Animals

Like rolling into a gas station during a road trip, whale sharks use oil and gas rigs as a pit stop during their migrations of thousands of kilometers across the oceans. The human-made structures attract marine life — including the sharks’ favorite snack: plankton. But experts worry that this lure could put the endangered behemoths at risk of ship strike or chemical pollution.

Satellite tracking of whale sharks off the coast of western Australia shows how oil and gas platforms influence the movements of these gentle giants, marine ecologist Ben D’Antonio and colleagues report January 18 in Diversity and Distributions. “As they migrate across the ocean, they are stopping over and moving between features to presumably grab an easy meal before continuing with their migration,” says D’Antonio, of the Australian Institute of Marine Science (AIMS) and University of Western Australia in Perth. More

If your city is getting rattier, climate change may be partially to blame.

In an analysis of 16 cities around the world, those that saw the biggest temperature rises over the years also had more rat complaints over time, researchers report January 31 in Science Advances. Increased urbanization was also connected with more rat reports. The results suggest that higher temperatures may make rats — and the diseases they can spread — even harder to keep at bay. More

Landscapes in Southeast Asia once thought to stifle biological evolution may instead stoke its fires.

Karst ecosystems have been referred to as arks of biodiversity, a term that highlights their biological richness but also implies they merely preserve ancient lineages. These landscapes, with their isolated caves, cliffs and sinkholes, were thought to shelter species from extinction without contributing much to evolution.

But the discovery over the past several years of nearly 200 gecko species in such regions reveals that karsts are far from stagnant. “They’re not museums, but centers of speciation,” says evolutionary biologist Lee Grismer of La Sierra University in Riverside, Calif.

Some geckos from the Cyrtodactylus genus, like this newfound one from Cambodia, are uniquely adapted to thrive in the karst landscapes in Southeast Asia. Their specialized bodies allow them to cling to sheer rock faces.L. Lee Grismer

When Grismer first explored Myanmar’s karst landscapes in 2017, the richness of life hidden within the limestone towers and caves left him stunned. During a 19-day expedition, these ancient rock formations, rising abruptly from the surrounding farmland, revealed geckos so distinct and unexpected that his team identified 12 new species.

Since then, Grismer and his colleagues have ventured into similar formations across Southeast Asia, delving into the evolutionary secrets they harbor. In early 2024, an expedition to western Cambodia uncovered three new species of bent-toed geckos and a slender gecko — all detailed in upcoming papers — bringing the number of gecko species he has described to around 185. “The biodiversity in these landscapes is just off the charts,” Grismer says.

The gecko discoveries highlight this dynamism. Many karst-dwelling geckos belong to Cyrtodactylus, the third largest vertebrate genus in the world with close to 400 species described so far. Geckos of this genus discovered by Grismer and his team are among the most recently evolved members of their groups. They exhibit unique adaptations, such as elongated limbs, larger eyes and flatter heads, that enable them to cling to sheer rock faces, much like expert climbers.

Researchers discovered the Sanpel Cave bent-toed gecko, Cyrtodactylus sanpelensis, in a limestone cave in Myanmar. It was hiding under water running down a stalactite, says evolutionary biologist Lee Grismer. “This has never been observed before,” he says.
L. Lee Grismer

Grismer likens the karst formations to islands in an archipelago. Each formation, he says, serves as an evolutionary microcosm, producing species entirely distinct from neighboring karsts. “Species are coming from completely different species groups and different times throughout history.”

The true extent of gecko diversity in the karsts remains unknown. Grismer and his colleagues have surveyed only about 20 percent of the formations in western Cambodia, and he plans to return there and to Myanmar in 2025. “It wouldn’t surprise me if there are another 200 species out there.” More

“Forever chemicals” are pervasive, and researchers have in recent years been ringing the alarms about the negative impacts on human health. But humans aren’t the only animals to be concerned about.

Freshwater turtles in Australia exposed to per- and polyfluoroalkyl substances, or PFAS, experienced changes to their metabolic functions, environmental biochemist David Beale and colleagues report in the Dec. 15 Science of the Total Environment. “We found a whole range of biomarkers that are indicative of cancer and other health problems within reptiles,” says Beale, of the Commonwealth Scientific and Industrial Research Organisation in Dutton Park, Australia. More

Courtship dazzle in spiders can lose some zing in uncertain climates. Males in places with hard-to-predict rain and temperatures devolve into suitors who woo mostly with cheap, useless gifts.

Researchers have described gift giving in courtship in only 15 or 20 of the world’s more than 50,000 known species of spiders, says evolutionary biologist Maria José Albo of Universidad La República in Montevideo, Uruguay (SN: 7/26/16). Since 2015, she and her lab have focused on spiders that flirt mostly in evenings and nights among the rocks and pebbles of rivers of Uruguay and southern Brazil. More

Pooping whales changed the course of Asha de Vos’ career.

