Scientific Research

Gaos et al. 2017_Natal foraging philopatry

Natal foraging philopatry in eastern Pacific hawksbill turtles

The complex processes involved with animal migration have long been a subject of biological interest, and broad-scale movement patterns of many marine turtle populations still remain unresolved. While it is widely accepted that once marine turtles reach sexual maturity they home to natal areas for nesting or reproduction, the role of philopatry to natal areas during other life stages has received less scrutiny, despite widespread evidence across the taxa. Here we report on genetic research that indicates that juvenile hawksbill turtles (Eretmochelys imbricata) in the eastern Pacific Ocean use foraging grounds in the region of their natal beaches, a pattern we term natal foraging philopatry. Our findings confirm that traditional views of natal homing solely for reproduction are incomplete and that many marine turtle species exhibit philopatry to natal areas to forage. Our results have important implications for life-history research and conservation of marine turtles and may extend to other wide-ranging marine vertebrates that demonstrate natal philopatry

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Gaos et al_NFP in EP hawksbills

Llamas et al. 2017_Hawksbills foraging at Coiba, Panama

Distribution, size range and growth rates of hawksbill turtles at a major foraging ground in the eastern Pacific Ocean

Hawksbill sea turtles (Eretmochelys imbricata) inhabiting the eastern Pacific Ocean are one of the world’s most threatened marine turtle management units. Despite the fact that knowledge about the status of sea turtles at foraging grounds is a key element for developing the effective conservation strategies, comprehensive studies of hawksbills at foraging habitats in the eastern Pacific remain lacking. For many years anecdotal information indicated Coiba Island National Park in Panama as a potentially important hawksbill foraging ground, which led to the initiation of monitoring surveys in September 2014. Ongoing mark-recapture surveys to assess population status, generate demographic data and identify key foraging sites have been conducted every six months in the park since that time. To date, a total of six monitoring campaigns consisting of four days each have been conducted, leading to the capture and tagging of 186 hawksbills, 51 of which were recaptured at least once. The size range of captured individuals was 30.0 to 75.5 cm and largely comprised of juveniles. Somatic growth rates of individual hawksbills were highly variable, ranging from -0.78 to 7.1 cm year-1. To our knowledge, these are the first published growth rates for juvenile hawksbill turtles in the eastern Pacific Ocean. When these growth data are combined with information on hawksbill demography and distribution, our findings indicate Coiba Island National Park is one of the most important known foraging sites for hawksbill sea turtles in the eastern Pacific Ocean.

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Llamas et al. 2017_Ei foraging Coiba

Gaos et al. 2017_Hawksbill nesting in the eastern Pacific

Living on the Edge: Hawksbill turtle nesting and conservation along the Eastern Pacific Rim

Prior to 2007, efforts to monitor and conserve hawksbill turtles (Eretmochelys imbricata) in the eastern Pacific Ocean were opportunistic and records were virtually non-existent. The first abundance estimates were published in 2010, but contained limited data on the species. Ongoing research since that time has led to the identification of several rookeries, including sites containing large proportions of the overall hawksbill nesting currently known to occur in the region. Monitoring projects were established at several sites and have since provided substantial nesting data on the species. Here we summarize data collected between 1983 and March 2016 from all sites (n = 9) confirmed to host >10 nests in any given season to provide an update on hawksbill nesting in the eastern Pacific. We documented a total of 3,508 hawksbill nests, 265,024 hatchlings and 528 individual nesting females in the region. The vast majority of these records (99.4%, 99.9% and 99.6%, respectively) were generated subsequent to 2007, coinciding with the discovery of eight of the nine rookeries included in this study and the organization of monitoring efforts at those sites, which led to the increased documentation conferred here. Our findings should not be misconstrued as increases in actual nesting or signs of recovery, which could diminish the ongoing need for conservation actions, but rather as optimism, that there is still an opportunity to restore the species in the eastern Pacific. The top three sites in terms of average annual number of nests were Estero Padre Ramos (Nicaragua; 213.2 ± 47.6 nests), Bahia de Jiquilisco (El Salvador; 168.5 ± 46.7 nests) and Aserradores (Nicaragua; 100.0 ± 24.0 nests), and all three sites are located in mangrove estuaries in Central America, highlighting the importance of these rookeries/habitats for the survival and recovery of hawksbills in the region. The remaining six sites received between 6.9 ± 7.3 nests (Costa Careyes, Mexico) and 59.3 ± 17.7 nests (Los Cobanos, El Salvador) annually. By integrating data collected on nesting hawksbills with local conservation realities at the most important known hawksbill rookeries in the eastern Pacific, we provide a more holistic view of the conservation status and management needs of the species in this ocean region.

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Gaos et al. 2017_Living on the edge

Zuñiga-Marroquin et al. 2017_Hawksbill genetics along Pacific Mexico

Genetic characterization of the Critically Endangered hawksbill turtle (Eretmochelys imbricata) from the Mexican Pacific region

The hawksbill turtle (Eretmochelys imbricata) is a Critically Endangered species and has been a species of interest for decades. Only in recent years attention has been focused on the populations of the Eastern Pacific Ocean. We present a genetic characterization of this species in the Mexican Pacific, based on mitochondrial DNA sequences. Six localities were sampled along the Pacific Coast, from the Gulf of California to Chiapas, between 2002 and 2007. Seventeen individuals found in marine habitats at six localities and six nests laid at three nesting sites were sampled along the Mexican Pacific. Our results show five haplotypes of 766 bp, three previously identified and two that to date were not reported. Genetic diversity indices indicate moderate to low variation for this region. Even with the small sample size reported here, our results show important relationships between the Mexican Pacific hawksbills and nesting populations of Central America and foraging areas along the Eastern and Indo-Pacific. These results, along with updated information on ecology and behavior, are essential for the future approach

