Humans have a complicated relationship with our non-human cousins. Some animals we invite into our homes, and treat as members of our families. Indeed, in November of this year singer Fiona Apple made headlines when she announced that she would cancel the South American segment of her tour to be with her dying dog. Some animals we brine, barbecue, bake, roast, fry, or saute. Strong opinions were expressed on all sides of the issue when a law passed by the California state legislature went into effect on July 1, banning the sale of foie gras. Still other animals we’d prefer to avoid entirely even while remaining endlessly fascinated by them. When Hurricane Sandy poured down upon New York City, one question on everyone’s mind was what would become of the subterranean rat populations, living deep underneath the city streets?

Whatever anyone’s personal thoughts about animals place within human society, stories about animals have a unique ability to captivate us. To celebrate our relationship with the rest of animalkind, we’ve compiled a list of what we consider to be the best animal stories of 2012. Some are scientifically important. Some provide commentary on the human-animal connection. Some are funny, quirky, or surprising. Some just made us smile. Here are our picks for the best animal stories of 2012.

Best tool-using species
As each year passes, more and more species are inducted into the club of the tool-wielding, making the group less and less exclusive. This year, a male Goffin’s cockatoo ( Cacatua goffiniana) named Figaro from the Department of Cognitive Biology at the University of Vienna paved the way for the inclusion of his species among the tool users of the world. Parrots such as cockatoos have long been known for their linguistic abilities. Now that there’s evidence for the possibility of tool use, researchers can begin to probe the relationship between language and tool use. Clever captive cockatoo creates tool, a first for his species by Jason; The Innovative Cockatoo by Virginia Morell.

Best Piece of Jargon We Learned this Year
Since the 1930s, we’ve been calling the chemical cocktail released by anxious fish – which they use to warn others of danger – schreckstoff, an excellent term that means “scary stuff” in German. All that time, we didn’t know what it was made of, though. This year, writes Ferris Jabr at Scientific American, researchers from Singapore and Switzerland, think they’ve isolated schreckstoff‘s key ingredient, “a sugarlike molecule named glycosaminoglycan (GAG) chondroitin.”

Best new species that was hiding in plain sight
Last summer, in a piece at the New York Times, Carl Zimmer reported that some scientists estimate that there are some 8.7 million species populating our planet (give or take 1.3 million; some scientists think the number is actually far higher). Many of the still undescribed species are microbes and fungi, others are found only in tiny corners of the world, and hundreds if not thousands are certainly gathering dust in museum basements. More surprising, however, is that a monkey species new to science might be found in the backyard of a local school director in the Democratic Republic of the Congo, a pet tethered to a post. The new species, called the Lesula monkey or Cercopithecus lomamiensis, is only the second new monkey species discovered in Africa in 28 years, after the Highland mangabey (Lophocepus kipunji) of Tanzania. Lesula: New species of African monkey discovered by Becky Crew.

A Reminder of What Sea Level Rise Can Do
The Caribbean is home to more than a few bat species today, but fossil evidence says that there was a lot more of them 25,000 years and many of them lived on parts of the islands that are now under water. What happened to them? One major driver of extinction, Annalee Newitz explains at io9, was sea level rise. As glaciers melted, the water came in and the edges of the island disappeared, causing a loss of habitat that the bats couldn’t bear.

Gorillas outsmart humans
Animal cognition researchers get excited whenever they see stunning examples of animal cooperation. They also get excited whenever they see younger animals learning from the older, more experienced members of their social groups. When both of those things occur simultaneously, as juvenile gorillas disable poachers’ snares, the story becomes not only impressive, but also heartwarming. Snares, while illegal, are quite common in Rwanda and are especially dangerous for the mountain gorillas who live in the area. Especially vulnerable are the youngest gorillas, who may not have the experience yet to identify and avoid them. Imagine the awe that John Ndayambaje, a field data coordinator for the Dian Fossey Gorilla Fund, must have felt when a silverback shouted a warning call to prevent him – a human! – from approaching the snare, only to then watch two juveniles and an adult work together to disable the snare, as well as a second snare that he hadn’t even noticed. Unpacking just how sophisticated the cognitive mechanisms are that can lead to such swift, coordinated behavior is a daunting task, but on its surface, it seems as if the gorillas were acting with intention in a highly efficient, practiced manner. Exploring the Mind of the Mountain Gorilla by Kimberly Gerson.

Rest in Peace, Lonesome George
Lonesome George, the last Pinta Island tortoise (Chelonoidis nigra abingdoni), died this June. He was more than 100 years old. In his death, the world lost an individual animal, a subspecies of tortoise and as the International Union for Conservation of Nature called him, a “symbol of our global never-ending struggle to preserve the richness and diversity and beauty of the planet we inherited.” Many great stories focused on one of those three aspects, and considered what George’s loss means in the larger picture. Alejandra Martins talked to Fausto Llerena, George’s keeper and best friend, on mongabay.com. Virginia Hughes looked at the sex life, or lack thereof, of this “most awkward of virgins” at The Last Word on Nothing. Matt Bardo asked just how much the loss of a subspecies means, genetically speaking, at BBC Nature. Ira Flatow talked to Linda Cayot, scientific advisor to the Galapagos Conservancy, about what George meant to biodiversity in the Galapagos on NPR. Kim Tingley asks if an “an individual ‘face’” for extinction, like George, “actually prevents us from asking the kinds of uncomfortable questions that might significantly improve our larger conservation efforts” at OnEarth.

