skip to main content


This content will become publicly available on January 17, 2025

Title: Diverse migratory strategies for a hawksbill sea turtle population
Abstract

Outside of short, infrequent visits to reproductive habitats, sea turtle lifespans are largely spent in foraging areas. Supporting imperilled populations in an era of biodiversity declines and environmental change requires improvements in the understanding of foraging distributions, plus the migratory corridors that connect foraging and reproductive habitats.

This study evaluates the migratory strategies and foraging geography of hawksbill sea turtles (Eretmochelys imbricata) in the Western Atlantic. The post‐nesting migrations of 22 females were tracked via satellite telemetry from Long Island, Antigua, during 2016–2019, and a state‐space model was utilized to estimate true turtle locations from Argos satellite fixes. Model output was used to characterize migratory routes and home ranges occupied during non‐migratory inter‐nesting and foraging periods.

Hawksbill migrations (N = 19) resulted in displacements to foraging areas ranging 7–2300 km. Foraging geography varied considerably—whereas eight turtles remained in the immediate vicinity of Antigua and Barbuda (<30 km), there were also longer‐distance migrations (>470 km) to locations such as The Bahamas and Nicaragua. Inter‐nesting core home ranges (50% utilization distributions) ranged from 7 to 72 km2, while foraging core areas ranged from 7 to 46 km2.

These results add to evidence suggesting that, broadly, post‐nesting hawksbills forage in neritic habitats throughout the Wider Caribbean, including several high‐use areas. Short displacements to foraging habitats relatively nearby to nesting beaches appear to be the most common migratory behaviour, but individuals in a single population may exhibit various migratory strategies, resulting in basin‐wide connectivity between nesting and foraging sites. Given that a single individual or nesting population may inhabit several management jurisdictions, an idealized scenario for regional hawksbill conservation would entail data sharing between managers at linked nesting areas, foraging habitats and migratory corridors such that policies to protect key habitats and mitigate human impacts are designed and evaluated based on best‐available science.

 
more » « less
NSF-PAR ID:
10486427
Author(s) / Creator(s):
 ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Aquatic Conservation: Marine and Freshwater Ecosystems
Volume:
34
Issue:
1
ISSN:
1052-7613
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Increasing green turtle abundance will lead to increased grazing within seagrass habitats—ecosystems that are important for carbon sequestration and storage. However, it is not well understood how carbon dynamics in these ecosystems respond to grazing and whether a response differs among meadows or locations.

    We measured seagrass ecosystem metabolism in grazed and ungrazed areas ofThalassia testudinummeadows with established green turtle foraging areas across the Greater Caribbean and Gulf of Mexico. We sampled meadows from five locations that differed in seagrass and environmental characteristics. Established meadows of the invasive seagrassHalophila stipulaceawere also present at two of these locations, and we measured ecosystem metabolism in these meadows for comparison to grazed and ungrazed areas of the nativeT. testudinum.

    Across all individual sites, rates of net ecosystem production (NEP) ranged from 56% to 96% lower in grazed areas than ungrazed areas ofT. testudinummeadows. Rates of NEP were also strongly, positively correlated with above‐ground seagrass biomass across sites. While metabolic carbon capture rates were lower in grazed areas, heterotrophic respiration was not stimulated, and grazing therefore did not result in significant metabolic remineralization of carbon in these meadows. NEP inH. stipulaceameadows was similar to rates inT. testudinummeadows at all three sites, suggesting that metabolic carbon capture may remain similar in Caribbean meadows where this invasive seagrass is replacing native species.

    Synthesis. Our results show that there is a consistent response in metabolic carbon dynamics to green turtle grazing inT. testudinummeadows across the Greater Caribbean region. An increase in grazing will not likely stimulate remineralization of carbon as these important habitats are returned to a natural grazed state.

