It may be time to retire the term “gentle giant”.
Researchers in the Seychelles have filmed a giant tortoise chasing and devouring a tern chick in one go. The scientists involved in the discovery say it is the first time that such an act has been caught on camera. Even they are shaken up.
“This is completely surprising and quite terrifying,” says Justin Gerlach, island ecologist at Peterhouse, Cambridge, England. “The turtle purposely chases this bird and kills it and then eats it. So yes, it’s the hunt. “
Giant tortoises, which are now only found in the Seychelles and the Galápagos Islands, were considered herbivores. In fact, their vegetarian diet is believed to have shaped their ecosystems, much like elephants or bison. But in an article published Monday in Current Biology, Dr. Gerlach and Anna Zora, co-authors of the Frégate Island Foundation, that there have been indications that the vigorous reptiles might supplement their diet from time to time. Turtles sometimes eat snail shells and bones from dead birds, goats, and even other turtles. But hunt?
There have been rumors of turtles ambushing seabird chicks who become helpless after falling from their nests. But by the time the video was taken – revealed a scene a bit like PD Eastman’s “Are You My Mother?” if instead it had been written by Roald Dahl – Dr. Gerlach suspected that such an observation was at best a misunderstanding.
“Nobody looked for it because why should you? Turtles don’t hunt, ”said Dr. Gerlach. “You’re not just wasting your time looking for a hunting turtle.”
Now he wonders what more can we learn from these creatures that live to be more than 200 years old and can reach over 500 pounds.
“It’s quite a mystery they’ve uncovered here,” said James Gibbs, a herpetologist at the State University of New York and the Galápagos Conservancy who was not involved in the research.
When Dr. Gibbs watched the video, he was surprised at how slow and cumbersome the attack was.
“It’s a very interesting combination of hard work and incompetence,” he said.
Dr. Gibbs has studied the giant tortoises for about 30 years in the Galápagos Islands, where he said that tortoises have developed strange relationships with birds.
“The turtles will get up and stretch out all their limbs and tails, and finches will come and clean them of ticks,” said Dr. Gibbs. “I’ve heard over the years that the turtles sometimes fall down and flatten the finches and eat them. But those were just anecdotes, and since I’ve spent many, many years there, I’ve never seen it myself. “
But there is no mistaking what is happening in the Seychelles video. In fact, the scientists note that the turtle is showing signs that it previously hunted chicks of sea birds.
For example, when turtles eat leaves, grass or fruit, they stick out their tongues and pull the food into their mouths. But the turtle in the video has withdrawn its tongue and closed its eyes – signs that it is aware of some danger with this food source.
“It behaves differently than with normal feeding,” says Dr. Gerlach. “It’s not just about collecting food. It is deadly to collect food. “
According to Dr. Gibbs, the fact that the giant tortoise is female may be an important clue of the shocking behavior. Island systems typically lack calcium, a critical mineral for building eggshells.
While the video of a giant turtle attacking a helpless tern chick may be difficult for some people to watch, the act of predation could simply be one way the animals are ensuring the success of the next generation.
“We’re used to thinking of them as not particularly interesting, slow, and probably quite stupid,” said Dr. Gerlach about giant tortoises. “But these animals clearly have so much more to offer.”