Primates are not pets
Monkeys typically do not wear double-breasted shearling coats, they don’t usually wear diapers, and they never shop at Ikea. Earlier this month, however, a five-month-old Japanese macaque was discovered wearing the coat and diaper running around an Ikea parking lot in Toronto, Canada. While the monkey – named Darwin – will now be socialized with other monkeys and cared for properly at the Story Book Farm Primate Sanctuary in Canada, the story serves as an important reminder for why wild animals are not suitable pets. When monkeys who have been raised as humans transition into adulthood, with the strength, aggressiveness, and muscle power (and teeth!) that accompany their maturation, the story always ends the same: the animal winds up dead or abandoned. In the best cases, the animal might wind up in a zoo where even the best of care can’t entirely undo the years of being socialized with the wrong species. The best thing for Darwin was always being a monkey. Since he’s still relatively young, I suspect his chances for full monkey recovery at the primate sanctuary are good. Does Darwin the IKEA monkey need a human mother? by Andrew Westoll.

Best Use of Recycling by a Non-Human
Tobacco plants use nicotine to defend themselves against hungry bugs. Birds, it turns out, use the the chemical for the same purpose, but get it from a strange source. By lining their nests with discarded cigarette butts, birds protect their kids from parasites. Hannah Waters at Culturing Science calls the study a “wonderful example of wildlife adaptation to urbanization–or at least that birds are resourceful and can still follow their noses in urban environments.”

Best animal story that should not have been news
Grandpa is the name of a forty year old black handed spider monkey that lives at the Staten Island Zoo. He’s something of a local celebrity, having successfully “predicted” not only the winners of this year’s Super Bowl and six out of nine U.S. Open winners. Given a choice between six bananas labeled with the names of those in the Republican primary race, he picked the one assigned to Newt Gingrich. Maybe Grandpa should stick to sports, or perhaps the idea of animal psychics is even more ridiculous than the notion that humans can foretell the future. In order, he ate Newt’s banana, followed by Rick Santorum’s, then Rick Perry’s, and finally Jon Huntsman’s banana. The Romney banana, along with Ron Paul’s, became a snack for a nearby female spider monkey. Grandpa the spider monkey picks Gingrich to win N.H. primary, via NY Daily News.

Best Rhetorical Lede
“If a penguin falls in the forest and no one is there to hear it, I don’t know what kind of forest that is…” muses Elizabeth Preston on Inkfish. What’s clearer is that, in the Antarctic, there are plenty of people around to hear and see everything Antarctic penguins do, and they’re changing the nature of the birds. Ecologists found that the familiarity that comes with regular interaction with humans makes the birds more tolerant to stress, maybe because they’d gotten used to being harassed by humans, or maybe because the most stress-sensitive penguins had already fled human-heavy territory. Either way, people are inadvertently practicing a kind of artificial selection on penguins by getting too cozy with them.

Best blog fodder
Ah, springtime. The snow is thawing, flowers are blooming, many species are giving birth. Humans mark the season in their own ways as well – Christians give up eating meat for Lent while Jewish people turn to matzah instead of bread for Passover. In Ethiopia, even the spotted hyenas get spring fever. They replace their typical meals with donkeys, thanks to the Ethiopian holiday Abye Tsome. If you’re a regular reader of animal blogs, you know the rest of this story. Hyenas are treated in the big cities of Ethiopia as “municipal workers” – they scavenge the leftovers of meat left out by humans. In other words, they eat garbage. But when humans give up eating meat for the holiday, the hyenas’ supply of table scraps dwindles, so they predate instead on livestock. This causes problems for the human farmers, which, as you might expect, causes further problems for the hyenas. It’s an important story about how humans and non-human animals interact within a larger ecosystem, but it’s included in our year-end compilation for a different reason. The story, which served as obvious blog-ready material for many of us, shows how different writers can approach the same story in different yet equally engaging ways. Hyenas Give Up Eating Garbage for Lent, Hunt Donkeys Instead by Jason; Giving up trash for Lent: How a human custom forces hyenas to hunt by Matt; Hyenas Fast During Lent Too by Liz Preston; In run-up to Easter, fasting Ethiopians force hyenas to kill donkeys by Ed Yong.

The Best “Best Laid Plans of Mice and Men” Story
Rabies in Latin America usually comes from vampire bats, and governments usually respond by culling them. Yet the disease is on the rise, and scientists reported this summer that every colony they examined showed signs of infections. Those colonies that were periodically culled, Erik Stokstad reports for ScienceNOW, had higher rates of exposure. It seems that the cull method kills adults, which are more likely to have acquired resistance to the rabies virus and not spread it, and spares more juvenile bats that are susceptible to developing rabies. The standard solution, it appears, has backfired, and reminds us that “host-pathogen systems are complex and can respond to management in unexpected ways.”

Most heartwarming animals that pretend to be people
Can animals learn to communicate with humans? Well, that depends what you mean by “communicate.” All the training in the world can’t teach language to an animal. But that doesn’t mean that some animals can’t fool us. This year, two stories appeared within weeks of each other about animals that learned to mimic human speech. NOC is the name of a beluga whale who was the guest of the National Marine Mammal Foundation in San Diego who produced sounds that, as Ed Yong put it, sounded like “a drunkard playing a kazoo.” Two weeks later, Koshik, a twenty year old Asian elephant at a Korean zoo made headlines for his ability to mimic at least seven Korean words. Writing at Double X Science, Emily Willingham pointed out that “when Korean speakers came in as stenographers for his communication, they could clearly distinguish his words.” The beluga and elephant aren’t speaking English or Korean any more than than the lyrebird speaks chainsaw. But as vocal learners, they could provide researchers with insight into how speech is acquired.

Best Feel-Good Invertebrate Story of the Year
The United States Army, in addition to protecting the country’s citizens, is obligated to protect threatened and endangered non-humans on its installations. In Hawaii, that means protecting kahuli tree snails from cannibalistic Rosy wolfsnails, chameleons and rodents. To give give the snails a safe haven, writes John R. Platt at Extinction Countdown, the army constructed a predator-proof enclosure about the size of a basketball court to house three hundred snails.

