on the other hand, tend to anchor the head and flip the rest of the body forward, which can sometimes leave behind marks that look like footprints.

The new research is an important reminder that however good our fossil record gets, it can only show us the shape or anatomy of an organism. The genetic, neural and behavioural features that determine what an animal does are ultimately the drivers of that anatomy. The links between living animals can often tell us as much, if not more, about our ancestors as fossilised bones and footprints.

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Peter Falkingham, Lecturer in Vertebrate Biology, Liverpool John Moores University

This article was originally published on The Conversation. Read the original article.

The remarkable chase scene was caught on film by safari-goer Louis Le Roux during a visit to the Kgalagadi Transfrontier Park, a vast swathe of sandy savannah in the Kalahari Desert region of Botswana and South Africa.

A smaller relative of its more familiar spotted cousin, the shaggy-haired brown hyena is a ubiquitous carnivore in this harsh, arid region, but a sighting is still considered lucky given its largely nocturnal habits and elusive nature. 

The band of big cats, meanwhile, had made its presence keenly felt in the area around Le Roux's camp the previous day and night, so he had a camera at the ready just as the unwitting hyena stumbled into an ambush near the local waterhole the next morning.

The Kalahari's sparsely populated desert vastness means its reigning carnivores (and the brown hyena ranks among them here) can mostly keep out of each other's way – but not this time. And while the shaggy beasts have more than enough moxie to stand up to less brawny rivals (they've been known to rob not only cheetahs but also leopards of their kills in these parts), lions are one competitor that will not be messed with.

The big cats may have been eyeballing the local antelope fare for their dinner, and likely pursued the hyena first and foremost as a rival, but they probably wouldn't have passed up the sustenance had their chase ended in a successful kill. So the hyena's nimble sprinting no doubt saved its life. 

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Top header image: Ian White/Flickr

The incredible set of images was captured by photographer and eagle enthusiast Frank Coster in Jenner, California, a small coastal town in Sonoma County. Tucked away atop a bluff on North America's Pacific coast, Jenner is a known hotspot for interesting wildlife sightings. The water here is cold and rich in nutrients; the pristine coastline is flanked by a 5,630-acre swathe of protected redwood forest; and the Russian River forms a breathtaking estuary where it joins the sea. 

Thousands of harbour seals use the Russian River estuary as a nursery each year, and with pupping season running from March through to August, the animals have begun to show up in droves in recent weeks. Other portly pinnipeds, like elephant seals, northern fur seals and California sea lions also take advantage of the estuary's shelter and abundance of food ... and the local eagles have noticed. 

"I took these photos at the mouth of the river," says Coster. "It was not until the last several months that I personally have seen eagles actively stealing (or trying to steal) from sea lions and harbour seals."

Much to his amazement, Coster watched on as one of the daring birds swooped down to snatch a lamprey – an eel-like animal that slurps its food with a sucker-like rasping mouth structure – straight out of a sea lion's jaws. 

Interestingly, Jenner isn't the only spot in California where this robbing strategy has been documented. Back in 2013, photographer Bradley Oliver witnessed similar behaviour off the coast of San Fransisco. During that encounter, the sea lion actually attempted to chase down the avian thief, but the eagle managed to escape unscathed, with its fishy spoils in tow. 

"It's an absolute prize series of shots!" Cascades Raptor Center Executive Director Louise Shimmel says of Coster's photographs. "I haven't seen this behaviour before, but bald eagles are such kleptoparasites that it doesn't totally surprise me. They steal from each other constantly, and from osprey all the time."

Ospreys (also known as "sea hawks") have a unique "bait and tackle" set of adaptations that makes them incredibly successful at fishing. Spiked pads on their feet help with gripping slippery prey, and reversible outer toes lock cargo down during flight. And yet, they regularly lose their lunch to their white-headed cousins:

"Young osprey typically need to learn to just let go, or they get hurt," says Shimmel. "We get them in with talon punctures to the breast and shoulders from such interactions."

According to Coster, the sea lion didn't put up much of a stand either. It seems that even for a hulk of blubber and brawn weighting up to 350 kilograms, a full belly isn't worth the risk of potentially serious injury.  

Despite their propensity for scavenging and stealing, bald eagles are apt hunters capable of taking down animals as large as deer, and their talons can reach five centimetres (2in) in length.

Jenner local Joan Bacci, who has been observing the town's eagle population for five years, has seen the impressive birds race seal lions for the same lamprey. "Sometimes the eagles win, and sometimes the sea lions win," she says. "But we rarely see them engage. The eagles generally pick a different spot on the beach than the hauled-out seals."

Stealing food might take far less energy, but there's another potential reason behind the bald eagle's act of piracy here. 

Sea lions tend to shake lampreys above the water in order to dismember them before eating (we've seen the pinnipeds do this with sharks as well), and during all this thrashing activity, a sea lion's head may "stand" about a metre above the surface. Since bald eagles are unable to take off from the water (unlike ospreys, who regularly submerge themselves), this gives them a shot at landing an easy meal without getting wet. 

