On October 7th, 2018 we learned about

Proximity to sick peers causes healthy mice adopt an odor of illness

Being sick is bad enough, but the social stigma that goes along with looking like a runny-nosed zombie certainly doesn’t help things. Humans are generally repulsed by the visible symptoms in sick peers, overlooking other signs of illness like body odor. For a scent-oriented mouse though, the smell of a sick cage-mate is a bit more obvious, and would seemingly be a way for healthy individuals to avoid unnecessary exposure to contagion. However, studies have found that healthy neighbors of sick mice strangely start smelling sick themselves, although at this point its unclear how or why this helps either mouse.

Sniffing out sickness

The first step in testing all this was to expose healthy mice to infected neighbors. Some mice were allowed to have direct contact with their suffering peers, while others were separated by plastic barriers in their cages. None of the healthy mice were ever infected themselves, but their urine and body odor seemed to tell a different story. While the change in smell was nothing a human nose could detect, trained ‘sniffer’ mice and gas chromatography could detect a new, sickly scent.

The ‘sniffer’ mice were trained to move towards the smell of a sick mouse in a Y-shaped maze. When asked to sniff out unwell odors, urine samples from healthy mice smelled sickly around 63 percent of the time. Once it was established that mice could indeed detect the change in the odor of their healthy peers, researchers set out to identify exactly which chemical components were responsible.

Source of the scents

The three main components of a sick scent were all products of pheromones. This was unexpected, as these chemicals were normally associated with male mice looking to assert dominance or attract a mate. It’s then unclear why those pheromones would be tied to smelling like you’re sick. Actually, considering how most sick animals are avoided by their peers to avoid the transmission of pathogens, researchers aren’t sure if there’s any evolutionary advantage to imitating the scent of illness in the first place.

One possibility is that there is no significant benefit to smelling like you’re sick. It’s possible that the healthy mice exposed to sick cage-mates experienced an immune response to prepare them for possible infections. That physiological activity may be creating the pheromone by-products, and that the smell is simply sort of an inconsequential side effect. While evolution generally pushes organisms to be successful or efficient in their environments, smelling sick may be harmless enough that there was no pressure on mice to avoid it.

Source: Healthy animals mimic body odour of sick companions by Katrina Kramer, Chemistry World

On October 2nd, 2018 we learned about

Goats seek out smiling humans, expanding the audience for our facial expressions

Smiles are not universally valued among people around the world, but even cultures that don’t smile as much as your average American understand that a smile isn’t a sign of aggression or anger. Even a beaming smile may seem slightly suspect, it’s a consistent enough expression that animals have even learned how to read human faces. The assumption was that a dog or horse’s ability to differentiate between smiling and scowling humans was the result of generations of selective breeding- humans would favor the animals that could best adapt to our interests, leading us to promote those abilities in domesticated species’ gene pools. However, a recent study with goats has complicated matters, as our cloven-hooved companions were found to also discriminate between happy and angry faces, even though humanity as only been influencing goat genomes for a relatively short time.

Goats prefer grins

Goats at the Buttercups Sanctuary for Goats were shown photos of unfamiliar humans taped up to a wall. Each pair of photos showed the same close-up of a person’s face either smiling or scowling. Not only did the goats show an interest in the grayscale print-outs, but they also spent the majority of their time gazing at the smiling face instead of the angry one. Hinting at the neurological processing behind this decision, the goats were especially drawn to the smiling faces when they were more easily visible to the goat’s right eye. While the goats didn’t have an EEG cap to monitor brain activity directly, this preference suggests that the positive emotions were primarily processed in the goats’ left brain hemisphere.

The most significant aspect of these finding may be that they were somewhat of a surprise. People who work around goats have likely learned their personalities and behavior, but there was still an assumption that only heavily-bred animals like dogs and horses could read a human face so well. By demonstrating that goats are sensitive to this kind of human expression, it raises the possibility that other livestock is as well. This may require changes to how guidelines about working with animals, as humans may inadvertently be communicating with animals more than we’ve realized.

