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Marine Turtle Newsletter 75:1-4, © 1996

Is the Surinam Olive Ridley on the Eve of Extinction? First Census Data for Olive Ridleys, Green Turtles and Leatherbacks Since 1989

Willem E. J. Hoekert¹, Arnoud D. Schouten¹, Luc H. G. Van Tienen² and Mariska Weijerman^2
1BIOTOPIC, Saenredamstraat III, 1072 CA Amsterdam, The Netherlands
²STINASU, P. O. Box 436, Paramaribo, Suriname

The olive ridley (Lepidochelys olivacea) population that nests in the Galibi Nature Reserve in Suriname is the largest and most important olive ridley population in the Western Atlantic. In the late 1960's, this population was abundant enough to produce arribadas (mass nesting events). At that time, almost all of the eggs were harvested in an uncontrolled manner by inhabitants of two nearby Carib villages. Despite conservation measures carried out by STINASU (Foundation for Nature Preservation in Suriname), which reduced poaching (Reichart and Fretey, 1993), the numbers of nesting females decreased drastically in subsequent years. In 1968, an estimated 3065 olive ridley nests were laid in the Galibi Nature Reserve (Schulz, 1975). In 1989, the estimated number of nests laid was only 424 (Reichart and Fretey, 1993), a decrease of more than 80% in 20 years. The number of olive ridleys elsewhere in the Guianas did not increase during this time, making it unlikely that the population had moved elsewhere (H. Reichart, STINASU, pers. comm., 1996).

The nesting population of green turtles (Chelonia mydas) in Suriname was relatively stable between 1968 and 1989, and has been estimated at 3700-7200 females (see Reichart and Fretey, 1993). During this same time, the number of leatherback turtles (Dermochelys coriacea) nesting in Suriname increased from 200 in 1968 to 12,401 in 1985 (Reichart and Fretey, 1993), probably due to the erosion of nesting beaches in neighboring French Guiana (Schulz, 1975). At the end of the 1989 nesting season, armed Carib villagers forced STINASU personnel out of the Galibi Nature Reserve. As a result, no data are available for the period 1990-1993. Nest counts restarted during the 1994 nesting season, but data are incomplete. Poaching of eggs has increased significantly in the intervening years.

In this article we present the first data on the number of olive ridley, green, and leatherback turtles nesting in the Galibi Nature Reserve since 1989. Data were collected by the authors and by STINASU employees from 1 February31-July 1995, spanning virtually all of the olive ridley, green turtle and leatherback nesting seasons. All the beaches of the Galibi Nature Reserve were monitored (about 13 km) during this period. The Spit (a newly formed sand bank about 4 km in front of Eilanti) was monitored only during the olive ridley nesting season (mid-May to 1 August). In addition, we collected data on strandings, hatch success of relocated and in situ nests, and on beach quality.

In 1995, the number of nesting olive ridley turtles (n=335) was the lowest ever recorded in the Galibi Nature Reserve (cf. Table 3 in Reichart and Fretey, 1993), making it clear that this population has not recovered in Suriname. Although stabilisation at some future time cannot be excluded, the Surinam olive ridley is presently in great danger of extinction. The number of nesting green turtles (n=6313) is comparable with data from previous years, suggesting that the Surinam green turtle population is stable, as it apparently has been since data collection began in 1968. The number of nesting leatherback turtles (n=1808) was low compared to previous years, but falls within apparently normal annual fluctuations and does not seem alarming.

The distribution of the olive ridley nesting effort is shifting. Arribadas are described at Eilanti, the northernmost beach in the Galibi Nature Reserve, in the late 1960's and this has traditionally been the main nesting beach for the olive ridley in Suriname. Today Eilanti appears to be less attractive as a nesting beach than the other beaches of Galibi. Table 1 shows clearly that the percentage of olive ridleys nesting on Eilanti has declined dramatically over the past decade (for more information, see Hoekert et al., 1996). In 1995, for the first time on record, more olive ridleys nested elsewhere in Galibi; namely, Pruimenboom and Baboensanti beaches. A possible cause for this may be that Eilanti is less accessible because of the recent formation of a sand bank ("the Spit") offshore. Observed high numbers of olive ridleys nesting on the Spit reinforces this idea.

Table 1. The numbers of olive ridleys nesting at Eilanti beach, the total numbers of olive ridleys nesting in the Galibi Nature Reserve (NR), and the percentage of olive ridleys nesting at Eilanti in 1984, 1989 and 1995. Source: 1984 and 1989 (Reichart and Fretey, 1993).

While the Spit which has formed offshore the Eilanti beach was visited by substantial numbers of olive ridleys (31% of the total) and leatherbacks (27% of the total) in 1995, the site does not constitute suitable nesting beach habitat. It is almost completely flooded at spring tide; moreover, the ground water level is quite high, sometimes resulting in nest chambers being filled with water while turtles are digging. Finally, the Spit is very dynamic, sometimes experiencing considerable changes in beach condition during a spring tide. The percentage of false crawls at this site was significantly higher than at other beaches in Galibi in 1995 (Hoekert et al., 1996).