     
    more » « less
  2. Abstract

    Sexual segregation has been intensely studied across diverse ecosystems and taxa, but studies are often limited to periods when animals occupy distinct seasonal ranges. Some avian and marine studies have revealed that habitat segregation, when sexes differ spatially or temporally in use of the physical landscape, is common during the migratory period and characterized by sex‐specific differences in migratory behaviors. Recent research highlights the importance of understanding movement patterns in the context of the full annual life cycle and highlights the need to extend relevant theories of sexual segregation to the migratory period. We tested predictions from two leading hypotheses of sexual segregation, the forage‐selection hypothesis (FSH) and the reproductive strategy hypothesis (RSH) as applied to the migratory period. We collected global positioning system (GPS) location data for male and female mule deer (Odocoileus hemionus) in south‐central Wyoming and northwest Colorado and tested the main predictions of the FSH and RSH. Both sexes showed high fidelity to their migratory routes, but route fidelity was more variable in males. Males also started spring migrations earlier, ended spring and autumn migrations later, and spent 22% more time on stopover sites during spring migrations. Consequently, males took twice as long in spring and 44% longer in autumn to complete migration. Our results revealed clear sex‐specific migratory behaviors and supported predictions of the RSH that male foraging behaviors optimize body condition for the autumn rut, and females prioritize foraging while balancing reproductive constraints. Specifically, males timed their movements with spring green‐up as optimally as females, and the timing of male migrations and use of stopovers suggested that males prioritized time in areas of high‐quality forage. This refutes predictions of the FSH during the migratory period that males should consistently choose habitats with abundant, low‐quality forage. Our findings provide an important contribution to sexual segregation theory by extending relevant theories to understand male and female movements during the migratory period.

     
    more » « less
  3. Climate change is a threat to marine turtles that is expected to affect all of their life stages. To guide future research, we conducted a review of the most recent literature on this topic, highlighting knowledge gains and research gaps since a similar previous review in 2009. Most research has been focused on the terrestrial life history phase, where expected impacts will range from habitat loss and decreased reproductive success to feminization of populations, but changes in reproductive periodicity, shifts in latitudinal ranges, and changes in foraging success are all expected in the marine life history phase. Models have been proposed to improve estimates of primary sex ratios, while technological advances promise a better understanding of how climate can influence different life stages and habitats. We suggest a number of research priorities for an improved understanding of how climate change may impact marine turtles, including: improved estimates of primary sex ratios, assessments of the implications of female-biased sex ratios and reduced male production, assessments of the variability in upper thermal limits of clutches, models of beach sediment movement under sea level rise, and assessments of impacts on foraging grounds. Lastly, we suggest that it is not yet possible to recommend manipulating aspects of turtle nesting ecology, as the evidence base with which to understand the results of such interventions is not robust enough, but that strategies for mitigation of stressors should be helpful, providing they consider the synergistic effects of climate change and other anthropogenic-induced threats to marine turtles, and focus on increasing resilience. 
    more » « less
  4. Abstract

    Resource subsidies of energy and nutrients can be transported via physical forces, such as gravity, wind or water and biotic processes, such as animal migration or emigration. Migratory transport of nutrient subsidies may be associated with reproductive processes, such as the deposition of eggs or emigration of juveniles to adult habitats.

    We quantified net nutrient fluxes associated with amphibian migrations across aquatic–terrestrial boundaries of eight temporary ponds in Illinois,USA. We measured carbon (C), nitrogen (N) and phosphorus (P) subsidies from terrestrial environments to ponds, in the form of eggs, and the reciprocal subsidies from ponds to terrestrial environments via juvenile emigration.

    Juvenile emergence biomass did not follow patterns of egg biomass, as not all species bred successfully in each pond, resulting in variability in the magnitude of nutrient fluxes both across ponds and species.

    The terrestrial environment was not always the recipient system of net nutrient fluxes. Hydroperiod, trophic interactions and species composition explained some dynamics of N and P subsidies.

    Anthropogenic alterations that affect amphibian communities, such as habitat fragmentation and conversion for agriculture and urbanisation, could have large‐scale impacts on nutrient fluxes and connectivity of temporary pond–forest systems.

     
    more » « less
  5. Marine protected areas (MPAs) are among the most widely used strategy to protect marine ecosystems and are typically designed to protect specific habitats rather than a single and/or multiple species. To inform the con- servation of species of conservation concern there is the need to assess whether existing and proposed MPA designs provide protection to these species. For this, information on species spatial distribution and exposure to threats is necessary. However, this information if often lacking, particularly for mobile migratory species, such as marine turtles. To highlight the importance of this information when designing MPAs and for assessments of their effectiveness, we identified high use areas of post-nesting hawksbill turtles (Eretmochelys imbricata) in Brazil as a case study and assessed the effectiveness of Brazilian MPAs to protect important habitat for this group based on exposure to threats. Most (88%) of high use areas were found to be exposed to threats (78% to artisanal fishery and 76.7% to marine traffic), where 88.1% were not protected by MPAs, for which 86% are exposed to threats. This mismatch is driven by a lack of explicit conservation goals and targets for turtles in MPA management plans, limited spatial information on species' distribution and threats, and a mismatch in the scale of conservation initiatives. To inform future assessments and design of MPAs for species of conservation concern we suggest that managers: clearly state and make their goals and targets tangible, consider ecological scales instead of political boundaries, and use adaptative management as new information become available. 
    more » « less