Enlarge / "The only species of fish confirmed to be able to escape from the digestive tract of the predatory fish after being captured.” (credit: Hasegawa et al./Current Biology)

Imagine you're a Japanese eel, swimming around just minding your own business when—bam! A predatory fish swallows you whole and you only have a few minutes to make your escape before certain death. What's an eel to do? According to a new paper published in the journal Current Biology, Japanese eels opt to back their way out of the digestive tract, tail first, through the esophagus, emerging from the predatory fish's gills.

Per the authors, this is the first such study to observe the behavioral patterns and escape processes of prey within the digestive tract of predators. “At this point, the Japanese eel is the only species of fish confirmed to be able to escape from the digestive tract of the predatory fish after being captured,” co-author Yuha Hasegawa at Nagasaki University in Japan told New Scientist.

There are various strategies in nature for escaping predators after being swallowed. For instance, a parasitic worm called Paragordius tricuspidatus can force its way out of a predator’s system when its host organism is eaten. There was also a fascinating study in 2020 by Japanese scientists on the unusual survival strategy of the aquatic beetle Regimbartia attenuata. They fed a bunch of the beetles to a pond frog (Pelophylax nigromaculatus) under laboratory conditions, expecting the frog to spit the beetle out. That's what happened with prior experiments on bombardier beetles (Pheropsophus jessoensis), which spray toxic chemicals (described as an audible "chemical explosion") when they find themselves inside a toad's gut, inducing the toad to invert its own stomach and vomit them back out.

Conventional wisdom would suggest that all dogs love to play fetch, while most cats would simply refuse to do so. But a new paper published in the journal PLoS ONE suggests that cats not only play fetch with their owners, they do so far more frequently than previously believed. And while most dogs play fetch at least sometimes, about 12 percent do not. More-trainable dog breeds are more likely to exhibit fetching behavior, while in both species, animals that are more active and playful—and usually male—are more likely to enjoy playing fetch, suggesting that it is a form of play.

"We were surprised to find that there were very few studies of fetching behavior in dogs," said co-author Mikel Delgado, a veterinary medicine researcher at Purdue University. "And personally, as a life-long cat person, I have to admit that I thought all dogs fetched. So it was interesting to get a better sense of how common this behavior is in cats and dogs. We hope that the study draws more attention to fetching behavior in cats, who are often portrayed as independent and aloof. In fact, they can be very social, and this is a nice example of one way they are interactive with humans."

As previously reported, many different animal species exhibit play behavior, and it's most common in mammals and birds. Contrary to what one might expect from cats, fetching behavior has been observed across multiple cat breeds all over the world, usually emerging in kittenhood. One owner who participated in a 2022 study noted that their cat was so obsessed with fetch that it would sometimes drop its favorite toy on their face in the middle of the night.

Enlarge / As female macaques age, the size of their social network shrinks. (credit: Jon G. Fuller/VW Pics/Universal Images Group via Getty Images)

Walnut was born on June 3, 1995, at the start of what would become an unusually hot summer, on an island called Rum (pronounced room), the largest of the Small Isles off the west coast of Scotland. We know this because since 1974, researchers have diligently recorded the births of red deer like her, and caught, weighed and marked every calf they could get their hands on—about 9 out of every 10.

Near the cottage in Kilmory on the northern side of the island where the researchers are based, there has been no hunting since the project began, which allowed the deer to relax and get used to human observers. Walnut was a regular there, grazing the invariably short-clipped grass in this popular spot. “She would always just be there in the group, with her sisters and their families,” says biologist Alison Morris, who has lived on Rum for more than 23 years and studies the deer year-round.

Walnut raised 14 offspring, the last one in 2013, when she was 18 years old. In her later years, Morris recalls, Walnut would spend most of her time away from the herd, usually with Vanity, another female (called a hind) of the same age who had never calved. “They were often seen affectionately grooming each other, and after Walnut died of old age in October 2016, at the age of 21—quite extraordinary for a hind—Vanity spent most of her time alone. She died two years later, at the grand age of 23.”

Enlarge / The intrepid three-legged lion Jacob and his brother Tibu prepare for a hunt. (credit: Alexander Braczkowski)

On February 4, scientists monitoring lion populations in Uganda captured nighttime thermal drone footage of two lions—brothers dubbed Jacob and Tibu by the Uganda Wildlife Authority—swimming across the predator-infested Kazinga Channel connecting two lakes, most likely to find mates. While there have been prior reports of lions swimming short distances, Jacob and Tibu covered about 1.5 kilometers (nearly one mile)—the longest swim yet recorded, according to a new paper published in the journal Ecology and Evolution.

"The fact that [Jacob] and his brother Tibu have managed to survive as long as they have in a national park that has experienced significant human pressures and high poaching rates is a feat in itself—our science has shown this population has nearly halved in just five years," said co-author Alexander Braczkowski of Griffith University, who has been working with the government of Uganda since 2017 to monitor the lion population in the area. "His swim, across a channel filled with high densities of hippos and crocodiles, is a record-breaker and is a truly amazing show of resilience in the face of such risk.”