Smiling among simians

This does not mean that a western-style grin is completely understood across all animals on earth though. Humans may have convinced dogs and goats to look forward to a big smile, but chimpanzees and other primates don’t quite see our smiles as something pleasant. Chimps do have a friendly smile, but they take care to keep their upper teeth covered when doing so. Instead of being perceived as attractive or friendly, exposed upper teeth are seen as a threat, so save your bigger smiles for the species who have had a little more practice living around humans.

Source: Goats prefer happy people by University of London, Phys.org

On September 24th, 2018 we learned about

Zebra finches studying songs demonstrate pros and cons of social and solo learning

Despite remembering how annoying it was to hear it as a kid, I still nag my kids about the importance of practicing a new skill. There may be some debate about how much practice is needed to learn a particular task, but there’s little doubt that our brains learn through repetition, piecing together the right and wrong way to do something each time we attempt it. This might not be terribly motivating if you’re feeling frustrated with your piano or swim practice though, especially when you feel like your practice isn’t making any difference in your abilities. As it turns out, there may be a faster way to learn a new skill, although it as some annoyed zebra finches learned, it comes with cost.

Songbirds like a zebra finch (Taeniopygia guttata) are born with the anatomy to sing, but they don’t instinctually know the repertoires they’ll perform throughout their lives. They must learn particular songs, and seem to rely on listening to their older relatives, building their own version of a tune over time. Some songbirds have more direct mentors for their singing, but they can also piece together a song on their own if need be. These two styles of learning allowed researchers from the University of Zurich to devise an experiment to see if one kind of learning was more advantageous than the other. Essentially, do the finches who learn by example do better than those that have to figure things out through trial and error?

Speedier but shallower learning

While zebra finches definitely learn songs from each other, the first part of the experiment needed the birds to actively compare songs they were listening to. Birds were tasked with learning to differentiate between either “long” or “short” songs. Half the birds could observe other finches work through the same process, while the other half were left to figure out the comparison on their own. This made a huge difference, as birds that could learn from the efforts of their peers could successfully compare the songs after only 900 attempts, while birds who had to work on their own required closer to 4,700. Clearly, the social nature of zebra finches gives them a huge boost, allowing them to benefit from the efforts of other birds.

A second phase of the experiment found that the apparent advantage of social learning might not be better in every circumstance though. After learning the long and short songs, finches were offered a perch where they could see other birds but listen to two other recorded bird songs. These songs were similar to what had already been practiced, except that the longer song in this case was followed by an unpleasant puff of air in the listener’s face. Researchers then tracked how long the finches took to learn this new association and be ready to move their head out of the way of the harmless but annoying negative reinforcement.

The finches that learned from their peers in the first phase of the experiment didn’t fare as well in this scenario. On average, they took 3,600 tries before they put together the clues about when they’d be puffed in the face. The birds that had to figure out the first phase on their own did significantly better, requiring only 800 tries to learn this new task. So while they took longer to figure out the songs on their own, these birds seemed to have a better grasp of the underlying concepts which allowed them to generalize and reuse those ideas in new situations.

Information versus understanding

We can’t necessarily say that all learning can be compared to a zebra finch trying to avoid a puff of air in its face. However, researchers did put together a model that could help explain how these two sets of behaviors work on a neurological level. They believe that the finches that learned the first task by watching peers probably ended up with a broad but relatively weak set of synaptic connections associated with comparing the songs. In addition to forming connections in their brain that helped them listen to different song structures, they may have also been recording less relevant information, such as how their peers were sitting, if it was time to eat or not, etc. All that left them with a good blueprint for that first scenario, but it fell apart when too many of those irrelevant details were changed. In contrast, the birds that had to figure out the first songs on their own probably retained fewer details, but had a more robust foundation to build on in the second phase of the experiment. They likely had fewer synaptic connections in their brain, but what they had was strong and ready to work with new information in a more useful way.

None of this diminishes the need for practice. Many schools purposely try to use both forms of learning, asking students to both mimic a tutor and spend time in more experimental, trial-and-error activities. The former may help get someone up to speed a little quicker, which is great for a sense of accomplishment, but it turns out those difficult periods of more iterative learning will likely lead to a deeper understanding of an idea for future use.

