Scientific Research

Liles et al. 2015_Hawksbill nest site selection in El Salvador and Nicaragua

One size does not fit all: Importance of adjusting conservation practices for endangered hawksbill turtles to address local nesting habitat needs in the eastern Pacific Ocean.  

Conservation biologists frequently use data from the same or related species collected in diverse geographic locations to guide interventions in situations where its applicability is uncertain. There are dangers inherent to this approach. The nesting habitats of critically endangered hawksbill sea turtles (Eretmochelys imbricata) cover a broad geographic global range. Based on data collected in the Caribbean and Indo-Pacific, conservationists assume hawksbills prefer open-coast beaches near coral reefs for nesting, and that individual hawksbills are highly consistent in nest placement, suggesting genetic factors partially account for variation in nest-site choice. We characterized nest-site preferences of hawksbills in El Salvador and Nicaragua, where >80% of nesting activity occurs for this species in the eastern Pacific, and !90% of hawksbill clutches are relocated to hatcheries for protection. We found hawksbills preferred nest sites with abundant vegetation on dynamic beaches within mangrove estuaries. Nests in El Salvador were located closer to the ocean and to the woody vegetation border than nests in Nicaragua, suggesting female hawksbills exhibit local adaptations to differences in nesting habitat. Individual hawksbills consistently placed nests under high percentages of overstory vegetation, but were not consistent in nest placement related to woody vegetation borders. We suggest conservation biologists use caution when generalizing about endangered species that invest in specific life-history strategies (e.g., nesting) over broad ranges based on data collected in distant locations when addressing conservation issues.

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Liles et al. 2015_Hawksbill nest site selection in El Salvador and Nicaragua

Chacón-Chaverri et al. 2014_Golfo Dulce, Costa Rica, an important foraging ground for the Pacific hawksbill turtle

Golfo Dulce, Costa Rica, an important foraging ground for the Pacific hawksbill turtle (Eretmochelys imbricata)

Limited quantitative information is available for hawksbill turtles (Eretmochelys imbricata) at foraging grounds in the Eastern Tropical Pacific (ETP), where the species composes one of the most endangered marine turtle populations on the planet. Between August 2010 and March 2013 we captured individual hawksbill turtles using entanglement nets along the edges of mangroves and seagrasses of the Golfo Dulce, in southwest Pacific Costa Rica. A total of 62 hawksbills were captured, including 14 recaptures, of which 46 (74.19%) were juveniles (CCL<66cm) and 16 (25.81%) were adults. The catch per unit effort (1 unit: 100m of net for 7h) during the study ranged between 0.03 and 0.07. The Golfo Dulce is highly turbid during the rainy season (May-November), particularly at our study area, as high sediment loads due to intensive runoff lead to poor water clarity. The probability of detection of hawksbills was considerably higher in the dry season (December-April) compared to the rainy season, suggesting these turtles may prefer waters with higher clarity. None of the individuals captured had evidence of internal or external tags, making it possible to conclude that they had not been previously marked at other feeding or breeding sites. A total of 28 (45.16%) individuals were found to host the ectoparasitic barnacle Stephanolepas muricata, which in high concentrations can be harmful by limiting the mobility of organs and limbs. Although consistent in-water quantification of hawksbills in the ETP remains scant, this study represents the longest and most robust marine monitoring dataset for hawksbills in the region to date. Our findings highlight the relevance of the Golfo Dulce as an important foraging ground for hawksbill turtles in the ETP and emphasize the need to monitor and protect this habitat to aid efforts to recover this critically endangered marine turtle population.

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Chacon-Chaverri et al. 2014_Golfo Dulce, Costa Rica, an important foraging ground for the Pacific hawksbill turtle

Heidemeyer et al. 2014_New foraging grounds for hawksbill and greens in Costa Rica

New foraging grounds for hawksbill (Eretmochelys imbricataand green turtles (Chelonia mydas) along the northern Pacific coast of Costa Rica, Central America