Image: ”Allen’s Swamp Monkeys at the San Diego Zoo” copyright Jason G. Goldman.

One May morning in 2009, a group of white-faced capuchins were foraging on a hillside on Barro Colorado Island, Panama. Two researchers from the Smithsonian Tropical Research Institute, Anyuri González and Lucia Tórrez, were watching the group from nearby, but when one of the monkeys started shrieking, they realized they weren’t the only voyeurs.

The screams were an alarm call indicating a predator on the ground. The group’s alpha male took off in the direction of the noise and was joined several other adult members of the group, and they all began making facial and vocal threats and shaking and throwing branches toward a dense tangle of liana vines.

There was something in there, and the monkeys didn’t like it.

Mob Rules

While many animals go to great lengths to hide or flee from predators, some animals take the opposite tack and confront their attackers. Some species of primates, birds, fish and squirrels will harass and assault potential predators with mobbing behavior that involves loud vocalizations and physical attacks at close range.

The mobbing of a predator by capuchins is a real sight. Led by adult and subadult males, the monkeys will make loud threat and alarm calls while breaking large branches from trees and dropping them on the predator like bombs.

Researchers have been mistaken as predators themselves and received blows – at least one admitted to being knocked unconscious – from branches broken and dropped over their heads. Scientists working in capuchin territory quickly learn to to stop taking data and get out of the way when they see a monkey scanning the canopy directly above them, a sign that its looking for a branch that it will be able to break.

Some monkeys will get closer to predators if the aerial assault doesn’t work. In 1988, biological anthropologist Susan Boinski watched as a group of capuchins in Costa Rica killed a terciopelo, or fer-de-lance, after pinning it to the ground with a heavy branch and then approaching on the ground to beat it with sticks. One monkey rained down a flurry of 55 strikes to the snake’s body and head with a stick that it clumsily wielded like a club. Boinsky later approached the snake and found a mangled mess of bleeding wounds, exposed tissue and broken bones.

A Death in the Family

As González and Tórrez watched, a sense of alarm spread through the capuchin group. Juvenile monkeys and an adult female with a clinging infant gathered some distance away from the liana tangle, while the rest of the adults joined the alpha male on the frontline.

The capuchins’ alarm calls intensified and González, who was downwind from the liana tangle, noticed a distinct smell. A cat. She could see the right side of whatever was in the liana, and based on its size and fur color and patterns, decided it was not one the ocelots normally seen on the island, but a jaguar visiting from the mainland.

The cat growled loudly, making the capuchins visibly nervous. They glanced repeatedly at one another and one of the adult females retreated to where the juveniles were waiting. Together, they moved further away from the liana. The jaguar growled again and moved around in its hiding spot, and most of the remaining capuchins also retreated.

As far as González and Tórrez could see, only six adult and subadult males remained near the liana tangle, and their vocalizations had decreased in both frequency and intensity. They looked back and forth at one another and then moved silently away from the jaguar, following their groupmates.

Only one monkey stayed behind, and continued to make alarm calls. González and Tórrez weren’t able to see the monkey, and as they attempted to get close enough to verify which one it was, the cat made a very loud, very aggressive growl, and the researchers decided to retreat a little themselves.

From a safer distance, they could still hear the lone capuchin making alarm calls. Then, there was the sound of sudden movement and the rustling of branches. The alarm calls stopped and they heard two weak moans.

After that, there was only silence.

González and Tórrez encountered the capuchin group later that morning. The group was quiet, and had returned to foraging for insects. They took a headcount and found that one of the subadult males, named LK, was missing. Every other group member was accounted for but LK was not seen again over the course of their study.

At What Cost?

Approaching and mobbing predators appears to invite some obvious risks, as LK’s death shows. The true costs of mobbing are hard to suss out, though, because reports of primates being injured or killed while mobbing are very rare. The LK incident is, as far as González, Tórrez and their colleagues know, the first documented fatality arising from a mobbing event.

With limited observations, researchers have hypothesized several risks. The risk of injury and/or death seems to depend somewhat on the predator. Many snakes are cryptic hunters, and, once discovered, will freeze and can be mobbed with relatively little risk. Other predators, like large cats, continue to pose a significant threat to monkeys even after they’ve been discovered, and some will even chase their prey into the trees, giving them no quarter.

There are also other less grisly losses to consider, like the effort that goes into fighting back and opportunity costs of taking time from other activities. Some monkeys have been known to remain at the site of a spotted, attacked or even injured or dead predator for up to two hours after mobbing. That’s time and energy that could be spent foraging or mating sacrificed to a risky behavior, and even a “win” for mobbers might compromise the animals’ health and reproductive success, making it a Pyrrhic victory.

Figuring out the costs of mobbing, in turn, would help explain its benefits. If the price that primates are willing to pay to harass their predators are as large and varied as they seem, the rewards should be enough to make the risk worthwhile.

The obvious benefit of mobbing for social primates is that chasing off or killing predators helps protect their social group, relatives, mates and offspring. It’s also possible that mobbing events act as a learning opportunity for younger monkeys. Juveniles are able to study the animals that provoke alarm calls and defensive behavior and compare them to animals that don’t, and learn to know danger when they see it.

Another benefit to mobbing may be that, because it is so costly, it acts as an honest signal of an individual monkey’s quality as a mate. Attacking a predator gives a monkey the opportunity to display their physical condition, agility, and speed. Mobbing might be a way for females to evaluate the ability and willingness of males to protect them and their future offspring against threats.

Unfortunately, with so little data from the field or the lab, we don’t know how often mobbing ends lethally, or the likeliness of a fatal attack when a primate does vs. doesn’t mob, so it’s hard to weigh the costs and benefits that play on a monkey’s decision to stand its ground or retreat, maybe to fight another day.

