New in Wildlife Science: Fluorescent Mammals & Penguin Power Naps

Mammals: even more fluorescent than we thought; how chinstrap penguins power nap to protect nests; counting bats with AI

By Mark Wexler
Wildlife Science
Sep 26, 2024

Mammals’ Hidden Glow

Fluorescence—an organism’s ability to absorb ultraviolet (UV) light and reemit it in glowing colors imperceptible to humans—was long considered a rare trait among mammals, showing up in just a handful of obscure species such as wombats, platypuses and springhares (shown under UV light, above right, and natural light, above left). But a recent study suggests that fluorescence is the rule rather than the exception for mammals. Using equipment that analyzes how various objects react under UV light, Australian scientists tested museum specimens of 125 species representing 79 mammalian families. In Royal Society Open Science, they report that all 125 species had fluorescent chemicals in their fur or other body parts—from domestic cats to polar bears to African lions. “Fluorescence basically is the default for mammals,” concludes lead author Kenny Travouillon, curator of mammalogy at the Western Australian Museum. He and his colleagues also confirmed previous thinking that fluorescence is particularly intense in nocturnal mammals, suggesting animals use their glow to help communicate at night. Yet overall, the researchers write, “the biological function of fluorescence remains undetermined.”

An image of a chinstrap penguin in Antarctica.

Penguin Parents Power Nap

To successfully fledge their chicks, nesting chinstrap penguins (above) must remain vigilant. Throughout the birds’ several-month-long nesting season—which starts in November, during Antarctica’s springtime—males and females each spend several days straight guarding their pebble nests from predators while their partners are away feeding. Extended periods of sleep would put the penguins’ offspring at risk of predation, but according to research reported in Science, the birds have evolved a surprising solution: the power nap. For two weeks, an international team of biologists continuously monitored the sleep behavior of several nesting chinstraps in a colony on Antarctica’s King George Island. They discovered that the penguins nod off more than 10,000 times per day—but only for about 4 seconds at a time. Adding up to as many as 11 hours of sleep daily, these “microsleeps” allow the birds to meet their daily sleep needs while still protecting their nests. “What is really weird is that the penguins can sustain this in-between-wake-and-sleep state constantly,” says lead author Paul-Antoine Libourel, an ecophysiologist at France’s National Centre for Scientific Research.

An image of a large group of straw-colored fruit bats in flight during migration.

Counting Bats With A.I.

Each November, scores of straw-colored fruit bats migrate from across Africa to Zambia’s Kasanka National Park (above) to feed on its abundant fruits, departing three months later to disperse across the continent. By scattering seeds as they migrate, the bats help restore degraded land. Calling the mammals “the secret gardeners of Africa,” Dina Dechmann of Germany’s Max Planck Institute of Animal Behavior says, “losing this colony would be devastating.” Yet until now, scientists were unable to estimate the bats’ total numbers. In response, Dechmann and her colleagues developed a novel censusing tool combining GoPro cameras to film the animals and artificial intelligence (AI) to count them. Reporting in Ecosphere, they estimate that nearly 1 million bats are roosting at Kasanka, the continent’s largest bat colony. “We’ve shown that cheap cameras, combined with AI, can monitor large animal populations in ways that would otherwise be impossible,” says lead author Ben Koger, now at the University of Wyoming.

An image of marmoset embryonic stem cells forming neurons.

Microscope

Deep Wells of Cells

There are more living cells (such as marmoset cells, pictured) on Earth—1 million trillion trillion—than stars in the universe or grains of sand on the planet, reports a team of biologists and geologists who published their calculations in Current Biology.