Wikimedia Commons user Christian Svane
Wikimedia Commons user Christian Svane

These Baby Birds Puke on Predators with Third-Hand Weapons

Wikimedia Commons user Christian Svane
Wikimedia Commons user Christian Svane

When Eurasian rollers feed their babies grasshoppers, centipedes, and other insects, the chicks aren’t just getting the nutrition they need to grow—they’re getting an arsenal.

When animals can’t make their own defenses, they often borrow them from elsewhere. Poison dart frogs hang on to the toxic alkaloids in the beetles and mites that they eat, and then secrete the toxins through their skin. The caterpillars of tobacco hornworms eat tobacco leaves and then exhale the nicotine in a cloud of “defensive halitosis.” African crested rats gnaw on the roots and bark of certain trees and then slobber the poison onto their fur. 

Rollers—stocky, blue-and-cinnamon-colored birds related to kingfishers—also take out a chemical loan to defend themselves, but they go through a middleman. Their diets consist mostly of poisonous insects, and they’re not only resistant to the bugs’ toxins, but are able to absorb them and use them for themselves. Many of these insects, in turn, sequester those same toxins after eating poisonous plants that they’d become resistant to. At two different points in the food chain, animals have worked out ways both to defeat and co-opt their meals’ defenses—and chemicals originally produced by plants to protect them get passed around to do the same for other organisms. 

Poison dart frogs advertise their toxicity with bright colors and bold patterns. Young rollers also warn potential predators that they don’t taste good, but do it in a more active, and unsavory, manner—they puke up a pungent orange liquid at them.

Scientists had puzzled for years over roller chicks’ propensity for vomiting. Because it costs the young birds precious bodily fluids, they thought it had to have an important purpose. Deseada Parejo, a biologist at Spain’s Arid Zones Experimental Research Station, first encountered the brightly-colored vomit while she was studying the species’ family dynamics a few years ago. One day, when she plucked a chick from a nest to measure its size and weight, it let about a teaspoon’s worth of vomit loose at her. The next chick she grabbed did the same thing. And the next. And the next. 

She describes the smell of the puke as orange juice and insects, and she’s not the only one who notices it. Roller parents who return to a nest that smells of vomit approach their home more cautiously than usual and spend less time feeding the kids they’d left there, as if they’re scared of something. Maybe the vomit is a defensive reaction, Parejo thought, and the lingering smell also warns the parents that a predator still might be lurking near the nest. 

To test the idea, Parejo and her team went to south-eastern Spain, where they worked with wild rollers to see what they ate, what prompted them to puke, what their vomit contained, and how other animals reacted to the sticky orange liquid. The birds’ diet was almost 90 percent grasshoppers, with some butterflies and centipedes mixed in. What was left of those bugs came back up at the researchers whenever they picked the birds up or moved them, but not when they touched the birds gently or simply got close to them without any contact. The chicks also puked more after they’d just eaten. When the scientists deprived them of food for an hour or more, fewer of the birds puked. 

When Parejo’s team analyzed the vomit, they discovered hydrobenzoic and hydroxycinnamic acids and psoralen, which are all produced by plants to deter pathogens and insects. The same chemicals have been found in the secretions of different grasshoppers and other insects, including ones hunted by rollers.

The pieces were starting to fall into place: The rollers were eating toxic insects, and poisons originally produced by plants had found their way into the birds’ puke. Their vomiting also depended directly on recently consumed food (that is, they didn’t seem to have a way to produce the toxic stew on their own) and they only employed the trick when they were seriously disturbed or harassed. Specifically, Parejo had to grasp and move the chicks, the same way that a predator like a snake or weasel might try to grab one and flee, to get a reaction.

It definitely looked like the puke was a defensive weapon, but did it work? To see if the third-hand poisons would deter the chicks’ predators, the team wetted pieces of chicken meat with either roller vomit or water than then offered both treats to dogs. The pooches overwhelmingly went after the water-covered chicken first, but almost two-thirds of them also ate the vomit meat a few minutes after their first snack. 

