Marine Turtle Newsletter 52:16-17, © 2001
Leatherback Turtles in Trinidad
Brendan Godley, Kate Kirkwood, Sandra Raffan and Rachel Taylor
Zoology Department, University of Glasgow, University Avenue, Glasgow G12, Scotland
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Marine Turtle Newsletter 52:16-17, © 2001
Brendan Godley, Kate Kirkwood, Sandra Raffan and Rachel Taylor
Zoology Department, University of Glasgow, University Avenue, Glasgow G12, Scotland
In July 1989, four life-science undergraduates conducted a largely observational project on the leatherback sea turtle (Dermochelys coriacea) on Matura Beach in Trinidad, West Indies. The group was part of a larger expedition from Glasgow University undertaking various conservation projects under the supervision of the Wildlife Section of the Forestry Division, Government of Trinidad and Tobago. The main aim of the project was to study human disturbance on turtle nesting habits and behavior. Life history and other data were collected to add to previous information gathered by the Wildlife Section.
Two kilometers of Matura Beach were patrolled on 13 nights in July. Thirty-five nests, seven 'false crawls', 34 hatched nests, and one slaughtered carcass were recorded. When turtles were encountered, various features were recorded: time, position on the beach, whether eggs were laid, debris present, and behavior of proximal people. Once a turtle began to lay eggs, a tag was applied to the trailing edge of her front left flipper. Monel tags and supervision were supplied by Emperor Valley Zoo personnel. One tagged turtle renested during our study; there was evidence of tissue necrosis around the tag after 21 days. When hatchling tracks were found they were traced back to the nest and the nest then thoroughly excavated. Any hatchlings trapped were released and allowed to crawl to the sea. Sand samples from the top of the nest were collected. All eggs, hatched and unhatched, were collected and their position (top/middle/bottom) noted. Shells were later washed and dried and used to assess clutch size and hatchability. Samples of shells from hatched and unhatched eggs were brought back to Glasgow under CITES permit for further study (Solomon et al., in prep.).
During the period of the survey, beach-goers were classified as
Turtle watchers were frequently in contravention of established guidelines for behavior and sometimes unintentionally disturbed the turtles, unaware of the consequence(s) of their actions. Fishermen generally posed no direct threat to the turtles, but by lighting fires and using vehicles and torchlight on the beach, they may have a detrimental effect. On only one occasion did we encounter men on the beach who told us it was their intention to kill turtles. They were drunk and armed with cutlasses. In order to avoid violence, we had been instructed not to challenge poachers. We withdrew. On our return the next morning we discovered a butchered carcass with flippers removed and plastron separated to remove eggs. Although we found only the one carcass, local residents told us that three turtles had been slaughtered that night; two of the cacasses had been concealed. We learned a great deal from conversations with residents, and it became obvious to us that, although protective legislation existed, it was inadequate. In addition, insufficient resources were available to enforce the existing laws.
Other than the direct effects of human disturbance, we noted environmental hazards (such as natural and man-made debris) and predators of hatchlings and eggs. Of the environmental hazards, sand erosion was clearly the most important, as found on St. Croix, U. S. Virgin Islands (Eckert 1987). Pollution did not appear to be a major problem at Matura. No evidence of bird predation was discovered, but one nest was disturbed by dogs, two by manicou (opossum), and one hatchling was seen taken by a ghost crab.
Since the time of our study, Matura Beach has been declared a 'prohibited area' (1 March to 31 August) under the Forests Act, Chapter 66:01 of the laws of Trinidad and Tobago. This means that any person who wishes to visit this area should obtain a permit from the Wildlife Section at a nominal cost (N. Gyan, Scientific Officer, Wildlife Section, pers. comm.). It is clearly very important to monitor this scheme to determine how effective it is in affording protection to the turtles.
A detailed account of the work done is included in the report of the Glasgow University Trinidad and Tobago Expedition 1989, available from Dr. J. R. Downie, Department of Zoology, University of Glasgow, Scotland. We intend to take a further expedition to Trinidad and Tobago between June and August 1991 to build on work done in 1989. At present the projects planned include
Any comments on previous work or suggestions regarding that of 1991 would be appreciated and any liaison welcomed.
Basford, S. J., R. L. Brandner, and R. H. Boulon. 1988. Tagging and nesting research on leatherback sea turtles (Dermochelys coriacea) on Sandy Point, St. Croix, U. S. Virgin Islands, 1988. Annl. Rept. to the U. S. Fish Wildl. Serv. 32 p. /+append.
Eckert, K. L. 1987. Environmental unpredictability and leatherback sea turtle (Dermochelys coriacea) nest loss. Herpetologica 43(3):315-323.
Solomon, S., R. Tippett, and D. Brown. (in prep.) A management programme designed to increase hatchability rate in marine turtles.