It's been around for 100 million years — a giant reptile that has long outlived its distant dinosaur cousins, can weigh more than a Smart car and accumulate nearly as much mileage every year.
But a new study of the endangered leatherback turtle by three Canadian scientists has, for the first time, documented how one of the world's most majestic and enduring species — and one only recently shown to inhabit key feeding grounds along Canada's Atlantic shore — is being seriously threatened by the lowliest artifact of modern consumer culture: the plastic bag.
Tragically, the biggest member of the turtle family is prone to mistaking the discarded bags that litter the world's oceans with jellyfish, its only source of food.
The researchers' analysis of nearly 400 turtle autopsies conducted since 1968 showed that 37.2 per cent of the dead leatherbacks examined had ingested some form of plastic — mostly bags, but also fishing lines, balloons, picnic cutlery and candy wrappers.
In some cases, the plastic posed such an obstruction to digesting food that it was considered the direct cause of death. But the scientists observed that even non-lethal amounts of plastic, "by reducing the extent of the gut from which absorption (of nutrients) can occur, may well impair health and reproduction."
The study, published in the latest edition of the scientific journal Marine Pollution Bulletin, was co-authored by biologists Nicholas Mrosovsky of the University of Toronto, Geraldine Ryan from the University of Guelph and Mike James, a leatherback turtle specialist with Dalhousie University and the federal Department of Fisheries and Oceans.
"Unfortunately," the study states, "an animal that can gulp down a toxin laden Portuguese man-of-war does not necessarily survive eating an inert plastic bag."
Ship strikes, entanglements in fishing nets, habitat destruction and the human harvesting of turtle eggs in some southern countries are other threats faced by leatherbacks worldwide.
James, whose research over the past decade has demonstrated the significance of Nova Scotia's and Newfoundland and Labrador's offshore feeding zones to the survival of the species' Atlantic Ocean population, described the MPB study as a "monumental effort that looked back at necropsies over the last century from all over the world."
In a statement released by Dalhousie University, James noted that "plastics ingestion doesn't always cause death, but there are clearly health risks to the turtles.
"The frustrating, yet hopeful aspect is that humans can easily begin addressing the solution, without major lifestyle changes," he added. "It's as simple as reducing packaging and moving toward alternative, biodegradable materials and recycling."
Leatherbacks, which can live at least 80 years and grow beyond 650 kilograms, are born on beaches in tropical waters but migrate vast distances to such places as Canada's East Coast, where jellyfish are plentiful.
"Since jellyfish and marine debris concentrate where ocean water masses meet, leatherbacks feeding in these areas are vulnerable to ingesting plastic," the university statement said. "Once leatherbacks ingest plastic, thousands of spines lining the throat and esophagus make it nearly impossible to regurgitate."
The scientists also speculate in the study that the decline or eventual extinction of leatherback turtles and resulting jellyfish blooms could cause major problems for commercial fishing in certain parts of the world.
"It may be asked, for instance, whether the proliferation of jellyfish off the coast of Namibia and the associated decline in fish stocks there might result from too few turtles," the scientists note, "or, to put it the other way round, whether increased numbers of leatherbacks would result in a rebound of fish stocks."
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