STC Programs: Research: Hawksbill Turtle Population Recovery and Research – 2003 Season

Hawksbill Turtle Population Recovery and Research in the Comarca Ngöbe-Buglé Chiriquí Beach/Escudo de Veraguas and the Bastimentos Island National Marine Park

Results through December 10, 2003
Cristina Ordoñez, Research Coordinator, Sea Turtle Conservancy
Anne and Peter Meylan, Wildlife Conservation Society
Argelis Ruíz, Smithsonian Tropical Research Institute
Sebastian Troëng, Sea Turtle Conservancy

Chiriquí Beach (8º56′ N, 81º39′ W), Bocas del Toro Province, Panama, was once described as the most important nesting beach in the Caribbean for the Critically Endangered hawksbill turtle (Eretmochelys imbricata). In 2002, a series of meetings was held between Drs. Meylan, local authorities, conservation groups and communities to determine the level of interest in establishing a long-term hawksbill conservation program at Chiriquí Beach and nearby nesting localities. Meetings continued into early 2003, funding was secured, and program activities began in April 2003. The objective of this report is to present results of research, monitoring and conservation activities to date.

Monitoring Methods and Preliminary Results
Markers were placed every 500 m along the 24-km long Playa Chiriquí beach. Natural markers (land features) were used to delimit zones on the Zapatilla Cays. The zones of all nesting beaches were mapped using GPS. Daily track surveys by foot or horse (Chiriqui Beach only) to record hawksbill nesting activity were initiated on all beaches by 12 June (Table 1). Observed nests were marked and a GPS location recorded. Nesting on Playa Chiriquí dropped to very low levels by early November and track surveys were subsequently reduced to every three days. Track surveys will be reduced to once a week by December 15. Nesting on the Zapatilla Cays dropped off by September (1 nest in November). Periodic surveys will continue on the Zapatilla Cays.

Table 1. Track survey effort and results.

Beach section Daily track surveys Ei
Río Caña June 12-November 4 271   69 520 91 3 0
Río Chiriquí June 14-November 8 118   38 354 38 6 4
EscudoVeraguas August 5-November 22   19     2 0 0 0 0
Subtotal 408 109 874 129 9 4
Small ZapatillaCay May 29-October 30 45 37 0 0 0 0
Big ZapatillaCay May 30-October 30 42 NR 0 0 0 0
Subtotal 87 37 0 0 0 0
TOTAL 495 146 874 129 9 4
(Ei = Eretmochelys imbricata, hawksbill; Dc = Dermochelys coriacea, leatherback; Cm = Chelonia mydas, green turtle; NR = not recorded)

Beach monitors marked nests by attaching flagging tape to nearby vegetation (Playa Chiriquí) or stakes (Zapatilla Cays) and recording the location of the egg chamber through triangulation. Preliminary results for Playa Chiriquí suggest that predation of nests by domestic and wild dogs represent the major threat to hatchling survival (Table 2). In some cases, hatchling tracks indicated that dogs had not dug up the nest until after the hatchlings had emerged. On the Zapatilla Cays, erosion was the only recorded cause of nest loss; 58 of 59 nests followed through incubation produced hatchlings.

Table 2. Preliminary results from hawksbill nest monitoring.

Location n Dug up by dogs after hatching Poached Washed out
Río Caña 271 103   5 28
Río Chiriquí 118   47   2 30
Escudo de Veraguas   19     0   3 11
Subtotal 408 150 10 69
Small Zapatilla Cay 35* 0 0 1
Big Zapatilla Cay 24* 0 0 0
Subtotal 59* 0 0 1
TOTAL 467 150 10 70
*Only nests that were followed through incubation are included here.

Local Threats to Marine Turtle Survival
Although the Zapatilla Cays are part of the Bastimentos Island National Marine Park and are essentially unoccupied, both nesting turtles and their eggs are still threatened by poachers. The threat to turtles and their eggs from poachers is much greater on Playa Chiriqui which is bounded by two communities. The small amount of data that we have collected so far suggests that the nearly continuous presence of surveyors on these beaches during the entire nesting season is certain to have conferred a high level of protection to nesting females and their nests.

Anecdotal information suggests that a major threat to hawksbill survival is harpooning of hawksbills by members of the Kusapin, Tobobe and Playa Roja communities. In the latter community, hawksbills are occasionally taken from the nesting beach. In the vicinity of the Palo Blanco, San Pedro and San Pedrito communities, marine turtles are caught with nets. Informants estimated that at least five green turtles and 12 hawksbill turtles (some reportedly carrying tags from Playa Chiriquí) were harpooned from Kusapin and as many as ten marine turtles with Playa Chiriquí tags were caught at the other sites. If these numbers are correct, local fishing may represent a major threat to the Playa Chiriquí hawksbill turtles. Similarly, turtle harpooners are visible from the Zapatilla Cays daily after June 1. Most of these boats pass through the waters of the Bastimentos Island National Marine Park on their way to and from striking. The primary target of these strikers is the green turtle, but hawksbills are taken whenever found.

Post-hatching nest predation by dogs on Playa Chiriquí is a major concern. Cristina Ordoñez held meetings in Río Caña (August 7) with 14 people present and Río Chiriquí (August 27) with more than 50 people present and the issue of dog predation was discussed. Various dog control approaches were suggested but a consensus could not be reached.