The Once-Thriving Leatherback Population at Terengganu, Malaysia
By Jeanne A. Mortimer
A leatherback turtle returns to the Indian Ocean after nesting on Selaut Besar in Aceh, Indonesia. Southeast Asia is home to two subpopulations (regional management units) of leatherbacks (Northeast Indian Ocean and West Pacific). © Hiltrud Cordes
Each year in the late 1960s, between June and September, an estimated 2,000 female leatherbacks laid approximately 10,000 egg clutches along a 15-kilometer (9-mile) stretch of coastline at Rantau Abang, Terengganu, on the east coast of Peninsular Malaysia. At that time, it was the nesting area of one of the largest and most famous leatherback populations in the world. The eggs had been collected by the coastal inhabitants since at least 1920, and in 1960 an estimated 1.66 million leatherback eggs were consumed annually. The eggs appeared to be an inexhaustible resource. Unfortunately, from the 1960s onward, the leatherback population declined precipitously. By the late 1980s, only 40 females were nesting annually; that dropped to a mere 5 animals by the early 2000s, and by 2010, the population was considered functionally extinct.
What went wrong? In short, almost everything. By the late 1950s nearly 100 percent of all leatherback eggs laid were consumed by people. So a hatchery management program was implemented during the 1960s. Sadly, resource managers at the time believed that protecting 1 percent of all the eggs laid and consuming the other 99 percent would be sufficient to maintain the population. Apparently, it was not. To make matters worse, high incubation temperatures in the hatcheries produced primarily females. By the late 1980s, a high proportion of the hatchery eggs were infertile, possibly because too few males had been produced and adult females were unable to find mates.
But those were not the only problems faced by the leatherbacks of Terengganu. Reportedly, the greatest population decline coincided with the rapid expansion of fisheries in Malaysia. Studies showed that trawl nets, drift nets and gillnets, and bottom longlines were capturing at least several hundred turtles each year within Malaysian territorial waters during the 1970s and 1980s. In the late 1980s, at least 8 percent of the estimated 40 females nesting annually were found washed ashore dead at Rantau Abang, tangled in fishing gear. Meanwhile, outside of Malaysian waters where the pelagic leatherbacks spent most of their lives, they were often caught incidentally by fishers in the high seas.
In 1988, the Terengganu state government enacted several remarkable measures based on recommendations spearheaded by Dr. Chan Eng Heng (see “Living Legends” ). The measures stopped the commercial sale and consumption of leatherback eggs, mandating that 100 percent of eggs be incubated in hatcheries; and the government established the Rantau Abang beach sanctuary to prevent disturbance to turtles and further development of the critical nesting beaches. In 1989, the government banned large-meshed gillnets throughout Malaysian coastal waters. And in 1990 and 1991, it established the Rantau Abang Offshore Turtle Sanctuary—extending to 18.5 kilometers (11.5 miles) offshore along some 30 kilometers (18 miles) of coastline—and it banned destructive fisheries practices within the sanctuary’s boundaries. Unfortunately, those actions, which probably would have met with success had they been implemented two decades earlier, came too late to save the leatherback turtles of Malaysia. Nevertheless, the lessons learned are being applied toward saving the hard-shelled turtles of Malaysia, especially the green turtles and the hawksbills.
Author Affiliation
Jeanne A. Mortimer, Turtle Action Group of Seychelles (TAGS), Mahé, Seychelles
This article originally appeared in SWOT Report, vol. 19 (2024). Download this article as a PDF.