Slow but deadly! ‘Vegetarian’ giant tortoise attacks and EATS a seabird in a ‘horrifying’ encounter filmed in the Seychelles
- Footage of a tortoise hunting a tern was filmed on the Seychelles’ Frégate island
- It is likely that efforts to improve the island habitat led to bird population growth
- This made the birds more readily available and likely to fall to the ground below
- Researchers don’t know if the hunting is a new behaviour or the reappearance of a natural activity that is happening again due to the conservation efforts
In an incredibly unlikely encounter, a ‘vegetarian’ giant tortoise has been filmed attacking a seabird – including biting its head off and consuming the rest.
The event, involving the large reptile and a tern seabird living on the Seychelles’ Frégate island, was ‘completely unexpected,’ according to researchers from the University of Cambridge’s Museum of Zoology, who witnessed the encounter.
It was the first time a tortoise has been caught deliberately hunting prey in the wild – previously they have been seen feeding on bones and snail shells for calcium.
Researchers believe this behaviour was driven by the large 265,000-strong tree-nesting noddy tern colony and the 3,000 tortoises, living closely on the island.
The chick likely fell from the tree above, landing on a log where the giant tortoise slowly approached, and over a seven minute encounter killed and fed on the bird.
In an incredibly unlikely encounter, a ‘vegetarian’ giant tortoise has been filmed attacking a seabird – including biting its head off and consuming the rest
GALAPAGOS GIANT TORTOISE: FAMILY OF MASSIVE REPTILES
The Galapagos giant tortoise is a species of 15 very large tortoises, 12 of 2-3 of which are extinct.
They are the largest living species of tortoise and some can weigh up to 919lb with lifespans of over 100 years.
The number of giant tortoises in the wild declined from over 250,000 in the 16th Century to about 3,000 today, due to hunting and habitat clearance.
While they are seen as herbivores, one species in Frégate island has been seen eating seabirds whole.
They have also been known to consume snail shells and bones, assumed to be for extra calcium.
The hunting on Frégate island may have been the result of habitat conservation driving population growth in noddy tern seabirds.
The ground under the colony is littered with dropped birds and chicks that have fallen from their nests.
The ‘hunting camera’ video shows the bird standing there as the tortoise approaches, suggesting this type of interaction happens frequently.
In most places, potential prey are too fast or agile to be caught by giant tortoises.
On the Galapagos and Seychelles islands, giant tortoises are the largest herbivores and eat up to 11 per cent of the vegetation.
They also play an important role in dispersing seeds, breaking vegetation and eroding rocks.
That is according to Anna Zora, Frégate Island conservation manager, who filmed the hunting of the bird.
She said: ‘When I saw the tortoise moving in a strange way I sat and watched, and when I realised what it was doing I started filming.’
The encounter was likely possible due to recent extensive habitat restoration on the island that allowed the tern colony to grow so dramatically.
‘I couldn’t believe what I was seeing,’ says study author Dr Justin Gerlach, Director of Biology Studies at the University of Cambridge’s Peterhouse College.
The scene was filmed in the woodlands of Frégate Island in the Seychelles, an archipelago off the coast of East Africa.
‘It was horrifying and amazing at the same time,’ according to the researcher.
The event, involving the large reptile and a tern seabird, living on the Seychelles’ Frégate island, was ‘completely unexpected,’ according to researchers from the University of Cambridge’s Museum of Zoology, who invested the encounter
In the video, an adult female tortoise makes a direct beeline at normal walking pace toward its target: a tern chick stranded on a log.
‘It was looking directly at the tern and walking purposefully toward it. This was very, very strange, and totally different from normal tortoise behaviour,’ said Gerlach.
Slow and steady, the tortoise stalks closer. When it gets within biting distance, it reaches out with its mouth open.
The chick tries to defend itself by pecking at the tortoise, but its efforts are futile.
It was the first time a tortoise has been caught deliberately hunting prey in the wild. Previously they had been seen feeding on bones and snail shells for calcium
Once the chick reaches the end of the log with nowhere else to go, the tortoise crushes its jaws directly on the head of the chick.
