On April 23rd, 2018 we learned about

Crocodiles can change their skin coloration based on environmental color cues

Few predators would antagonize an adult saltwater crocodile (Crocodylus porosus). Weighing close to a thousand pounds, these huge reptiles have little to fear in their local ecosystems. Their hatchlings, on the other hand, are usually around 2.5 ounces at birth, and need to be a bit more wary about becoming someone’s lunch. To stay safe, these tiny crocs, as well as other members of the Crocodylidae family, have developed the ability to better hide themselves by changing the color of their skin. Through a series of experiments, researchers have been able to isolate the exact mechanisms that allow these scaly predators to obscure themselves according to environmental conditions.

Shading skin according to what they see

The color changes in question are noticeable to the naked eye, assuming you’re comfortable staying in proximity to a crocodile for 60 to 90 minutes. While no crocodile was observed creating new patterning or bright shifts in hue like a chameleon, they could shift their skin from lighter to darker shades of their normal coloration. Members of the Crocodylus genus, like saltwater crocodiles, would make their tails, backs, and heads turn darker in darker environments, while members of the Gavialidae family did the opposite, lightening their backs when placed in dark environments.

In the context of this study, dark environments consisted of black or white tubs of water. It was easy to see the crocodiles change color according to their surroundings, but researchers needed to make sure that this was really triggered by what each animal was seeing, rather than other conditions like body temperature or stress levels. One way to do this was to place a crocodile in one color tub, blindfold it, then move it to the opposite lighting conditions. In those cases, the crocodiles’ coloring didn’t change according to the new environment- they kept the color that matched the last environment that their eyes were able to see. This was fairly conclusive, particularly after factors like temperature and stress hormones were found to be consistent between light and dark tubs. Finally, tests with red lights, which crocodiles don’t see as well as colors like blue, showed that if the crocodile didn’t visually perceive the difference, their skin didn’t react either.

Pinching and stretching pigments

Of course, visual stimulation can only be part of the story. Researchers also examined the crocodiles’ skin to see how it could change color once the animal noticed it was in a dark or light environment. They found that an α-melanocyte-stimulating hormone was released in the body, which triggered changes in cells’ melanosomes. When a crocodile needed to darken, the pigment in the melanosome would spread out, increasing the percentage of each cell that would absorb light. When a crocodile lightened, the same melanosomes would contract into tight packets, leaving more surface area without pigment to absorb light. This expansion and contraction is all that’s needed to achieve the relatively quick but reversible color change seen across multiple species’ skin.

Estimating when this abilities evolved

The species of crocodile that change colors revealed some information about when this ability likely evolved. Alligators, for instance, don’t change colors, which suggests that this ability had not developed when that family split from Crocodylidae 80 million years ago. Outside the genus Crocodylus, two African members of Crocodylidae showed little to no color-shifting ability, which then suggests that this trait evolved after that branch in the family tree occurred 30-40 million years ago. However, Crocodylus diversified a lot around 12 to 17 million years ago, so researchers assume that this trait was likely established by then in order for it to turn up in species that have since become separated from each other.

My third-grader asked: Do adult crocodiles do this too, or is it just the babies? Why do some of them turn the opposite color? Are they sure the pigment isn’t to help prevent sunburns?

The tests were done with baby crocodiles, possibly because they’re a lot easier to move between tubs of water. However, adults would benefit from dynamic coloration, as hiding from prey would aid in the ambush-style hunting crocodiles typically rely on.

The benefits of Gavialidae crocodiles’ reversed coloration wasn’t directly tested in this study. Researchers speculate that it acts like a form of countershading, similar to the way a shark’s white belly makes it harder to see when viewed as a silhouette from below. If true, this further supports the notion that adult crocodiles make use of these abilities to help them surprise their prey.

The sunburn question was likely sparked by Claude, the albino alligator living at San Francisco’s California Academy of Sciences. As an albino, Claude had no pigment it his skin, putting him at greater risk from ultraviolet light damage (and predation! and being spotted by prey!) While it might seem handy to be able to activate built-in sunscreen on command, it’s hard to see how that would benefit an animal more than good protection all the time. Since these animals mostly live in equatorial regions, they wouldn’t really have a pressure to decrease their ultraviolet light protection at any point, making the perception to hormone to melanosomes system needless complicated. Temperature control would seem like a better tool for a cold-blooded reptile to have, but the study directly controlled for temperature changes, and found that it didn’t influence the crocodile’s coloration.

