On February 21st, 2018 we learned about

The sounds of snapping shrimp used by scientists, and whales, to estimate the abundance of coastal wildlife

Your alarm clock may play soft, soothing sounds of distant waves to help you nod off to sleep, but you’re only getting a tiny portion of the cacophony of noise echoing through the ocean. From whale greetings to acoustic gravity waves, there are a lot of vibrations moving through the water. Researchers are learning to listen in more carefully, as these sounds are a great way to monitor what’s happening in underwater ecosystems, although they may be a bit late to the party. Some studies are finding that the residents of the ocean, like Pacific gray whales, may regularly be tuning into specific sounds as indirect indicators of where to find a bite to eat.

Popping as a population proxy

One of the louder sea creatures capturing human and cetacean ears is the snapping shrimp. Like its infamous cousin, the mantis shrimp, this crustacean can snap its claw shut so quickly that it causes a tiny, temporary vacuum in the water, called a cavitation bubble. That bubble then collapses, releasing a lot of energy in the process, hopefully stunning the shrimp’s prey so it can capture its dinner. Like less dramatic bubbles, the bubbles also make a loud popping noise that can be heard from a considerable distance away.

When enough snapping shrimps are hunting at once, these pops start to sound like a bit like something sizzling and splattering in hot oil. Because it’s coming from groups of shrimp hunting at once, researchers have started using the sound to estimate shrimp populations and activity levels. For instance, summer waters off the coast of North Carolina see a 15 decibel increase, as shrimp crackle and pop up to 2,000 times a minute. In the winter, they calm down considerably, with no more than 100 pops being recorded in a minute.

Signaling snack time

Snapping shrimp surprised researchers off the coast of Oregon when they dipped a hydrophone into the water. The shrimp were previously unknown in the area, and yet they were clearly turning up in sizable numbers in researchers’ recordings. What’s more, the researchers apparently weren’t the only one’s listening for snapping shrimp, as Pacific gray whales often turned up when the shrimp started hunting.

The whales weren’t following the popping sounds to eat the shrimp though, as the noisy crustaceans just aren’t part of their diet. The best guess at this point is that the whales understood that the shrimp’s activity meant there was other food nearby. Since so much of the ocean is essentially devoid of food, following the sound of the popping bubbles saves the whales a lot of trouble. They’ve learned that when the shrimp are hunting, there’s probably something for whales to eat in the same location. With whales’ keen sense of hearing, the noisy bubbles must be hard to ignore.

Like those whales, ecologists are looking to figure out just how reliable a signal the snapping shrimp can be. If they’re consistent enough, listening for the sound of shrimp bubbles may be a relatively quick and inexpensive way to assess the health of coastal ecosystems, and maybe find some hungry whales at the same time.

Source: Snapping Shrimp May Act as 'Dinner Bell' For Gray Whales Off Oregon Coast, AGU.org

On February 14th, 2018 we learned about

Magpies’ mental capabilities may stem from the size of their social circle

As a brain-heavy species, it can be hard for humans to imagine how more brains aren’t always the best option for an animal’s evolution. After all, without our cognitive abilities, how could we synthesize medicines, build rockets, and argue on social media all day? Oddly enough, as stupid as the “discussions” on social media can feel sometimes, they may be a part of what drives cognitive development in the long run. A study of highly social birds has found a correlation between social interactions, intelligence and even reproductive success. At least for Australian magpies, a bigger social group seems to be tied to better problem solving and a fitter family.

Like other crows, ravens other notably-brainy birds, Australian magpies (Gymnorhina tibicen) are very social animals with excellent memories. In the course of their 25- to 30-year life spans, they can build lifelong bonds with their social groups, which can vary anywhere from three to 12 birds in a flock. Like crows, they’ve even been known to learn the faces of specific humans, remembering how those humans treated them in the past to interact more appropriately in the future. This alone seems like a benefit of their intelligence, but clearly that intelligence has been developing before the birds had to react to humans on a daily basis. It’s been hypothesized that needing to understand and interact with their fellow magpies may have been enough to push the birds’ brain development.

