The giant tortoise, one of world’s slowest vegetarians, has just ruined its diet.
Researchers have recorded the first known footage of a tortoise killing and devouring a baby bird, in a startlingly slow-motion attack by an animal that typically only eats plants.
The July 2020 footage shows a giant tortoise preying upon a tern chick on Fregate Island, one of the Seychelles islands in the Indian Ocean.
The video plays out like a slasher movie, if the relentless killer were a giant tortoise.
The Terminator-like tortoise marches slowly and determinedly along a log toward the tern chick, ignoring its attempts to defend itself with its wings. The tern hops away a few times but the tortoise just keeps coming, opening its mouth as it draws nearer before chomping down on the little bird’s head with one bite.
Researchers say the tern died immediately and that the tortoise picked it up and swallowed it whole.
Terns can be heard screeching in the background throughout the kill, though it’s unlikely they were reacting to the tortoise’s unexpectedly bloodthirsty turn.
“This is completely unexpected behaviour and has never been seen before in wild tortoises,” lead researcher Justin Gerlach said in a statement released by his school, the University of Cambridge.
“The giant tortoise pursued the tern chick along a log, finally killing the chick and eating it. It was a very slow encounter, with the tortoise moving at its normal, slow walking pace — the whole interaction took seven minutes and was quite horrifying.”
The footage was recorded by Anna Zora, a conservation manager on the island and co-author of a study about the incident. The study was published in the journal Current Biology.
“When I saw the tortoise moving in a strange way I sat and watched, and when I realized what it was doing I started filming,” Zora said.
Zora and Gerlach suggest that this is likely not be a lone-wolf killer tortoise, as they’ve seen other tortoises harassing birds in the past. More study is needed to determine how common the tactic is on the island.
Fregate Island is home to about 3,000 giant tortoises and 265,000 noddy terns, the latter of which are known to nest in trees. The terns’ chicks occasionally fall out of their nests before they are able to fly, leaving them vulnerable to predators on the ground — including the occasional killer in a half-shell.
The researchers point out that it’s unusual to see the slow-moving tortoise making a kill, but it’s not completely surprising to see one eating meat, as others have been known to eat carrion when the opportunity presents itself.
“I couldn’t believe what I was seeing,” Gerlach said in a statement released by the journal. “It was horrifying and amazing at the same time.”
He added that there are plenty of plants available for a hungry tortoise on the island, so there must be a more bloodthirsty motivation for this sort of behaviour.
“It’s clear that they enjoy eating terns,” he said. “Compared to the ease of eating plants, they’re going to quite a lot of trouble.”