Source: Crocodiles Alter Skin Color in Response to Environmental Color Conditions by Mark Merchant, Amber Hale, Jen Brueggen, Curt Harbsmeier & Colette Adams, Scientific Reports, volume 8

On April 17th, 2018 we learned about

Mosquitoes let researchers indirectly monitor the movements of invasive pythons

Burmese pythons (Python bivittatus) often grow up to twelve-feet long, but they’re still surprisingly hard to find in the wild. This is bad enough for the prey these snakes want to ambush, but it’s created challenges for researchers tracking their activity as well, even in environments where these snakes aren’t supposed to live. Since the 1980s, failed pet-owners have been importing and releasing pythons in the Florida Everglades, harming the native wildlife in those swamps. Fortunately, one local species seems to be quite adept at locating pythons, which is why researchers are “recruiting” mosquitoes to help track the snakes.

Following snakes via swarming mosquitoes

Despite the mobility of an individual mosquito, they’re still easier to capture than a single Burmese python. The work starts with cardboard funnels and hand-held vacuum cleaners, but is then followed with DNA sequencing in the lab to see what species of animals the mosquitoes have been eating. When python DNA turns up, it lets researchers construct a map of where they’re moving, and possibly how they’re multiplying across the Florida swamps.

Since this work started in 2015, a few trends are already clear. Python populations have been growing, and expanding northward. At this point researchers don’t have a strict head-count on the snakes, but they know that there are enough to be making an impact on other species in the Everglades. Raccoons, for instance, have been getting eaten often enough that the turtle and alligator eggs they usually eat are hatching at unusually high rates.

Other types of tracking

If digging through mosquito stomachs seems too indirect, conservationists have a few other ways to follow invasive pythons. One option is to collect samples of dirt found near burrows, then dig through them for traces of python DNA. Each time a snake slithers by, it sheds a bit of DNA, eventually leaving enough to confirm activity in specific locations.

For something a bit more actionable, there’s the sentry snake program, conducted by the Conservancy of Southwest Florida. Male pythons are outfitted with radio trackers, then released back into the wild where they’ll hopefully find a mate, and possibly some friends. Once contact seems to be made, conservationists can raid the “aggregation” of snakes, capturing other males and any fertile female snakes that were fertilizing eggs. This method is rather labor intensive, but it has led to the removal of over 3,000 fertilized eggs from the Florida swamps before they had a chance to hatch.

Source: A UF researcher is tracking snakes using mosquitoes by Wyatt Schreiber, The Alligator

On April 15th, 2018 we learned about

Beyond bugs, mammals, birds and reptiles play big roles in the pollination of flowering plants

On paper, the tongue of a Pallas’ long-tongued bat (Glossophaga soricina) may sound a bit like something from a horror movie. The South American bat’s tongue is made of spongy, erectile tissue, allowing it to increase its length by 50 percent when engorged with blood. It’s covered in an array of tiny, densely-packed hairs, which then stand perpendicular to the tongue when fully extended, allowing it to better capture the fluids the bat devours to stay alive. In practice though, none of this seems very grotesque, because G. soricina only uses its tongue to lap up nectar out of flowers, placing this bat in a niche closer to a honeybee than a vampiric parasite.

Scientists studying pollinators have found that the importance of vertebrate pollinators like G. soricina may be widely underappreciated. For all the attention played to pollinating bees and butterflies, a large number of plant species largely depend on bigger critters like bats, mice and even lemurs to fertilize their flowers. These aren’t strictly fringe cases either, as some flowers have evolved to be highly specialized, and thus dependent on just the right species of mammal or bird to be able to reproduce.