Better brains from bigger groups

To test the connection between a magpie’s social group and problem solving skills, researchers tested individual wild birds with different sorts of tasks, generally designed around gaining access to some food. The birds were different ages, but all generally younger to reduce the chance that they would have prior experience with these tasks. The challenges consisted of things like retrieving food from a clear tube, requiring the bird stop approaching it directly from the side of the tube, and muster the self-control to go after it from the ends where an opening was. Another task required that the birds remember a specific color cue over time to earn a food reward.

In each case, birds that lived with larger social groups performed better than those that lived in smaller groups. That alone doesn’t really explain the origin of the birds’ intelligence though, as it doesn’t demonstrate that one attribute lead to the other. However, researchers also found that the more successful female magpies tended to have more offspring than their more befuddled peers. Since the average magpie only has a 14 percent chance of successfully breeding, even a small reproductive advantage would be important. While this doesn’t specify how problem solving or living in a large group directly benefits reproduction, there’s a least a model for how these traits would be propagating in the magpie population.

My third-grader asked: What if the bigger groups just have more teamwork to solve problems? Or what if they can share more information with each other?

By working with juvenile birds, they hopefully had to approach their food-finding tasks without prior knowledge of how to solve them. With that said, magpies have been observed watching and apparently learning from each other’s behavior, so the idea that these birds are sharing knowledge as some kind of culture can’t be written off entirely.

Source: Large-group living boosts magpie intelligence by University of Exeter, Science Daily

On February 13th, 2018 we learned about

Panda’s plant-eating triggered a transformation in their taste-buds

In a move that may baffle veggie-fearing kids everywhere, pandas are trying to get better at tasting bitterness. While human diets today often include safe amounts of bitter greens, those flavors are generally the result of toxins a plant produces to avoid being eaten. The trick to being a plant-eater then is to be able to taste which leaves are delicious and which might be deadly. Since pandas’ ancestors used to be carnivores, their taste buds are now playing catch-up with their modern, bamboo-centric diet.

Tracking genes for taste-buds

Panda’s taste-transition was recorded in their DNA. Researchers analyzed genomes from both red (Ailurus fulgens) and giant pandas (Ailuropoda melanoleuca), comparing them to carnivorous relatives like polar bears, wolves and tigers. There was special interest in genes known to encode for umami taste receptors, which can detect the flavor of meat, and bitter receptors, which detect toxins in plants. Since pandas likely started giving up meat only seven million years ago, it was expected that many of the changes to their genome would stand out as recent modifications.

As predicted, there was a lot of activity with these genes for taste receptors. One of the earliest changes was dropping the ability to taste umami altogether. Without any kind of flesh, fungi or marine plants like nori in their diets, these receptors would be a waste of real estate on the panda’s tongues. Instead, pandas apparently started increasing the number of active copies of genes in the TAS2R family, which detect bitterness. Every creature wants to have some sense of bitterness in their mouths, but while carnivorous cousins only have 10 to 14 copies of these genes, pandas are now carrying around 16. One gene in particular, TAS2R42, was found to be accumulating mutations at a notable clip, suggesting that individuals with working copies of this gene were notably more likely to survive and spread it further through the gene pool. As one would expect, natural selection has been driving this increase to help pandas to more safely navigate their bamboo-based diet.

Making progress on plant-eating

This transition from meat to potentially-toxic plants probably isn’t complete. Panda’s still sport sharp canine teeth from their meat-eating days, and their digestive tract is notoriously slow at extracting nutrients from bamboo. It’s unknown exactly how specific their new sensitivity to bitter flavors is at this point, although researchers are now working on matching panda’s taste buds to the particular bitter compounds found in bamboo. At the very least, there’s probably further room for improvement, as pandas still have fewer bitter taste receptors than other herbivores. This may be part of the reason they’re so picky about which plants they eat, as they’re not really ready to safely taste flora other than bamboo.

Source: Panda tongues evolved to protect them from toxins, study suggests by Erica Tennenhouse, Science

On February 12th, 2018 we learned about

Cheetahs’ high speeds are viable thanks to their uniquely-sized inner ears

Cheetahs don’t run fast to set records. They run to catch food. From that perspective, it makes sense that some of their most important adaptations aren’t only found in their long legs or flexible spines, but in their heads to help guide them towards their prey. A study of the big cats’ inner ears has found that they’re possibly the most advanced, and most recently developed, feature that helps cheetahs not just run after, but also catch their elusive prey.