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Zuniga et al. 2017_Ei genetics Pac MX

Liles et al. 2017_Hawksbill bycatch in lobster gillnets

Survival on the rocks: high bycatch in lobster gillnet fisheries threatens hawksbill turtles on rocky reefs along the Eastern Pacific coast of Central America

Small-scale coastal fisheries can cause detrimental impacts to non-target megafauna through bycatch. This can be particularly true when high-use areas for such species overlap with fishing grounds, as is the case with hawksbill turtle (Eretmochelys imbricata) aggregations at lobster gillnet fishing sites in El Salvador and Nicaragua. We quantified hawksbill bycatch by partnering with local fishers to record data for 690 gillnet sets on rocky reefs at Los Cóbanos Reef Marine Protected Area (2008-2009) and Punta Amapala (2012-2014) in El Salvador, and La Salvia (2012-2014) in Nicaragua. Based on 31 observed hawksbill captures, the mean bycatch-per-unit-effort (0.0022; individuals per set = 0.0450) and mortality (0.74) are among the highest reported for the species across fishing gear types and oceanic regions worldwide, and we conservatively estimate that at least 227 juvenile hawksbill captures occurred in lobster gillnet fishing fleets at our sites during the study. Estimated mortality for the 227 hawksbills -which could approach the 74% observed mortality of total captures- from interactions with lobster gillnet fisheries at these sites during the study period may constitute the greatest single source of human-induced in-water mortality for juvenile, sub-adult, and adult hawksbills in the eastern Pacific, and is of grave concern to the population. Based on our findings, we discuss neritic habitat use by hawksbills during their ‘lost years’ and offer recommendations for bycatch reduction strategies, including community-based efforts to enhance sustainable self-governance via the establishment of locally crafted conservationist norms and marine protected areas at important developmental habitat.

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Liles et al. 2017_Survival on the rocks

Kelez et al. 2016_1st record of hawksbill-green hybrid in Southeast Pacific

First record of hybridization between green Chelonia mydas and hawksbill Eretmochelys imbricata sea turtles in the Southeast Pacific

Hybridization among sea turtle species has been widely reported in the Atlantic Ocean, but their detection in the Pacific Ocean is limited to just two individual hybrid turtles, in the northern hemisphere. Herein, we report, for the first time in the southeast Pacific, the presence of a sea turtle hybrid between the green turtle Chelonia mydas and the hawksbill turtleEretmochelys imbricata. This juvenile sea turtle was captured in northern Peru (4°13′S; 81°10′W) on the 5th of January, 2014. The individual exhibited morphological characteristics of C. mydas such as dark green coloration, single pair of pre-frontal scales, four post-orbital scales, and mandibular median ridge, while the presence of two claws in each frontal flipper, and elongated snout resembled the features of E. imbricata. In addition to morphological evidence, we confirmed the hybrid status of this animal using genetic analysis of the mitochondrial gene cytochrome oxidase I, which revealed that the hybrid individual resulted from the cross between a femaleE. imbricata and a male C. mydas. Our report extends the geographical range of occurrence of hybrid sea turtles in the Pacific Ocean, and is a significant observation of interspecific breeding between one of the world’s most critically endangered populations of sea turtles, the east Pacific E. imbricata, and a relatively healthy population, the east Pacific C. mydas.

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Kelez et al. 2016_1st record of hawksbill-green hybrid in Southeast Pacific

Gaos et al. 2016_Conservation genetics of eastern Pacific hawksbills

Hawksbill turtle terra incognita: conservation genetics of eastern Pacific rookeries

Prior to 2008 and the discovery of several important hawksbill turtle (Eretmochelys imbricata) nesting colonies in the EP (Eastern Pacific), the species was considered virtually absent from the region. Research since that time has yielded new insights into EP hawksbills, salient among them being the use of mangrove estuaries for nesting. These recent revelations have raised interest in the genetic characterization of hawksbills in the EP, studies of which have remained lacking to date. Between 2008 and 2014, we collected tissue samples from 269 nesting hawksbills at nine rookeries across the EP and used mitochondrial DNA sequences (766 bp) to generate the first genetic characterization of rookeries in the region. Our results inform genetic diversity, population differentiation, and phylogeography of the species. Hawksbills in the EP demonstrate low genetic diversity: We identified a total of only seven haplotypes across the region, including five new and two previously identified nesting haplotypes (pooled frequencies of 58.4% and 41.6%, respectively), the former only evident in Central American rookeries. Despite low genetic diversity, we found strong stock structure between the four principal rookeries, suggesting the existence of multiple populations and warranting their recognition as distinct management units. Furthermore, haplotypes EiIP106 and EiIP108 are unique to hawksbills that nest in mangrove estuaries, a behavior found only in hawksbills along Pacific Central America. The detected genetic differentiation supports the existence of a novel mangrove estuary “reproductive ecotype” that may warrant additional conservation attention. From a phylogeographic perspective, our research indicates hawksbills colonized the EP via the Indo-Pacific, and do not represent relict populations isolated from the Atlantic by the rising of the Panama Isthmus. Low overall genetic diversity in the EP is likely the combined result of few rookeries, extremely small reproductive populations and evolutionarily recent colonization events. Additional research with larger sample sizes and variable markers will help further genetic understanding of hawksbill turtles in the EP.

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Gaos et al 2016_EP hawksbill nesting conservation genetics

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