Nectar-eating bats and birds

Among mammals, bats are the most common pollinators, sometimes accounting for 83 percent of fruit production in a geographic region. They’re known to pollinate close to 530 species of plants around the world, often in relatively exclusive arrangements. For example, the blue agave cactus (Agave tequilana) which is used to make tequila, only open their flowers at night in order to attract greater (Leptonycteris nivalis) and lesser (Leptonycteris yerbabuenae) long-nosed bats. These bats don’t have hairy tongues, but the hair on their bodies collect and spread pollen just like the fuzz on a bumble bee.

As the specialized beak and tongue of a hummingbird indicates, many species of our feathered friends also act as important pollinators. Beyond hummingbirds, 920 species of bird are known to spread pollen between flowers, and are estimated to account for five percent of flower fertilization where they live. In more isolated environments, like islands, that number goes up, with birds being responsible for at least ten percent of flower pollination.

No need to fly to flowers

The success of pollinating bees, bats and birds may suggest that flight is somehow necessary to pollinate a flower, but that’s not the case. Any animal that wants to sip nectar without destroying the flower that produced it can potentially act as a pollinator, which has lead to at least 85 plant species around the world that get regular visits from non-winged mammals. Mice, squirrels, possums and lemurs may all stick their noses into flowers enough to transport pollen. Even without fur, bluetail day geckos (Phelsuma cepediana) can act as pollinators, carrying sticky pollen on the tips of their noses.

As humans become more appreciative of how insect pollinators help keep ecosystems alive, this research shows that we need to also consider the bigger-bodied pollinators as well. As policies and even substitutes are being developed to help protect creatures we associate with plants humans grow on farms, we need to make sure the wider range of pollinators around the world are protected as well. After all, some of these pollinators have become very adept at their sticky, hairy line of work, and won’t be easily replaced.

Source: Lizards, mice, bats and other vertebrates are important pollinators too by Ecological Society of America, Phys.org

On April 11th, 2018 we learned about

Individual lemurs’ social status gets a big lift from learning to grab a grape

Despite stereotypes about the unpopularity of nerds, primates seem to find learning fairly attractive. In the case of ring-tailed lemurs (Lemur catta), acquiring a single grape from a puzzling, Plexiglas drawer proved to be enough to greatly improve an individual’s social status, even if that individual didn’t change any of its behavior after the fact. This not only suggests a mechanism to incentivize learning and exploration in social animals, but also adds a layer of complexity to primate relationships that haven’t been previously considered.

The task itself was fairly straightforward. A Plexiglas box containing a single grape was placed in an enclosure with a group of lemurs. In most cases, a younger individual was the first to play with the box enough to open a drawer and win their prize, kicking of a cascade of responses from nearby witnesses. Some tried to apply the newfound knowledge directly, going to investigate the box themselves. Others began to flock to the successful individual, providing “affiliative behaviors” like grooming well beyond what that lemur ever received before getting the grape. Further visits to the box only boosted that lemur’s status, as their peers apparently loved the idea of their newfound friend’s mastery of the puzzle.

Gratification without the grape

Unlike previous experiments in this vein, researchers carefully designed this experiment to only provide a direct reward to the animal that opened the box. Previous studies rewarded curious individuals with enough food to potentially share, raising the possibility that a lemur’s new fans were only interested in getting a bite to eat themselves. By limiting the reward to a single grape, this study made it clear that the social group saw some other value in their new relationship. What’s more, the doting lemurs didn’t receive any reciprocal grooming or care from the successful individual either, suggesting that solving the initial puzzle was somehow valuable beyond immediate gratification.

One possible explanation is that friendships with successful individuals may yield benefits later on. While there was only one grape today, a lemur might feel like it’s good to be friends a clever peer in case they turn up with more grapes tomorrow. While this may sound rather subservient, these lemurs were likely learning from their new friend’s success as well. Lemurs that started spending a lot of time with a puzzle-solving individual were more likely to be successful with puzzle boxes in the future. They liked their hero’s mastery, but they also made a point to learn from it as well. It shows how learing and social status may be intertwined in social primates, and how the give and take in these relationships may not be obvious at first glance, especially if the prized grape has already been eaten.

