The Leatherback is the largest living turtle. Its bluish-black carapace (shell) is composed of skin with small bones embedded in it and has seven prominent ridges that run from the head region towards the tail. As is the case with all sea turtles, the front limbs are flippers and have no claws. Leatherbacks can measure up to 2.4 m in total length and 3.6 m in width; they weigh up to 725 kg.
Leatherbacks are migratory sea turtles that breed in tropical or subtropical waters and move to temperate waters in search of food (chiefly jellyfish) at other times of the year. There are Atlantic and Pacific populations that travel along the coasts of North America. In Canada, Leatherbacks are often sighted on the east coast between June and October; there are fewer sightings on the west coast, and these occur between July and September. This turtle has a remarkable ability to maintain its body core temperature as much as 18°C above that of its surroundings, enabling it to stay active in relatively cold waters.
The Pacific population was facing imminent extinction, but is now considered critically endangered, while the Atlantic population contains approximately 15,000 females and is cautiously considered stable.
Leatherbacks are strong swimmers that spend most of their lives at sea, but they must come ashore to lay their eggs. They reach sexual maturity at an unknown age. In the Atlantic, Leatherbacks nest from November to April, while Leatherbacks in the Pacific nest at any time of the year. Individual Leatherbacks can nest 4 to 10 times in a season. Clutches contain 50 to 170 eggs. Many of the eggs have no yolks and so never hatch. The incubation period is 53 to 74 days.
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Nesting success has been diminished by the collection of eggs by humans, natural predation, loss of nesting beaches to commercial development, illumination of nesting beaches (which disorients hatchlings, preventing them from heading directly for the ocean), shoreline pollution, and ingestion of plastic and other debris mistaken for prey. Entanglement in fishing gear throughout the species' range is another limiting factor. While not all entangled Leatherbacks drown, there is an appreciable amount of adult mortality.
As recently as 1990, Leatherbacks were considered extremely rare in Canadian waters. Because Leatherbacks stay at sea, hardly anyone saw them. When the Nova Scotia Leatherback Turtle Working Group (LTWG) recruited fishermen to count and photograph Leatherbacks they saw at sea, it became clear that hundreds of leatherbacks migrate to Canada’s Atlantic coast each year.
A collaborative research project conducted by fishing associations and government biologists is aimed at reducing mortality of Leatherbacks on fishing lines. In 1999, LTWG researchers and fishers became the first team in the world to put satellite tags on leatherbacks in their feeding waters. This project has revealed migratory routes to breeding grounds in Costa Rica, Panama and Trinidad. Tagged Leatherbacks have also been discovered to aggregate at foraging sites in coastal and shelf waters of Atlantic Canada and the United States, where they were not previously known to feed. This important finding suggests that turtle-fishery interactions in coastal and shelf waters may represent a greater threat to Leatherbacks than previously realized, and should be addressed in recovery planning.
Although accidental capture or entanglement, collision with boats, and ingestion of garbage appear to be the major threats to Leatherbacks in Pacific waters, a lack of information makes it difficult to ascertain the level of risk each threat poses. Therefore, the Pacific Leatherback recovery team has identified a number of key questions about Leatherback biology and threats that need to be addressed prior to commencing full-scale recovery activities. Key knowledge gaps include the species’ distribution and seasonal movements in Pacific Canadian waters, habitat requirements, feeding behaviour, and rate of interaction with fishing gear.
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Nature Canada lobbied to create the National Marine Conservation Areas Act to ensure species like the Leatherback received protection. Now, with support from our members, Nature Canada is calling for the establishment of a national system of marine protected areas by 2012 to preserve sites that are essential to the survival of the Leatherback.