Chiriqui Beach, Panama, the Most Important Leatherback Nesting Beach in Central America
ABSTRACT
Chiriqui Beach, in the Comarca Ngöbe-Buglé on the Caribbean coast of Panama, is the most important nesting beach for leatherback turtles (Dermochelys coriacea) in Caribbean Central America. Beach surveys during the 2003 and 2004 nesting seasons documented 3077 leatherback nests in one season and a minimum of 234 individual leatherbacks. Monitoring of nest fate revealed that predation by dogs represents the greatest human-related survival threat to leatherbacks at Chiriqui Beach, although the killing of leatherbacks from the same nesting population on beaches near the Panama–Costa Rica border also is of concern.
Carr (1956) described the 24-km long Chiriqui Beach (09°00.739′N, 081°42.767′W to 08°50.807′N, 081°34.208′W), located in the Comarca Ngöbe-Buglé, Bocas del Toro Province, Panama, as the most important nesting beach in the Caribbean for the hawksbill turtle, Eretmochelys imbricata (Fig. 1). Extensive exploitation of hawksbill turtles from this population for the international tortoiseshell trade has resulted in a severe decline in nesting numbers, estimated at 98% between the 1950s and the 1990s (Meylan and Donnelly 1999).
Citation: Chelonian Conservation and Biology 6, 1; 10.2744/1071-8443(2007)6[122:CBPTMI]2.0.CO;2
During 1979–1983, aerial and ground surveys, as well as interviews with local residents, revealed the importance of Chiriqui Beach for leatherback nesting (Meylan et al. 1985). On the night of 24 May 1980, at least 14 leatherback turtles nested on the northern 19 km of Chiriqui Beach, and, on the night of 13 June 1981, at least 16 leatherbacks nested (Meylan et al. 1985). During a ground survey conducted 13–14 June 1981, 834 leatherback tracks or bodypits of varying ages were recorded (Meylan et al. 1985).
Unlike hawksbill turtles, leatherbacks and their eggs are not used by Ngöbe residents and other inhabitants in the communities adjacent to the nesting beach. On other beaches in Caribbean Panama, however, leatherback eggs are actively collected, and some females are killed to allow the collection of their eggs and follicles (Troëng et al. 2002). A survey of 1.6 km of beach south of the Sixaola River (Fig. 1) on 22 May 1987 documented 3 dead females and the majority of the 37 recorded nests poached (A. Meylan and P. Meylan, unpubl. data). Six dead leatherbacks were counted at the northern end of Soropta Beach (Fig. 1) during an aerial survey on 2 May 2001 (S. Troëng, pers. obs.). During the same month, approximately 30 dead leatherbacks were counted during a ground survey of Soropta Beach (C. Ordoñez, pers. obs.).
A local organization, Association for the Protection of the Ngöbe-Buglé Natural Resources (APRORENANB), began hawksbill protection efforts at Chiriqui Beach in 1995. During 1999–2002, the Institute for Tropical Ecology and Conservation (ITEC) undertook hawksbill and leatherback monitoring and conservation efforts in collaboration with APRORENANB during mid-March to August. The northern 10 km of beach was monitored on a daily basis, and the remaining 14 km of beach was surveyed sporadically. In 2002, a total of 1113 leatherback nests were counted along the northern 10 km of the beach during mid-March to August (Ordoñez et al. 2003). The same year, nesting along the northern 10 km accounted for 67% of all leatherback nests counted during surveys of the entire beach (n = 3).
Aerial surveys conducted in March 2002 and February 2003 established that Chiriqui Beach hosts more leatherback nests than any other nesting beach between the San Juan River in Nicaragua (10°56.83′N,083°43.13′W) and the eastern limit of Bocas del Toro Province, Panama (08°48.72′N,081°05.29′W) (Troëng et al. 2004). Based on the aerial surveys, it was estimated that Chiriqui Beach hosts 37%–52% of all leatherback nests deposited along the 370 km of Caribbean coast in Nicaragua, Costa Rica, and Panama (Troëng et al. 2004).
