Vol. 30: 117–124, 2016 ENDANGERED SPECIES RESEARCH Published May 12 doi: 10.3354/esr00733 Endang Species Res OPENPEN ACCESSCCESS Post-breeding migration routes of marine turtles from Bonaire and Klein Bonaire, Caribbean Netherlands L. E. Becking1,2,*,**, M. J. A. Christianen1,2,3,**, M. I. Nava4,*, N. Miller4, S. Willis4, R. P. van Dam5 1Marine Animal Ecology, Wageningen University & Research Centre, PO Box 3700 AH Wageningen, The Netherlands 2Institute for Marine Resources and Ecosystems Studies (IMARES), Maritime Department, PO Box 57, 1780 AB Den Helder, The Netherlands 3Groningen Institute for Evolutionary Life Sciences, University of Groningen, PO Box 11103, 9700 CC Groningen, The Netherlands 4Sea Turtle Conservation Bonaire, PO Box 492, Kralendijk, Bonaire, Caribbean Netherlands 5Chelonia Inc, PO Box 9020708, San Juan 00902-0708, Puerto Rico ABSTRACT: The management of small rookeries is key to conserving the regional genetic diver- sity of marine turtle populations and requires knowledge on population connectivity between breeding and foraging areas. To elucidate the geographic scope of the populations of marine tur- tles breeding at Bonaire and Klein Bonaire (Caribbean Netherlands) we examined the post-breed- ing migratory behavior of 5 female loggerheads Caretta caretta, 4 female green turtles Chelonia mydas, and 2 male and 13 female hawksbill turtles Eretmochelys imbricata during the years 2004−2013. After leaving Bonaire, the 24 tracked turtles frequented foraging grounds in 10 coun- tries. The distances swum from Bonaire to the foraging areas ranged from 608 to 1766 km for log- gerhead turtles, 198 to 3135 km for green turtles, and 197 to 3135 km for hawksbill turtles, together crossing the waters of 19 countries. Males represented the minority in this study, but we made 2 key observations that require further research: males remained in the vicinity of the breeding area for 3−5 mo, which is 2−5 times longer than females, and males migrated greater distances than previously recorded. Although the turtles dispersed widely across the Caribbean, there appeared to be 2 benthic foraging areas of particular importance to all 3 species of marine turtles breeding at Bonaire, namely the shallow banks east of Nicaragua and Honduras (n = 8 tracked turtles) and Los Roques, Venezuela (n = 3). Marine turtles breeding at Bonaire face threats from legal turtle harvesting, illegal take, and bycatch in the waters that they traverse across the Caribbean. KEY WORDS: Chelonia mydas · Caretta caretta · Eretmochelys imbricata · Migration · Foraging areas · Population connectivity · Satellite telemetry INTRODUCTION ibbean Netherlands, are used regularly for breeding by 3 marine turtle species: loggerheads Caretta It is by now well established that marine turtles can caretta, green turtles Chelonia mydas and hawksbills migrate long distances between their breeding areas Eretmochelys imbricata. Klein Bonaire beaches har- and foraging grounds (Hays & Scott 2013). However, bor the highest concentration of nesting hawksbill for small rookeries, such as those utilizing the islands and loggerhead turtles in the southern Caribbean of the Caribbean Netherlands, knowledge of turtle (excluding Panama) (Debrot et al. 2005, Dow Piniak migratory behavior remains scarce. The beaches and & Eckert 2011). Post-breeding adult turtles do not near shore areas of Bonaire and Klein Bonaire, Car- appear to remain near the islands after the reproduc- © The authors 2016. Open Access under Creative Commons by *Corresponding authors: [email protected], Attribution Licence. Use, distribution and reproduction are un - [email protected] restricted. Authors and original publication must be credited. **Joint first authors, contributed equally Publisher: Inter-Research · www.int-res.com 118 Endang Species Res 30: 117–124, 2016 tive season (Stapleton et al. 2014), yet it is unknown For the 3 species (loggerhead, green and hawksbill what their migration routes are and to which forag- turtles) combined, the breeding season spans the ing grounds these adults migrate. period from May to December, with a peak in nesting All marine turtles have been legally protected on between July and September (Stapleton et al. 2014). and around the islands since 1991. Klein Bonaire, the Turtles were selected based on their size (straight most important nesting area, received full protection carapace length > 80 cm). Further behavioral obser- from development when it was purchased by the vations and recapture data on tagged individuals government in 1999 and incorporated in its entirety showed that the tracked turtles can be considered into the Bonaire National Marine Park. In order to set ‘breeding turtles’; females emerged on nesting up biologically sound management strategies, com- beaches of Bonaire and tagged males were mating, prehensive baseline knowledge is required on turtle as observed during in-water surveys. Additionally, migration in the Dutch Caribbean. There is, however, mature-size turtles were not ob served during in- a significant lack of knowledge on the migration water surveys outside the