Inner ears aren’t used for hearing. They’re a specialized structure in the skull that tells vertebrates how their heads are oriented, like the accelerometers in your phone or video game controller. Each inner ear consists of three semicircular canals that contain fluid and sensitive hair cells. The fluid levels off thanks to gravity, tickling some hair cells but not others. With each canal handling a different direction of motion, such as side-to-side versus tilt, the combined data can be used by the brain to figure out how a head is not only oriented, but how it’s moving through space. This kind of information is crucial for movement and balance, especially when that movement is coming from a 65 mile-per-hour sprint after an unpredictable gazelle.

Steering at top speed

For a cheetah (Acinonyx jubatus) to stay on target, it needs to maintain visual contact with its prey. Even when their body is careening in a new direction, cheetahs do a great job at keeping their head steady so they can keep track of how their prey is moving. Researchers suspected that their inner ears were somehow enhanced to make this possible, and started scanning the skulls of cheetahs and other big cats with X-ray computed tomography, giving them a detailed, 3D view of how each animal’s ears worked. As expected, cheetahs were found to have larger and longer inner ear canals than other cats, which would give the fluid and hair cells more granularity in the signals they could provide. To put it another way, these super-sized sensors could pick up smaller variations in tilt and movement, plus have a slightly bigger range before those signals were “maxed out” at one extreme or the other.

By including the skulls of extinct cat species in this study, researchers were also able to estimate when cheetahs acquired this degree of sophistication in their inner ears. An extinct relative, Acinonyx pardinensis, was also specialized for running, but its ear canals wouldn’t have provided the same feedback found in a modern cheetah. That bulkier relative lived only a few hundred-thousand years ago, showing just how recently this line of cats evolved this degree of sensitivity. That timing may make sense, since A. pardinensis probably wasn’t as fast as a modern cheetah either, and thus didn’t need quite as much control and maneuverability as today’s record-holding runners. As top speeds increased over time, it seems that the sensors and feedback systems to help the animal steer grew as well.

My third-grader asked: If balance is connected to your ear, do deaf people have problems with balance?

They can. One estimate says that as many as 30 percent of deaf people may experience some kind of persistent balance problem. Apparently the cause of the hearing loss, such as meningitis versus  something like Usher’s Syndrome, can affect how severe the balance issues may be.

Source: Cheetahs' inner ear is one-of-a-kind, vital to high-speed hunting by American Museum of Natural History, EurekAlert!

On February 11th, 2018 we learned about

Migrating mallards may be moving a considerable quantity of seeds and spores in their stool

A nearby park has become home to over a growing number of both domesticated and mallard ducks. At busier times, it almost seems like the shores of the two artificial ponds are completely lined with ducks. This naturally means that the plants and paths nearby end up nearly completely covered in poop, to the point where my four-year-old is looks like he’s playing hop-scotch to avoid stepping in it. Soiled shoes aside, the poop from the mallards in particular may be making an important impact on the ecology of the park. Since those birds migrate from other locales, they’re likely bringing seeds and spores with them, although scientists are only just starting to measure how much of an impact their poop might make.

Deposits from digestive tracts

The duck poop at my local park wasn’t tested, but a more extensive study was recently completed that looked specifically at mallard (Anas platyrhynchos) migration in central and eastern Europe. Even ignoring the larger seasonal migrations these ducks make each year, a mallard may fly as far as 12 miles in 30 minutes, giving them ample opportunity to disperse seeds around an ecosystem. Scientists knew that seeds may sometimes get stuck to the birds’ wings or feet, but this was the first serious look at ducks’ endozoochory, or seed and spore dispersal, as a product of their digestive tracts. Basically, the question was how many seeds are these birds eating and indirectly planting in new places?

The 200 fecal samples collected in the wetlands of Hungary showed a fair amount of diversity. 21 species of flowering plants were found, including 13 that were terrestrial enough to grow outside a pond. More unusually, the duck poop was also turned up with spores from the watermoss Salvinia natans. This adds mallards to the short list of animals like deer, mice and fruit bats, that was previously known to help spread ferns across large distances. So while most expectations about seed and spore dispersal point to frugivores, or fruit-eaters, it turns out that the common mallard may also be shaping ecosystems around the world.

How significant are these seeds?

