London: Few animals have a less intimidating public image than the tortoise, but for the first time a study has found that they are also hunters that will, given the opportunity, kill and eat other animals.
Dr Justin Gerlach, of Cambridge University’s Museum of Zoology, was involved in a conservation project on Fregate Island, a private island in the Seychelles. Anna Zora, his colleague, caught on camera the first direct evidence of a tortoise hunting when she stumbled across an adult female pursuing a bird chick that had fallen out of its nest and was standing on a log.
The bird, a tern, was too young to fly and feared leaving the log and hopping on to the ground because it would likely have been eaten by a lizard or crab. Zora saw the footage of the incident after returning home from a day of counting the island’s tern population on July 30 last year.
A 45-centrimetre female giant tortoise had seen the chick and made a beeline for it at walking pace. The reptile approached with its mouth open and tongue retracted, a sign of tortoise aggression.
The tortoise was unrelenting in its slow pursuit of the bird and kept pushing forwards, constantly trying to bite the chick, who was becoming increasingly distressed, say researchers.
“The chick tried to defend itself by pecking at the tortoise without making contact, and fluttering its wings,” they added in their paper, published in Current Biology.
But as the bird reached the end of the log and ran out of space, it was faced with a decision: ignore its hard-wired fear of the forest floor, hop off the log and run away from the current threat; or stay on the log and take its chances with the rampaging tortoise.
It opted for the latter and the consequences were fatal. The tortoise’s next attack landed and its jaws clamped around the head of the bird and killed it instantly. The tortoise picked up the bird, which had tumbled to the floor, and swallowed it whole.
The pursuit and killing of the chick took 92 seconds, Gerlach said. He also said that, previously, there had only been anecdotal reports of tortoises crushing and eating other animals, but no hard evidence.
“Eating other animals was not surprising, pretty much any herbivore will eat a bit of meat if it comes across it, it’s a bit of free extra protein, so eating carrion is expected. But actually killing was astonishing to see,” said Gerlach.
“This video clearly shows deliberate pursuit and killing of another animal, which can only be described as hunting.
“It’s more than simple opportunism, in that it saw the chick from a distance and made a direct approach to it. It didn’t just find itself next to the chick and take a lucky bite.”
However, their lack of speed and dexterity mean the tortoises are still one of the least efficient predators on the planet.
“In most ecosystems, potential prey would be too fast or agile for giant tortoises. For birds, only flightless chicks that will not attempt to run away would be vulnerable,” they wrote.
The Telegraph, London
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