The limp chick plummets from the log. The tortoise climbs down and swallows it whole. The entire process takes seven minutes.
The giant tortoises on the island have been seen consuming bones and snail shell, but it was assumed these weren’t hunted, and it was done to increase calcium levels.
‘It’s always been impossible to tell if the tortoise had directly killed the animal, or if it had just happened to sit down on one and find it conveniently squashed dead,’ says Gerlach. ‘Why turn down a bit of free protein?’
Researchers believe this behaviour was driven by the large 265,000-strong tree-nesting noddy tern colony and the 3,000 tortoises, living closely on the island
The chick likely fell from the tree above, landing on a log where the giant tortoise slowly approached, and over a seven minute encounter killed and fed on the bird
Giant tortoise found on the Galapagos islands is from a species thought to have gone extinct 100 YEARS ago
A giant tortoise found on the Galapagos islands has been confirmed to be a species thought to have gone extinct 115 years ago.
The adult female was discovered in 2019, and now a genetic analysis has confirmed her to be a Fernandina Giant Tortoise (Chelonoidis phantasticus).
Ecuador’s Environment Minister, Gustavo Manrique, confirmed the news on Twitter, writing: ‘Hope is alive!’
Many species of giant tortoises were over-hunted for their meat by European and other colonists who travelled to the Galapagos archipelago.
The sighting came during an expedition to the island of Fernandina in the western Ecuadorian region of the archipelago in 2019.
To prove the link, scientists from Yale University took samples from the female to compare to the remains of a male from the species Chelonoidis phantasticus.
The last previous sighting of the species had been in 1906.
He said in the video it appeared that the tortoise had previous experience capturing chicks on the logs, as if it was something that happened regularly.
When chicks fall, their instinct is to avoid the ground at all costs, ‘this is likely why the chick remained on the log even while the tortoise crept closer,’ Gerlach said.
He added, ‘it looked to me like that individual had hunted successfully before; it seemed to know what it was doing.’
While this tortoise appears to be an experienced hunter, questions remain about how many tortoises hunt, how often they do it, how much nutrition they get from it, and if this is happening in other locations too.
‘Could we be seeing a population of tortoises that is developing a new type of behaviour with evolutionary implications, or is it just an interesting observation at the moment?’ Gerlach pondered.
He suspects that the conservation efforts on Frégate Island could be part of what is driving the emergence of this unusual behaviour.
Though seabird and tortoise populations have been on the decline for the past few hundred years, efforts on the island have revived the population of both to create a very unique combination of high bird and high tortoise populations.
Gerlach said the conservation efforts were ‘recreating conditions for natural behaviours that people haven’t seen for hundreds of years.’
‘There’s a lot of stories of tortoises eating snail shells for the calcium to make their own skeletons, but I don’t see why they couldn’t also systemically eat snails,’ he said.
The researcher said that despite all the unknowns, the effort the tortoise goes to in order to eat a tern is considerable, compared to munching on plants, which suggests the seabirds are something of a delicacy to the reptiles.
The findings were published in the journal Current Biology.
WHAT ARE THE GALAPAGOS ISLANDS?
The Galapagos islands are situated 563 miles west of mainland Ecuador, of which they are a part. They are some of the most remote land masses in the world.
There are 21 islands but only four of them are inhabited, with a population of around 25,000.
They contain more than 1,300 species found nowhere else on earth. With the islands at the intersection of three ocean currents, the sea is a mecca for marine life.
The most famous species unique to the Galapagos include the giant tortoise, marine iguana, flightless cormorant and the Galapagos penguin – the only penguin species to be found in the Northern Hemisphere.
Unesco decided to declare Galapagos a World Heritage Site In Danger in 2007 due to a boom in tourism.
Indeed, annual visitor numbers have increased from 12,000 in 1979 to more than 300,000 today.
Dozens of Galapagos species are now ‘critically endangered’.
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