It's still a risky tactic: one wrong move from the sea lion, and this eagle may have been forced to "swim" to shore. 

Just how a defensive sea lion may have reacted to that turn of events is hard to say, but exhaustion would probably pose a bigger threat to a water-bound eagle in that scenario. 

"To my knowledge no one has witnessed a sea lion or seal kill or eat an eagle," says Coster, who, along with Bacci, is a contributing member of the Jenner Bald Eagles Study Group.

On the other hand, a lengthy voyage towards shore has been known to cause bald eagles to drown.

One of the area's resident female bald eagles has recently gone missing, and it could be that a mishap during a theft of this nature had something to do with her disappearance, though it's impossible to know for sure.

"There are many possibilities as to why the adult female has not been seen for the past month," Coster says. "She was quickly replaced with a four-year-old sub-adult female. [That bird] was recently seen mating with the resident male."

Bacci adds that bald eagles will sometimes also steal placenta off newborn sea-lion pups, or scavenge the carcasses of any youngsters that don't make it. Even in those instances, she has not witnessed any kind of attack on the birds.

"A newborn pup that dies is valiantly guarded by its mom," she says. "Only after she finally gives up [and vacates the area], will an eagle move in along with the turkey vultures."

"I think the story goes that Benjamin Franklin questioned whether we should have a thief and bully as our national symbol," jokes Coster. 

Like so many great discoveries, this one happened completely by chance. During a 2015 survey off the coast of the Galapagos Islands, a collaborative team aboard the Ocean Exploration Trust research vessel Nautlius noticed a peculiar pattern: the region's towering, sulphide-rich hydrothermal vents (known as 'black smokers') were frequently visited by ghostly skates, close shark and ray relatives. The seafloor around these structures, meanwhile, was littered with ochre-coloured eggs.

Perplexed by the unusual sighting, the team reached out to Dr Dave Ebert, programme director at the Pacific Shark Research Center, who was able to identify the alabaster animals seen near the vents as Pacific white skates (Bathyraja spinosissima). Later genetic tests conducted on four of the eggs confirmed they harboured the same species behind their silky, collagen walls.

"For me, it was like being a kid on Christmas morning. I felt like yelling, 'Wahoo! This is awesome!'" says Ebert. "These fish live one, even two, thousand metres deep. We know almost nothing about them."

Like their close kin, skates take their time growing, but deep-dwelling members of this group (order Rajiformes) take "slow" to a whole new level: in some cases, it can take up to four years for a baby skate to emerge from its egg case as a fully formed smiling ravioli.

Add a little heat to the mix, however, and that time can be cut in half.

"We think these Pacific white skates are using the vents to speed up development," explains Ebert. "We know from past studies that if you take these egg cases and you warm them up, even by half a degree, or a degree Celsius, it will rapidly decrease the incubation period. So instead of being three to four years, it might be one to two."

With the help of geologists, marine biologists and geneticists from four countries, this heating-up hypothesis was published today in a study led by Charles Darwin Research Station senior scientist Dr Pelayo Salinas de León. If the hunch proves correct, it will mark the first time this strategy has been documented in any marine animal.

"This is a really cool finding!" says Dr Thomas Farrugia, a skate and ray researcher at the University of Alaska Fairbanks who was not involved with the study. "In one sense, it's not too surprising: skate egg cases are often found in high densities in specific areas, such as canyons or kelp beds. You would assume that they are laid in those areas for some purpose. But it is really intriguing that they might be using the thermal advantages of hydrothermal vents!"

Even for co-author Dr Brennan Phillips, a deep-sea biologist who has been piloting remotely operated vehicles (ROVs) for 14 years, the egg cases came as a surprise. Phillips studies the relationships between sharks and underwater volcanoes (he refers to this overlap as "sharkcanoes!"). Hydrothermal vents are often associated with volcanic activity beneath the sea floor, so the discovery piqued his interest right away.

"When I was piloting on this trip, and I saw the skate eggs, I was really pleased," says Phillips. "The egg cases added to the story of why these animals are there."

Sharks and their kin have been around for over 500 million years. (For a bit of perspective, there were shark-like animals swimming in ancient oceans 280 million years before the first dinosaurs.)

"And in that time, there have been periods of extreme vulcanism on this earth – periods where the volcanoes have become really active," says Phillips. "When that happens, most things die. So it's really interesting to me that we have a lot of sharks, skates and rays around still, that seem to not only be resilient to these harsh [volcanic] environments, but also to be using them to their advantage."

Hot water spewing from these underwater chimneys can reach an unimaginable 300°C (572°F), and the Iguanas-Pinguinos site, where the eggs were discovered, is known for especially vigorous venting.

Most of the 157 eggs observed by the team were nestled within 20 metres (66ft) of the openings. Even at this range, the surrounding water can be nearly a degree above the 2.76°C (37°F) average (that's positively balmy by deep-sea standards). What's more, the instruments used to measure the ambient temperatures weren't positioned quite as deep as the eggs themselves, so the water around the clutches could have been even warmer. "It might even be another half degree warmer," says Ebert.