Scarce information is available on the foraging grounds of Eastern Pacific sea turtle populations, which hinders the design of efficient national and regional conservation strategies. We surveyed five locations along Costa Rica’s North Pacific between 2010-2013 using 45cm mesh turtle tangle nets, with the aim to explore and document new foraging sites (Cabo Blanco, Punta Coyote, Punta Pargos, Punta Argentina, and Bahía Matapalito). We standardized Catch Per Unit Effort (CPUE) as turtles caught per 100m of headrope length per one-hour soak time, which ranged from 0.06 at Punta Pargos to 0.58 in Bahía Matapalito for hawksbill turtles (Eretmochelys imbricata), and from 0.01 in Punta Coyote to 0.10 in Cabo Blanco for Eastern Pacific green turtles (Chelonia mydas). We found site-specific size ranges for E. imbricata with mean ± Standard Deviation (SD) Curve Carapace Lengths (CCL) of 42.46±17.55cm in Bahía Matapalito and 61.25±13.08cm in Cabo Blanco. Only one individual was found at each of the other sites with CCLs from 49.6cm to 60.5cm. Green turtles were found at three of the surveyed locations with mean CCLs of 67.67±19.44cm at Cabo Blanco and 69.40±9.40cm at Punta Coyote and only one individual at Bahía Matapalito with a CCL of 56.2cm. The absence of adult size classes for E. imbricata and of small juvenile size classes for C. mydas at most of these sites stresses the complexity of species-specific distribution during different life stages in the Eastern Pacific and the urgent need to implement long-term monitoring at different coastal sites along the North Pacific to understand habitat connectivity. This study reveals the existence of fragile, non-protected foraging grounds for hawksbill and green turtles in Costa Rica’s North Pacific, and serves as a guide for future research initiatives to strengthen national and regional conservation strategies.

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Heidemeyer et al. 2014_New foraging grounds for hawksbills & greens

 

Tobón and Amorocho 2014_Hawksbills in southern Colombia

Population Study of the Hawksbill Turtle Eretmochelys imbricata (Cheloniidae) in the Southern Pacific region of Colombia.

The objective of this research was to determine biological and ecological population characteristics of the hawksbill turtle (Eretmochelys imbricata) found in the southern Colombian Pacific department of Cauca. Morphometric measurements were recorded, the health status of individuals was reviewed, and blood samples were taken for a biochemistry assessment. During the seven months of the investigation, 25 hawksbill turtles were caught (16 different individuals) on the reefs of Gorgona Natural National Park. Forty-six percent of the total numbers of turtles assessed were recaptured during the study period. While no obvious health problems were noted, most animals possessed epibionts and filamentous algae covering the carapace, some parts of the limbs, as well as on their neck. Curved carapace length (CCL) showed the highest proportion of individuals were between 37 and 45 cm. Sixteen individuals captured in Gorgona Natural National Park were compared with 11 individuals captured in the coastal zone of the department of Cauca. Using the Mann-Whitney U test, a significant difference in CCL was found between these two groups; the animals from Gorgona National Park were larger than those present on the coast of themainland (Z = -2.59, p = 0.007). Uric acid concentrations were found to be higher than previously referenced values.

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Tobon y Amorocho_2014_Carey en el sur de Colombia

 

Liles et al. 2014_International priorities & human wellbeing associated with hawksbills

Connecting international priorities with human wellbeing in low-income regions: lessons from hawksbill turtle conservation in El Salvador.

Hawksbill turtles (Eretmochelys imbricata) are highly endangered in the eastern Pacific Ocean, yet their eggs continue to be an important subsistence resource for impoverished coastal residents in El Salvador. In this study, we use naturalistic inquiry to explain the realities experienced by coastal residents who share habitat with hawksbills in El Salvador, and then suggest implications of the disparities between these realities and international priorities for hawksbill conservation and community development in El Salvador and other low-income regions. To provide a context for understanding hawksbill conservation and its implications for similar challenges related to conservation and wellbeing, we first summarise the conservation context, including the emergence of sea turtle conservation in El Salvador. We then describe our naturalistic approach, including the ethnographic methodology for this study. Finally, we detail the analysis of interviews conducted with tortugueros (i.e. local sea turtle egg collectors), to help explain how hawksbills fit into local realities. Our results demonstrate that, from the perspective of tortugueros, (1) the primary importance of hawksbills is the economic value attached to egg sales, but there exists a deeper connection to local culture; (2) egg purchase by hatcheries is a socially just conservation strategy that benefits both hawksbill and human wellbeing; and (3) opportunities for local residents to participate in decision-making regarding sea turtle conservation are limited, and should be increased. We argue that harmonising international conservation priorities with local community development realities is one path towards simultaneously contributing to long-term sea turtle recovery and human wellbeing in low-income regions.

