Giddy up! New study reveals some crocodiles can gallop

Transcript

The water's edge is indisputably the reptile's domain, but veterinary scientists have discovered some species of crocodiles are pretty agile on land too.

In fact, some crocs can gallop.

"We discovered this behaviour in several species of crocodiles that were never known to do it before," John Hutchinson, evolutionary biomechanics professor at the Royal Veterinary College in London, told As It Happens guest host Helen Mann.

"They go airborne, which is pretty cool. ... Their hind limbs launch them off the ground. Then they go airborne and land on their front legs and their backbone bends up and down as they do that."

Hutchinson was the lead researcher on the study, which documented galloping in five different species of crocodile. The findings were published this month in the journal Scientific Reports.

Hutchinson says the idea to study the reptile's locomotion came about when he looked through the existing scientific research. He found references of crocodiles galloping and decided to do a more comprehensive study.

"No one had ever described any sort of alligator or caiman using that kind of locomotion," Hutchinson said. 

"Whereas, there were plenty of descriptions of crocodiles doing it. So we decided to really look carefully, which no one had done before."

Hutchinson says the origin of the gait is still unknown.

"That is the million-dollar question," he said. "The long-standing idea has been that it's a very old way of moving that the ancient, extinct ancestors of crocodiles had."

In the Triassic period, the ancestors of crocodiles looked very different, Hutchinson said. He compared them to a cat-like, semi-aquatic creature.

"They were very long-legged — long, skinny legs," Hutchinson said. "And very terrestrial. They had not gone into the water really so much. So they look like they were built to move quickly."

In order to test which species of crocodiles still possessed the galloping trait, Hutchinson and his team built a simple runway for the crocodiles to move — and, ideally, gallop — through. 

"We released crocodiles at one end and tried to encourage them to move to the other end past some cameras," Hutchinson said.

But the crocodiles were unpredictable. Some charged the cameras, and Hutchinson said encouraging them to run was a challenge. 

"They would just sit there and do nothing or hiss or just kind of be annoyed," he said. "They were tough animals to work with — hard to motivate."

Once Hutchinson and his team got the reptiles moving there were other problems.

"They'd climb over the walls of the runway. They'd burst through the walls. Once we had a glass wall and immediately as we set that glass wall up one of the big crocodiles just smashed it," Hutchinson said. "Lots of hijinx."

The galloping behaviour is primarily an escape response, he said. Often, only the younger and smaller crocodiles will break into a full gallop if they feel threatened.

Hutchinson says crocodiles can hit about five metres per second at their top speed — which, thankfully, is still slower than a human can run.

"It's still pretty impressive for a reptile like that," Hutchinson said.

The other surprising finding was that further down the crocodile family tree, the galloping trait is lost. Alligators and caimans can't gallop, but they can still reach similar speeds by trotting.

"The cool remaining mystery is did they lose that ability from their ancestors, or did they never have it?" he said. 

"The fossils suggest that they lost it — that it was always there in the ancestors and alligators therefore have lost it for some reason. But then, why?"

As for the old adage that if you're being chased by a crocodile or gator, it's best to run in a zig-zag, Hutchinson says as long as you don't get ambushed near the water's edge, you should be fine.

"That'll work — but a straight line works probably even better. I would just run away," Hutchinson said.

As predators, crocodiles are near perfect. They've mastered the surprise ambush. With a swift snap of their impressive jaws, they pull unsuspecting prey into the murky depths they patrol. 

"They can accelerate quickly. But once they get going, they reach their top speed pretty fast and we can outrun them in a few steps."

Written by John McGill. Interview with John Hutchinson produced by Samantha Lui.