Source: How birds learn, Science Daily

On July 24th, 2018 we learned about

Like humans, tree shrews’ taste buds make spicy peppers palatable

Chile peppers are great, if you don’t mind the whole “sensation of pain” thing. By activating the TRPV1 receptor in an animal’s mouth, the capsaicin in the peppers “burns” and scares off most of the creatures that would otherwise enjoy munching on a colorful, crunchy source of vitamin C. Other animals, like birds with diminished TRPV1 receptors, can just eat chiles without knowing what they’re missing. The real weirdos in all this are the mammals that do experience that harmless bit of pain and then actively seek out more of it. While many humans certainly fall into this last category, the more surprising chile lovers were recently realized to be Chinese tree shrews.

Eating more peppers with less pain

Tree shrews (Tupaia belangeri chinensis) don’t normally eat chile peppers, so it’s a bit odd that this connection was ever uncovered. It started when researchers planning to use the shrews in medical experiments were looking for the animals’ preferred foods, apparently “stumbling” upon the fact that the rat-sized mammals would eat a pepper without the slightest hint of discomfort. In fact, when given the option of corn snacks with or without spicy infusions, the shrews actually preferred hotter blends over blander options. This was in direct contrast mice in the same facility who notably recoiled from any food with spicy capsaicinoids in it.

Aside from the shrews’ overall interest in eating peppers, this gap in the two critters’ reactions wasn’t completely surprising. Despite their name, these tree shrews aren’t rodents, being more closely related to primates like us than to mice, which is why they were of interest to the laboratory in the first place. That said, the real difference in how each animal experienced capsaicin came down to only a single amino acid missing from the shrews’ TRPV1 receptors, making it slightly more difficult for the spice-triggering molecule to do its job. Essentially, the shrews could still taste the spiciness, but just less of it per bite.

Partnering with a spicy plant

Of course, this would be of little use if the shrews never needed to eat something spicy. Without peppers in their natural diet, it’s assumed that the shrews evolved their taste for capsaicin by eating Piper boehmeriaefolium. These plants also produce capsaicinoids, and the shrews may be the only creature evolved to eat them. This has essentially forced the two organisms into a partnership, where the shrews have access to a food source nobody else has the tongue to tackle, while the plants rely on the shrews to scatter their seeds. It’s unclear if this leads to the enjoyment capsaicin-loving humans get from eating spicy food, but the shrews did show a preference for foods that burn like their favorite P. boehmeriaefolium plants they grew up with.

Source: Hot Take: Tree Shrews Love Chili Peppers by Mindy Weisberger, Live Science

On July 23rd, 2018 we learned about

Echolocating bats squeak softer when they’re flying in stealth mode

One of the best things a nocturnal animal can do to hide its location is to stay quiet. For example, the cats soft feet and owls’ fringed feathers allow these predators to approach their prey in near silence, keeping their approach hidden for as long as possible. Of course this strategy is a lot to expect from bats though, as echolocating species depend on making sound to not only find their prey, but navigate around obstacles in the dark as well. Nonetheless, difficult doesn’t mean impossible, as some bats have been found to purposely reduce their sound “footprint” in order to better mask their locations.

Modulating volume to trick moths

Barbastelle bats (Barbastella barbastellus) like to hunt a variety of insects, including tiger moths. After generations of being eaten by bats, these moths have evolved hearing ranges that let them detect and even interfere with bats’ echolocation calls, making it harder for the bats to surprise their targeted prey. To compensate, barbastelle bats have learned to turn down the volume on their echolocation squeaks as they approach a moth. To figure out exactly how much effort the bats put into this strategy, researchers attached a microphone over a bait-moth in the forest, allowing them to record exactly what prey would hear as a bat attacks.

Since the relative loudness of sound greatly increases with distance, the bats have to be very careful in how they modulate their voices. To keep the moths in the dark concerning the bat’s approach, the bats lower the volume of each squeak just the right amount to make the sound stay consistent to the listening moth. So the moth can certainly hear the bat’s echolocation, but it won’t sound like it’s getting any closer. The bat isn’t hiding its presence, but it does hide its location well enough to get the drop on its prey.