breeding season in routes of post-breeding adults and on how nesting Bonaire’s waters (Stapleton et al. 2014). colonies from Bonaire are linked to regional neritic Breeding turtles were held for tagging, measure- foraging aggregations. Knowledge of such linkages ment, and transmitter application on nesting beaches is valuable, as foraging aggregations are not homo- (14 females, after oviposition) or in waters immedi- geneously distributed across the Caribbean Sea and ately adjacent to the beaches (3 female loggerheads, migration routes can vary among individuals of the 2 female hawksbills, 2 male hawksbills) (see Table 1, same nesting colony (e.g. Bowen et al. 2007). Bio - Fig. 1A). All animals in this study were double-tagged geographical information on migratory be havior is on their front flippers using metal Inconel No. 681 therefore required for prioritizing research and con- flipper tags (www.nationalband.com) and their lengths servation efforts, for example, in the assignment of were measured (straight [SCL] or curved [CCL] cara- Regional Management Units (Godley et al. 2008, pace length taken from the nuchal notch to the pos- Hamann et al. 2010, Wallace et al. 2010). terior tip of the longest post-central scute). Turtles In order to identify migration routes and key neritic were kept on the beach in a custom-built box or, at foraging habitats, we used satellite telemetry to track sea, constrained in a small boat. Satellite transmitters the movements of marine turtles after breeding at used were the models ST-20 (size: 12 × 6 × 3 cm; Bonaire and Klein Bonaire. Our specific aims were to weight in air: 280 g; Telonics), Spot4 (mold203: size: (1) identify current post-breeding migration routes 16 × 4 × 3 cm; weight in air: 260 g; Wildlife Comput- with the aid of satellite tracking and (2) establish the ers), or Spot5 (size: 8 × 5 × 2 cm; weight in air: 95 g). location of neritic foraging grounds of breeding pop- Prior to transmitter attachment the carapace was ulations at Bonaire. cleaned by removing external commensals, then the instrument was applied at the highest point on the carapace using a silicone or latex elastomer base and MATERIALS AND METHODS covered with resined fiberglass, following Balazs et al. (1996). A fiberglass reinforcement strip was placed This study was carried out during the period 2003− anterior to the point of antenna attachment to reduce 2013 in the marine turtle breeding areas at Bonaire abrasion to the antenna. An angled piece of fiber- and Klein Bonaire: No Name Beach on Klein Bonaire glass was positioned anterior to the flat frontal area of (12.0953° N, 68.1756° W), Playa Chikitu on NE Bo n - the ST-20 transmitters to reduce hydrodynamic drag. aire (12.1650° N, 68.20540° W), and South Bonaire Turtles were released at the location of capture (re - (12.0233° N, 68.1557° W). Since the year 2010 Bonaire corded by GPS) after the 2−4 h transmitter application has formally been part of the Caribbean Netherlands procedure. In subsequent years, whenever possible, as a special municipality (‘Bijzondere Geme ente’) of study animals were recaptured, and, if transmitters The Netherlands. As a signatory of diverse interna- remained attached, these were removed (n = 3). tional treaties (e.g. Cartagena/Specially Protected Location data for instrumented turtles were received Areas and Wildlife [SPAW] protocol, Convention on through Argos. Studies by Argos (2013) and Hays et Biological Diversity, CITES Convention, Convention al. (2001, 2014) have shown that Argos Location for Migratory Species, Inter-American Convention Classes (LC) 3, 2, 1 are the most reliable; thus, data in for the Protection and Conservation of Sea Turtles), LCs 0, A, and B were removed prior to the plotting of The Netherlands is obliged to protect marine turtles tracks. Locations (n = 134) were filtered to exclude inhabiting Dutch Caribbean waters. biologically unreasonable results for travel speeds Becking et al.: Post-breeding migration routes from Bonaire 119 >5 km h−1 (Luschi et al. 1998, 2001, Seminoff et al. mined by the first occasion of the animal reaching an 2008). As post-breeding turtles were not travelling in area <20 km in radius, wherein later LC 1, 2, and 3 straight lines on post-nesting migrations, but rather positions were located during a period of 7 d or were ex pected to be moving in complex ways in longer. The location was subsequently evaluated to coastal waters, we did not use a turning angle filter. be a foraging site based on the literature, ground- Final maps were produced with QGis software (QGIS truthing (Puerto Rico), or the assessment of habitat Development Team 2015). Minimum turtle migration and depth from remote sources (e.g. maps, Google track length was measured by examining the total Earth). path connecting all coordinates with Argos LCs 1, 2, and 3. Date of departure from the breeding grounds was the date when a distance post-breeding >20 km RESULTS from the transmitter application location was attained and the turtle exhibited sustained departure momen- A total of 24 turtles were tracked; all migrated to tum (Blumenthal et al.