There's evidence to suggest that skate development across the board is almost entirely driven by water temperature. The Alaska skate, found in the frigid Bering Sea, takes about three years to develop. Skates found in tropical waters or coastal shallows, on the other hand, hatch faster. This means the incubation period required to produce a healthy baby skate probably has far less to do with biology than it does with habitat. And that would mean denizens of the deep are at a serious disadvantage: the deeper you go, the colder it gets, and the longer a skate's babies take to join the watery world. It seems Pacific white skates have learned to cheat that system.

"It is ingenious, but we probably have to check our assumption that the fish 'know' to do this specifically," notes Farrugia. It's very possible that the behaviour is simply the result of evolution over time: skates that deposited their eggs near vents in the Galapagos Rift had shorter incubation periods, and were therefore able to produce offspring with greater success.

"On the other hand, I wouldn't rule out that they actually do seek out areas with warmer temperatures," he says. "Many elasmobranch species give birth or lay eggs in specific 'nursery' areas which present advantages for their young – either warmer temperatures, fewer predators or more food."

Ebert suspects that the latter scenario could be true. "But I doubt they came from far away," he adds. "Rather, I think these skates are generally in the area of these seamounts and rifts, but find the vents to specifically lay their eggs."

Hundreds of animal and microbe species have been documented near the planet's hydrothermal vents, even though these areas are among the most extreme habitats for life, with low oxygen content and monumental pressures. What's more, when hot, acidic seawater rises through volcanic rock, it releases all kinds of toxic minerals.

So, could the noxious chemicals emitted from Iguanas-Pinguinos have any negative effects on skate embryos? It's unlikely. For starters, these fish are quite hardy, and egg cases are closed off to the outside environment most of the time. When a baby skate is nearing the end of its stay, a small hole opens in the case to allow more oxygen in.

"In fact, the skate embryo will actually beat its tail to create some water flow and replenish the oxygen," explains Farrugia. "As long as sufficient oxygen comes in, they may be able to tolerate some of the other gases. But since the adults would have to be able to survive while they are depositing the egg cases, I'm guessing they are depositing them in areas that don't have a lot of the noxious gases while still having warmer temperatures."

Keeping toasty can pay a role in the development of other animals, too – the sex of many reptiles, for example, is determined by their "hot or not" status. Still, only very few species have been known to harness the heat from geothermal activity to help their young go from embryo to hatchling. It's thought that some sauropod dinosaurs built nests in volcanically heated soils during the Cretaceous period, some 145 to 66 million years ago. And today, just one dinosaur descendant – the Polynesian megapode (an endangered bird native to Tonga) – employs this tactic.

More work is needed to find out just how many Pacific white skates prefer their eggs "soft boiled", or if this behaviour happens in other locations, too. However, layers of hatched cases also discovered around the Galapagos vents indicate that the species has been using the site for years. It just took a pinch of serendipity to reveal it.

Ebert has seen similar egg deposits off the coast of both California and Oregon. "I thought it was interesting, but I didn't make the connection," he says. "I didn't have the full scope – and these guys were able to get it with their survey. Most of the team members who stumbled upon this discovery are geologists, and it opens up a whole new world that we don't know about."

It's possible that skates along North America's Pacific coast also lay their eggs near underwater seamounts, but that's just speculation for now. An unexpected twist during the study, however, may have shown scientists where to look for answers.

When the team was digging into genetics data from the eggs collected in the Galapagos, they found that their genetic signature matched that of a skate caught during a survey in Vancouver, Canada back in 2008. That animal was thought to be a spiny-tailed skate (Bathyraja spinicauda), but Ebert and his colleagues realised it had been misidentified all those years ago.

The skates from that Canadian survey had been stored in a museum fish collection in Victoria, and photographs of the supposed "spiny-tailed skate" revealed it was actually a Pacific white. This revelation extends the known range for the species, and because British Columbia has some notable geothermal activity, any nearby rifts or seamounts could be a starting point to hunt for egg cases.  

A closer look at the haul from this decade-old survey also resulted in the identification of two more skates – the broad skate and the fine-spine skate – which have now been added to the roster of Canadian fauna.

"Two completely different studies, done ten years apart, together filled in blanks about these animals," says Ebert. "From so many angles, it is such a cool story!"

The team hopes to continue this multidisciplinary collaboration, and to extend it as deep-sea surveys continue springing up in the coming years. We don't know just how unique the use of geothermal "incubators" might be, but at least for now, the Galapagos skates get to keep their shiny title as the only known example in our oceans.  

"This all happened on one dive," adds Phillips. "Just fifteen hours flying around underwater. Imagine what we might find if we were expressly looking for this."

Maps created during the project have helped see Iguanas-Pinguinos included in the Galapagos Marine Reserve, a recently established World Heritage Site – but many other vent fields around the world remain unprotected. And because valuable minerals abound near black smokers, sea floor-mining initiatives are often in conflict with conservation efforts. A mountain of skate eggs, the team explains, gives conservationists leverage: it demonstrates that the ocean's volcanic habitats are also crucial to the survival of some species, likely far more than we realise.

