Richard Collins: Leatherback turtles are long-distance seasonal migrants to Irish waters
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In the future, everyone will be world-famous for 15 minutes — Andy Warhol.
On June 24, 1930, Portmarnock became, briefly, the focus of world aviation. At half-four in the morning Charles Kingsford-Smith’s plane, the Southern Cross, took off from the ’velvet strand’, bound for Newfoundland. An impressive stone monument on the promenade commemorates the event.
Two years later, 24-year-old Jim Mollison would fly from the strand to New Brunswick, Canada.’
I was very sad to see this poor turtle RIP this morning 😢
— Niamh Griffin (@griffinniamh) December 5, 2024
Does anyone know what it was or where it might have come from?#portmarnock pic.twitter.com/5hMs2PnuqQ
Another world traveller arrived in Portmarnock on December 8 last. This time, however, there was no cause for celebration; the leatherback turtle was found dead.
The Irish Marine Institute confirmed: "From the photos seen online, scientists at the Marine Institute believe this to be a leatherback turtle."
Leatherbacks were once considered rare visitors to Irish waters. Caught in fishing gear occasionally, they were classed as ‘vagrants’, misguided souls which had wandered northwards from warmer seas. But, with increased sightings in recent years this, the world’s largest turtle and second largest living reptile, is now recognised as an annual ‘migrant’ to our shores.
Individual leatherbacks can exceed 2.5 metres in length and weight up to half a tonne. All other sea-turtle species have bony shells, but this giant has a tractor-tyre dark-leathery ‘carapace’. The front flippers, with which the creature propels itself through the water, are the longest limbs, in relation to body size, of any turtle.
The Marine Institute said: "Leatherback sea turtles have been recorded all around Ireland, in the Atlantic, as well as the Irish and Celtic Seas. However, this species is not seen very regularly. Sightings of leatherback sea turtles in Ireland have mostly been recorded during the summer months from July to September, as this is when jellyfish are most abundant in our waters.
Leatherbacks are l ong-distance seasonal migrants to Irish waters, and migrate to temperate waters for feeding and then return to waters near to where they are from to find a mate and for nesting."
Leatherbacks have remained relatively unchanged since they first appeared in the fossil record around 110 million years ago. The sole survivors of an ancient clade, our species became known to science when one was captured at Ostia, Rome’s ancient port, in 1761. It was presented to Pope Clement XIII, who donated it to the University of Padua.
Its favourite food, j ellyfish, is also a fatal attraction; turtles swallow drifting plastic bags, mistaking them for jellyfish. When plastic blocks its food-canal, the diner starves to death. According to a US Fish and Wildlife Service report, around 115,000 females nested worldwide in 1980, but fewer than 43,000 were doing so by 2007.
Creatures of southern seas, leatherbacks breed on sandy beaches on both sides of the Atlantic. They mate at sea; males never leave the water once they have entered it as juveniles.
Ocean warming is tempting sea-turtles to travel northwards increasingly. Some even venture beyond the Arctic Circle.
The species is better adapted to cooler waters that other turtles. Its huge size helps it cope with the cold; large bodies retain heat more effectively than small ones. Like whales and seals with their blubber, leatherbacks have layers of insulating brown fat.
Reptiles don’t generate their body-heat internally. They rely instead on the environment to warm them. The leatherback, however, is an exception. A vascular heat-exchange mechanism harvests the warmth generated by the powerful front-limb muscles and uses it to increase core body temperature.
Although the occurrence of a leatherback at Portmarnock is no longer front-page news, finding one there in mid-winter raises questions. Turtles return southwards to nest, but they don’t breed every year.
Was the Portmarnock visitor an out-of-season tourist remaining on here for the winter, just as some swallows now stay on in Spain? Or had it died in late summer, ocean currents having carried its slowly-decomposing body northwards into the Irish Sea?
Fingal Council said the turtle was buried in situ on the advice of the National Parks and Wildlife Service.
They said they have not received a report on any cause of death at this stage.
Sic transit Gloria mundi!
- Additional information from Imasha Costa and Niamh Griffin