Source: Lessons from lemurs: To make friends, show off your smarts by Princeton University, Science Daily

On April 4th, 2018 we learned about

Staying warm in a hot spring lowers Japanese macaques’ stress hormones

Humans have enjoyed bathing in Japanese hot springs, or onsen, since at least 712 AD. The other local primates, macaque monkeys (Macaca fuscata), took a bit longer to catch on, waiting until 1963 to take a dip in the geothermally warmed waters. That first female apparently told her friends though, because the hotel where she took her bath was shortly swarmed with other bathing macaques. Rather than potty train every furry guest, certain springs were designated as exclusive to the macaques, eventually leading the founding of the Jigokudani Monkey Park in Nagano. The hot springs have only grown in popularity since that first bath, but researchers have only recently been able to confirm why the monkeys have adopted this unusual behavior.

To a human bather, the motivation for the bathing monkeys may seem obvious. Judging by the somewhat serene looks on the macaques’ faces, it’s safe to assume that they enjoy their visits to the onsen for the same reasons we do- the warm water is relaxing and pleasant. The fact that the monkeys are more likely to use the hot springs in the winter further supports the idea that they’re just interested in warming up when the weather gets cold. However, only one-third of the female monkeys living in the park seem to bathe, suggesting that this behavior may have a bit more nuance to it than a desire for hot water.

Measuring stress hormones in the monkeys’ scat

While the macaques are now adept at mimicking human bathing in the onsen, they’re not about to answer questions about their motivations. So researchers looked to their lack of hygiene for answers, testing the poop of various individuals for levels of stress hormones like faecal glucocorticoid (fGC). As expected, the warm water helped the monkeys maintain their body temperature, lowering stress levels. Less obviously, dominant females were found to demand more access to the warm pools, but also raise their stress levels more in various conflicts with other monkeys. So every bather benefited, but dominant females felt more of a swing between their stressed and relaxed moments.

So it’s not a huge surprise that our fellow primates enjoy a warm bath in cold weather, but it’s important for wildlife managers to understand. These monkeys have not only adopted behavior modeled by humans, but they’ve also grown accustomed to being fed barley over the winters in the park, partially to keep them in the area for the pleasure of tourists. These are some significant changes in behaviors, which may prove to have implications in the macaques’ health and reproduction. At this point, only 50 or so monkeys are actually bathing on a regular basis, but it’s worth understanding what that means to the macaques if humans are actively protecting this change in their ecology.

Source: Spa therapy helps Japan's snow monkeys cope with the cold, Science Daily

On April 3rd, 2018 we learned about

Living in the sea limits how big or small a marine mammal can be

50 million years ago, a dog-sized mammal called Pakicetus apparently decided that it was increasingly tired of walking on its own legs like a sucker. Why use energy to support one’s own weight on land when it’s so much easier to just float in the water? Growing bigger would essentially be “free,” since a larger body would also provide more buoyancy, meaning there’d be no limit to how big an aquatic mammal could get. That line of thinking seemed to work out for Pakicetus‘ descendants, who now include blue whales as the largest animal to ever live on Earth. The only problem is that it seems to be wrong, as new analysis shows how marine mammals are actually in a tightly-constrained balancing act between large bodies and the difficulty of finding enough food to feed them.

Bounded by body heat and hunger

This study doesn’t dispute the idea that whales are bigger the average terrestrial mammal. Whales and walruses are big, but they have to be. In fact, they have to fall in a very narrow range of body sizes, unlike the diversity of creatures you find on land. So while a Eurasian water shrew (Neomys fodiens) is fine only growing a half-ounce body, any mammal living in the ocean needs to scale-up their body so that they don’t shed more heat into the water than their metabolism can keep up with. After a survey of 3,859 living and 2,999 extinct species, it would seem that the oceans require mammals, on average, to be at least 1,000 pounds, which is a pretty high floor to contend with.

That big, but warm, body creates its own constraints. Warm blooded mammals need a lot of food to operate, a need that scales up the larger an animal grows. So while a sperm whale (Physeter macrocephalus) can withstand cold temperatures deep underwater thanks to its thick body and layers of blubber, it’s probably as big as any hunter can get without inventing protein shakes to make calorie delivery easier. The big picture is that marine mammals simply can’t be as diverse as their counterparts on land because they’re trapped between the cold water and energetic demands of maintaining a big body.

