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

On June 10th, 2018 we learned about

Skinks use blue tails and tongues to trick attacking predators

Green means “go,” red means “stop,” and blue apparently means “don’t eat me,” at least if you’re a lizard. Don’t feel bad if you’ve somehow never noticed this message in all the lizards you thought about eating, because the blue in question is primarily in the ultraviolet (UV) light spectrum, which human eyes can’t see. Predators of bluetongued skinks and Plestiodon latiscutatus are very likely to notice this bright color though, which the lizards have come to rely on as a way to stay safe.

Bewildering tongues in ultraviolet and blue

As their name implies, bluetongued skinks like Tiliqua scincoides intermedia focus their predator-deterring coloring on their tongues. Of course, this means that the blue isn’t visible at all times, which allows the lizards to utilize it only when necessary. Most of the time, the brown, banded coloration on these lizards works to camouflage them among the dirt, rocks and foliage of northern Australia where they live, as the easiest way to deal with predators is to avoid interacting with them at all. If the lizard is spotted though, it will wait until nearly the last second before being struck down to open its mouth wide and reveal its intensely-colored tongue, which is visibly blue to humans at the tip, but more saturated in ultraviolet color towards the back of the mouth.

When coupled with some good hissing and puffed-up body language, this display has a chance to startle a predator enough to stop their attack. In tests with dummy predators, it appeared the the skink did make some judgment about the severity of the incoming attack, reacting more for a fake snake than for a piece of wood moving in their direction.  The lizards also made sure to time their big reveal carefully, since revealing a bright tongue from a distance would just make them easier to target. By waiting until the last second, particularly for a diving bird, the skink would have the best chance to significantly disrupt an attack, buying itself time to escape. This strategy also indicates that predators wouldn’t be deterred simply by the bright color, suggesting that the element of surprise is the key mechanic at play, versus the warning of potential poisoning behind the coloring of a poison dart frog in the Dendrobatidae family.

Drawing predators’ interest with indigo

Not every lizard hides it’s ultraviolet side though. Many species of lizard, particularly young skinks, start their lives with bright blue tails. Unlike the bluetongued skinks, these bright tails are meant to draw predators’ attention, allowing the lizards to use autotomy to escape serious harm. As long as predator only strikes the blue portion of the lizard’s tail, that bit of flesh can be safely detached to spare the target’s life.

With no way to hide and reveal these tails, lizards seem to have tailored exactly how eye-catching they are according to the threats in their local ecosystem. If lizards face snakes and weasels, tails are likely to be colored in blue and UV-reflecting pigments. If a snake is the only predator to worry about, the lizards’ tails are only distracting in ultraviolet, allowing them to draw a little less attention to themselves in other color spectra. Birds almost reverse this trend, since their ability to spot a lizard tail from a distance makes drawing their attention more trouble than it’s worth. So when lizards need to worry most about predatory birds, they’re most likely to skip blue and UV colors altogether, opting for more easily hidden tails and bodies.

Source: Australian lizard scares away predators with ultra-violet tongue, Science Daily

On June 6th, 2018 we learned about

Domesticated dogs’ survival depends on puppies leveraging their looks

We’re currently dog-sitting a mutt that most people think looks a bit like a ten-pound Ewok. Many onlookers seem to find his small size, button nose and large, dark eyes look pleasingly puppy-like. Just about all of our neighbors have commented on how quite the little fluffball looks on walks, although I don’t think anyone actually believes that he’s a puppy. Somehow people have a sense of what a truly young dog looks like, even to the point of finding a specific age more adorable than all the rest. It may seem like looking pleasing would only provide a benefit to human breeders, but researchers have found that peak-puppiness likely boosts dog survival rates exactly when they need the most help.

Judging the best babyfaces

In general, humans like to look at things that remind us of our own babies. This concept, called kinderschema, is so ingrained in us that adoring an infant’s chubby cheeks and bright eyes often triggers the release of hormones like oxytocin. This in turn helps us feel an emotional bond with the cute face we’re looking at, even if that face belongs to a puppy instead of our own offspring.