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Liles et al. 2014_International Priorities & Human Wellbeing with Hawksbill

 

Trujillo-Arias et al. 2014_Phylogeography of hawksbills in the Colombian Pacific and Atlantic (Spanish)

Relaciones filogeográficas de algunas colonias de alimentación y anidación de la tortuga carey (Eretmochelys imbricata) en el Pacífico y Caribe Colombianos.

The sea turtle Eretmochelys imbricata inhabits tropical waters of all oceans. IUCN considers this species to be critically endangered and its populations are affected by illegal international shell traffic. We present a pioneer research for Colombia and the Tropical Eastern Pacific, since populations located in 1) Parque Nacional Natural Gorgona, 2) Corales del Rosario y San Bernardo, and 3) Cabo de la Vela (Guajira) were genetically characterized using mtDNA control region sequences. Two new haplotypes for the Eastern Pacific were found, although with low diversity indexes (h: 0.2857 ± 0.1964; π: 0.0009 ± 0.0008). Five haplotypes were found for Corales del Rosario and San Bernardo’s populations, with high diversity indexes (h: 0.9333 ± 0.1217; π: 0.0089 ± 0.0056). Finally, Cabo de la Vela population presented relatively high diversity indexes (h: 0.6429 ± 0.0539; π: 0.0076 ± 0.0041). The genetic distance analysis revealed no significant differentiation between the Colombian Caribbean rookeries (Φst = 0.002, p > 0.05; Fst = 0.083, p > 0.05). However, significant differences were found between Cabo de la Vela nesting rookery and eight nesting rookeries along the Caribbean Sea, which is a genetic pattern characteristic of sea turtles on a global scale. Our phylogeographic analysis revealed a deep split between the Atlantic and the Pacific-Indian Ocean. For Atlantic phylogroup no clear clustering between haplotypes was perceived, while in the Pacific-Indian phylogroup a possible distribution of isolation by distance was observed. The divergence time reported in this study between the Atlantic and Pacific-Indian lineages suggests a separation that may have occurred between the Pliocene and Pleistocene (7 Ma), possibly influenced by the rise of the Panama Isthmus.

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Trujillo-Arias et al. 2014_Phylogeography of hawksbills in the Colombian Pacific and Atlantic

 

Gaos et al. 2014_Hawksbill research in the Gulf of Fonseca_Programmatic report

Hawksbill research in the Gulf of Fonseca_Programmatic report

Current nesting numbers of hawksbill turtles (Eretmocheyls imbricata) in the eastern Pacific suggest it is one of the most endangered marine turtle populations in the world. The Gulf of Fonseca (GOF) is an at-sea-inlet under joint jurisdiction of El Salvador, Honduras and Nicaragua that was identified by the Eastern Pacific Hawksbill Initiative (ICAPO) as critical habitat for hawksbill turtles. Via this two-year project we conducted systematic surveys of the GOF to identify nesting, foraging and fisheries interactions in the area.

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Gaos et al. 2014_Hawksbill research in Gulf of Fonseca_Programmatic report

Carrion et al. 2013_Habitat and diet of juvenile hawksbills in Costa Rica

Habitat Use and Diet of Juvenile Eastern Pacific Hawksbill Turtles (Eretmochelys imbricata) in the North Pacific Coast of Costa Rica.