Explaining the outliers

Of course, sea lions aren’t the smallest mammals in the ocean, and sperm whales aren’t the biggest. However, outliers like sea otters (Enhydra lutris) and blue whales (Balaenoptera musculus) don’t necessarily disprove this model, because they’re both cheating to achieve their smaller and larger sizes. Otters do live in cold water, but not 24 hours a day. When they are in the water, their thick fur helps make up for the lack of insulation in their 50 pound bodies. Finally, sea otters are a relative newcomer to the ocean, probably adopting their semi-aquatic lifestyle in the last seven million years. If it eventually makes sense for them to spend more time in the open sea, they could very well balloon up to look more like seals and sea lions, probably giving up their fur in the process.

Blue and other filter-feeding whales have outgrown their toothed cousins by making significant changes to how these cetaceans eat. By giving up biting and chewing, they’ve managed to make their calorie intake more efficient, gobbling up over one thousand pounds of krill in a single mouthful. This doesn’t mean that filter-feeding removes the all calorie constraints on an animal’s growth any more than swimming freed animals from the work of walking on legs. It has helped whales grow larger, although they still have to work at it, carefully managing when and how to lunge for food so they don’t waste energy propelling their huge mass through the water. As such, we’re unlikely to see any animal grow much larger than a blue whale, unless they somehow simplify their calorie intake even further.

Maybe it’s time we introduced them to milkshakes so they can stop collecting krill like suckers?

Source: Why are whales so big? by Stanford's School of Earth, Energy & Environmental Sciences, Science Daily

On March 13th, 2018 we learned about

Wing size gives larger hummingbirds an edge on metabolic efficiency

Hovering is an enormously demanding task for hummingbirds. The smallest bee hummingbirds (Mellisuga helenae) to the largest Giant hummingbirds (Patagona gigas) all have to flap their wings at least 50 times a second to stay aloft. Since they all feed on nectar from flowers and feeders, it makes sense that these creatures would invest in this ability, but that doesn’t explain their size differences. What advantage would a Giant hummingbird, which has ten times the mass of a bee hummingbird, gain by weighing so much more? An investigation into the birds’ metabolisms found that fighting gravity isn’t the only concern a hummingbird faces when flying out for feeding time.

It is true that larger animals face a bigger tug from gravity, and have more inertia to overcome when they want to move. Other studies have even found a sort of speed-limit for creatures of different sizes, as being big just requires more work. However, being tiny doesn’t always mean a creature is more efficient in its movements. The fact that smaller hummingbird species generally have to flap their wings more times per second suggests that they may have inefficiently small wings. Thus slightly larger species may be making up for their extra weight by simply being better at pushing air with their wider wingspans.

Measuring burn-rates in their breath

Instead of measuring the lift capabilities of each bird’s wings, researchers quantified hummingbird efficiency by seeing how hard their metabolism worked while hovering. Birds from 25 different species of hummingbird were trained to use special feeders equipped with something like a breathalyzer, but instead of measuring alcohol, it measured the bird’s oxygen and carbon dioxide levels. By comparing how much oxygen was inhaled, and how much carbon dioxide was exhaled, the rate of metabolic activity could be calculated and compared, allowing researchers to skip worrying about aerodynamics, weight, etc. The effect of all those factors would be boiled down to just how hard each bird had to work in order to stay in the air.

As predicted by the wing flaps, larger hummingbirds turned up with slower metabolic function than smaller hummingbirds. As they a body gets bigger, it seems that the gains from the wings outpace the penalty of extra mass, at least to a point (even Giant hummingbirds weigh less than an ounce.) Researchers suspect that this may explain why larger species generally live at higher elevations. Higher elevations have thinner air with less oxygen, and so the birds that live their need to be more efficient with their movements to get by. If smaller species tried to live in the same environment, they’d have to flap even faster to stay in the air, burning that limited oxygen even more. The difficulty of that scenario means that they stayed where the air is thicker, seceding that ecological niche to their larger kin.

