每日跟讀#754: See you later, trotting alligators: many crocodiles can gallop
Crocodiles have never had a friendly reputation, but they may just have become even scarier. Veterinary scientists have discovered that a surprising number of species are capable of galloping when they reach their top speeds.
Previously it was thought that only a couple of crocodile species were able to use this horse-like gait, but the latest observations show that the ability extends to eight different species. Alligators and caimans, by contrast, can manage only a trot.
Since the gait is shared across many species, the researchers believe galloping may have first emerged in crocodiles’ ancient land-dwelling ancestors, called crocodylomorphs, which were cat-sized creatures with long legs.
John Hutchinson, a specialist in evolutionary biomechanics at the Royal Veterinary College, London, who led the study, said a surprising finding was that despite the different gaits and sizes, almost all the species studied had a top speed of about 18km per hour. “We suspect that bounding and galloping give small crocodiles better acceleration and maneuverability, especially useful for escaping from danger,” he said. “It seems like alligators and caimans stand their ground rather than run away with an extreme gait.”
The researchers found that bigger crocodiles were less likely to gallop, the largest galloping species being a Cuban crocodile, typically measuring more than 2m long. “That’s as big as crocs can get and still bound and gallop,” said Hutchinson. “The Cuban crocs are incredibly active on land and incredibly athletic. This species is notorious for being really aggressive.”
Other, smaller species, were more likely to gallop into the water to escape rather than to chase prey. Hutchinson said galloping appears to have emerged multiple times in evolution in different species, as an energetically efficient way to get around. Some toads and spiders gallop, he said.
The scientists carried out the study at St. Augustine Alligator Farm Zoological Park in Florida, US, where they recorded videos of 42 individuals from 15 species. The creatures were placed at the end of a runway and coaxed to run to the other end. “Every animal it took a different motivation,” said Hutchinson. “Some of them wouldn’t go at all. The caimans and alligators tended to just sit there and hiss and fight.” The findings are published in the journal Scientific Reports.
Source article: http://www.taipeitimes.com/News/lang/archives/2019/12/22/2003727949