Science news in brief: From how flying snakes glide to special eating tricks from dolphins

And other stories from around the world

A paradise tree snake, one of five kinds of flying snakes, glides through the air in Malaysia (Photography by New York Times)

How do flying snakes glide through the air?

Jake Socha, an expert on flying snakes, uses detailed scientific terminology, such as “this big, wiggly, ribbon thing”, to describe his soaring quarry.

It is an apt description, but don’t be fooled. When a snake launches off a tree in its southeast Asian habitat and lands on another tree dozens of feet away, there is nothing random about those wiggles.

A professor of biomedical engineering and mechanics at Virginia Tech, Socha and his colleagues published a study in Nature Physics supporting the hypothesis that the midair undulations (the wiggles) are actually carefully coordinated and highly functional processes that enhance the dynamic stability of the snake in flight.

“I wouldn’t say all the mysteries are solved,” Socha says, “but we have a big piece of the story filled in.”

Flying snakes wiggle and undulate to remain stable in flight (Jake Socha via NYT)

Flying is a bit of a misnomer for what the snakes do. The slithering airborne creatures tend to fall strategically or glide, meaning they do not gain altitude like a bird or an insect. Their flights generally last only a couple of seconds, at a speed of around 25 mph, and they land without injury. To the untrained eye, it might look as if the snake just fell out of a tree by accident, wiggling frantically as it plummets to earth. Not so.

Once it goes airborne – after inching out on a tree limb and pushing off the branch – the snake moves its ribs and muscles to extend the width of its underside, transforming its body into a structure that redirects airflow like a parachute or a wing. A cross-section of the snake’s body midair would show that its normal circular shape becomes triangular and the whole body undulates as it glides towards its target.

Once in Singapore, Socha and a group of researchers witnessed a snake jump from 30 feet up and travel over 60 feet in the air on a windless day.

“It was like an athlete hitting its stride,” he says. “It was like, ‘I know what I’m doing, I’m off and you’ll never see me again.’”

David Waldstein

A broad-tailed hummingbird near Gothic, Colorado (Noah Whiteman via NYT)

Hummingbirds navigate an ultraviolet world we never see

Hummingbirds were already impressive. They move like hurried insects, turn on aerial dimes and extract nectar from flowers with almost surgical precision. But they conceal another talent, too: seeing colours that human eyes can’t perceive.

Ultraviolet light from the sun creates colours throughout the natural world that are never seen by people. But researchers working out of the Rocky Mountain Biological Laboratory reported in Proceedings of the National Academy of Sciences that untrained broad-tailed hummingbirds can use these colours to help them identify sources of food.

Testing 19 pairings of colours, the team found that hummingbirds are picking up on multiple colours beyond those we can see. From the bird’s-eye view, numerous plants and feathers have these as well, suggesting that they live in a richer-hued world than we do, full of signs and messages that we never notice.

Compared with the colour vision of many other animals, that of humans leaves something to be desired. The perception of colour relies on cone cells in the retina, each of which responds to different wavelengths of light. Humans have three kinds of cone cells, which, when light reflects off an apple, a leaf or a field of daffodils, send signals that are combined in the brain to generate the perception of red, green or yellow. Birds, however, have four types of cones, including one that is sensitive to ultraviolet light. (And they are far from the most generously endowed – mantis shrimp, for instance, have 16.)

In lab experiments, birds readily pick up on UV light and UV yellow, a mixture of UV light and visible yellow wavelengths, says Mary Caswell Stoddard, a professor of evolutionary biology at Princeton University and an author of the new study. Likewise, researchers have long known that UV colours are widespread in the natural world, though we can’t see them. However, experiments to see whether wild birds would use UV colours in their daily lives had not yet been performed.

To find out, she and her colleagues spent three summers in a mountain meadow near Gothic, Colorado, watching hundreds of hummingbirds.

Among the wildflowers, the researchers planted an experimental setup: two tripods, each topped with a saucer filled with liquid and a coloured LED light. The lights attached to the tripods often looked identical to the human eye. But in many of the pairings, one was actually a mixture of visible light, like green, red or yellow, and ultraviolet light, while the other produced just the visible light version. To the hummingbirds, the two LEDs would look completely different.

The team tracked around 6,000 visits by passing hummingbirds, which sampled the fluids of these man-made blossoms. They swapped the tripods’ positions when the birds were away, to keep them from simply returning to the same location for a dose of sugar, and kept track of how many times birds chose the saucer with sugar water.

To the researchers’ excitement, it rapidly became clear that distinguishing the colours and learning which signalled food posed no problem for the hummingbirds.

“Even though we expected birds to tell these colours apart, seeing them do it with my own eyes was really remarkable, because these two colour light tubes look identical to me,” Stoddard says. “Watching the birds reveal to us some truth about their visual world was really amazing.”

Veronique Greenwood

A fluorescent image of the visual system of the planarian Schmidtea Mediterranean (Whitehead Institute via NYT)

A worm’s hidden map for growing new eyes

Planarians have unusual talents, to say the least. If you slice one of the tiny flatworms in half, the halves will grow back, giving you two identical worms. Cut a flatworm’s head in two, and it will grow two heads. Cut an eye off a flatworm — it will grow back. Stick an eye on a flatworm that lacks eyes — it’ll take root. Pieces as small as one-279th of a flatworm will turn into new, whole flatworms, given the time.