Source: When it comes to fuel efficiency, size matters for hummingbirds by University of Toronto, Phys.org

On March 12th, 2018 we learned about

The Chirocopter drone observes bats from up close by flying among them

Bats are some of the most advanced aerialists on the planet, but they’re hard to observe in the wild. Between flying in the dark and navigating with ultrasonic sounds human ears can’t hear, it’s difficult to make observations about how bats conduct themselves without the help of technology. For a long time, that’s been done with microphones and cameras on fixed towers, although that limits the distance and viewing angles from which researchers could gather data. Now with a modified quadcopter, nicknamed the Chirocopter, biologists can gather much more dynamic, detailed data on bat behavior from within the moving center of colony of flying bats.

Observing from the air

The Chirocopter gets its name from bats’ scientific order Chiroptera, although the device doesn’t bear much resemblance to the animals it’s meant to study. Like other bat observation posts, the drone carries thermal imaging cameras and microphones to listen in on bat’s high-pitched vocalizations. The major advantage is that Chirocopter’s mobility allows it to position these tools in much closer to proximity to the animal’s its observing, allowing researchers to more easily match specific echolocation vocalizations to activity seen on the camera. This should allow them to start to ‘decode’ when a bat uses a certain squeak, and how it then uses that information to plot its trajectory, somehow avoiding collisions with the thousands of swarming animals flying around it.

Of course, Chirocopter’s four propellers aren’t exactly silent either. To avoid overwhelming their recordings with sounds of the buzzing motors, or reflecting the bats’ echolocation, Chirocopter’s microphone was housed in large, Styrofoam ball, which acted as a lightweight but effective insulator. Overall, Chirocopter was likely quite conspicuous to the bats it observed on its initial test runs, but that probably helped avoid any collisions between the flying mammals and the drone.

Chirocopter’s first tests were just outside a cave in New Mexico, recording 84 minutes of activity from a colony of Brazilian free-tailed bats. At heights ranging from 16 to 160 feet above the ground, the drone recorded 3,847 echolocation signals, or around 46 chirps per minute. When comparing that activity to what was seen on the quadcopter’s camera, researchers realized that bats were sometimes diving at speeds of up to 62 miles-per-hour.

Smarter drones and safer bats

The success of Chirocopter is suggesting a number of paths for further development. Once the methods of the bats’ flight are better understood, that data may help inform how we program future drones to fly and maneuver without collisions. In the more immediate future, researchers are looking to expand where Chirocopter will be used, such as near wind turbines that may be a health hazard for bats in flight. Chirocopter’s microphones may also be altered to target other ranges of sound, making the device useful for tracking other animals’ vocalizations, although that would also require a new name, of course.

Source: With “Chirocopter” Bat-Detecting Drone, Scientists Are No Longer In The Dark by Sarah Whittaker, Drone Below

On March 8th, 2018 we learned about

Reptiles’ detachable tails first evolved, and died out, with Permian era lizards

As a general rule, you don’t want cracks in your bones. Then again, you probably don’t want to lose major portions of your anatomy either, and yet lizards apparently love this survival strategy to have had it evolve at least twice in their history. Known as autotomy, this seemingly unpleasant strategy is actually a way that prey animals can stay safe, as their lost tail can confuse or distract a predator long enough for the rest of the lizard (or crab or even mouse!) escape to safety.

Autotomy was thought to have first evolved in Lepidosaurs, or non-crocodile or turtle reptiles, around 70 million years ago. However, fossils indicate that captorhinids, a group of small reptiles from the Permian period 251 million years ago were also dropping their tails to avoid danger. These small omnivores and herbivores weren’t much of a match for larger predators of their time, but they managed to escape being eaten enough to spread across the lost supercontinent of Pangea. Captorhinus and its relatives seem to have been the only reptiles making use of autotomy at the time, and it may have been the critical component that let them dominate their ecological niche. On the other hand, since Captorhinus effectively had a monopoly on autotomy in the Permian period, when they went extinct they apparently took their pre-cracked tails with them.

Best way to break one’s tail bones

The cracks in question aren’t the long, skinny fissures you’d imagine in a fractured bone. They look more like small perforations, similar to the holes between paper towels or toilet paper squares. They worked the same way, as they basically created a point where stress on a yanked tail would be concentrated, ensuring the tail would break at exactly that point as cleanly as possible. Since jettisoning one’s tail is such a high-stakes maneuver, modern lizards with this kind of “intravertebral autotomy,” give themselves a bit more control with muscles that can contract to help break the bone. That’s followed-up by muscle contractions around the caudal artery to minimize bleeding. With no soft tissue preserved, we can’t say for sure if captorhinids also had this kind of control with their version of autotomy, but controlling bleeding seems like an useful adaptation in any era.