Navigating without being noticed

Hiding an attack on a moth is one thing, but what about bats that want to hide from other bats? This is apparently a concern of hoary bats (Lasiurus cinereus) migrating for mating season, who want to go and find potential mates without attracting unwanted conflict from rival suitors. Obviously, these bats are quite well attuned to the sound of their own species, which is probably why the bats revert to navigating with what researchers are calling ‘micro-calls.’

These super-soft squeaks are three orders of magnitude quieter than most echolocation, making the bats’ voices nearly inaudible. The catch is that these quiet bats are also nearly flying blind, as their echolocation is only able to report on their immediate surroundings. In an experiment, mist nets were set up on a bat migration routes in norther California, and the bats only seemed to notice the nets at the last second. Despite a few full-strength squeaks to assist with evasive maneuvers, many of the bats still collided with the net, indicating that flying in “stealth mode” carries a degree of risk for the incognito bat.

Conservation concerns

While there hopefully aren’t too many nets set up on the bats’ migration routes, there are wind turbines. The bats relying on micro-calls are much less likely to avoid the spinning blades of the turbines, thanks to their reduced range of “visibility.” They’re also less likely to be detected by conservationists, who have generally relied on the sound of full-throated echolocation to determine where to build turbines in the first place. Knowing that those checks may have missed these very quiet bats will hopefully shape future conservation studies, possibly driving the adoption of alternate methods of bat detection. Just don’t tell the moths about it.

Source: Bats go quiet during fall mating season by Wake Forest University, Phys.org

On July 17th, 2018 we learned about

Cleaner shrimp communicate with their client fish via a set of specific visual signals

Cleaner shrimp have been found to stake a lot of their survival on their eyesight, which is impressive because their eyesight is terrible. Tiny crustaceans like Ancylomenes pedersoni were long thought to depend on their sense of smell to figure when they were safe to go out and forage, but new experimental data suggests that they get by with visual cues alone. It might help that these cues are somewhat interactive, and so the source of the shrimp’s food helps inform them when it’s time to eat, or when they might be eaten themselves.

A. pedersoni forage on the parasites and debris found on the gills, scales and even in the mouths of predatory fish in coral reefs. Blue tangs, parrotfish and snappers that could happily gobble up the shrimp themselves have learned that A. pedersoni provide bigger benefits if left to their work, and thus make a point to cooperate with the crustaceans’ foraging. Cleaning sessions start when a shrimp waves its white antennae in the water, signalling that it is ‘open for business’ to nearby fish. The fish then indicate their intent by darkening their body color as they approach, letting the shrimp know that they’re there to be serviced instead of posing a threat. Both parties stick to the script quite consistently, leading to successful partnerships over 80 percent of the time.

Which signals are sufficient?

To pin down exactly which signals mattered, researchers showed captive shrimp a variety of images on a tablet computer outside their aquarium. Thanks to the shrimps’ poor eyesight, these images didn’t need to closely resemble fish as long as they followed the expected protocol of a potential cleaning client. So as long as a collection of circles and triangles wiggled and then darkened, the shrimp were happy to go to work, wiggling their antennae and even attempting to hop on top of the the imaginary fish outside the tank. It may not seem like the shrimp were being especially discerning in their response, but it does prove that they’re looking for visual signals from cooperative fish instead of olfactory or auditory signals.

As a final step, researchers modeled the visual perception of both fish and A. pedersoni using a simulator. Software called AcuityView confirmed that the shrimp can’t make out shapes or colors clearly, which is probably why fish who want to be cleaned need to announce themselves with a light-to-dark color change. The fish, on the other hand, have slightly better vision, and can likely spot a shrimp’s waving antennae from a few feet away in the reef’s shallow water. So on both sides of this partnership, visual signals alone are coordinating how these two species manage their cooperative behavior.


My kindergartner said: Oh, it’s like the guys waving signs at the car wash. A shrimp car wash!

Source: When cozying up with would-be predators, cleaner shrimp follow a dependable script by Duke University, EurekAlert!