"Now experts [from different fields] know what to look for," adds Ebert. "We're going to try to look at some other areas. Hopefully we're going to start gathering more information. It's wide open now."

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Top header image: MBARI

In Disney's film version of "Pinocchio, the boy-puppet rescues his creator Geppetto by lighting a fire inside Monstro the whale, who has swallowed them both. The fire causes the whale to sneeze, freeing Pinocchio and Geppetto from their gastric prison.

Before you dismiss this getaway as incredible fantasy, consider that new research shows that a kind of fire in the belly can actually be an effective strategy for escaping predators in the real world. In fact, the animal kingdom is full of amazing examples of unusual defence mechanisms that help small creatures avoid a nasty fate.

In a new paper in Biology Letters, scientists at Kobe University in Japan describe how bombardier beetles can survive being eaten by a toad by releasing a hot chemical spray that makes the hungry amphibian vomit.

Bombardier beetles are so named because, when threatened, they emit a boiling, irritating substance from their backsides with remarkable accuracy, to deter potential predators. They produce the caustic mixture by combining hydrogen peroxide, hydroquinones and chemical catalysts in a specially reinforced chamber at the base of their abdomen, which shields the beetle's own organs from the resulting explosive reaction.

The Japanese researchers fed two different species of bombardier beetles to captive toads. They were then able to confirm that the beetles used their weapon inside the toads by listening carefully for the explosive pop that accompanies each discharge.

Toads are ambush predators, quite used to swallowing first and asking questions later. When they start to feel a dose of diner's remorse, they can literally turn their stomachs inside out and scrape out the contents, rather than suffering meekly from indigestion. Many of the toads in this experiment did just that, disgorging the beetles up to 107 minutes after ingestion. Remarkably, the ejected beetles all survived.

In a further experiment, the researchers poked beetles with forceps to deplete their spray reserves. Compared to those with full tanks of fuel, the exhausted beetles were much less likely to be ejected. This showed that it really was their chemical arsenals that saved them, rather than just their taste or behaviour in the gut.

The bombardier beetle is of course not the only animal escape artist. The diverse getaway tactics of animals are a testament to the fascinating creativity of evolution. Subject to millions of years of abuse and exploitation by predators, natural selection has shaped an array of ingenious strategies for cheating death in the face of would-be devourers.

Animal Houdinis

Some examples are probably familiar to most people. For instance, many lizards drop their tails to distract a predator or escape from its venom. But others are more exotic. Sea cucumbers don’t have tails so they eject and regenerate their internal organs instead. Loud sounds (such as the "gunshots" of snapping shrimp) and bright colours (as on band-winged grasshoppers) are also effective means of startling predators. Mantid insects unite movement, sound and colour in an elaborate display that can stop an attack or at least give them a chance to escape.

Some animals fight back, such as the frogs that can erect sharp bony splinters from their claws that pierce their own skin, like X-Men's Wolverine. Other animals, including the mimic octopus, prefer to pretend to be dangerous, adopting the appearance of more deadly prey when threatened.

The stunning variety of defensive mechanisms would be impressive even if we only counted variations of chemical warfare, similar to the bombardier beetle's steam treatment. There are the defensive toxins in pufferfish and poison arrow frogs, the nauseating odours of skunks, the charmingly named but actually revolting repugnatorial glands of some millipedes, and the projectile vomiting and faecal egg decorating of some birds.

Why should nature have created such an impressive array of defensive tactics? One possible explanation can be summarised as the life-dinner principle, articulated by biologists Richard Dawkins and John Krebs in the late 1970s. The argument is that predator and prey often face asymmetrical selection pressures, meaning that the stakes are different for the two competitors. If a predator fails to capture its target, it loses dinner, but if the prey fails to escape, it loses its life. Because the stakes are greater for prey, we shouldn't be surprised they have developed so many impressive defences.

Understanding nature's tremendous capacity to adapt should make us be careful. Humans interact with other organisms all the time, and usually we're the predators. When we try to take action against other creatures to stop them spreading disease or eating crops, we should be mindful that evolutionary innovation can produce remarkable adaptations. For example, our widespread use of antibiotics and pesticides has spurred the evolution of organisms that are resistant to these methods.

Only by having a healthy respect for the relentless power of evolution can we hope to generate sustainable solutions to these kinds of problems. If we grow complacent and inattentive, we may some day soon find ourselves facing newly evasive diseases and pests, sputtering to breathe and dyspeptic amid all the fire and smoke in our bellies.

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Top header image: Andrew/Flickr

Luc Bussiere, Lecturer in Biological Sciences, University of Stirling

This article was originally published on The Conversation. Read the original article.

