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Why Do Cicadas Spend So Much Time Underground?

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In 1996, the cicadas of Brood II (the “East Coast Brood”) swarmed the northeastern United States and then disappeared almost as quickly as they came, leaving only their eggs and molted exoskeletons behind. Once the eggs hatched, the new generation of cicada nymphs crawled underground, where they’ve spent the last 17 years biding their time and living off of tree roots. 

This year, when the time is right and the soil is warm, they’ll emerge again to molt, enter their adult stage, mate, make a lot of noise, and lay their own eggs. Seventeen years is a long time to hang out underground. It’s long enough for Bill Pullman to go from an awesome fictional president to an awful one. Why do cicadas spend so much time out of sight and out of mind?

Not all cicadas play this long game of hide and seek. Most North American species are “annual cicadas” that have unsynchronized, 2 to 5 year life cycles and emerge every summer. It’s only a handful of species, grouped into broods based on the calendar year they emerge,  that have longer, synchronized life cycles and burst forth, all at once, from the ground every 13 or 17 years. 

These species, known as “periodical” cicadas, have had scientists scratching their heads since at least the 1600s, when a visitor to the American colonies made mention of the mass emergence in first volume of Philosophical Transactions, the oldest scientific journal. For a while, one leading hypothesis was that the long cycles kept broods from emerging at the same time and competing for limited resources. 

Another idea, argued by Stephen Jay Gould in his 1977 book Ever Since Darwin: Reflections in Natural History, is that the cycles protect the cicadas from predators and parasites with shorter life cycles. He wrote:

They are large enough to exceed the life cycle of any predator, but they are also prime numbers (divisible by no integer smaller than themselves). Many potential predators have 2-5 year life cycles. Such cycles are not set by the availability of periodical cicadas (for they peak too often in years of nonemergence), but cicadas might eagerly be harvested when the cycles coincide. Consider a predator with a cycle of five years; if cicadas emerged every 15 years, each bloom would be hit by the predator. By cycling at a large prime number, cicadas minimize the number of coincidences (every 5X17, or 85 years, in this case).”

In other words, staying out of sync with predators’ life cycles keeps the cicadas from becoming a reliable, annual source of food, and keeps the predators from adapting to specialize in hunting them or feeding on them. The hitch is that because cicada emergences are so far apart, Gould’s hypothesis is difficult to test, but mathematical models, like those created by Glenn Webb and Mario Markus, lend his argument some support. 

Even though there are no predators that feed exclusively on periodic cicadas, there are plenty of animals—birds, rodents, snakes, lizards and fish, for example—that will feed on them when they emerge just because they’re there, they’re abundant, they’re easy to catch (cicadas don’t really have any defenses to speak of) and they look about the right size for a meal. 

Fortunately for the cicadas, their abundance works in their favor, at least for some of them. Since so many of them emerge at the same time, the number of cicadas in any one place is far higher than the predators in that place would be able to eat. A few do get eaten, but once the predators are full, the rest can go about the business of mating and egg laying without being harassed. 

If you live in cicada territory (Brood II will emerge in parts of Connecticut, Maryland, New Jersey, New York, North Carolina, Pennsylvania and Virginia) and want to help scientists predict and track their emergence, consider building or buying a soil thermometer and taking part in WNYC’s “Cicada Tracker” citizen science project. 

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Slow Motion Is the Only Way to Appreciate a Chameleon’s Lightning-Fast Tongue
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From the unusual way they walk, to their ability to change color, the evolutionary adaptations of chameleons are pretty bizarre, and some of them remain mysterious even to scientists. Their super-powered tongues, for instance, can dart out so quickly that the movement can barely be seen with the naked eye. But modern high-speed cameras have enabled researchers at the University of South Dakota to observe this appendage at work like never before. The video below, shared over at The Kid Should See This, includes some of that groundbreaking footage, and it's pretty amazing to watch.

Shooting at 3000 frames per second, the camera was able to capture every split-second aspect of the chameleon's tongue strike. Slowed down, the video allows you to see how every component of the process works in harmony: First, muscles in the lizard’s tongue contract like the string of a bow. Then, when that tension is released, the bony base of the tongue shoots forward, pushing the sticky, elastic part toward the chameleon’s prey.

According to Christopher Anderson, one of the scientists who conducted the high-speed camera research, larger chameleons can catapult their tongues forward at distances of one to two times their body length. For smaller chameleons, this distance can reach up to two and a half times their body length. “Small chameleons need to be able to eat more food for their body size than large chameleons,” he tells bioGraphic in the video, “and so by being able to project their tongues proportionately further than these large species, they basically are opening up additional feeding opportunities to themselves that they wouldn’t have if they had a shorter tongue.”

To see one of nature’s greatest hunting tools in action, check out the full video below.

[h/t The Kid Should See This]

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There May Be an Ancient Reason Why Your Dog Eats Poop
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Dogs aren't known for their picky taste in food, but some pups go beyond the normal trash hunting and start rooting around in poop, whether it be their own or a friend's. Just why dogs exhibit this behavior is a scientific mystery. Only some dogs do it, and researchers aren't quite sure where the impulse comes from. But if your dog is a poop eater, it's nearly impossible to steer them away from their favorite feces.

A new study in the journal Veterinary Medicine and Science, spotted by The Washington Post, presents a new theory for what scientists call "canine conspecific coprophagy," or dogs eating dog poop.

In online surveys about domestic dogs' poop-eating habits completed by thousands of pet owners, the researchers found no link between eating poop and a dog's sex, house training, compulsive behavior, or the style of mothering they received as puppies. However, they did find one common link between the poop eaters. Most tended to eat only poop that was less than two days old. According to their data, 85 percent of poop-eaters only go for the fresh stuff.

That timeline is important because it tracks with the lifespan of parasites. And this led the researchers to the following hypothesis: that eating poop is a holdover behavior from domestic dogs' ancestors, who may have had a decent reason to tuck into their friends' poop.

Since their poop has a high chance of containing intestinal parasites, wolves poop far from their dens. But if a sick wolf doesn't quite make it out of the den in time, they might do their business too close to home. A healthier wolf might eat this poop, but the parasite eggs wouldn't have hatched within the first day or two of the feces being dropped. Thus, the healthy wolf would carry the risk of infection away from the den, depositing the eggs they had consumed away in their own, subsequent bowel movements at an appropriate distance before the eggs had the chance to hatch into larvae and transmit the parasite to the pack.

Domestic dogs may just be enacting this behavior instinctively—only for them, there isn't as much danger of them picking up a parasite at home. However, the theory isn't foolproof. The surveys also found that so-called "greedy eaters" were more likely to eat feces than dogs who aren't quite so intense about food. So yes, it could still be about a poop-loving palate.

But really, it's much more pleasant to think about the behavior as a parasite-protection measure than our best pals foraging for a delicious fecal snack. 

[h/t The Washington Post]

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