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Snake Moms-To-Be Seek Out Toxic Prey

In the great menagerie of poisonous creatures, there are some animals that don’t make their weapons on their own. Instead, they sequester toxins from other animals that they eat. Many poison dart frogs, for example, get their toxins from insects in their diet. Sometimes, this is just a fringe benefit. The poison pilferer is probably going to eat the poison producer because that’s the prey that’s available, or that’s what they evolved to eat or that’s what they prefer, and the poison they get to use for their own protection is icing on the cake.

But every once in a while, there’s a case where toxic prey is not normally on the menu, and an animal who needs a little poison deliberately seeks it out to boost its defenses. In Japan, zoologists Yosuke Kojima and Akira Mori have found one of these, a snake that switches up its diet when it gets pregnant in order to arm its babies before they’re even born. 

The Ashiu Forest is a mountainous area in Kyoto with diverse habitats like grasslands, forests and rice paddy fields. The area is home to the tiger keelback (Rhabdophis tigrinus), and for most of the year, these snakes split their time evenly between the grasslands and the forests. They usually eat frogs that are plentiful in both places—just two species make up 89 percent of their diet—but will occasionally also eat poisonous toads. From these, they sequester toxins that they use to defend themselves and, by depositing the poison in their eggs, their young.* The toxins, called bufadienolides, find their way into fluid that oozes from glands on the snakes’ necks and irritates the skin and eyes and alters the heart rhythms of would-be predators. Toads that produce bufadienolides are rarer in Ashiu Forest than other prey (an amphibian census taken by Kojima and Mori turned up just 41 of them) and live only in the wooded areas, so they’re a rare treat for the snakes and normally account for only 0.9 percent of their diet. 

By tracking radio-collared snakes for several months and checking their stomach contents, Kojima and Mori found that these patterns in diet and habitat change come May and June. While male keelbacks shun the forests and spend almost all of their time in the grass during these months, pregnant females continue to use the forests, do most of their hunting there and dine mainly on poisonous toads while ignoring their usual prey. 

After ruling out other factors that might explain the change in behavior, Kojima and Mori thought that the females might be seeking out toads so they could provision their eggs with bufadienolides. In late spring and early summer, snakes that mated the previous fall would be about ready to lay their eggs, so the timing made sense. To test that idea, the pair caught male, pregnant female, and non-pregnant female snakes and put them in a Y-shaped maze. Each arm of the “Y” was baited with paper that had been rubbed on either a frog that the snakes typically eat or a toxic toad. When the snakes reached the fork in the path and caught a whiff of the bait, they went into hunting mode and investigated, smelled, and bit the papers. The males and non-pregnant females showed a strong preference for the scent of frogs, but the pregnant females went after the toad-rubbed papers around three times more often than the froggy ones. 

All this points to a shake up in the keelbacks’ diet based on whether or not they’ve got buns in the oven. The snakes appear to deliberately switch their behavior and seek out toxic prey when they’re pregnant, most likely so they could give some of the poison to their young. 

The toads are relatively hard to come by in Ashiu Forest, and the grassland is a much better place for a pregnant snake to be so she can regulate her temperature and that of her developing eggs, so going on a toad-heavy diet isn’t easy. But when keelbacks hatch, they’re highly vulnerable, and unable to steal toxins on their own until they’re big enough to hunt juvenile toads some six months later. Until then, a supply of poison from mom is essential to their survival, so the effort of hunting down toads is well worth it to make sure the kids are alright. 

*The snakes are actually a toxic double threat. They’re not only poisonous thanks to the toads, but also venomous (if you’re curious about the difference, see here). They produce the venom on their own and use it to incapacitate prey. It’s rarely used defensively against predators or bothersome humans because the keelback’s fangs are far back in its mouth and not much use for striking large animals.  

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Big Questions
Why Do Cats 'Blep'?
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As pet owners are well aware, cats are inscrutable creatures. They hiss at bare walls. They invite petting and then answer with scratching ingratitude. Their eyes are wandering globes of murky motivations.