References:
S. Boinski (1988). Use of a Club by a Wild White-Faced Capuchin (Cebus capucinus) To Attack a Venomous Snake (Bothrops asper) American Journal of Primatology, 14 (2), 177-179 DOI: 10.1002/ajp.1350140208

Tórrez, L., Robles, N., González, A., & Crofoot, M. (2012). Risky Business? Lethal Attack by a Jaguar Sheds Light on the Costs of Predator Mobbing for Capuchins (Cebus capucinus) International Journal of Primatology, 33 (2), 440-446 DOI: 10.1007/s10764-012-9588-1

Dugatkin, L., & Godin, J. (1992). Prey approaching predators: a cost-benefit perspective. Ann. Zool. Fennici, 29, 233-252

Lloyd, E., Kreetiyutanont, K., Prabnasuk, J., Grassman, L., & Borries, C. (2006). Observation of Phayre’s leaf monkeys mobbing a clouded leopard at Phu Khieo Wildlife Sanctuary (Thailand) Mammalia, 70 (1/2), 158-159 DOI: 10.1515/MAMM.2006.028

Caro, T. Antipredator Defenses in Birds and Mammals. University of Chicago Press. 2005.

Fragaszy, D., Visalberghi, E., Fedigan, L. The Complete Capuchin. Cambridge University Press. 2004.

Images: “Deux capucins moines Cebus capucinus” by Jean-Baptiste LECA & Noëlle Gunst. Public Domain. “Jaguar at the Belieze Zoo” by Bjørn Christian Tørrissen, used under a Creative Commons License.

Where there’s cows, there’s manure. Where there’s manure, there’s flies. On many farms in Germany, there’s also Natterer’s bats (Myotis nattereri), which flock to cow sheds for the convenient feast. Scientists couldn’t figure out how the bats got their meal, though. Bats usually hunt by echolocation, sending out a series of high frequency calls and finding prey based on the echoes that bounce back. It’s great for finding bugs in mid-flight, but less so when they’re sitting still or just walking around. It’s especially hindered in the cow sheds, where the roughly textured wall and ceiling surfaces almost completely mask the flies’ weak echoes. Over four years, a team of researchers led by Björn M. Siemers from the Max Planck Institute for Ornithology filmed thousands of flies in a shed in Weitershausen, Germany. The flies wisely refrained from flying at night, and when they walked over the walls and ceiling, not a single one of them was ever hunted by the 45 bats that lived there.

As soon as the flies started having sex, though, the bats embraced their inner Michael Myers and attacked the love-making couples. The researchers found that a quarter of mating flies were preyed on and over half of those attacks were successful, with the bat devouring both partners in all but two instances.

What is it about sex that got the bats’ attention? When the researchers stuck dead flies together in a morbid post-mortem sex simulation, they were ignored, so it isn’t the more conspicuous echo that a mating pair creates. Instead, the researchers suggest that its the sweet sounds of fly love that dooms them.

During sex, the female fly spreads her wings while the male flutters on top of her. This creates a series of clicks between 9 kHz and 154 kHz. We hear the lower end of that as a buzzing sound, but the higher pitches are loud and clear to the bats. When the researchers played a recording of the sexy soundtrack, the bats attacked the speakers, but not when they played other noises at the same frequency band and amplitude, suggesting that those specific sex sounds are important prey cues that ring like a dinner bell for the bats.

If all that noise means a fly winds up in a bat’s stomach post-coitus, one would like to think that there would be strong natural selection against it. The researchers say that the fact that it continues despite predation pressure suggests that might be a courtship element and a signal of the males’ quality as mates and fathers. The noise is perhaps an integral step to getting it on, important enough to run the risk of being noticed by a killer lurking in the shadows.

Reference: Björn M. Siemers, Eva Kriner, Ingrid Kaipf, Matthias Simon and Stefan Greif (2012). Bats eavesdrop on the sound of copulating flies. Current Biology, 22 (14), 563-564 DOI: 10.1016/j.cub.2012.06.030

Image: “Myotis nattereri“ by Guido Gerding. Used under a Creative Commons License.

When the sun goes down in the subtropical forests of Puerto Rico, hundreds of thousands of bats emerge from the caves that stud the island’s northern end. After a day of sleeping, the animals are ready for a hard day’s night of hunting insects. For some of them, though, there will be no feast of beetles and mosquitos, and they’ll instead wind up a meal themselves for the snakes that have set up an ambush at the cave’s entrance.

After providing a warm, safe place to sleep all day, the caves become death traps once darkness falls. Puerto Rican boas slither in from all over the forest to turn the bats’ exodus into their own hunting ground. At the mouth of the caves, they lay on the ground, cling to roots and vines on the walls or hang down from the ceiling, their tails finding footing in the tiniest cracks and crevices. As the bats flit past them on all sides, the snakes wait, swinging like clock pendulums. When a bat brushes by or collides with a snake’s head, the snake grab it in its jaws, squeeze it in its coils and eats it whole.

The nightly ritual is played out on its largest scale at La Cueva de Los Culebrones, or the Cave of the Long Snakes. The cave’s estimated 300,000 bats can empty out in as little as three hours, providing the boas with an all-you-can-eat bat buffet. Biologists observers have seen as many as 20 boas hanging around the cave entrance, grabbing all the bats as they care to and chowing down.

Even with the steady stream of food flying right into their mouths, the snakes can be picky, and competitive. Several species of bats can inhabit the same cave, and the smaller ones tend to exit first. Although the snakes are in position and waiting as soon as the first bats, they often wait half an hour to an hour to start hunting, when the larger bat species take flight. This might be a strategic choice to save their energy for prey that gives them more calories in reward for their effort.