The full extent of the ducks’ poop isn’t known yet. While they clearly carried a number of plants seeds in their stomachs, the most frequently found seed was for the fig Ficus carcica, and none of those seeds seemed to actually germinate in their new Hungarian home. This is probably good news, as some less-welcome seeds were discovered as well. The hackberry tree is normally found in North America, and while only one such seed was found in this sample, it would likely function as an invasive species around the wetlands of Hungary. The combination of both diversity and unpredictable germination suggests that we really need to find out more about what these ducks are depositing around or ponds, parks and paths.

Source: Duck faeces shed light on plant seed dispersal by Sabrina Weiss, British Ecological Society

On February 7th, 2018 we learned about

Skin temperature may offer a less intrusive way to measure wildlife’s well-being

Mood rings may soon be making a comeback, at least among the animal conservation crowd. While jewelry for animals probably isn’t a great idea, the underlying principle that skin temperature is tied to a creature’s overall well-being does make sense. Thanks to improvements in thermal imaging cameras, biologists can now measure an animal’s temperature from afar, avoiding the need for intrusive practices like trapping and sedating an animal just to see how healthy it is. Even better, the gaudy rings are now unnecessary too.

The basic idea behind a mood ring is that your stress levels affect your skin temperature. As your body is stressed, or even just concentrating on a difficult problem, blood is diverted from less critical anatomy, like your fingers and nose, towards areas that are likely to need more oxygen and nutrients, like your brain and major organs. The reduced blood flow in those skinny extremities leads to lower temperatures, which in the case of a mood ring causes the liquid crystals in the ‘stone’ to change color, not unlike some thermometers.

Finding clues in birds’ faces

These changes in blood flow have now been confirmed in animals such as the blue tit (Cyanistes caeruleus). Rather than rely on an object in contact with the bird’s skin, thermal imaging of their face may provide enough detail to tell which birds are doing well and which are being affected by poor nutrition or health. Blood was found to be reduced in the area around the blue tit’s eye in particular, a correlation later verified by measuring the level of cortisol, a stress hormone, in the bird’s blood.

As this method is validated in other species, it should allow for easier surveys of animal welfare without the need for a blood sample. This would be more pleasant for the animals who wouldn’t need to be captured and handled by humans, but also allow for measurements of animals that are just too difficult to capture on a regular basis. So surveys of wildlife could be expanded to a wider range of species, giving scientists a more complete picture of how a particular ecosystem is functioning.

Source: Thermal imaging can detect how animals are coping with their environment, avoiding the need for capture by University of Glasgow, Phys.org

On January 29th, 2018 we learned about

New Caledonian crows’ clearly profit from the care and craftsmanship they put into their tools

As the world’s premier tool-users, humans are used to living in, with, and sometimes even for, our stuff. We put enormous amounts of resources into making our tools, trinkets and other creations in a way that most organisms on Earth wouldn’t begin to understand. New Calendonian crows probably ‘get’ us though, as they not only make use of tools, but appreciate them enough to craft and care for them as well.

Making and maintaining a high-quality hook

Now, the toolbox of a New Caledonian crow (Corvus moneduloides) is relatively simple, since they only worry about one thing— a hook that’s used to pull bugs out of crevices. The forest-dwelling birds have been observed carefully selecting twigs from specific plants so that they can be bent into something resembling a crochet-hook, allowing the birds to dig their dinners out of trees and rocks. Younger crows are more likely to put extra effort into this process, using their beaks to clip twigs instead of simply yanking on them, which earns them a deeper, more efficient hook to work with. Researchers suspect that there’s possibly a trade-off in durability at play here, but in either case the birds aren’t finding objects that can be used as tools— they’re specifically crafting a device for a specific purpose.

The crows seem to appreciate the investment and utility this craftsmanship represents. While no hooked stick lasts forever, New Caledonian crows will try to care for their hooks as best they can. Since they can’t eat while holding their hooked sticks, they’ll carefully tuck their tools into loose park on a tree, under their foot, or in any other crevice that will keep things secure. Appropriately, the higher the crow is in a tree, the more careful the bird will be about keeping their tool safe, presumably to avoid losing it among other branches and leaves if it fell. When crows do end up dropping their hooks, researchers have reported that the birds can become visibly upset or frustrated by the loss. (Note: at this point, my third-grader feels compelled to demonstrate this behavior by stomping around the room and pouting.)