Sonora was only ten months old when she made the long trek from Chihuahua, Mexico to private ranchland in the Chiricahua region of southern Arizona. She had travelled more than 90 miles (140 km) and arrived alone and undoubtedly hungry. For several days, she was spotted by a wildlife manager from the Arizona Department of Game and Fish, as well as local ranch-hands. She had spent half of her life in captivity – born at a captive-breeding centre in Cananea, Mexico – so perhaps it's not surprising that she didn't seem too perturbed when people tried to scare her off the ranch. Only five months earlier, Mexico's Comisión Nacional De Areas Naturales Protegidas (CONAP) had released her and her family with the optimistic hope that her pack would thrive. It didn't. So Sonora wandered north though patchy habitat until she reached the US.

But failing to flee at the sight of humans in Arizona was a mistake. Particularly when ranchers reported livestock killed in the area. Wildlife officials determined that a wolf had killed at least one of those animals and Sonora was the prime suspect. So, soon after she crossed the border, she was promptly recaptured.

Social engineering

As a potentially fertile female Mexican wolf, Sonora is extremely valuable. With no other wolves at the Arizona border, she was transferred to a holding facility at the Sevilleta National Wildlife Refuge in New Mexico, where she stayed until November. Then, USFWS moved her to the Sedgwick County Zoo in Kansas, one of more than 50 captive-breeding facilities scattered throughout the US and Mexico where wolf DNA is closely examined and wolf mating carefully planned. That's because the roughly 400 Mexican wolves alive in the world today – most of them in captivity – are descended from only seven animals that survived the American slaughter of predators for centuries. If the subspecies is to stand a chance at recovery, every pairing must be carefully engineered to minimise inbreeding and maximise what little genetic diversity remains. Because Sonora is from Mexico, she brings valuable new genes into the US population. And according to USFWS biologist Maggie Dwire, she pairs well with the males at Sedgwick.

A few weeks after Sonora's transfer, I shivered in the cold dark of a December dawn at Sevilleta along with about two dozen volunteers helping USFWS biologists oversee the capture and transfer of four other captive wolves to another facility: a mated pair and their two teenage pups. In the one-acre enclosure, we humans formed a formidable walking wall of boards, nets and poles, to scare the wolves into their wooden den. The pups hid first – seeking refuge in the den together. But they were no match for the transfer team. Muzzled and hooded, they endured the blood samples, physical exam and shots administered by the team. Then they were lifted into crates on the back of a pickup truck for a three-hour ride south. The parents were harder to corner, but soon they too were on their way. Once settled in their new home, they would likely breed again, with some of their offspring "cross-fostered" with wild wolves.

Cross-fostering captive pups with wild ones helps reduce the controversy surrounding wolf reintroduction, according to Dwire. "When releasing a captive pack, you need to find an area without an existing pack. And you're introducing a naïve adult wolf with pups into the area," she notes. "But with cross-fostering, you just add two more pups from captivity to a wild wolf. This eliminates the naïve component and eliminates putting wolves where they weren't before." 

How many wolves do we need?

I was at the Sevilleta facility just one week after USFWS released its final recovery plan. More than 100,000 Americans had submitted comments on the draft plan in previous months, the vast majority supporting the reintroduction of wolves into the wild. But that part of the equation was no longer in question. USFWS has been releasing captive-bred wolves into an "experimental population area" south of Interstate Highway 40 in Arizona and adjacent New Mexico since 1998. By 2016, those wild wolves numbered 113 across both states.

But there were other urgent questions that remained. How many wolves would it take to recover the subspecies? How many populations are needed? Would they be allowed to roam north of the highway? With wolf numbers even lower in Mexico, won't populations on both sides of the border need to mix if the subspecies is to survive? And what about that border wall President Donald Trump wants to build?

In general, ranchers and hunters call for fewer wolves in a smaller area. Wolves prey on livestock and hunt wild elk as a mainstay of their diet. In contrast, conservationists want more wolves with additional populations in northern Arizona near the Grand Canyon and up into the states of Utah and Colorado – far north of the current Interstate 40 boundary. They cite a previous draft recovery plan from 2012 that called for three separate populations in the US totalling at least 750 wolves across the states of Arizona, New Mexico, Utah and Colorado to allow Mexican wolves to recover. But all four governors of those states oppose any reintroductions north of Interstate 40, maintaining that the southern region, combined with habitat in Mexico, represents the wolf's historical range. Both the Arizona and New Mexico Game and Fish Commissions, which set wildlife policies in their states, have voted in recent years to deny releases of wolves.

Conservationists and many wolf biologists, meanwhile, cite genetic analyses suggesting that the Mexican wolf's historical range spread far beyond the limited area identified by USFWS and the states. They argue that as the climate changes, Mexican wolves will need the freedom to expand into prime stomping grounds farther north. And they note that habitat in Mexico is questionable: it's largely private ranchland, not public, with scanty data on available prey and lots of illegally killed wolves.