Sometimes, a snake that’s not having any luck with its own hunting will attempt to steal a bat from another snake. On one occasion, a biologist watched three snakes fight over a large bat carcass for over an hour and a half. By the end of it, the snakes were exhausted and the bat went uneaten.

Last summer, Neil Losin and Nate Dappen, a pair of biologists and filmmakers who run Day’s Edge Productions, were in Puerto Rico and heard stories about the snakes, and had to see and film it for themselves. The resulting video, Snakes in a Cave, is awesome, and captures some closeup, slow motion bat snatching action.

Snakes in a Cave from Day's Edge Productions on Vimeo.

Reference: Rodriguez-Duran, A. (1996). Foraging Ecology of the Puerto Rican Boa (Epicrates inornatus): Bat Predation, Carrion Feeding, and Piracy Journal of Herpetology, 30 (4) DOI: 10.2307/1565698

All over the world, the expansion of urban areas and other human activities has pulled the natural prey base out from under many ecosystems and brought large predators in close contact with people and the resources they can provide – livestock, garbage, unattended pets, etc.. Many predators will take advantage of these food sources, often leading to human-animal conflicts (see wolves in the western U.S., lions in Africa and a range of others). Sometimes, though, humans and wild carnivores will become fairly friendly neighbors.

On the Horn of Africa, spotted hyenas (Crocuta crocuta) have adapted well to dense human populations, and the two species have a unique relationship that benefits both of them. The hyenas almost never attack people and mostly leave their livestock alone, preferring to scavenge on waste and refuse from homes and businesses. The hyena’s iron stomach helps them fit in well here, and they can choke down almost any organic matter they find at the dump – from leftover porridge, to feces, to putrid, anthrax-infected carcasses. The people aren’t exactly thrilled with the hyena presence, but many villages and towns tolerate them as walking garbage disposals. The locals call them “municipal workers,” and refrain from harassing or killing them.

Every year in the spring, this arrangement collapses when members of the Ethiopian Orthodox Tewahedo Church celebrate the fasting period of Lent. For 55 days leading up to Easter, Ethiopian Christians abstain from meat and other animal products, which causes a slow couple of months for the local butchers, and a dearth of carcasses at the dumps.

Without the fat of the land to live off of, what’s a non-Christian hyena to do? Gidey Yirga from Ethiopia’s Mekelle University and colleagues from Africa and Europe observed the animals during last year’s Lent and found that thy turn to hunting instead. Despite their reputation as strict scavegners and opportunists, hyenas are formidable, efficient hunters. Stalking alone or in packs, they favor large prey (150-400 pounds) and a lone adult hyena can take down an animal four times its own size. In East African ecosystems where scavenging opportunities are rare, they hunt and kill 60–95% of their food.

Last spring, Yirga and his team went to three different sites around the city of Mek’ele and collected all the hyena droppings they found on the first day of Lent, the last day of Lent and 55 days after that. Several months worth of dropping gave them a glimpse of what the hyenas were eating before, during and after the fasting period. There isn’t much to be found in a hyena turd, since they can digest pretty much all parts of their prey except hair, hooves and a few inorganic components found in bones. It was enough for the researchers to go on, though, and they compared the hair from the 553 droppings they found to hairs from a reference collection to ID the animals the hyenas had been eating.

The scat studying revealed that before and/or after Lent, most of the hyenas’ diet is made up of goat, sheep, horse and cow – usually scavenged waste parts. While humans are fasting, though, the hyenas scavenge less (while the butchers’ supply dried up, the local veterinary school still provided some carcasses) and fill the gaps in their menu by actively hunting donkeys. The donkey is a natural choice of prey if an urban hyena has to go after a live animal. They’re the right size and, unlike the other local livestock, they’re not kept penned in in compounds. They’re easy pickings, and during Lent, the hyena’s donkey consumption can double from surrounding weeks.

Faced with a carnivore’s dilemma, the hyenas showed how adaptive they can be to the sometimes strange behaviors of their human neighbors. Yirga’s study is not only evidence of the hyena’s versatility, but also highlights trash as a delicate factor in urban carnivore management. If you give predators an inch, they’ll take a mile, or a donkey, and better waste management would create a less inviting environment for them. In areas where wild carnivores have grown dependent on livestock and garbage for lack of other prey, though, a too-tight lid on the garbage can could thin their numbers and have an ecological ripple effect.

Hat tip to Barbara J King for bringing the study to my attention. 

Reference: Yirga, G., De Iongh, H., Leirs, H., Gebrihiwot, K., Deckers, J., & Bauer, H. (2012). Adaptability of large carnivores to changing anthropogenic food sources: diet change of spotted hyena (Crocuta crocuta) during Christian fasting period in northern Ethiopia Journal of Animal Ecology DOI: 10.1111/j.1365-2656.2012.01977.x

Images: “Portrait of a Spotted Hyena” by Marieke Kuijpers. “Spotted Hyenas, Crocuta crocuta, at carcass of an Impala” by Jerry Friedman. Both used under a Creative Commons License

With their long, serrated snouts, the sawfish might strike you as a little like aquatic versions of Leatherface. Scientists used to think the two were behaviorally comparable: sluggish and maybe a little dimwitted, just waving their saw around blindly and waiting for something to run into it. New research by Barbara Wueringer and colleagues from Australia and the US, though, shows that the fish actually wield their saws with considerable skill. They’ve also learned that the sawfish’s nose knows, too, and is a complex sensor as well as a weapon.

The sawfish family has not been heavily studied (a shame considering that all seven species are endangered), and with only a few firsthand accounts of how the fish hunt, researchers could only speculate on how the saws were used. One of the more common suggestions was that they were bottom feeders and raked their snout through the sand to snag buried prey on the saw’s teeth. Other ideas were that the fish cut into the sides of whales or slashed their way through schools of fish.