The Sri Lankan marine biologist was aboard a research vessel near her home island in 2003 when she spotted six blue whales congregating. A bright red plume of whale waste was spreading across the water’s surface.

Seeing whale poop, colored red thanks to the whale’s diet, was the first clue that Sri Lanka’s blue whales don’t migrate between feeding and breeding areas.A. de Vos

De Vos, then a master’s student, recalls being “super excited.” What she witnessed went against prevailing dogma: Her textbooks and professors had taught that blue whales, like other large whales, embark on long-distance migrations between colder feeding areas and warmer breeding and calving areas. But seeing whales pooping in tropical waters meant the behemoths must be feasting locally.

Intrigued, de Vos spent the next few years documenting how blue whales near Sri Lanka differ from those elsewhere in the world. For one, the population feeds on shrimp rather than krill. The whales also have unique songs. But the key difference, she realized, is that they remain year-round in the waters between Sri Lanka, Oman and the Maldives — making them the only nonmigratory blue whales in the world. Abundant upwellings of nutrient-rich water from the ocean depths support a steady food supply for the whales.

Eventually, the International Whaling Commission, the intergovernmental body dedicated to protecting whales, recognized Sri Lanka’s blue whales as a distinct subspecies called Balaenoptera musculus indica.

By studying the blue whales around Sri Lanka, marine biologist Asha de Vos discovered they are the only nonmigratory blue whales in the world.Franco Banfi/Nature Picture Library/Alamy Stock Photo

This distinction is crucial for conservation management, explains retired whale biologist Phillip Clapham, formerly of the U.S. National Oceanic and Atmospheric Administration’s National Marine Fisheries Service. Small, localized populations — like the one in Sri Lanka — face higher risks of being wiped out in the face of environmental or human threats, such as deep-sea mining.

More than two decades on, de Vos is now one of Sri Lanka’s most renowned scientists — famed for nurturing the country’s nascent marine biology scene. She is also an ardent champion for greater diversity among researchers in ocean conservation. More

Some tadpoles don’t poop for the first weeks of their lives. At least, that’s the case for Eiffinger’s tree frogs (Kurixalus eiffingeri), scientists report September 22 in Ecology.

Eiffinger’s tree frogs are tiny frogs that live in Taiwan and on two Japanese islands: Ishigaki and Iriomote. The tree-dwelling amphibians lay their eggs in puny puddles, which are often nestled in plant stems, tree hollows and bamboo stumps.

Once the tadpoles hatch, they spend their early lives in these puddles. However, in pools as small as these, there’s not a lot of water to dilute ammonia — a toxic chemical animals release when they pee or poop.

Bun Ito and Yasukazu Okada, biologists from Nagoya University in Japan, now have uncovered the tadpoles’ secret sanitation strategy — self-induced constipation. The tadpoles store their poop in an intestinal pouch until they start to metamorphize into full-fledged frogs.

The tadpoles of Eiffinger’s tree frogs (Kurixalus eiffingeri) spend their first few weeks of life in tiny puddles of water nestled within tree hollows and bamboo stumps.Bun Ito

Ito and Okada raised tadpoles from four different frog species in makeshift nurseries. Once the experiment began, they moved the tadpoles to smaller cribs, plastic cases with a little more than a tablespoon of water. The team measured and compared how much ammonia each species released. They also measured the amount of ammonia each species stored in their guts.

Eiffinger’s tree frog tadpoles released less than half as much ammonia on average than the species that released the most. And compared with two of the other species, the tadpoles kept more ammonia in their guts. The researchers note that unlike Eiffinger’s tree frogs, the other species typically lay their eggs in open ponds where ammonia is easily diluted. More

In 1998, at the age of 22, conservation biologist Ximena Velez-Liendo came face-to-face with South America’s largest carnivore on her first day of field research in Bolivia. Her life changed forever when she turned around to see “this beautiful, amazing bear coming out of the forest,” Velez-Liendo says. “It was like love at first sight.” She thought in that moment: “If I can do anything for you, I’ll do it.”

Also known as spectacled bears, Andean bears are easily recognized by the ring of pale fur that often encircles one or both eyes. Bolivia is home to about 3,000 adult bears, or roughly one-third of the world’s total Andean bears, whose range arcs through five countries along the western edge of South America. Listed as vulnerable by the International Union for Conservation of Nature, or IUCN, the species (Tremarctos ornatus) suffers mainly from habitat loss and conflicts with humans, who sometimes kill the bears in retaliation when bears raid crops or hunt livestock. More