Sometimes, you may catch your cat staring off into the abyss with his or her tongue lolling out of their mouth. This cartoonish expression, which is atypical of a cat’s normally regal air, has been identified as a “blep” by internet cat photo connoisseurs. An example:

Cunning as they are, cats probably don’t have the self-awareness to realize how charming this is. So why do cats really blep?

In a piece for Inverse, cat consultant Amy Shojai expressed the belief that a blep could be associated with the Flehmen response, which describes the act of a cat “smelling” their environment with their tongue. As a cat pants with his or her mouth open, pheromones are collected and passed along to the vomeronasal organ on the roof of their mouth. This typically happens when cats want to learn more about other cats or intriguing scents, like your dirty socks.

While the Flehmen response might precede a blep, it is not precisely a blep. That involves the cat’s mouth being closed while the tongue hangs out listlessly.

Ingrid Johnson, a certified cat behavior consultant through the International Association of Animal Behavior Consultants and the owner of Fundamentally Feline, tells Mental Floss that cat bleps may have several other plausible explanations. “It’s likely they don’t feel it or even realize they’re doing it,” she says. “One reason for that might be that they’re on medication that causes relaxation. Something for anxiety or stress or a muscle relaxer would do it.”

A photo of a cat sticking its tongue out
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If the cat isn’t sedated and unfurling their tongue because they’re high, then it’s possible that an anatomic cause is behind a blep: Johnson says she’s seen several cats display their tongues after having teeth extracted for health reasons. “Canine teeth help keep the tongue in place, so this would be a more common behavior for cats missing teeth, particularly on the bottom.”

A blep might even be breed-specific. Persians, which have been bred to have flat faces, might dangle their tongues because they lack the real estate to store it. “I see it a lot with Persians because there’s just no room to tuck it back in,” Johnson says. A cat may also simply have a Gene Simmons-sized tongue that gets caught on their incisors during a grooming session, leading to repeated bleps.

Whatever the origin, bleps are generally no cause for concern unless they’re doing it on a regular basis. That could be sign of an oral problem with their gums or teeth, prompting an evaluation by a veterinarian. Otherwise, a blep can either be admired—or retracted with a gentle prod of the tongue (provided your cat puts up with that kind of nonsense). “They might put up with touching their tongue, or they may bite or swipe at you,” Johnson says. “It depends on the temperament of the cat.” Considering the possible wrath involved, it may be best to let them blep in peace.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
Why Crows Hold Noisy Funerals for Their Fallen Friends
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The next time you hear a murder of crows cackling for no apparent reason, show a little respect: You may have stumbled onto a crow funeral. Crows are among the few animals that exhibit a social response to a dead member of their species. Though their caws may sound like heartbroken cries, such funerals aren't so much about mourning their fallen friends as they are about learning from their mistakes.

In the video below from the PBS series Deep Look, Kaeli Swift, a researcher at the University of Washington's Avian Conservation Lab, investigates this unusual phenomenon firsthand. She familiarized herself with a group of crows in a Seattle park by feeding them peanuts in the same spot for a few days. After the crows got used to her visits, she returned to the site holding a dead, taxidermied crow and wearing a mask and wig to hide her identity. The crows immediately started their ritual by gathering in the trees and crying in her direction. According to Swift, this behavior is a way for crows to observe whatever might have killed the dead bird and learn to avoid the same fate. Flocking into a large, noisy group provides them protection from the threat if it's still around.

She tested her theory by returning to the same spot the next week without her mask or the stuffed crow. She offered the crows peanuts just as she had done before, only this time the birds were skittish and hesitant to take them from her. The idea that crows remember and learn from their funerals was further supported when she returned wearing the mask and wig. Though she didn't have the dead bird with her this time, the crows were still able to recognize her and squawked at her presence. Even birds that weren't at the funeral learned from the other birds' reactions and joined in the ruckus.

Swift was lucky this group of crows wasn't particularly vengeful. Crows have been known to nurse and spread grudges, sometimes dive-bombing people that have harmed one of their own.

[h/t Deep Look]

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