Hatch success was calculated for relocated and in situ olive ridley, green turtle and leatherback nests. Most nests were transferred to a hatchery directly after deposition. The hatching success of relocated nests appeared to be somewhat (but not significantly) lower than that of natural nests for the green turtle and the leatherback. Relocated green turtle nests had an average hatch success of 62% (sd=25%, n=17), while undisturbed nests had an average hatch success of 76% (sd=16%, n=13). The figures were 28% (sd=22%, n=40) and 31% (sd= 23%, n= 24), respectively, for leatherbacks. A statistical comparison between relocated and undisturbed olive ridley nests could not be made because only two undisturbed nests were observed. Relocated olive ridley nests had an average hatch success of 63% (sd=24%, n=19), whereas the two nests left in situ had hatch successes of 2% and 56%.

Despite the current ban on harvesting olive ridley eggs, more than 40% of olive ridley nests were poached during the peak season in 1995. The three STINASU employees that patrol a limited beach area are not sufficient to stop or greatly reduce the occurrence of poaching. To achieve a significant reduction of egg theft, it is necessary that abandoned field stations be repaired and staffed once again.

We observed 13 stranded leatherbacks and two dead green turtles during the study period. Some leatherbacks showed injuries (e.g., fractured skull, pierced carapace); in one case, the head and flippers had been severed. Leatherbacks are accidentally caught by coastal fishermen, who often kill them to reduce net damage. Except for an occasional incident, no adults are slaughtered for food. However, there are recent reports of marine turtles being eaten by fishermen on shrimp vessels operating off the coast of Suriname (H. Reichart, pers. comm., 1996). The two stranded green turtles had been decapitated. They were probably killed by a jaguar (cf. Autar, 1994). The number of stranded turtles in 1995 was markedly lower than in 1993 or 1994 (H. Reichart, pers. comm., 1996), but exact data are not available and the cause of the decline is unclear.

Recently the U. S. has admonished the Surinam government once again to enforce the use of TEDs (turtle excluder devices). There are about 150 Surinam-based Korean and Japanese trawlers operating in Surinam waters. They all report the incidental catch of marine turtles, mostly olive ridleys. Mortality resulting from drowning in shrimp trawls occurs at a high level in Suriname. The use of TEDs in Surinam waters has been mandatory since 1992, but enforcement of the law is lacking. Insufficient evidence of TED compliance has been provided to the U. S. government so far, and for this reason Surinamcaught shrimp have been embargoed by the U. S. since May 1993 (for background see Reichart and Fretey, 1993).

In conclusion, it has been difficult to protect the Galibi beaches properly in recent years due to political problems between local inhabitants and STINASU and Government personnel. It is obvious that the local inhabitants need to be made more aware of the importance of sea turtles as a natural resource, and that they need to be more seriously involved in the management of the Galibi Nature Reserve. A management program for the Galibi Nature Reserve has been developed (Reichart, 1992) and should be implemented. The highest priority at this moment, however, should be given to (1) mandating and enforcing the use of TEDs in all trawlers plying Surinam waters and (2) enacting and enforcing a complete ban on the harvest of olive ridley eggs until such time as data indicate that the population has recovered. If these two recommendations are not achieved, the Surinam olive ridley is bound to become extinct.

Acknowledgements: We would like to thank Henk Reichart, Carol Bram, Ricardo Pané and Murial Held for making it possible to work in the Galibi Nature Reserve, Ronnie, André, Gerard, Saulus en Jan for collecting data, and Colex Watersport and Van Rheenenautoparts for providing us with an outboard motor. Financial support came from WWF, STINASU, the Treub society (Society for the Advancement of Research in the Tropics), the Beijerinck-Popping Foundation, and BIOTOPIC.

Autar, L. 1994. Sea turtles attacked and killed by jaguars in Suriname. Marine Turtle Newsletter 67:11-12.

Reichart, H. A. and J. Fretey. 1993. WIDECAST Sea Turtle Recovery Action Plan for Suriname (K. L. Eckert, Editor). CEP Technical Report No. 24. UNEP Caribbean Environment Programme, Kingston, Jamaica. xiv + 65 pp.

Reichart, H. A. 1992. Galibi Natuurreservaat beheersplan 1992-1996. World Wildlife Fund (USA and The Netherlands), Dienst's Lands Bosbeheer.

Schulz, J. P. 1975. Sea Turtle Nesting in Suriname. Zool. Verh. Rijksmus. Nat. Hist. Leiden, No. 143:1-143.

Hoekert, W. E. J., A. D. Schouten, L. H. G. van Tienen, and M. Weijerman. 1996. Zeeschildpadden van Galibi, Suriname. Een update van de status en de nest-ecologie. Amsterdam, Nederland.