Sea turtle stocks are declining throughout most of the Wider Caribbean region; in some areas the trends are dramatic and are likely to be irreversible during our lifetimes
Dermochelys coriacea, Leatherback Sea Turtle
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- 2.4 Eretmochelys imbricata , Hawksbill Sea Turtle
2.3 Dermochelys coriacea, Leatherback Sea TurtleThe leatherback turtle is the largest (adults often weighing 300‑500 kg, or 660‑1100 lb) of the sea turtles. The Galibi Indians sometimes refer to this species as Kawana, but the more common name is aitkanti. In addition, some fishermen recognize a smaller leatherback that they call siksikanti. They claim that siksikanti nests at a different time, exhibits different nesting behavior, and is a distinct species (Schulz, 1975; Reichart, 1992). Their contention has yet to be examined scientifically and at the present time the leatherback is believed to be monotypic. Leatherbacks lack a bony shell and the smooth black skin is spotted with grey‑white blotches. The carapace is strongly tapered, measuring 130‑165 cm in length (straight line, nuchal notch to posterior tip), and is raised into seven prominent ridges (Figure 4). Powerful front flippers extend nearly the length of the body. The upper mandible is deeply notched. The species is a seasonal visitor to Suriname, migrating from temperate foraging areas to nesting beaches in the Guianas. Nesting is from April through June, at times as early as January (Table 2). Eggs av‑erage 5.3 cm in diameter and each clutch contains an average of 85 yolked eggs, with a variable number of markedly undersized "yolkless" eggs also present (Schulz, 1975). Studies elsewhere in the Wider Caribbean region have shown that leatherbacks typically nest six or seven times per season and return to the nesting beach on multiple year intervals, with the biennial cycle predominating. In 1991, 11 nests were laid by one tagged individual at Sandy Point National Wildlife Refuge (St. Croix, USVI) (Dutton et al., 1992). Since leatherbacks prefer high energy beaches with unobstructed and often deep offshore access, rookery sites are often spatially unpredictable (Mrosovsky, 1983a; Eckert, 1987). This is the situation in the Guianas where, due to natural erosion, the reduction in beaches suitable for nesting by leatherbacks in French Guiana has caused the females to come in greater numbers to the coast of Suriname. Consequently, over the last 16 years leatherback nesting frequency has more than doubled. Although nesting takes place between January and August, the nesting peak for this species occurs from March to July in Suriname. Of the 9,816 nests laid in 1987 (nationwide, see Table 1), some 838 (8.5%) were harvested and 214 (2.2%) were poached (Mohadin, 1987). In 1988, 11,436 leatherback nests were laid, of which 454 (4.0%) were harvested and only 60 (0.05%) were poached (H. Reichart, unpubl. data). A secondary peak in leatherback nesting has recently been noted in December. That could possibly be a different nesting population, but supporting data have not yet been collected (L. Autar, pers. comm.). Leatherbacks are rarely seen offshore during the nesting season, but recent studies deploying time‑depth recorders on gravid females nesting in the West Indies have shown that individuals spend the inter‑nesting interval diving continuously and can attain depths greater than 1,000 m (Eckert et al., 1986, 1989). Leatherbacks feed predominantly on jellyfish and other soft‑bodied prey (Den Hartog and Van Nierop, 1984; Davenport and Balazs, 1991). The impetus behind the diving behavior may be to feed on deep water siphonophores in the "deep scattering layer" (DSL); that is, to feed within the strata of plankton that migrate to the surface of the ocean at night and descend to just below the depth of light penetration during the day. The diving may also represent thermoregulation behavior or predator escape. Preferred offshore habitats for this species have not been defined in Suriname, but tagging studies have shown that after nesting the animals disperse widely across the Atlantic Ocean (Schulz, 1975). Tag returns from females marked on Surinam nesting beaches have come from as far north as Nova Scotia, as far south as Argentina, and as far east as Ghana in West Africa (e.g., Pritchard, 1976). Age at maturity is not known. 2.4 Eretmochelys imbricata, Hawksbill Sea TurtleThe local name is karèt. The species is distinguished by a narrow, pointed beak with which it pries sponges and other soft‑bodied organisms from coral reefs and other hard bottom habitats. The carapace is often posteriorly serrated and, particularly as the animal matures, the carapace scutes overlap one another (Figure 4). Adults rarely exceed 80 kg (175 lb) in weight and seldom have a carapace length of more than 90 cm (straight line, nuchal notch to posterior tip). Amber coloration with red‑brown (to black‑brown) and yellow markings is common (Schulz, 1975). Hatchlings are uniformly brown or grey. Hawksbills are "spongivores" and feed mainly on reef‑associated sponges in the Caribbean region. Sponges contributed 95.3% of the total dry mass of all food items in digestive tract samples from 61 animals from seven Caribbean countries (Meylan, 1988). Surinam waters are turbid and coral reefs are not known to occur. Thus, it is not likely that Suriname provides important foraging grounds for this species. Hawksbills are difficult to study and little is known about Caribbean/Atlantic populations. Individuals are migratory, high‑density nesting is rare, and the relatively few tagging programs have not been in place long enough to generate a useful number of tag returns (that is, a sufficiently large number of recaptures to illustrate post‑nesting movement). Nesting often takes place on isolated beaches which are difficult to monitor on a consistent basis. Gravid females generally retreat into supralittoral vegetation before nesting, leaving little evidence of the nest site aside from a faint asymmetrical crawl (about 0.7 m wide) to and from the ocean. Data collected in Antigua, West Indies, indicate that the average female deposits five clutches of eggs per year, each separated by intervals of 13‑18 days (cf. Corliss et al., 1989). Neither intra‑ nor inter‑seasonal nesting frequency is known for Suriname, but Schulz (1975) reports that an average of 146 eggs are laid per nest. A low level of nesting (perhaps 30 nests per year) takes place in Suriname approximately between April and August. 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