Is the extra work worth it?

Of course, from an evolutionary standpoint, the big question is if the hooks are really that helpful. The crows are putting time and effort into crafting these sticks, and the spread of this behavior suggests that its advantageous, but that’s not necessarily proof that the hooks are really worth the time it takes to make them. To rule out other explanations, (is the IKEA effect at play here?) researchers simply checked on how the hooks change the birds’ feeding habits. While the winkle beetles the crows were after needed some kind of stick to be pried from their hiding places, researchers compared how well straight sticks performed against a well-crafted hook.

The results were very clear— a good hook makes a big difference. Hooked sticks were two- to ten-times more efficient than their more basic counterparts. So unless a young crow spends an entire day perfecting their hook’s design, taking the time to make a good hook is worth it. The birds will more easily fill their own bellies, giving them more time to keep themselves safe, find mates, etc. In the long run, the investment in creating tools has even been linked to longer life spans and more offspring, which is a rather affirming notion for us tool-loving humans to hear.

Source: New Caledonian crows extract prey faster with complex hooked tools by University of St Andrews, Phys.org

On January 28th, 2018 we learned about

Slow prey present special challenges to big predatory cats

Cheetahs probably wish their favorite food was faster. This isn’t because they want to burn more calories during every hunt, or necessarily have some deep enjoyment of speed. It’s because the hardest impalas (Aepyceros melampus) to catch aren’t the fastest runners, but the individuals who move slower and less predictably. Rather than race the fastest runners on Earth past their 60 mile-an-hour speeds, evolution has taken prey species in a different direction, or rather, as many different directions as they can manage, in order to out-maneuver the cats that want to eat them.

To test the dynamics between predators and prey, lions, cheetahs, zebras and impalas were outfitted with motion-sensing collars. While none of the test subject directly interacted, researchers were able to use the compiled speed, acceleration and directional data to build a model about how each species interacts. What became clear was that a zebra or impala that tried to simply outrun a lion or cheetah respectively was doing the cat a favor— an animal running at top speed can’t change directions very well, nor can it adjust its speed to avoid the final lunge of a chase. Instead, the most successful targets moved at slower speeds, enabling them to dodge and surprise their pursuer. Outmaneuvering the cats effectively put the prey in the driver’s seat, greatly increasing their chances of survival.

The roles of size, speed and strength

This isn’t to discount the physicality of these encounters. A zebra couldn’t hope to outrun or out-maneuver a cheetah, but their relative size allows them to scare those cats away. An impala could simply out-run a lion, but is an attractive size for a cheetah to tackle. Even when properly matched up in these ways, the cats still hold an athletic edge over their targets, as they were on average 38 percent faster, 37 better accelerators, and pound-for-pound were simply more powerful, with 20 percent stronger muscles. This would be a hard evolutionary race for prey to catch up with, so it makes sense that they’ve come to survive by learning to swerve at just the right moments.

As much as an impala running at full-speed would help a cheetah out, there’s an upside for predators here too. Big cats catch around one-third of the prey they chase, which is apparently just enough to keep them healthy if hungry. This balancing point then helps avoid over-hunting a herd, which may fill a cat’s belly in the short-term, but could lead to a food shortage if the herd’s population is stressed too far. Even if they can’t see every facet of the relationship, it’s probably good that these big cats can’t catch everything they chase after.

Source: Big cats in evolutionary arms race with prey: study by Marlowe Hood, Phys.org

On January 21st, 2018 we learned about

Rooster’s skulls automatically cover their ears when they crow

Some animals establish dominance with size alone. Others sprout elaborate, bony growths from their heads to smash against their rivals. Roosters have developed a more obnoxious display of their personal prowess, crowing before sunrise every day to tell everyone within earshot where their territory starts and ends. While the timing of this announcement makes it unpleasant enough, roosters can actually crow loud enough to permanently damage your ears. This has led them to have to evolve defenses against their own voices, since it seems that roosters don’t want to hear themselves any more than the rest of us do.