In 2003, a project to monitor and recover the Chiriqui Beach hawksbill population commenced as part of a collaborative effort of several local, national, and international organizations and agencies. Continuous monitoring of sea turtle nests by local beach monitors began on Chiriqui Beach in June 2003 and was extended to the entire year in 2004. In 2004, Chiriqui Beach was included in a protected area declared by the National Environmental Authority of Panama (ANAM 2004). The objectives of this paper are to report on results of leatherback monitoring in 2003 and 2004, and suggest research and conservation priorities for the Chiriqui Beach leatherback population.
Methods
Track surveys to record all leatherback nesting activity were conducted daily from 13 June to 31 August 2003 and from 1 March to 31 August 2004. In addition, track surveys were conducted weekly during January 2004 and every 2 days in February 2004. Tracks associated with a body pit and with large amounts of sand displaced were classified as nests and continuous tracks, without sand displacement, were recorded as non-nesting emergences.
Sporadic night patrols to tag nesting leatherbacks were conducted from 13 June to 23 July 2003 and from 9 March to 18 July 2004. Monel no. 49 flipper tags (National Band & Tag Company, Newport, Kentucky, USA) were attached to both rear flippers of nesting leatherbacks. The tags have a unique tag number and carry a message rewarding the finder (US$5.00) for returning the tag by mail to the University of Florida.
A subset of leatherback nests were marked and monitored in 2003 (n = 81) and 2004 (n = 243). Marked nests were inspected daily until they were predated, washed out, or hatchling tracks were observed. The nests were excavated after hatchling tracks were observed or after a maximum of 65 days.
Results
During the night patrols in 2003, 9 leatherbacks tagged in previous years or on other nesting beaches were observed, and 58 untagged leatherback females were seen and subsequently tagged. In 2004, 56 previously tagged leatherbacks were observed, and 234 turtles were newly tagged. Previously tagged leatherbacks were originally tagged on Chiriqui Beach and beaches in Colombia (Playona), Costa Rica (Gandoca, Pacuare, and Tortuguero), and Panama (Playa Bluff, Playa Larga, San San, and Soropta). Also, a leatherback captured in-water and tagged by researchers off Nova Scotia, Canada, nested on Chiriqui Beach in 2003 (M. James, pers. comm.). A leatherback tagged on Chiriqui Beach on 28 June 2002 was observed nesting on Levera Beach, Grenada (12°13.656′N, 061°36781′W), on the night of 12 April 2004 (C. Lloyd, pers comm.). Levera Beach is located approximately 2260 km from Chiriqui Beach.
A total of 250 leatherback nests were recorded between 13 June and 31 August 2003 (Fig. 2). In 2004, 3077 leatherback nests were recorded between 1 January and 31 August (Fig. 3). Of these nests, 241 were deposited between 13 June and 31 August, the same interval as was monitored the previous year. The leatherback nesting levels recorded for the northern 19 km of the beach on the nights of 24 May 1980 and 13 June 1981 are similar to the levels of nesting recorded in 2004 (Table 1).
Citation: Chelonian Conservation and Biology 6, 1; 10.2744/1071-8443(2007)6[122:CBPTMI]2.0.CO;2
Citation: Chelonian Conservation and Biology 6, 1; 10.2744/1071-8443(2007)6[122:CBPTMI]2.0.CO;2
No poaching of leatherback nests was observed in 2003. The major non-natural survival threat was predation of nests by domestic dogs, which affected 54.3% of the monitored nests (Table 2). Preliminary results from 2004 suggest no poaching, but 7.8% of leatherback nests were predated by dogs (Table 2). Dogs often dug up the nests after hatching, and it is not known if any hatchlings managed to emerge before dog predation took place.
