Number of nests per year has been estimated for 13 nesting seasons between 1978 and 1995. A general increase in the number of nests has been observed in the last few years as compared to the first years, but the actual trend is unclear. We estimated the number of leatherbacks, Dermochelys coriacea , nesting on 28 beaches throughout the world from the literature and from communications with investigators studying those beaches. The estimated worldwide population of leatherbacks in 1995 was about 34,500 females on these beaches with a lower limit of about 26,200 and an upper limit of about 42,900. This is less than one third the 1980 estimate of 115,000.
Leatherbacks are rare in the Indian Ocean and in very low numbers in the western Pacific Ocean.
The largest population is in the western Atlantic. We formulated a hypothetical life table model based on estimated ages of sexual maturity at 5 or 15 years. Leatherbacks that mature in 5 years would exhibit much greater population fluctuations in response to external factors than would turtles that mature in 15 years. Simulations indicated that leatherbacks would maintain a stable population only if both juvenile and adult survivorship remained high. Leatherback populations in the Indian Ocean and western Pacific Ocean cannot withstand even moderate levels of adult mortality.