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Michael Habib, Pterosaur Flight Expert

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The American Museum of Natural History's latest exhibition, Pterosaurs: Flight in the Age of Dinosaurs, opens today (check out just a few of the things we learned at the exhibit here). At the media preview, we spoke with pterosaur flight expert Dr. Michael Habib about figuring out how these reptiles flew.

When you and other scientists are trying to figure out how pterosaurs flew, do you start with the fossils? Or do you start with an animal alive today because we know the flight mechanics and work backward?

We do a little bit of both. Mostly, you start with fossils. Then you go to the principles of physics—things that are fundamentals that you know are true, because physical laws make them true and they're going to be true for everything. Then you build models from that and validate them using the living things: Does the model make good predictions in birds? Does it make good predictions in bats? If it does, I'm relatively confident that it will make good predictions in pterosaurs.

The trick, of course, is the predictions all have to do with anatomy, and make predictions about the anatomy. To say, "Alright, if this hypothesis is true, then it would look like this and if it was false, it would not look like this." And then you test to see if that is what the anatomy looks like in the animals you have. That's kinda tricky, and part of what you do to make it reasonable, is you pick the tractable questions and tractable approaches. An intractable question for pterosaur flight is "Exactly how fast does a Quetzalcoatlus fly?" And a tractable question is, "Would quetzalcoatlus fly faster or slower than a living large bird?" Comparable questions are more tractable than absolutes.

That question is actually not completely intractable. I can get a good idea of how fast it could probably fly. But I couldn't give you an absolute answer because we don't know exactly what the wing shape was on the animal. So actually the answer would be—it would vary. Flying animals change their speed based on how much fat they've burned on that long trip, for example. They start off as a big fat bird and show up as a little skinny bird. So there is no single answer to that anyway. But I can give you an idea of range. What I can say with more confidence is how pterosaurs would fly relative to certain first principle models and relative living animals.

Pterosaurs came in a huge array of sizes. How would you say the 10 inch little guy, Nemicolopterus cryptus, flies compared to something bigger like Quetzalcoatlus?

Small things tend to be more maneuverable. They fly slowly in terms of mass of speed, but they tend to be more maneuverable. And landing and takeoff is less energetic for them. In this particular case, the animal is not just smaller, it also has other wing characteristics that are associated with highly maneuverable flights, so it would be less efficient but more maneuverable. Quetzalcoatlus would be a faster flyer, overall, because it's so much larger. It would probably be a flat glider that would flap in bursts and they would glide for long periods; it would probably be a soaring animal. Soaring is what we call it when you have an external source of lift—you're gliding, but you're not dropping relative to the ground because you've got some rising air, which is your source of external lift. Quetzalcoatlus probably hunted on the ground and flew between places to eat or escape predators or things like that. 

Would there be differences in take off and landing, too, depending on the animal's size?

We have some good ideas. Take off is sort of my specialty. It turns out that in all fliers—including unpowerfliers like gliding snakes, for example, even flying squirrels, things like that—in all the ones we've measured, launch is effectively ballistic. So the launch is not initiated with the wings. You don't flap yourself into the air, you jump yourself into the air. And then you engage your wings. Now, we don't see that. It's so fast. What it looks like to us is that a pigeon is pulling himself into the air with his wings, but he's actually pushing his feet and then pulling himself higher with his wings. Which might seem like a nitpick, but in terms of physics, it is fundamentally different.

Some animals run into the jump—especially on water; that's mostly where you see them running—some just jump. For pterosaurs, we're fairly certain they would leap as well. Since they walked on both feet and hands, the expectation is that they would probably leap with all four limbs—we call it a quadripedic launch. I have not run the test for all known pterosaurs by any stretch of the imagination. For all the ones I have done analysis on, it appears that that is true, so I would expect small and large ones use quadripedic launch.

That said, a little guy has a much larger room for error than a big one in the sense of, it doesn't have to put as much "oomf" into it. It could, from a power perspective, maybe launch bipedally, but there's no reason to think that it would. A small pterosaur wouldn't have to leap nearly as hard [as a big one] before it could engage its wings. It would probably get relatively much higher, launch more vertically, if it wanted, when it took off.

Big guys would have to launch at a much more shallow angle. That means they need some clearing in front of them in order to take off, which limits their habitat a little bit, and they're going to have to devote a lot of their muscle power to launch, which means you would expect those animals—as per the predictions I’ve mentioned before—if this model were true, you'd expect that there'd be certain anatomical features related to launch that would be exaggerated in big pterosaurs that wouldn't be in small ones. And that seems to hold true. Big pterosaurs are devoting more of their anatomy to that initial takeoff phase because it's a more rigorous phase for them.

What kind of computer programs are you using to model pterosaur flight?

For me personally, I do a lot of my stuff on a Matlab. It's the big bruiser on the market, but it's flexible. The equations it collapses through are surprisingly simple structures. The best expressions are the ones that are as simple as possible. I spend most of my time on a white board, quite frankly.

There's another Jurassic Park movie coming out. What would you want the director to get right about the pterosaurs in that movies if they include them?

Take off is my personal bias. Might as well see if they get that right. And it would actually be kind of embarrassing if they didn't, because they’ve done TV shows and gotten it right. So if Jurassic Park 4 didn't get it right, that would be embarrassing.

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Animals
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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