They are found throughout the Pacific, Atlantic, and Indian Oceans. In the Pacific, their range extends as far north as Alaska and south beyond the southernmost tip of New Zealand.
In the Atlantic, they can be found as far north as Norway and the Arctic Circle and south to the tip of Africa. They are mainly pelagic (open ocean) wanderers but migrate to tropical and subtropical coastal regions to mate and nest.( Osborne,2015)
In 1982, scientists estimated that there were 115,000 adult female leatherback sea turtles worldwide. Recent estimates have placed the number between 20,000 and 30,000 (Singh,2007).
Trends in Population:
The global population for this species was estimated to be 115,000 adult females in 1982. By 1996 this had been revised down to about 30-40,000. Leatherback populations in the Pacific and Indian Oceans have undergone dramatic declines in the past forty years. For example, the nesting colony at Terengganu, Malaysia went from more than 3,000 females in 1968, to 20 in 1993, to just 2 in 1993 – there are no signs of recovery.
Similar scenarios have occurred in Indonesia, Sri Lanka, Thailand, and Mexico. Numbers of females recorded at four formerly major Pacific rookeries have declined to about 250 in Mexico, 117 in Costa Rica, two in Malaysia, and fewer than 550 in Indonesia(Anonymous, 2006)
Leatherbacks mate offshore in shallow waters near the nesting area. The females dig their flask-shaped nests at night on sloping sandy beaches backed by vegetation. Six clutches can be laid in a season, with a 10-day period between nesting. The females may renest up to 7 miles from the first nest. An average clutch contains 80 to 85 eggs and incubation takes from 55 to 74 days. The 3-inch hatchlings emerge at night and head toward the ocean. The turtles reach sexual maturity at 6 to 10 years of age; the females nest every second or third year.
In the U.S., nesting occurs from about March to July. Female leatherbacks nest an average of 5 to 7 times within a nesting season, with an observed maximum of 11 nests. Most leatherbacks remigrate to their nesting beaches at 2 to 3-year intervals. (Department of energy and environmental protection, 2014)
It is the greatest threat for leatherback sea turtles, while they accidentally eat balloons and plastic bags floating in the water which they mistaken as jellyfish. (Leigh,2015)
2-Overharvesting and illegal:
Egg collection on many turtle nesting beaches is a very serious threat, especially in Southeast Asia where a culture of legal egg collection leads to the removal of tens of thousands of eggs. This practice has contributed to the local extinction of leatherbacks in Malaysia. Within the last several decades extensive egg collection and the killing of adult turtles in Indonesia has resulted in huge population declines throughout the region. Despite protective legislation, many eggs produced each year in Central America are still collected for subsistence or commercial use. Hunting and egg collection persists throughout the Indian Ocean as well. (Leigh,2015)
Sea turtles are dependent on beaches for nesting. Sea level rise, uncontrolled coastal development, vehicle traffic on beaches, and other human activities have directly destroyed or disturbed sea turtle nesting beaches around the world. Turtle feeding grounds such as coral reefs and sea grass beds are also damaged and destroyed by activities onshore, such as sedimentation from clearing of land and nutrient run-off from agriculture. (Leigh,2015)
4-Fisheries by catch:
Worldwide, hundreds of thousands of sea turtles a year are accidentally caught in shrimp trawl nets, on longline hooks and in fishing gillnets. Sea turtles need to reach the surface to breathe, and therefore many drown once caught. (Leigh,2015)
The World Wide Fund for Nature (WWF) is trying to save leatherback turtles from extinction by doing several things.
First, WWF works to reduce turtle bycatch by helping the fisheries to switch to more turtle-friendly fishing hooks and advocate the use of devices that exclude turtles from nets. WWF runs an international competition to solve bycatch problems. Winning devices was designed to minimize the bycatch of turtles on tuna longlines and help turtles avoid gillnets. Also,WWF works with fishermen to help them save turtles caught in fishing gear and they use satellite devices to track turtle movements to help prevent future interactions between fisheries and turtles.
Second,WWF establishes marine protected areas (MPA) all over the world to make sure marine turtles have a safe place to nest, feed and migrate freely. For example,In the Bird’s Head Seascape of the Coral Triangle, WWF works to protect the nesting area of the largest remaining population of leatherback turtles in the Pacific Ocean. WWF also supports the patrolling of leatherback turtle nest beaches helps equip local turtle conservationists (Leigh,2015)