Conservation Status: Vulnerable. The WWF (Worldwide Life Fund) estimates suggest that only 2,300 adult females of the Pacific leatherback remain, making it the most endangered subpopulation of marine sea turtle.

Habitat: wide-ranging, found in all tropical and subtropical oceans and extends well into the Arctic circle. Mainly found in the open ocean, though they tend to follow their jellyfish prey into shallower water at night.

Weight: 250-700kg (550-1,540lb)

Length: 1.83-2.2m (6-7.2ft)

Physical Appearance: the largest living turtle, it is the only one with no bony shell. Instead its teardrop-shaped carapace is covered by skin and oily flesh. Its back is dark grey-black in colour with white blotches and spots, and its underside is lightly coloured. The leatherback’s large body leaves symmetric tracks in the sand from its clawless flippers when it comes onto the beach to nest.

Diet: jellyfish and other soft-bodied organisms

Predators: the eggs are preyed on by many coastal predators, such as ghost crabs, coatis, dogs, raccoons and birds. The hatchlings are also prey to cephalopods and requiem sharks, while the adults are only prey for very large marine predators such as killer whales, great white sharks and tiger sharks.

Threats: leatherbacks often ingest plastic bags, mistaking them for jellyfish. The eggs are also preyed upon by humans and exploitation in this manner has been attributed as the most significant factor for the species’ global decline.

Mating: the leatherback migrates from its feeding ground in colder waters to warmer waters to mate in the sea. Males mate every year, females every 2-3 years. Leatherbacks choose soft sandy beaches to nest to protect their soft bodies. The gestation period is 60-70 days before the hatchlings emerge at nightfall and head to the sea. In Costa Rica, the nesting season is February-July.

Lifespan: unknown. Estimates vary between 30 and 100 years.