Discussion
Observations at Chiriqui Beach of leatherbacks tagged elsewhere demonstrate that the nesting aggregation forms part of a population that nests along the Caribbean coast of Central America and Colombia. The observation of a leatherback tagged on Chiriqui Beach nesting at Levera Beach, Grenada, suggests that the population's nesting distribution may even be more wide-ranging. However, more tag returns and genetic information are necessary before concluding that there is substantial exchange between nesting beaches in Central America and the eastern Caribbean. The exchange between nesting beaches in Central America and Colombia means that activities negatively impacting leatherback survival on other beaches in the region may have negative consequences for the Chiriqui Beach nesting aggregation. The killing of leatherback turtles for their eggs on the beaches close to the Panama–Costa Rica border continued in 2004 and 2005 (C. Ordoñez, pers. obs.) and is of particular concern. Detailed information on the migratory routes and marine habitat use of Chiriqui Beach leatherback turtles is currently not available. The leatherback tagged in Canada and later seen nesting on Chiriqui Beach shows the considerable migrations undertaken by leatherback turtles from the Chiriqui nesting aggregation. Tag returns and satellite telemetry of turtles from nesting beaches in Caribbean Costa Rica revealed that the leatherbacks travel through the Caribbean, Gulf of Mexico, and the North Atlantic, and range at least as far as from 2° to 50°N and 9° to 97°W (Troëng et al. 2004; Troëng et al. 2007). Thus, fisheries by-catch in these waters may also impact Chiriqui leatherbacks. It would be desirable to conduct postnesting satellite telemetry to determine the exact movements of Chiriqui Beach leatherback turtles. There are plans to fit at least 2 leatherback turtles with transmitters during future nesting seasons.
A comparison of results from track surveys conducted on the ground at Chiriqui Beach in 2004 with nesting levels on other beaches (Troëng et al. 2004) confirms that Chiriqui Beach hosts more nests than any other beach in Caribbean Central America. In 2004, the Chiriqui Beach hosted more than twice the combined number of leatherback nests laid at Gandoca, Pacuare, and Tortuguero beaches in Costa Rica (Troëng et al. 2004).
The number of tagged females recorded at Chiriqui Beach should be interpreted with care. Firstly, night patrols were not conducted throughout every night of the nesting season, so many nesting females were missed. Secondly, tag loss in leatherbacks is high (Rivalan et al. 2005), so some females could have been tagged more than once. Even with these methodological limitations, the leatherback nesting levels at Chiriqui Beach clearly establish it as a priority area for conservation efforts. Comparison of the nesting activity in 1980 and 1981 with that of 2004 suggests very similar levels. However, the limited number of data points from the 1980s prevents any firm conclusions regarding the long-term nesting trend for leatherback turtles at this site. The decline in leatherback nesting on beaches in Caribbean Costa Rica between 1995 and 2003 is a cause for concern, because it suggests that the leatherback population is in decline (Troëng et al. 2004). Several more years of complete nesting data are needed to determine the trend of leatherback nesting activity at Chiriqui Beach, and it is hoped that the current project partners will be able to continue monitoring efforts for at least 10 years.
It is encouraging that no leatherback nests were observed to have been destroyed by poaching at Chiriqui Beach in 2003 and 2004. Local residents, mainly Ngöbe indigenous people, do not consume leatherback turtles or their eggs for traditional reasons. Dog predation represents the main human-related threat to this species at Chiriqui Beach. In 2004, 2 dogs were captured by beach monitors, and the local organization APRORENANB demanded a reward to return the dogs to their owners. This resulted in many local residents tying up their dogs (pers. obs.) with a subsequent drop in nest predation. A long-term strategy for dealing with dog predation of leatherback and hawksbill nests at Chiriqui Beach is urgently needed.
In August 2004, the National Environmental Authority (ANAM) declared the Damani-Guariviara Wetland of International Importance, which includes Chiriqui Beach and adjacent areas (ANAM 2004). Local response to sea turtle conservation and monitoring efforts has been great. Hopefully, the protected area designation and future conservation efforts of authorities, local communities, and conservation organizations will serve to provide adequate management for the Chiriqui leatherback nesting aggregation, at least on the beach. Local conservation efforts, however, will be insufficient if survival threats to leatherback turtles on other nesting beaches in the region and in-water are not successfully addressed.
Chiriqui Beach, Comarca Ngöbe-Buglé, and other leatherback nesting beaches in Bocas del Toro Province, Panama.
Leatherback nesting at Chiriqui Beach, June–August 2003.
Leatherback nesting at Chiriqui Beach, January–August 2004.