Many Captorhinus fossils have been found, allowing researchers to see how an individual’s age changed their bones. The intravertebral autotomy-enabling cracks were more pronounced in young animals than in adults, which makes sense since younger lizards would be at greater risk of predation (similar to just about every animal on Earth).

My third-grader asked: Does it hurt to lose a tail? What if it doesn’t tear off right, like when you rip a paper towel wrong?

There’s no information about lizards appearing to be in pain after dropping their tails, which makes sense from the perspective of survival. The animal’s goal is to escape, and being gripped by pain would probably just be a distraction in the critical moment they’re trying to avoid being eaten. That said, not every break is clean— pet owners are advised that if their lizard’s dropped tail is accompanied by heavy or continuous bleeding, something has gone wrong and the animal will need veterinary care.

Even when things go smoothly, caudal autotomy is still a taxing course of action. The lizard will have to invest more energy in healing and growing a new tail, while at the same time suffering from reduced balance, a loss of fat storage and lacking an escape route if a predator attacks too soon.

Source: Ancient reptile Captorhinus could detach its tail to escape predator's grasp by University of Toronto, Science Daily

On March 7th, 2018 we learned about

Studies investigate what kinds of interactions and incentives dogs find most motivating

Dogs are famous for their devotion and loyalty, but that doesn’t mean they don’t have preferences about how we interact with them. Does Spot really want that chew toy, or maybe some kibble? In a variety of tests, researchers are finding that most dogs generally prefer to interact with people. Especially squeaky people.

A dog’s favorite form of discourse

For many people, a dog is a member of the family, most often treated as some sort of proxy baby that doesn’t need diapers. That dynamic is frequently expressed in the way people talk to their dogs, adopting a higher-pitched, sing-song cadence similar to a parent cooing to their baby. Some studies have suggested that puppies may enjoy that attention, but adult dogs outgrow it, leaving humans to squeak at the dogs for our own emotional satisfaction. However, that study simply played recorded voices to dogs without a human in view, so adult dogs may have felt there wasn’t a human to show interest in no matter what the voice sounded like.

To investigate dogs’ favorite style of conversation further, researchers had people speak to dogs in a variety of speech patterns. By having participants speak to their dogs about dog- or human-focused topics in “doggy” or normal speech patterns, researchers could see if the style or topics of a human’s words mattered more to a listening dog. So for example, if a human talking about going to the movies in a squeaky voice held a dog’s attention, it would indicate that dogs are listening more for style than for substance.

The results are that dogs are fairly picky about how humans talk to them. They certainly preferred doggy speak about doggy topics over more human-oriented speech patterns, and showed no preference either way when those attributes were mixed and matched. So if you really need your dog to listen, raise the pitch of your voice, and make sure it’s something your dog is interested in in the first place.

Friends versus food

Of course, knowing what a dog is really interested in might not be clear either. As much as a dog seems happy to see their owner, that affection can sometimes feel overshadowed by the dog’s anticipation for her next meal. To find out how companionship really stacks up next to food or other external rewards, dogs were tested in a variety of circumstances, complete with brain scans to see what part of their brains were stimulated in different scenarios. Were people more enticing than toys? How about toys versus treats? A final test literally pitted owners against bowls of dog treats in a simple Y-shaped maze, forcing the dog to pick one over the other.

For almost all the dogs in the study, attention from their human was preferred over material rewards. This interest was seen both in direct behavior, and in the brain activity of dogs who picked their owners over toys and snacks. This doesn’t mean that the more treat-oriented dogs should be written off as asocial ingrates though- researchers pointed out that being motivated by a delayed, material reward instead of immediate companionship is actually a great trait for a dog doing rescue work, where they can’t be getting tummy rubs all day long.

Source: Who's a good boy? Why 'dog-speak' is important for bonding with your pet by University of York, Phys.org