To figure out what was really going on, Wueringer and her team captured young freshwater sawfish in northern Australia and watched them feed on mullet and pieces of tuna. The fish went after the food in two different ways, depending on whether it was floating in the water or lying at the bottom of the tank. In the water, they quickly slashed at the prey to impale it on their saws’ teeth or knock it to the bottom or into position to eat. Some of these strikes were strong enough to cleave the fish in half. At the bottom of the tank, the sawfish used the underside of their saws to pin prey down and then move them into position to ingest, and usually preferred to eat the mullet headfirst. This video shows all of these maneuvers.

The sawfish weren’t just spearing wildly, either, and the study found that their snouts are part lance and part smart missile, with buit-in tracking systems. Sawfish are closely related to rays, skates and sharks, and share their sensitivity to electrical fields and their ability to use them to navigate and detect other animals.  Wueringer discovered a few years ago that sawfishes’ saws are covered in electroreceptors, and when she presented the sawfish in this new study with electrodes that mimicked the electric signals prey would give off, the fish reacted the same way they did to the food.

The sawfish’s saw has turned out to be more impressive than anyone thought, but cause the fish a lot of trouble, too. Every sawfish species is listed as Critically Endangered by the IUCN Red List, in part because their saws are prized by shamans in Asia as tools for expelling demons and disease, and are easily caught on fishing hooks and lines.

Reference: Barbara E. Wueringer, Lyle Squire, Stephen M. Kajiura, Nathan S. Hart, & Shaun P. Collin (2012). The function of the sawfish’s saw
Current Biology, 22 (5), 150-151 : 10.1016/j.cub.2012.01.055

Image: “What a saw” by Lorenzo Blangiardi. Used under a Creative Commons license

People’s feelings toward, and relationship with, snakes have varied greatly depending on the time period, location and culture. Today in the U.S., if fear isn’t the most common reaction (it was our #1 fear 10 years ago), then it’s at least very high profile…

You might assume it’s an old fear, too. Certainly our ancestors, whether two hundred or two million years ago, encountered snakes more often than most of us do. In a new study published this week in Proceedings of the National Academy of Sciences, anthropologist Thomas N. Headland and ecologist Harry W. Greene suggests that pre-modern humans and the lower primates have indeed had a long shared history with snakes, and its more complex than we had thought. Because constrictors usually swallow their prey whole and intact and venomous snakes attack soft tissue, there’s almost nothing in the fossil record to tell us anything about snakes attacking and/or eating humans and other primates. To figure out the relationship extinct hominins and pre-modern humans might have had with snakes, examining bones wouldn’t cut it, so the Headland and Greene had step back in time, in a way.

In 1962, three weeks after their wedding, Headland and his wife left Minnesota for the Philippines. For the next 24 years they lived among the Agta Negritos, the indigenous people of Luzon, the country’s largest island. By the time the Headlands arrived, the Agta couldn’t fairly be called primitive, but their lifestyle and size made them both similar to our prehistoric hominin ancestors and susceptible to attacks from large snakes. They were only recently hunter-gatherers and nomads, living in temporary shelters in family-based groups and subsisting on foraged plants and wild meat from the rainforest. Adult male Agta are, on average, a little under five feet tall and tip the scales at 97 pounds, while the reticulated pythons (Python reticulatus) that share the rainforest with them grow as long as 23 feet and weigh in at 165 pounds. An Agta male walking through brush is not only open to an attack from a big python, but also just the right size to be considered a decent meal for a snake, which has been known to eat pigs as big as 130 pounds.

Sure enough, when Headland started interviewing the Agta in the mid-1970s about their experiences with pythons, 15 of 58 men and 1 of 62 women said a python had attacked them. Of the men, two had been attacked twice and 11 still had scars from their attack. The interviewees could also collectively remember six people who were killed by pythons in the previous 40 years, including a man who’s son found the snake, cut it open and retrieved his body for burial.

The hunters also became the hunted sometimes. Every Agta man interviewed said they had killed at least one small python (up to six feet) during their lives, and some had killed larger ones. While Headland was living with them, an Agta hunter shot a 22-foot-long python and butchered it for some 55 pounds of meat.

The 22.6-foot reticulated python, shot by Kekek Aduanan (right) on June 9, 1970

The skin of the same python, post-butchering.

When the Agta and the pythons were not stalking each other, it turns out they were often hunting the same game. Until the 1970s, the Agta routinely hunted and ate Philippine deer, Philippine warty pigs and long-tailed macaques, three species that they often found in the bellies of the snakes they butchered.

The Agta and the pythons, the interviews make clear, have had a complex relationship, acting as each other’s predator and prey, and even directly competing for resources. Headland wanted to see if these same relationships showed up elsewhere in our family tree, so he turned to Cornell ecologist Harry Greene, who searched the natural history literature for primate-snake encounters and found a batch of stories that make the serpent in the Garden of Eden look like nothing. While no living serpent feeds exclusively on primates, Greene found anecdotal evidence that several constrictors prey on them regularly, and that venomous and constricting snakes have attacked at least 26 species of non-human primates, including lemurs, lorises, tarsiers, eight species of New World monkey and ten species of Old World monkey.

Green found that, like the Agta, nonhuman primates have stood up to snakes and attacked them. He found stories of capuchins using branches to kill a terciopelo, and lemurs ganging up on Madagascan ground boas. In some of these battles, the primates were probably defending themselves, but snakes are also potentially great prey choices for a primate, since their flesh isn’t toxic and they stay and confront attackers instead of fleeing.