Coexistence

People like Sisto Hernandez walk the middle ground. Hernandez is a member of the White Mountain Apache Tribe in Arizona – an official partner in the recovery effort – and is the tribe's range management specialist. Much of the tribe's economy depends on ranching. He chairs the Mexican Wolf/Livestock Coexistence Council, a public-private effort involving ranchers, conservationists, tribes and counties that helps ranchers live alongside wolves. "People don't have to love the wolf," says Hernandez. "They just have to feel they can live with it."

Members of the council have differing views on the wolf, but they've committed to work together on three goals: healthy western landscapes, self-sustaining wolf populations and viable ranching. "We do a lot better when we help each other," says Hernandez. 

With the help of federal funds, the council goes beyond traditional programmes that compensate ranchers for the loss of livestock to wolves. It pays ranchers within wolf territory even if they don't lose any animals, and it encourages management actions that reduce livestock-wolf conflict. That includes increasing human presence through their range-riders programme.

"[Range riders] isn't just cowboy work," Hernandez told me. "It's about knowing where the wolves like to be, their dens, trails, roads they are likely to use. Range riders have to know what to anticipate to help ranchers make management decisions that lessen the likelihood of conflict. It's not an easy job. It takes the right person to do it."

Each year, the council also pays ranchers in wolf territory based on how many conflict-avoidance measures a rancher enacts and – perhaps most importantly – the number of wolf pups that survive on the ranch. Although many consider the initiative a success, not everyone has bought into it. The council keeps the names of ranchers who apply for assistance anonymous in order to avoid reprisals from what Hernandez calls "extremists" on both sides. "There are people who can make things difficult and we don't want to discourage [rancher] participation because [they fear] people might cut their fences, make threatening phone calls, or do worse things to sabotage their ranch." 

That's the world Sonora wandered into last spring.

Final recovery or more controversy?

The final recovery plan released in late November scales back the recovery goals recommended in 2012. In it, USFWS maintains that only two populations of wolves would be needed to "ensure a 90 percent probability of persistence over 100 years" – rather than the three populations determined by scientists in 2012. The two populations would consist of 320 wolves in southern Arizona and New Mexico, plus a smaller population of 200 in the Sierra Madre Occidental Mountains in Mexico, managed by CONAP. The US population would be limited to southern Arizona and New Mexico, south of Interstate 40. 

Draft recovery-planning documents suggest that USFWS considers 320 animals to be what it calls the level of "social tolerance" for wolves. Conservation groups call it caving to the states. On January 30th, several groups sued the agency for, as they claim, violating the Endangered Species Act.

Moreover, under the final plan, the US and Mexican populations won't even have to be connected. The agency expects few wolves will cross the questionable habitat between the Sierra Madre Occidental Mountains in Mexico and the US border, at least not enough to ensure adequate gene flow. If that dispersal were completely stopped – such as by a border wall – the impact would be minimal, according to USFWS. To compensate, it intends to continue its intensive, hands-on breeding programme and translocations, what it calls "artificial or assisted connectivity".

Sonora seems to be an outlier – one of only a handful of natural dispersals across the border in recent years. For now, she'll remain in captivity, to breed pups that might or might not roam the wilds of the American Southwest. Meanwhile, with fresh legal challenges now facing it, the recovery plan remains in limbo. And the centuries-old feud between rancher and predator continues. But there is hope.

"Just remember," Hernandez told me as we ended our conversation, "we're not all like that."

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Top header image: USDA Forest Service

Jurassic Park may be the first thing that comes to your mind when you hear about this subject – any time an ancient DNA news story surfaces, comments sections are sure to include questions about cloning or resurrecting extinct species – but there's more to this science than dreams of de-extinction (more on that topic later!): ancient DNA opens doors to answering many of palaeontology's perplexing questions, and has dramatically changed how scientists investigate the past.

Long-held secrets

Last summer, a study triumphantly announced that ancient DNA had solved the mystery of Macrauchenia, a bizarre South American mammal whose place on the mammal family tree had been a palaeontological puzzle ever since the days of Darwin. Several months later, another group of palaeo-geneticists presented a new name for the curiously stilt-legged extinct horses of the ancient Americas: Haringtonhippus.

If you follow palaeontology news, these are familiar sorts of stories. Most of what we know about fossil animals comes from skeletons, but bones and teeth aren't always enough to answer our questions about prehistoric life. Over the years, ancient DNA has built up a bit of a reputation for revealing secrets that bones alone could not.

"Bone morphology can be influenced by environment and behaviour," explained Leigha Lynch of Oklahoma State University over the phone. This variability is great for adaptable animals, but it can also make for a confusing time trying to discern the true identities and relationships of ancient species.

In her own research, Lynch turns to DNA for assistance. She studies North American martens – small carnivores related to weasels – ranging in age from several decades to 15,000 years old. Not only does their DNA help her sort out the relationships between the animals' various ancient populations, but by constructing the extended marten genealogy, she can also identify the location and timing at which new populations arose and new traits evolved. Combining this evolutionary info with the geologic record, she can then piece together how the animals responded to environmental changes such as Ice Age glacial cycles.

