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These Baby Birds Puke on Predators with Third-Hand Weapons

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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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Big Questions
Why Can't Dogs Eat Chocolate?
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Even if you don’t have a dog, you probably know that they can’t eat chocolate; it’s one of the most well-known toxic substances for canines (and felines, for that matter). But just what is it about chocolate that is so toxic to dogs? Why can't dogs eat chocolate when we eat it all the time without incident?

It comes down to theobromine, a chemical in chocolate that humans can metabolize easily, but dogs cannot. “They just can’t break it down as fast as humans and so therefore, when they consume it, it can cause illness,” Mike Topper, president of the American Veterinary Medical Association, tells Mental Floss.

The toxic effects of this slow metabolization can range from a mild upset stomach to seizures, heart failure, and even death. If your dog does eat chocolate, they may get thirsty, have diarrhea, and become hyperactive and shaky. If things get really bad, that hyperactivity could turn into seizures, and they could develop an arrhythmia and have a heart attack.

While cats are even more sensitive to theobromine, they’re less likely to eat chocolate in the first place. They’re much more picky eaters, and some research has found that they can’t taste sweetness. Dogs, on the other hand, are much more likely to sit at your feet with those big, mournful eyes begging for a taste of whatever you're eating, including chocolate. (They've also been known to just swipe it off the counter when you’re not looking.)

If your dog gets a hold of your favorite candy bar, it’s best to get them to the vet within two hours. The theobromine is metabolized slowly, “therefore, if we can get it out of the stomach there will be less there to metabolize,” Topper says. Your vet might be able to induce vomiting and give your dog activated charcoal to block the absorption of the theobromine. Intravenous fluids can also help flush it out of your dog’s system before it becomes lethal.

The toxicity varies based on what kind of chocolate it is (milk chocolate has a lower dose of theobromine than dark chocolate, and baking chocolate has an especially concentrated dose), the size of your dog, and whether or not the dog has preexisting health problems, like kidney or heart issues. While any dog is going to get sick, a small, old, or unhealthy dog won't be able to handle the toxic effects as well as a large, young, healthy dog could. “A Great Dane who eats two Hershey’s kisses may not have the same [reaction] that a miniature Chihuahua that eats four Hershey’s kisses has,” Topper explains. The former might only get diarrhea, while the latter probably needs veterinary attention.

Even if you have a big dog, you shouldn’t just play it by ear, though. PetMD has a handy calculator to see just what risk levels your dog faces if he or she eats chocolate, based on the dog’s size and the amount eaten. But if your dog has already ingested chocolate, petMD shouldn’t be your go-to source. Call your vet's office, where they are already familiar with your dog’s size, age, and condition. They can give you the best advice on how toxic the dose might be and how urgent the situation is.

So if your dog eats chocolate, you’re better off paying a few hundred dollars at the vet to make your dog puke than waiting until it’s too late.

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
7 Fun Facts for World Elephant Day
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Happy World Elephant Day! Celebrate the occasion with some facts about everyone's favorite gentle giant. 

1. ELEPHANTS CAN RECOGNIZE OTHER ELEPHANT CARCASSES.

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The University of Sussex's Karen McComb told National Geographic that elephants "become excited and agitated if they come across a dead elephant," and, in particular, will investigate skulls and tusks. McComb teamed up with researchers at the Amboseli Elephant Research Project in Kenya to study the behavior, showing wild elephants a range of objects that included skulls. They found that the elephants examined skulls—and tusks in particular—of their own kind twice as long as other skulls, and examined tusks six times as long as they did pieces of wood. They were even able to recognize elephant skulls with the tusks removed, but didn't show preference for certain elephant skulls over others, which suggests they didn't know which skulls belonged to their own relatives. "Animals that are intensely social in life may be most likely to display an interest in their dead," McComb told National Geographic. "But what goes on in their minds while they are doing this is a total mystery."

2. THEY'RE SCARED OF BEES.

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Forget about mice scaring off elephants: When farmers need to keep elephants away from their crops, they should use bees. Researchers in Kenya discovered that even the recorded sound of buzzing bees was enough to make elephants retreat—and cause them to emit low-frequency sound, inaudible to humans, that warns other elephants. "It's impossible to cover Africa in electric fences," Lucy King, author of the paper, told the Huffington Post. "The infrastructure doesn't exist in many places and it would restrict animals' movement." But something like a bee fence—hives strung on strong wires a certain distance apart that would move when elephants walked into them, disturbing the hives—"could be a better way to direct elephants away from farmers' crops," she said.

3. THEY MIGHT UNDERSTAND POINTING.

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Human adults and babies often use pointing as a way to nonverbally get a message across, but not many other animals grasp the concept. But according to a two-month study of 11 tame African elephants, these pachyderms might be able to: When presented with two identical buckets and pointed in the direction of the one containing food, elephants picked up on the cue fairly consistently: Elephants had a success rate of 67.5 percent (1-year-old humans have a success rate of 72.7 percent). But an earlier study of Asian elephants indicated that they don’t notice pointing gestures, which is a bit of a mystery.

4. ONE ELEPHANT CAN "TALK." 

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Koshik, an elephant in a South Korean zoo, developed the ability to imitate the sounds of five words he's heard from his trainer—annyeong (hello), anja (sit down), aniya (no), nuwo (lie down), and joa (good)—by sticking his trunk in his mouth. The scientists who first noticed Koshik’s ability speculate that he learned to “talk” because he was lonely.

5. THEY'RE DIGITIGRADES.

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It's Latin for "finger walking," and what it means is that elephants walk on their toes (there are five of them, as well a sixth false toe). According to the book Mammal Anatomy: An Illustrated Guidemost of the animals' weight "rests on a broad pad of elastic tissue behind the toes" which "acts as a shock absorber and prevents the skeleton from jolting too much when the animals walk. It also allows elephants to move surprisingly quietly despite their size."

6. AN ELEPHANT PREGNANCY LASTS ABOUT TWO YEARS.

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If you thought being pregnant for nine months was bad, be glad you're not an elephant, which can be pregnant for up to 680 days, according to the BBC. All that time in the oven has a benefit, though: Elephant calves are born with highly-developed brains, capable of learning their herds’ complex social structures and ready to put their trunks to use.

7. NINETY-SIX ELEPHANTS ARE KILLED IN AFRICA EVERY DAY.

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Unfortunately, elephant poaching remains a very big problem: An estimated 35,000 elephants are killed annually, their tusks sold illegally in the ivory market. Do the math, and that comes out to nearly 96 elephants every day. Find out what you can do to help elephants and stop poaching at 96Elephants.org.

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