The hawksbill turtle (Eretmochelys imbricata) is critically endangered throughout its global range and is particularly threatened in the eastern Pacific, a region where our knowledge of the ecological traits is very limited. Understanding habitat preferences of hawksbills at different life stages is necessary to create effective local and regional conservation strategies. We studied habitat use and the diet of juvenile hawksbill sea turtles at Punta Coyote, a rocky reef located along the Nicoya Peninsula on the north Pacific coast of Costa Rica, along the northern boundary of the Caletas–Ario National Wildlife Refuge. We tracked 12 juvenile hawksbills (36–69-cm curved carapace length) with acoustic transmitters to study their habitat use. Turtles were on the rocky reef more frequently than the sandy bottoms (X2 1 = 29.90, p = 0.00). The 95% fixed kernel density home range analysis revealed high-intensity use of the rocky reef, where hawksbills mainly dove in shallow waters (7.6 ± 3.3 m). Less than 5% of the 95% home range area overlapped with the Caletas–Ario National Wildlife Refuge. Hawksbills fed mainly on 2 invertebrate species regardless of season: a sponge (Geodia sp.) (mean volume = 67%) and a tunicate (Rhopalaea birkelandi) (mean volume = 51%). Our surveys along the Nicoya Peninsula suggested that use of rocky reefs by juvenile hawksbill turtles was common. To protect juvenile hawksbills in the study area, we recommend that this site be granted official protection status as part of the Caletas–Ario National Wildlife Refuge. We also suggest studying other discrete rocky reefs along the Nicoya Peninsula to determine critical habitats for the hawksbill turtle to improve conservation and management policy.

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Carrion-Cortez et al_Habitat and diet of hawksbills in Costa Rica

 

Brittain et al. 2012_Juvenile hawksbills along Pacific Guatemala

Two Reports of Juvenile Hawksbill Sea Turtles (Eretmochelys imbricata) on the Southeast Coast of Guatemala

Hawksbill sea turtles (Eretmochelys imbricata) are one of the rarest sea turtle species within the eastern Pacific region (Cornelius 1982; Gaos et al. 2010; Mortimer & Donnelly 2008) and published data on present or historic levels of nesting and foraging of the species remains scant. This paucity of information led to the formation of the Eastern Pacific Hawksbill Initiative (ICAPO), an organization established to compile information on, and promote conservation of hawksbill turtles in the eastern Pacific. Akazul: Community, conservation and ecology is a UK registered not for profit organization, working primarily with the coastal zone aspects of the conservation of olive ridley (Lepidochelys olivacea) and leatherback (Dermochelys coriacea) sea turtles as well as monitoring the habitat of eastern Pacific green (Chelonia mydas) and hawksbill sea turtles in the small coastal community of La Barrona, Guatemala. Akazul has recently become a member of ICAPO and has been contributing information about turtles since March 2011. Although there has previously been a small quantity of data published on nesting and stranding occurrences of hawksbills in Guatemala (see Gaos et al. 2010;Higginson 1989) it is thought that there are more incidents than are currently reported. Potential reasons attributing to the lack of reports include

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Brittain et al. 2012_Two juvenile hawksbills along Pacific Guatemala

Gaos et al. 2012_Dive behaviour of adult hawksbills in the EP

Dive behaviour of adult hawksbills (Eretmochelys imbricata, Linnaeus 1766) in the eastern Pacific Ocean highlights shallow depth use by the species.

Understanding the movement and dive behaviour of marine turtles directly informs spatial management strategies. Hawksbill turtles (Eretmochelys imbricata, Linnaeus 1766) are a globally endangered marine turtle species, with populations in the eastern Pacific Ocean identified as particularly threatened. To date, very little research on the dive behaviour of hawksbills has been conducted. Most studies have focused on juveniles in the Wider Caribbean region, and no dive behaviour has been described for hawksbills in the eastern Pacific. Using satellite-relayed dive loggers attached to five adult hawksbills, we analyzed dive trends and differences among individuals, movement phases and diel time periods, and compared our findings with those from hawksbills in other regions of the world. Our research indicates that adult hawksbills in the eastern Pacific predominantly use shallow waters (i.e. ≤10 m), with dives rarely occurring to depths >20 m. Additionally, in contrast to previous research, we found similar dive behaviour across diel time periods, suggesting nocturnal activity may be more prevalent than previously believed. Despite some similarities in dive behaviour across individuals, individual variability was also evident. More research on adult hawksbills is urgently needed to increase our understanding of basic hawksbill ecology and behaviour, and improve management of this critically endangered species in the eastern Pacific Ocean.

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Gaos et al. 2012_Hawksbill_dive_behaviour in the EP

 

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