Animals' bodies also change as they grow, which can be another potential source of confusion when examining fossils. "[Sometimes] we don't know if we're looking at an adult or a juvenile or a new species. So being able to get the DNA to clarify that is really helpful."

A creature's chromosomes can also reveal its sex, a boon in those cases where males and females are so physically different they might be mistaken for separate species (think elephant seals!).

Ancient DNA can even help us understand extinction. A recent study of Tasmanian tigers found unexpectedly low genetic diversity in these animals going back thousands of years – a tell-tale sign of a long-term population decline that may have set the species up for its eventual human-induced disappearance.

(Fun fact: we can even get DNA from fossilised poop! One group of scientists, for example, was able to determine the diet of giant flightless moas from New Zealand in part by testing the DNA of the plants in their droppings!)

Faded genes

"Ancient DNA gets degraded over time," explained Viviane Slon of the Max Planck Institute for Evolutionary Anthropology in a phone call, "so not every fossil will yield DNA, and not every fossil will yield enough DNA to reconstruct a full genome." (A genome is the complete set of genes of an organism.)

A dead cell is a hostile environment for DNA, full of enzymes whose very job is to break down genetic material. In a still-living organism, this is important for DNA replication, repair and recycling, but once the whole organism dies, it means that DNA begins to deteriorate very quickly. The best environments for preserving DNA tend to be cold, dry and stable over long time periods, including permafrost, some caves, and – for more recent specimens – environmentally controlled museum collections.

The oldest DNA sequence ever recovered comes from a 700,000-year-old horse from the frozen soil of northern Canada, and this might be about as old as we can hope for. Research indicates that DNA degrades to a non-usable point after one or two million years, even under perfect conditions (which are rare or non-existent in nature).

One-million-year-old DNA is extremely impressive ... although it leaves out the vast majority of the 3,500-million-year history of life on Earth.

So, no Jurassic Park. The last of the non-bird dinosaurs went extinct 66 million years ago. And yes, even the scientists are disappointed.

"I love the idea – in theory, I could have a little Triceratops hanging out in my backyard," Lynch said. "[But] I find it very hard to picture any scenario in which DNA was preserved in something that old."

Even in relatively young fossils, DNA can disappear very quickly in an unfriendly environment. The cold, dry Arctic is great for its preservation, but the warm, wet tropics are just the opposite, typically preserving very little genetic material. So the fossil record of ancient DNA is much more likely to give us information about, say, woolly mammoths than about island tortoises.

But when conditions are right, DNA can preserve spectacularly well. In fact, one of the biggest challenges facing researchers is that there's often too much of it: a fossil horse bone might retain some original horse genes, but it's likely to also have DNA from the bacteria and insects that have gotten into the bones, or the plants and fungi that grew around it (and it will pretty much always end up with DNA from the humans who excavated it). That means researchers have to pick through a lot of "noise" to get out the specific DNA they want.

For Slon, this is especially tricky: she studies ancient humans (and our relatives like Neanderthals), so her fossils include both ancient and recent human DNA. "You're always going to get contaminant. The trick is to be able to tell them apart," she explained. "And you're going to do that by taking advantage of a particular type of chemical damage [called deamination] that accumulates over time in DNA." Knowing how to identify this damage helps scientists separate the old DNA from the new.

Slon and her colleagues have also found a way to take advantage of DNA's tendency to contaminate its surroundings. She recently led a study that discovered ancient human DNA in cave sediment. Studies like this are very encouraging for palaeontologists because they suggest that we can explore the DNA of ancient organisms without even needing their fossils!

The take-home point here is this: ancient DNA has limits. It comes with a host of challenges, it only lasts so long, and only in certain environments. But when researchers do find it, modern techniques allow them to piece together an astonishingly complete picture. "In a fossil that is well-preserved," Slon said, "we can get a genome that is equal in quality to genomes that we get today, if you put enough sequencing effort into it."

Is extinction truly forever?

In 1990, Michael Crichton published the novel Jurassic Park, but he was not the first to explore the idea of bringing ancient species back from the dead using DNA. In fact, the idea has been bouncing around for a long time, and there are some scientists today who are working on doing something very much like that.

In Jurassic Park, the dinosaurs were essentially cloned from ancient DNA, but real-life cloning – such as in the case of Dolly the sheep or the recent monkey twins – only works with viable cells, which the fossil record doesn't preserve. (Famously, preserved cells of the recently extinct bucardo, a wild goat native to the Pyrenees, were used to create a short-lived revenant in 2003.)

"The technology that lets us preserve viable cells in a freezer is only about 50 years old," said Ben Novak, lead researcher at Revive & Restore, over the phone. "Anything that goes extinct prior to that, we have nothing viable from."

Revive & Restore is an organisation that aims to use genetic technology to aid struggling species and ecosystems, from collapsing coral reefs to unhealthy black-footed ferrets. Among their most ambitious missions is the de-extinction of the passenger pigeon.