Scientists have found in other animals, and even plants, that the shadow of an enemy looms long. Could it be that modern humans’ ophidiophobia is the relic of our long shared history with snakes? Is my girlfriend’s uneasiness an ancient, hard-wired instinct kicking in? Well, that’s tricky. Previous research has shown that very young children can detect snakes quicker than other objects, with the researchers suggesting that this is because they’re evolutionarily relevant threats. Subsequent research found that even with this quick detection, kids don’t associate fear, or any other emotion, with snakes until they learn to do so from adults. They only make the connection after seeing the reactions of people around them. If you see a snake, and your mom freaks out, you’ll learn to fear them, too, pretty quickly. Carnegie Mellon psychologist David Rakison, who did the research, points to the late crocodile hunter Steve Irwin’s kids, as examples of the opposite reaction. Irwin worked with dangerous animals very closely without any outward signs of fear, and his kids learned from that (sometimes very up close). Now, both kids are following in their dad’s footsteps.

Even though he and Headland don’t draw any conclusions about the question in their study, Greene told Cosmos magazine that he could “easily entertain as logical the hypothesis” that our fear of snakes is genetic and may formally investigate this in the future. Until we get a better idea of why fear of snakes is so seemingly widespread, it’s fascinating and sort of comforting for now to know that almost all members of our primate family have tangled with them. Since we came down from the trees, and maybe even while we were still in them, we’ve been listening carefully for a rustle in the leaves and a soft, low hiss.

References: 

de Lange, Catherine, (2011). “Fear of snakes? This could be why.” Cosmos.

Headland TN, & Greene HW (2011). Hunter-gatherers and other primates as prey, predators, and competitors of snakes. Proceedings of the National Academy of Sciences of the United States of America PMID: 22160702

Yong, Ed. (2011). “Meet the Agta, a tribe where a quarter of men have been attacked by giant snakes.“ Not Exactly Rocket Science. 

Images: “Beauty comes in all sizes and shapes :)” by spisharam; Python and Agta photos courtesy of Thomas N. Headland

While they’re less likely to occupy Wall Street than a barn upstate, bats are as concerned as we are about the economy. Their economy revolves around energy instead of money, though, and a problem on the balance sheet can be a matter of life and death. If they spend more energy catching a meal than that meal provides, they’ve created an energy deficit that impacts their health, growth and survival.

There’s no need to worry about bats during a recession, though. New research from biologists in Germany suggests that bats are actually pretty savvy shoppers and are able to use echolocation to make economic decisions while hunting and stay in the black, calorically speaking.

Bats gather information about their environment and prey by making clicking calls and then analyzing the echo patterns that bounce back at them. The conventional wisdom, backed by research, was that bats selected their prey based on biased information. That is, some prey had more conspicuous echo patterns because they were bigger or moved more and were over-represented in a bat’s perception. In the last few decades, though, that way of thinking has started to change, thanks to guano. Biologists began noting here and there that, in some colonies’ guano, there were more large insects than could be expected by chance and biased selection. In 2006, biologists from Frostburg State University in Maryland found that the proportion of beetles in the guano of one colony they were studying was greater than it should have been relative to the beetles’ abundance in the area. This all suggested to biologists that bats might be able to actively select their prey instead of just grabbing the most obvious things flitting about.

Since then, biologists have learned that some bats are indeed very sophisticated hunters. Greater horseshoe bats (Rhinolophus ferrumequinum) are known to be able to accurately discriminate between different types of insects based on information in the echoes of their fluttering wings (what’s more, they can change the frequencies of their echo calls to compensate for the of their own flight speed). More recently, Klemen Koselj, Hans-Ulrich Schnitzler and Björn M. Siemers from the University of Tubingen and the Max Planck Institute for Ornithology in Germany suggested that horseshoe bats are not only picking their prey selectively, but making those decisions based on energy economics.

Thinking about those piles of guano, Koselj wondered if the prey discrepancies other researchers had found could be explained by the bats hunting prey that optimize their energy profitability: They picked the certain insects not because they were obvious or especially tasty, but because they knew that some bugs gave them a better meal for their effort.

To find out, he’d need to watch them while they hunted, instead of just going through their waste. Koselj and his team captured half a dozen greater horseshoe bats and let them loose in a lab to hunt. To fully control the echo information the bats got, Koselj had them prey not on bugs, but computer-controlled propellers. The faux bugs came in different sizes and rotated at different speeds to produce echoes that resembled natural insects, some bigger and more energetically profitable than others. For a successful attack on a small propeller, the bats were rewarded with the wing of a mealworm and attacks on big ones netted them large, whole mealworms.

As the bats hunted, Koselj varied the conditions of the bug market, changing the frequency of small and big bugs and the amount of time between bug appearances to simulate different conditions of bug density and abundance. Throughout the hunts, Koselj paid close attention to the bat’s prey-selection decisions – catch or skip – in the context of abundance. Then, he then compared the results with standard models of prey choice to figure out if the bats were choosing prey based on energy costs and benefits. If they were, Koselj figured, they’d take the bigger, more profitable prey when they could get it and ignore the small ones, and be less picky when big bugs were scarce.

All six bats adjusted their prey selection to the different wait times between appearances of the large bugs, attacking both large and small bugs when the big ones didn’t show up as often and rejecting small ones and taking more of the big ones when they were more frequently available. One even rejected the small prey outright and took only the large prey when it showed up frequently enough. This selectivity didn’t appear to be just a matter of sensory bias, either. Often, when the small propeller started rotating, the bats would turn toward it, jerk their wings and get ready to take off, but then stand their ground, suggesting that they noticed the small prey and decided to skip it and wait for something worth the flight.