This suggests that the smell of the vomit is part of the defensive effect, but that it only works for a short time. Biting a puke-covered, toxin-filled bird would also give the predator a bad taste in their mouth and a serious stomach ache—or worse—but by that time the bird is already in danger of injury or death. What’s the point of the defense, then, if a hatchling might wind up in an animal’s jaws anyway? 

Parejo thinks the underlying strategy has to do with the survival of the nest, and not necessarily every bird in it. If a predator bites or eats one roller chick and doesn’t like the taste, it will probably leave the others alive and seek tastier prey. If the smell of the vomit alone isn’t enough to drive an animal away, the trick still works because it only costs one casualty instead of the whole brood. 

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13 Facts About Opossums
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Opossums, which include the roughly 100 species in the order Didelphimorphia, are some of the most misunderstood animals in the Americas. They’re often thought of as dimwitted, dirty creatures whose most impressive trick is acting like roadkill. The truth is just the opposite: Opossums are smarter, cleaner, and more beneficial to humans than many of their woodland neighbors. Read on for more opossum facts.

1. OPOSSUMS AND POSSUMS AREN’T THE SAME ANIMAL.

In North America, opossum and possum describe the same thing, but in Australia the word possum refers to a completely different animal. Among the most well known of their respective types are the Virginia opossum and the brushtail possum. Both are small to medium sized, omnivorous marsupials, but the similarities end there. The possum looks like a cute cross between a squirrel and a chinchilla and it belongs to a different order than the North American mammal that shares (most of) its name. Despite the potential for confusion, possum is accepted as the shortened version of opossum in this part of the world (and if you see the word possum in this list, you can assume it’s referring to the animal from the Americas).

2. THEY’RE THE ONLY MARSUPIALS FOUND NORTH OF MEXICO.

Marsupials—mammals that carry and nurse their young in pouches—are absent from much of the world, and in Canada and the United States opossums are the sole representatives of the group. Like other marsupials, mother possums give birth to tiny, underdeveloped offspring (called joeys) that immediately crawl into a pouch where they live and nurse during their first months of life. Only once they’ve grown big and strong enough do they venture out, transitioning between their mother’s back and the warmth of the pouch until they mature into adults.

3. THEY CAN’T CHOOSE WHEN THEY PLAY DEAD.

Possum playing dead.
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Perhaps the most famous characteristic of the opossum is its tendency to play dead in front of predators. When the animal experiences intense fear in the face of danger, it seizes up and flops to the ground where it can remain for hours staring blankly ahead and sticking out its tongue. It’s an impressive defensive mechanism, but its effectiveness can’t be chalked up to the possum’s acting skills. Possums have no control over when they play dead or for how long they do it: The comatose-like state is an involuntary reaction triggered by stress.

4. AN OFFENSIVE ODOR SELLS THE PERFORMANCE.

A picture of a possum playing dead doesn’t really do it justice. To get the full experience, you need to be standing over to it to smell the putrid odor it emits when pretending to be a corpse. The smelly substance it secretes from its anus is just one more reason for foxes and bobcats to look for their dinner elsewhere.

5. THEY SLOW THE SPREAD OF LYME DISEASE.

Even if possums aren’t the cutest creatures in the forest, they should be a welcome addition to your backyard. Unlike other mammals that carry ticks, and therefore spread Lyme Disease, possums gobble up 90 percent of the ticks that attach to them. According to the National Wildlife Federation, a single possum consumes 5000 of the parasites per tick season. That means the more possums that are in your area, the fewer ticks you’ll encounter.

6. THEIR MEMORIES ARE SURPRISINGLY SHARP.

Possum looking up at table.
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Opossums have impressive memories—at least when it comes to food. Researchers found that possums are better at remembering which runway led to a tasty treat than rats, cats, dogs, and pigs. They can also recall the smell of toxic substances up to a year after trying them.

7. THEY’RE IMMUNE TO MOST SNAKE VENOM.

While most animals look at a snake and see danger, a possum sees its next meal. The animals are immune to the venom of nearly every type of snake found in their native range, the one exception being the coral snake. Possums take advantage of this adaptation by chowing down on snakes on a regular basis.