Researchers from Arizona State University asked test participants to rate how attractive they found photos of dogs at different ages. By limiting the photos to just a few breeds and specific poses, researchers were able to tease out which age dog triggered the strongest reactions from the 51 participating humans. They found that Jack Russell Terriers were cutest at 7.7 weeks, Cane Corsos at 6.3 weeks, and White Shepherds at 8.3 weeks old. These ages weren’t a huge surprise to researchers, because they all coincided with the age these dogs were most likely to be weaned from their mothers.

Swapping maternal care for adoring surrogates

Unlike wolves, which care for their young for around two years, domesticated dogs expect their young to be independent at around two months old. The problem is that most puppies don’t really agree with this assessment, as around 80 percent of puppies don’t survive their first year when living on their own. Rather than work on their hunting skills, dogs have been shaped to as adorably baby-faced as possible at this age, enticing humans to step in and pick up where the dogs’ mothers left off.

Figuring out exactly how this arrangement fell into place is difficult at this point, but as far as we know nobody was consciously breeding their dogs to sync up weaning with being extra cute. Nonetheless, it’s now an important part of dog survival, and it’s easy to see how this concept may even play a role in some breed’s entire life. After all, being a cat-sized Ewok-impersonator probably doesn’t impress predators or prey as well as it convinces humans to share their food and homes.

Source: Age Of Optimal Puppy Cuteness by Karen B. London PhD, Bark

On May 30th, 2018 we learned about

Mongoose societies depend on specialized food sources and swapped services

No mongoose is an island. The main time they’re alone is when standing as sentry, guarding their multi-family colony while other individuals forage and rest. As this division of labor implies, mongoose society is fairly sophisticated, and researchers are still discovering ways that these slinky relatives of cats and hyenas cooperate and compromise to keep a colony going. Interestingly, these adjustments don’t necessarily require strict hierarchies or perfectly egalitarian access to resources. Instead, the mongooses just seem to do a great job of finding ways to work around each other, sometimes in ways that weren’t previously observed in non-primate animals.

Find your own food

An obvious issue for a large group is making sure everyone has enough to eat. One possible solution would be to control every individual’s portions, ensuring that every mongoose gets the same amount of food. That’s not always a safe strategy— social spiders, for example, share their food equally, but then face disaster if resources suddenly come up short. Banded mongooses (Mungos mungo) have learned to avert this risk by essentially avoiding sharing food altogether.

This doesn’t mean that every mongoose is hoarding food for themselves though. Rather than compete for shares of a single clutch of millipedes, ants, or small vertebrates, each mongoose just picks a favorite food to specialize in. Analysis of the proteins in mongoose whiskers indicates that the larger a colony is, the more each animal focuses its diet on a single source, presumably to avoid competing with friends and family for every meal.

Equitable exchanges

Dwarf mongooses (Helogale parvula) employ a different form of specialization, focusing more on how to share chores instead of chow. While various animals are known to keep tabs on other individuals’ past generosity, the mongooses add extra sophistication to these exchanges by trading asymmetric services with each other. So while vampire bats may trade blood for blood over time, a dwarf mongoose may trade grooming for sentry duty, indicating a complex understanding of how these activities benefit each other.

To test how much mongooses actually appreciated each others’ work, scientists manipulated how certain individuals’ efforts were received by their peers. A mongoose on sentry duty will periodically call out with reports about what they see, and so researchers played recordings of those cries when an individual was off duty, tricking other colony members into thinking that particular sentry was working overtime. The payoff for that “extra” effort was extra grooming from other mongooses, who apparently felt the need to reward their sentry’s long-shifts standing guard. Other recordings didn’t have the same effect, indicating that the groomers were keeping track of how much time their neighbors were out working.

Agreeing to anonymity

Not every facet of mongoose society is quite so benevolent though. Even if banded mongooses can learn to eat to accommodate each other,  they’re not so friendly to each other’s offspring. So to keep pups from being killed by rival adults, all the mongooses essentially agree to keep offspring anonymous so that they can’t be singled out. It’s a less friendly form of compromise, although the results are certainly worth it.

Source: Mongooses remember and reward helpful friends by University of Bristol, Phys.org