The bats, it seems, are savvy consumers, choosing their prey based on specific echo information associated with energy profitability and on that prey’s availability, estimated from how frequently they encounter it. This gives them a leg up on many other animals that also eat insects. Experiments with fish, amphibians, and birds have shown that these animals often reject the most profitable prey, an uneconomic decision that suggest they’re picking meals based on happenstance. As for other bats, which represent about a quarter of all mammals on earth, Koselj thinks that more species might be able to match the horseshoe’s decision-making, but that there might be a performance gap between bats that use short frequency-modulated (FM) calls and those, like the horseshoe bat, that use long continuous frequency ones.

Meanwhile, another German team has discovered that tropical bats balance their energy costs and gains with slower metabolisms.

Image: “Greater horseshoe bat, Rhinolophus ferrumequinum Schreb. 4/5 natural size,” by Friedrich Specht, via Wikimedia Commons.

References: Koselj K, Schnitzler HU, & Siemers BM (2011). Horseshoe bats make adaptive prey-selection decisions, informed by echo cues. Proceedings. Biological sciences / The Royal Society, 278 (1721), 3034-41 PMID: 21367788

Jones, G. (1990). Prey Selection by the Greater Horseshoe Bat (Rhinolophus ferrumequinum): Optimal Foraging by Echolocation? The Journal of Animal Ecology, 59 (2) DOI: 10.2307/4882

Salvatore J. Agosta, David Morton, & Kellie M. Kuhn (2003). Feeding ecology of the bat Eptesicus fuscus: ‘preferred’ prey abundance as one factor influencing prey selection and diet breadth
Journal of Zoology , 260 (2), 169-177 : 10.1017/S0952836903003601

Orb-weaving spiders are those spiders that build the spiral wheel-shaped webs that we often tend to think of as the Platonic ideal of spider webs. The ones you find draped between two dewy branches in a sun-dappled meadow, spider sitting in the dead center lying in wait for hapless flys and other insects to collide with the nearly invisible, impossibly sticky threads and get trapped.

While this technique keeps the spiders’ bellies full, it’s not without its problems. Those of us who’ve walked through a doorway or between two tree branches only to come away covered in thin, sticky web threads know that it’s not pleasant (for me, it is the stuff of nightmares). For the spider, it’s absolutely disastrous. Severe damage to the web by humans and other animals that the spider has no intention, or hope, of devouring costs them the production of more silk for a new web, exposure to predators, lost hunting opportunities and missed meals, and ultimately plays with the odds of their survival.

What’s a spider to do, then, when getting through the day requires a web that’s inconspicuous enough that prey don’t notice it, but has enough presence to warn animals that would just wreck it?

The species of the genus Argiope pull off a contradictory, but seemingly necessary, signaling paradox by constructing “decorations” of zigzagging bands of silk on their webs. They make the web very conspicuous to the naked eye, even from a distance, but don’t seem to tip off prey insects that they’re about to stumble into a trap.

Previous studies showed that decorated webs are damaged and destroyed less frequently than undecorated ones, and André Walter and Mark A. Elgar from the University of Melbourne wondered if this protective function was what motivated the spiders to build the decorations. It’s one of three explanations for the decorations that entomologists have tossed around for year, the others being that the decorations provide a signal for prey attraction, or conceal the spiders’ outlines and camouflage them from predators.

Walter and Elgar collected females of the species A. keyserlingi (above, also known as the St. Andrew’s Cross spider because the decoration they build at the center of their web resembles the X-shaped cross the Christian St. Andrew was crucified on) near their lab at the University of Melbourne and left them to build their webs on plastic frames set up in the lab.

Once the webs were built, Walter and Elgar rained destruction down upon them. They divided the spiders into three groups, left one group’s webs alone, “lightly damaged” another group’s by cutting web threads to simulate damage caused by prey impact and “heavily damaged” the third group’s by cutting ¼ of the web threads plus two diagonally opposite anchor threads to collapse the web. When the webs were rebuilt, they cut them down again and again for what might have been the most stressful 14 days of these spiders’ lives.

Throughout their reign of terror, Walter and Elgar kept tabs on two key characteristics of the webs: the size of the web’s “capture area” (the central sticky part where insects get stuck), and the pattern and the size of web decoration bands.

Capture area size didn’t change in the webs that experienced no damage or mild damage, but shrank by about 13% over the course of the experiment in the webs that experienced heavy damage. In all three groups, the proportion of spiders that built web decorations increased. At the start of the experiment, about a quarter of the spiders in the no damage group decorated their webs. At the end, a little more than half of them were building decorations. The decoration increase in the mild damage group wasn’t much greater than that in the no damage control, but the heavy damage spiders really got in touch with their inner Martha Stewarts, and the proportion of decorators shot up from 28% to 81%.

The post-damage decorating craze led Walter and Elgar to think that the spiders are using the decorations tactically to make their webs more obvious to passing animals that might unintentionally tear them down. But why the increase in decorating among spiders that didn’t get their webs wrecked too badly or even touched at all? Walter and Elgar think that the slight uptick there was because the captive spiders were well fed and could afford to invest a little more in their webs, whether their homes needed sprucing up or not.

Reference: André Walter, & Mark A. Elgar (2011). Signals for damage control: web decorations in Argiope keyserlingi (Araneae: Araneidae) BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY : 10.1007/s00265-011-1200-8

Image: “Argiope aetherea - St Andrew’s Cross spider” by Amos T Fairchild. Used under a Creative Commons License

This tarantula is about to go into a small, specialized MRI scanner so that researchers from Edinburgh University can see its blood flow through its heart. Gavin Merrifield and colleagues used a scanner built for medical research on rodents at the Glasgow Experimental MRI Center to get direct readings of tarantulas’ heart rates and cardiac outputs. Merrifield presented the team’s findings about the tarantula’s “double-beating” heart a few days ago at the Society for Experimental Biology Annual Conference.

Photo: Gavin Merrifield