Researchers have been trying to harvest possums’ antivenom powers for decades. A few years ago, a team of scientists made progress on this front when they recreated a peptide found in possums and and found that mice given the peptide and rattlesnake venom were successfully protected from the venom’s harmful effects.

8. THEY ALMOST NEVER GET RABIES.

While possums aren’t totally immune to rabies (a few cases have been documented), finding a specimen with the disease is extremely unlikely. Marsupials like possums have a lower body temperature than the placental mammals that dominate North America—in other words, their bodies don’t provide a suitable environment for the virus.

9. THEIR TAIL ACTS AS A FIFTH APPENDAGE.

Baby opossum hanging from a tree branch by its tail.
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Opossums are one of a handful of animals with prehensile tails. These appendages are sometimes used as an extra arm: They can carry grass and leaves for building nests or grip the sides of trees to provide extra stability while climbing. Baby possums can even use their tails to hang from branches upside down as they’re often depicted doing in cartoons. But it’s a myth that possums sleep this way: Their tails are only strong enough to hold them for a short amount of time.

10. THEY’RE CONSTANTLY SELF-GROOMING.

Thanks to their whole acting-and-smelling-like-a-corpse routine, opossums aren’t known as the most sanitary animals in nature. But they take cleanliness seriously: The Washington Department of Fish and Wildlife writes that possums, like housecats, use their tongue and paws to groom themselves frequently and thoroughly. Possums largely lack sweat glands, and this behavior is believed to help them cool down. It also has the added effect of rendering them odorless (when they’re not secreting stinky predator-repellant, that is).

11. THEIR EYES AREN’T TOTALLY BLACK.

Close-up on opossum's face.
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One of the opossum’s most recognizable features is its pair of opaque eyes. Opossum eyes do have whites and irises, but because their pupils are so large, their eyes appear completely black from a distance. The exaggerated pupil dilation is thought to help the nocturnal animals see after the sun goes down.

12. THEY’RE SOCIAL CREATURES.

It was long assumed that opossums like to keep to themselves, but a study published in the journal Biology Letters suggests they have a social side. Researchers at the Federal University of Pernambuco in Recife, Brazil observed some possums in captivity sharing dens even if they weren’t mates. In one case, 13 white-eared opossums of various age groups were cohabiting the same space. The scientists suspect that male and female possums living in the wild may even build nests together as a way to trigger the female’s reproductive hormones.

13. THEIR REPRODUCTIVE SYSTEMS ARE COMPLICATED.

The way it gives birth and raises its young isn’t the only thing that’s interesting about the opossum's reproductive life. Females have two vaginal tracts and two uteri, and males in turn have a forked or bifurcated penis. This is fairly typical for marsupials, but when European colonizers first landed in North America centuries ago, they didn’t know what to make of the confusing genitalia. One explanation they came up with was that male opossums impregnated females through the nose.

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Hero Crayfish Cheats Death By Removing Its Own Claw to Escape Pot of Boiling Water
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There remains a perpetual debate over the ethical consequences of taking a crustacean and boiling it alive. In early 2018, Switzerland actually made it illegal to give living lobsters a scalding hot bath. (Instead, chefs are expected to stun them electronically before submersion.) Scientists can’t reach a conclusion over whether decapods feel pain—or if we can even define what that means for them.

While humans argue, some clawed sacrifices are taking action. A crayfish filmed by a Facebook user in China is making the internet rounds and being hailed as a hero after taking dramatic measures to escape a boiling pot of water.

In the footage, the crayfish appears to be unable to extricate its left appendage from a bubbling vat of doom. Rather than succumb, the crayfish uses its right claw to sever its compromised claw and scurry off. At 11 seconds, it’s the best summary of a Saw film possible.

“Juike,” the user who originally posted the video to the Weibo social media site, says he has taken the crafty invertebrate home and put him in an aquarium as a pet. The tiny survivalist may even regrow his lost limb, as crawfish are able to do, although it might not reach its former size.

Crayfish are in inherent danger of being turned into soup in China, where specialty restaurants devoted to their preparation are popping up. Some observers believe their popularity is due to diners having to step away from phones and social media in order to use both hands to peel away at their shells.

[h/t BBC]

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