Before their extinction due to human activity in the early 1900s, passenger pigeons soared over eastern North America in flocks billions strong. Research has shown that these birds were major environmental influencers; a visiting flock of pigeons would cause a huge disturbance in a forest, creating a similar rejuvenating effect to that of a forest fire. Their disappearance left the forest ecosystems far less able to maintain healthy and stable conditions.

Novak and his colleagues want to bring those populations back with some help from the passenger pigeon's closest living relative: the band-tailed pigeon.

"Ninety-seven percent of the passenger pigeon's genome is still alive in the band-tailed pigeon, because that's how identical they are," Novak explained. The plan is to peruse the passenger pigeon genome for the features that made the species unique – those traits that allowed them to maintain huge flocks across North America – and edit them into the band-tailed pigeon, ultimately engineering a population of birds that can serve the same role as their extinct predecessors. 

This is de-extinction, but it's not exactly bringing a species back from the dead. "If we're going to get really technical, it [would be] a bird that is the genetic offspring of band-tailed pigeons and passenger pigeons," Novak said. "If that had been produced through natural breeding, we would call it a hybrid."

The goal here isn't to resurrect exactly what existed before, but to restore ecosystems to a healthy state by replacing a lost keystone species. Novak likens it to the reintroduction of wolves to Yellowstone: the predators had disappeared from this area, and a new wolf population was introduced to fill in that missing piece of local ecology. The passenger pigeon project simply takes more genetic innovation.

There are other species on the de-extinction radar, including the heath hen, which went extinct in the northeastern United States in 1932, and more famously the woolly mammoth, which has been extinct for thousands of years. These projects are in the exciting early stages, and may eventually play major roles in environmental conservation, but researchers are keen to remind us that we can never fully recreate the past.

"There's inevitably always something lost in extinction," Novak said, "things we don't know; things we can never know."

Our own past and future

"I think for me," said Slon, "the most amazing discovery of the last few years was the Denisovans."

In 2010, researchers sequenced the DNA of a very human-like finger bone in Denisova Cave in Siberia. The results were a surprise. It wasn't Homo sapiens and it wasn't Neanderthal; it was a closely related group that no one had ever seen. To this day, the only fossil remains known from this population – known as the Denisovans – are three teeth and one finger bone, and without ancient DNA we never would have realised they came from a totally separate lineage of ancient people.

From those bones, Slon and her colleagues have learned an immense amount of information about the Denisovans and their relationships. We know now, for example, that modern humans carry traces of not only Neanderthal DNA, but also that of the Denisovans.

"We know that Denisovans and Neanderthals must have mixed," Slon said, "and also Denisovans and modern humans mixed." More than perhaps any other species on Earth, the science of ancient DNA has taught us about ourselves.

Ancient DNA is an amazing resource for scientists aiming to learn about – and learn from – the past, and researchers are looking forward to a future filled with untold possibilities. Right now there are labs all over the world working at refining, improving and advancing the science of pulling DNA out of the past.

That's how diver Ben Laboy describes his recent encounter with an inquisitive gray whale in California's Monterey Bay. The animal surprised Laboy when it materialised behind his dive partner, but he managed to bottle up his excitement until the behemoth faded from view, as swiftly as it appeared. (It's hard to believe this was Laboy's first time diving with a GoPro!)

"I will never forget looking into the eye of this majestic animal," Laboy wrote on Facebook, noting the whale came within feet of him and his dive buddy, Nicole Guido-Estrada.

Despite being just an arm's length away, neither diver attempted to make contact with the passing giant. (It was the right move: intentionally touching – or even approaching – whales can be dangerous, and it's also illegal in US waters). 

A few high fives and underwater squeals later, the pair returned to the surface and excitedly shared their footage with staff at the Monterey Bay Aquarium (MBA). The team estimated the whale in Laboy's video was well over nine metres long (30ft) long. Adult gray whales can reach 15 metres (50ft), so despite its impressive bulk, this individual was still a young gun by those standards. Adults reach sexual maturity at only eight years, and live to be around 40.

"This took place a stone's throw from the Aquarium's back deck," Aquarium staff wrote in a Facebook post accompanying the clip. "It's perfectly poetic that Ben and Nicole came across this wandering whale off of McAbee Beach, once home to a whaling station and now host to impromptu underwater whale-watching."

Like so many of their close kin, gray whales were hunted almost to extinction between the seventeenth and twentieth centuries, but decades of conservation work have seen this species stabilise, with around 20,000 individuals now in existence. Many of those whales are currently en route south along North America's Pacific coast, towards breeding lagoons in Baja California, Mexico. That lengthy migration begins in the Bering Sea, so the animal in Laboy's clip had likely travelled over 3,000 miles to arrive in Monterey Bay

"Not so long ago, this proud parade of gray whales was nearly lost to history," the MBA team said. "Today, spotting them on their migration is commonplace up and down the coast. You're bound to see a few spouts as signals to this conservation success story."

With any luck, Laboy's curious visitor will reach Baja in the coming weeks, where it will join in on the "fun" in the region's warm shallows.

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Top header image: Joe McKenna/Flickr