On July 9th, 2018 we learned about

Crows strike first against ravens, preempting the risk supposedly posed by their fellow corvids

No bird wants to see more corvids move into their neighborhood. Aside from the likelihood that a magpie, crow or raven would outsmart their feathered kin, these birds are also likely to prey on smaller birds and their eggs. As much as that may threaten an individual chicken or swallow, it turns out that the corvids don’t really make a dent in overall bird populations; birds that corvids don’t catch are equally likely to be captured by some other predator. Nonetheless, it seems that some corvids have taken their dangerous reputation to heart, which may be why they attack each other so vigorously when there’s a nest that might need defending.

Aggressively preventing predation

After analyzing reports from thousands of amateur observers, a pattern became clear in crow and raven interactions. Without any kind of prompt, many of these observers noted how crows would seek out and drive ravens away from their territory, even before the ravens had made any kind of threatening movements on their own. In fact, the interactions were so one-sided that researchers found that the American and Northwestern crows were the aggressors in 97 percent of these interactions. The smaller crows did seem to avoid one-on-one interactions, preferring to form small teams to harass the larger ravens.

The aggression was most likely tied to nesting. Crows were most aggressive during breeding season, although they started to ramp up their attacks in the preceding winter months as well. Researchers believe that this was likely to defend a chosen territory and nesting site, blocking the ravens from gaining a foothold or access to resources anywhere near the crows’ eventual nursery.

Safe and sound?

Unfortunately, the actual predation of young crows by ravens likely isn’t as conspicuous as a team of crows driving a raven away, and so it’s less clear how much of an impact the crows behavior makes. If the pattern for corvids versus non-corvids holds true, it would suggest that while the crows may succeed in saving their young from the ravens, there’s a good chance some other threat may balance out their numbers nonetheless.

Source: Crows are always the bullies when it comes to fighting with ravens, Science Daily

On June 25th, 2018 we learned about

Orangutans observed preparing and treating muscle aches with medicinal plants

If your local pharmacist isn’t getting you medicine you need, you might be better off consulting an orangutan. They might not have an answer for every ailment, but orangutans have now been confirmed to both prepare and use medicinal plants to ease their own joint and muscle pain. The whole treatment only takes around seven minutes, but be warned- the inclusion of orangutan saliva means it’s not the most discreet way to ease an aching shoulder or back.

Lather, spit, repeat?

Like many medicines, the treatment begins an intensely bitter plant— a Dracaena cantleyi in this case. The patient/pharmacist chews the unpleasant leaves, working them into a white, frothy lather. They then rub the later into whatever muscle is in pain, allowing the active ingredients to be absorbed through the skin. Importantly, orangutans then spit the remaining bits of leaf out of their mouths, demonstrating that this behavior wasn’t idle, sloppy eating. The multiple steps taken to work up the lather suggest that the orangutan was deliberate in her actions, expecting a particular outcome of her slobbery treatment.

Researchers working in the Sabangua Forest have seen this behavior on seven occasions since 2003, making it hard to really be sure of the orangutans’ methods. However, the recently document treatment session by a female orangutan does follow an important trend in what was seen before. Only females have been seen medicating their muscles in this manner, which researchers believe may be because they want to alleviate pain and inflammation from carrying their offspring all day.

New avenues for drug discovery

While this is the first time an Asian ape has been documented self-medicating, it’s not completely unprecedented. Indigenous peoples on Borneo also use Dracaena cantleyi for medicinal purposes. Outside of Borneo, other animals are also known to self-medicate, using ground leaves as insect repellent, or ingesting bitter plants to possibly purge their digestive tracts of nematodes. Nonetheless, researchers are hopeful that orangutans may still be better pharmacists than these birds and primates, and plan to follow them closely in case they can reveal plants that can hold medicinal value for humans.

Source: Orangutans, like people, use medicinal plants to treat joint and muscle inflammation, Phys.org

On June 14th, 2018 we learned about

To avoid interactions with humans, more animals are becoming increasingly active at night

Millions of years ago, tiny mammals faced overwhelming competition from dinosaurs of all shapes and sizes. To avoid being gobbled up by hungry raptors or crushed under a distracted stegosaur, our shrew-like ancestors had to find a safe niche in their ecosystem where they wouldn’t be directly at odds with the dominant animals of the Mesozoic era. Their solution was to become nocturnal, allowing them to minimize contact with dinosaurs while continuing to live in the same locations. Once those dinosaurs were wiped out, mammals diversified and enjoyed more time in the sun, becoming the dominant vertebrates on land in the shape of deer, dogs, bears and more. However, research indicates that many species are being pressed back into the shadows, avoiding contact with the latest form of world-dominating creatures— humans.