Jacob and Tibu's impressive feat is likely the result of increased pressure from human encroachment, according to Braczkowski. He co-authored a 2020 paper proposing a novel census technique that could be used more broadly as an early warning of lion declines. Their method revealed a worrying movement parameter for both male and female lions in Uganda's Queen Elizabeth National Park, where the home range increased to 3.27 km (a 400 percent increase) for males and 2.22 km (a 100 percent increase) for females—likely a response to systematic prey depletion due to poaching, for example. And the sex ratio was dangerously skewed: one male to 0.75 females, a highly unusual occurrence.

Enlarge / Ariel and Caliban learned as kittens that scratching posts were fair game for their natural claw-sharpening instincts. (credit: Sean Carroll)

Ah, cats. We love our furry feline overlords despite the occasional hairball and their propensity to scratch the furniture to sharpen their claws. The latter is perfectly natural kitty behavior, but overly aggressive scratching is usually perceived as a behavioral problem. Veterinarians frown on taking extreme measures like declawing or even euthanizing such "problematic" cats. But there are alternative science-backed strategies for reducing or redirecting the scratching behavior, according to the authors of a new paper published in the journal Frontiers in Veterinary Science.

This latest study builds on the group's prior research investigating the effects of synthetic feline facial pheromones on undesirable scratching in cats, according to co-author Yasemin Salgirli Demirbas, a veterinary researcher at Ankara University in Turkey. "From the beginning, our research team agreed that it was essential to explore broader factors that might exacerbate this issue, such as those influencing stress and, consequently, scratching behavior in cats," she told Ars. "What’s new in this study is our focus on the individual, environmental, and social dynamics affecting the level of scratching behavior. This perspective aims to enhance our understanding of how human and animal welfare are interconnected in different scenarios."

The study investigated the behavior of 1,211 cats, with data collected via an online questionnaire completed by the cats' caregivers. The first section collected information about the caregivers, while the second asked about the cats' daily routines, social interactions, environments, behaviors, and temperaments. The third and final section gathered information about the frequency and intensity of undesirable scratching behavior in the cats based on a helpful "scratching index."

Enlarge / Extreme sportsman Ross Edgley comes face to face with a great hammerhead shark in the waters of Bimini in the Bahamas. (credit: National Geographic/Nathalie Miles)

Ultra-athlete Ross Edgley is no stranger to pushing his body to extremes. He once ran a marathon while pulling a 1-ton car; ran a triathlon while carrying a 100-pound tree; and climbed a 65-foot rope over and over again until he'd climbed the equivalent of Mt. Everest—all for charity. In 2016, he set the world record for the world's longest staged sea swim around the coastline of Great Britain: 1,780 miles over 157 days.

At one point during that swim, a basking shark appeared and swam alongside Edgley for a day and a half. That experience ignited his curiosity about sharks and eventually led to his new National Geographic documentary, Shark vs. Ross Edgley—part of four full weeks of 2024 SHARKFEST programming. Edgley matches his athletic prowess against four different species of shark. He tries to jump out of the water (polaris) like a great white shark; withstand the G forces produced by a hammerhead shark's fast, rapid turns; mimic the extreme fasting and feasting regimen of a migrating tiger shark; and match the swimming speed of a mako shark.

"I love this idea of having a goal and then reverse-engineering and deconstructing it," Edgley told Ars. "[Sharks are] the ultimate ocean athletes. We just had this idea: what if you're crazy enough to try and follow in the footsteps of four amazing sharks? It's an impossible task. You're going to fail, you're going to be humbled. But in the process, we could use it as a sports/shark science experiment, almost like a Trojan horse to bring science and ocean conservation to a new audience."

Enlarge / A Sixgill Hagfish (Eptatretus hexatrema) in False Bay, South Africa. (credit: Peter Southwood/CC BY-SA 4.0)

The humble hagfish is an ugly, gray, eel-like creature best known for its ability to unleash a cloud of sticky slime onto unsuspecting predators, clogging the gills and suffocating said predators. That's why it's affectionately known as a "snot snake." Hagfish also love to burrow into the deep-sea sediment, but scientists have been unable to observe precisely how they do so because the murky sediment obscures the view. Researchers at Chapman University built a special tank with transparent gelatin to overcome this challenge and get a complete picture of the burrowing behavior, according to a new paper published in the Journal of Experimental Biology.

“For a long time we’ve known that hagfish can burrow into soft sediments, but we had no idea how they do it," said co-author Douglas Fudge, a marine biologist who heads a lab at Chapman devoted to the study of hagfish. "By figuring out how to get hagfish to voluntarily burrow into transparent gelatin, we were able to get the first ever look at this process.”

As previously reported, scientists have been studying hagfish slime for years because it's such an unusual material. It's not like mucus, which dries out and hardens over time. Hagfish slime stays slimy, giving it the consistency of half-solidified gelatin. That's due to long, thread-like fibers in the slime, in addition to the proteins and sugars that make up mucin, the other major component. Those fibers coil up into "skeins" that resemble balls of yarn. When the hagfish lets loose with a shot of slime, the skeins uncoil and combine with the salt water, blowing up more than 10,000 times its original size.