This process of regeneration has fascinated scientists for more than 200 years, prompting myriad zany, if somewhat macabre, experiments to understand how it is possible for a complex organism to rebuild itself from scratch, over and over and over again. In a paper published in Science, researchers revealed a tantalising glimpse into how the worms’ nervous systems manage this feat.

Specialised cells, the scientists report, point the way for neurons stretching from newly grown eyes to the brain of the worm, helping them connect correctly. The research suggests that cellular guides hidden throughout the planarian body may make it possible for the worm’s newly grown neurons to retrace their steps. Gathering these and other insights from the study of flatworms may someday help scientists interested in helping humans regenerate injured neurons.

Maria Lucila Scimone, a researcher at MIT’s Whitehead Institute for Biomedical Research, first noticed these cells while studying Schmidtea mediterranea, a planarian common to bodies of freshwater in southern Europe and north Africa. During another experiment, she noted that they were expressing a gene involved in regeneration.

“In every animal she looked at, she’d see just a couple of these, right next to the eye,” says Peter Reddien, a professor of biology at MIT and also an author of the paper.

The team looked more closely and realised that some of the regeneration-related cells were positioned at key branching points in the network of nerves between the worms’ eyes and their brains. When the researchers transplanted an eye from one animal to another, the neurons growing from the new eye always grew towards these cells. When the nerve cells reached their target, they kept growing along the route that would take them to the brain. Removing those cells meant the neurons got lost and did not reach the brain.

Veronique Greenwood

An artist’s impression of a species of a 25-million-year-old marsupial named Mukupirna nambensis (Peter Schouten via NYT)

When 300-pound wombats roamed Australia

Wombats and koalas stand out as bizarre animals even in a continent famed for bizarre animals. They are also each other’s closest relatives.

Koalas munch on eucalyptus, resemble living teddy bears and, like Australia’s other imperilled native fauna, they need occasional rescuing. Wombats poop in cubes – yes, cubes – that they leave out and even stack to mark their territory. As for the animal itself, picture a burrowing ball of fuzz and fat powered by muscular little stub-legs.

Now multiply that five times. That’s the size of a new long-lost member of the same animal group, Mukupirna nambensis, a mega-wombat that tipped the scales at well over 300 pounds. Scientists believe it scrounged around in the rainforest soil of Australia some 25 million years ago.

“I would compare it to a black bear,” says Robin Beck, a palaeontologist at the University of Salford in England, who described fossils of the wow-inducing wombat in the journal Scientific Reports.

The hefty species is the newest member of a supersized menagerie. For millions of years up to the present day, big, unique marsupials flourished on Australia and New Guinea, isolated from the rest of the world.

Koalas and wombats are the only surviving remnants of an otherwise extinct group called the vombatiformes, “wombat-like” animals that were more diverse than any other type of marsupials.

Joshua Sokol

An example of ‘shelling’, where a dolphin chases a fish into an empty shell, brings it to the surface and shakes the fish out of the shell and into its mouth (Dolphin Innovation Project via NYT)

Dolphins have an eating trick, but how they learn it is more surprising

When hunger strikes, dolphins don’t mess around.

In Shark Bay, western Australia, these swimming mammals have devised devious tactics to snare slippery prey. In one trick, dolphins chase fish into empty seashells, then chauffeur the shells to the ocean surface, where they use their beaks to jostle the prey into their mouths.

This behaviour, called shelling or conching, is rarely documented by scientists.

“You never know when it’s going to happen,” says Sonja Wild, a behavioural ecologist at the Max Planck Institute of Animal Behaviour in Germany. Wild first witnessed shelling in 2013 and compares the behaviour to dislodging stray crumbs out of a near-empty bag of chips. “It’s really remarkable when all of a sudden there’s a giant shell popping up by the boat, being shaken by a dolphin.”

Most dolphins pick up tool-savvy skills from their mothers, and one might assume that the craft of conching would be inherited, too. But Wild and her colleagues have discovered that the smooth swimmers may also acquire this behaviour by mimicking the movements of unrelated peers. The study, published in Current Biology, adds to a growing body of evidence that toothed whales like dolphins can toggle between learning from both within and outside of their nuclear families, a talent usually associated with orangutans, chimpanzees and us humans.

A team led by Simon Allen, of the University of Bristol, and Michael Krützen, of the University of Zurich, first started surveying Shark Bay’s bottlenose dolphins in 2007. In the 11 years that followed, they amassed genetic and behavioural data on more than 1,000 dolphins, identifying 19 individuals that shelled a total of 42 times.

That’s not much, Wild says. The part of shelling that’s visible to boat-borne researchers – the shell-shimmying at the ocean surface – is fast, often lasting just a few seconds, and researchers are probably undercounting how often it occurs. But the tactic probably isn’t deployed frequently, and certainly not all dolphins do it, she says.

Still, the shellers in the study seemed to have something in common: each other. Though the conch-rattling dolphins weren’t very closely related, a computational analysis showed they belonged to many of the same social networks.

“The more time two individuals spend together, the more likely they are to copy behaviour from one another,” Wild says.

Katherine J Wu

© The New York Times