A pleasant morning sound, like a percolating coffee maker, is only around 55 decibels. Human voices are usually between 60 to 70 decibels, and bad alarm clock is likely to be around 80. However, roosters can eclipse all these sounds, eclipsing even the volume of a police siren. To get a specific measurement, researchers attached microphones to roosters’ ears, and found that the birds crow between 100 to 143 decibels. While 100 decibels is manageable, anything over 120 decibels creates enough air pressure to damage one’s hearing. Since roosters aren’t commonly deaf themselves, researchers then investigated their anatomy to see how they survived their own sounds.

The trick is that a rooster will never hear itself at full volume. Micro-CT scans of their ear and other skull anatomy found that when their beaks open to crow, their ear canals are mechanically protected. 25 percent of the ear canal is closed when the bird’s beak is wide open, and soft tissues end up closing another 50 percent of the eardrum. So instead of getting a full dose of their own voice, a crowing rooster only hears a portion of their own output.

Safer away from the sound’s source

Other chickens in the area are protected from hearing loss primary thanks to how sound travels across distances. The media and geometry of an area make a huge difference in how far a sound will travel, which has driven different species of birds to specialize in higher or lower sounds. For instance, a loud, low-pitched hum will be audible in dense foliage at a greater distance than higher-pitched tweets. In the case of roosters, even open air causes a fair amount of drop-off, reducing a 120-decibel crow to only 100 decibels just a few feet away. So even without mechanically blocking their ear drums, hens aren’t likely to be literally deafened each morning by a rooster’s crow.

If that weren’t enough protection, the hens also have a better chance to recover from hearing loss than humans do. The inner hair cells that get destroyed when exposed to sounds over 120 decibels heal regenerate faster in birds, ensuring they never miss a chance to be woken up by a rooster’s ear-splitting crowing.

Source: Roosters Have Special Ears So They Don’t Crow Themselves To Deaf by Christie Wilcox, Science Sushi

On January 15th, 2018 we learned about

The surprisingly specialized movements that let snakes scoot in a straight line

At long last, one snakes’ defining abilities has been explained. While not quite as flashy as venomous fangs or heat-detecting sensory organs, a snake’s ability to crawl forward in a straight line without bending its body is a trait that was probably instrumental in their evolution, as it enabled them to invade the burrows of their prey more easily. As it turns out, scooting along without scrunching up isn’t such a straightforward process.

To measure exactly how a snake engages in “rectilinear locomotion,” or crawls in a straight line, researchers needed to measure their movements both inside and out. Boa constrictors were outfitted with electrodes for an electromyogram (EMG), which could keep track of the electrical impulses sent to different muscle groups in the crawling snake. While those readings kept track of the exact sequence of muscular activities inside the snake, it was also filmed while wearing reference markers on its skin, similar to motion-capture suits used in special effects. The combined data let researchers piece together exactly how the boa would manage its movement as it moves through the jungle.

Most of the propulsion is thanks to the snake’s abs. The skin along the stomach was seen to stretch forward in sections, followed by the muscles along the ribs and spine. Sections of the snake’s belly would “reach” forward at a time, almost like a pulse of movement that would start at the head then continue down towards the tail. Even though each muscle group would be making discrete cycles of movement, this activity was so coordinated that the backbones actually end up moving at a constant speed.

Sliding and sticking with scales

Previous studies have found that belly-flexing is likely aided by a snake’s scales. By dragging snakes across different surfaces, researchers found that the stomach scales reduce friction when moving forward, but resist sliding backwards. While a treaded stomach would greatly complement the belly-flexing motions measured with the boa constrictor above, it’s still only part of how a snake can maneuver. They were also found to employ “dynamic weight distribution,” wherein they can control which part of their body is pressing against the ground the most, further gaining traction while reducing friction at the same time. That movement may play a role in rectilinear locomotion, but it likely plays a bigger part in snakes’ other forms of slithering, like sidewinding and serpentine motions.

A boost to biomimicry

This understanding of snake movement is good news for robotisists. A snake’s ability to move through narrow spaces to catch prey makes them a great model for robots that need to investigate pipelines or look through rubble to find disaster victims. Those robots probably don’t need to worry about imitating a boa’s constricting motions, but being able to reliably crawl forward in a space just wider than their mechanical bodies would be of great use to engineers.

Source: Researchers explain how snakes can crawl in a straight line by Michael Miller, Phys.org