Hints of this development have been noted for years. Nepalese tigers (Panthera tigris tigris), for instance, were documented shifting to a nocturnal schedule back in 2012. Motion-triggered cameras were set up in various locations around the tigers’ habitat, revealing a clear pattern in when the tigers were active. In places with less human activity, the tigers traveled day and night, but areas frequented by humans reduced their daytime activity by at least six percent.

Daily activities after dark

These night-owl tigers were apparently part of a larger trend. At this point, 76 studies of 62 species have seen similar shifts in animals’ schedules. From lions to otters, creatures around the world seem to be starting their day at night to minimize any contact with humans. That contact doesn’t even need to be explicitly dangerous their interactions with humans. While avoiding hunters may seem obvious, the analysis found that animals are changing their behavior around seemingly innocuous activities, like day hikes on footpaths. As much as people try to take only photos and leave only footprints, even a footprint may make some of our furry friends think twice about their daily routines.

This obviously isn’t the only time humans have functioned as an environmental pressure on wildlife, but it still stings a bit to realize how far other species will go to avoid being around us. Egos aside, biologists actually see an upside to this strategy, which is that it might work. While it’s obviously going to be disruptive to ecosystems if creatures like lions are staying up later to find food, the lions will probably still be better off avoiding potentially dangerous interactions with humans. As some species have found, coming out after people have gone to bed can work pretty well, allowing them to live in closer proximity to human developments than would otherwise be possible. Basically, if this strategy kept our ancestors safe from millions of years of dinosaurs, it will hopefully offer some of our current kin a way to stay safe from us.

Source: Many animals are shifting from day to night to avoid people by Emiliano Rodriguez Mega, Phys.org

On June 12th, 2018 we learned about

Monkeys will punish their peers to preempt larger outbreaks of violence

There’s a surprising degree of subtly in monkey-on-monkey violence. While a brief spat between two individuals is unlikely to have a large impact on a group, extended conflicts are much more likely to large-scale violence. As a fight wears on, researchers have found that combatants employ a sort of collective memory, and will make a point to fight every available adversary, which increases the duration of the battle as well as the risk of serious injury. The monkeys themselves seem to appreciate these risks, as species like vervet monkeys (Chlorocebus pygerythrus) from southeastern Africa make specific efforts to prevent bigger fights, even that means causing a bit of harm to one of their own allies.

If a conflict is brewing between two larger groups, female vervet monkeys have long been known to campaign either for or against brawls. In some cases, they will offer extra grooming to potential fighters to sway their opinion one way or the other. If the “carrot” approach doesn’t work, females will also use a “stick” in the form of harassment and coercion, even if that requires banding together in a group to be more intimidating to the generally larger male monkeys.

To dominate or deter?

Until recently, researchers assumed that the male vervet monkeys were always up for a fight. They didn’t seem to offer rewards to their peers, and the punishment and coercion they would use against males in their own social groups was thought to be a way to keep their peers from competing for the wrong mate. However, more careful observations found that the males never made a move to stop females from interacting with other males, even when those males were from other social groups. This acceptance of female autonomy seemed to indicate that monogamy wasn’t the primary motivation behind the males’ punitive behavior.

The final clue was that fathers of young offspring were the most likely to exhibit punitive behavior towards other male monkeys. Researchers now believe that males aren’t roughing up their peers to assert dominance as much as they’re stopping would-be troublemakers from starting fights. Since those intra-group fights could be dangerous to the males, but especially to their more vulnerable offspring, these male monkeys have a clear incentive to keep larger fights from threatening their family. It’s certainly a more noble incentive for coercion than simply asserting dominance, but the targets of this abuse probably wish the protective males would work a little harder on their diplomacy instead of their left hooks.

Source: Male vervet monkeys use punishment and coercion to de-escalate costly intergroup fights by University of Zurich, Phys.org