Environmental and anthropogenic impacts on intra-specific variation in leatherback turtles: opportunities for targeted research and conservation

Abstract

Intra-specific variation in life history traits and/or population trends provides 'natural experiments' to identify causes of observable differences among populations of organisms. Geographically widespread marine species, for example, can experience variation in both environmental and anthropogenic impacts across their ranges that can differentially influence expression of life history traits and population dynamics in separate populations. For example, body size and reproductive output differences among geographically separate, conspecific populations of leatherback turtles Dermochelys coriacea have been linked to variations in environmentally driven resource availability, which differentially affect the resilience of leatherback populations to anthropogenic pressures. Specifically, differences in life history traits and population trends among breeding populations of leatherbacks that forage in the eastern Pacific versus Atlantic Ocean reflect the variable nature of resource availability in the eastern Pacific. These environmentally driven life history differences have contributed to divergent population responses to anthropogenic sources of mortality. In this review, we provide a synoptic view of this body of research and conclude with strategic recommendations for future research and conservation initiatives. This approach has implications for other widely distributed marine species with variations in life history traits that make them more susceptible to humandriven population declines.

Fine-scale foraging ecology of leatherback turtles

“…explore the potential role of differences in foraging strategies as drivers of observed variation in life history and population dynamics among regional leatherback populations (Wallace and Saba, 2009;Bailey et al, 2012b). Our results have important implications for inferred foraging or "residency" areas for leatherbacks and other marine migratory species determined statistically from satellite tracking data (e.g., Jonsen et al, 2007;Fossette et al, 2010a,b;Block et al, 2011;Bailey et al, 2012a,b;Dodge et al, 2014).…”

“…Leatherbacks routinely migrate thousands of kilometers between nesting beaches and foraging areas, an energetically demanding feat that is fueled exclusively by a highly-specialized diet of gelatinous zooplankton (i.e., jellyfish). In recent years, broad-scale migrations of leatherbacks have been characterized in the Atlantic (e.g., James et al, 2005a,b;Hays et al, 2006;Fossette et al, 2010a,b;Dodge et al, 2014), Pacific (e.g., Shillinger et al, 2008;Bailey et al, 2012a), and Indian Oceans (Lambardi et al, 2008), and regional variation in resource availability driven by environmental conditions has been linked to intraspecific differences in leatherback body sizes, reproductive output, and population status (Wallace and Saba, 2009). Fine-scale analyses of leatherback foraging ecology are lacking in general, but are important not only for illustrating relationships between prey availability and foraging behaviors, but also for understanding the importance of discrete habitats for resource acquisition to leatherback bioenergetics and population dynamics.…”

Shifting the life-history paradigm: discovery of novel habitat use by hawksbill turtles

“…The eastern Pacific is characterized by substantial environmental forcing [20], which has led to the contraction and expansion of sea turtle populations over time [19,21] and such processes can play a major role in the development of new life-history strategies (see refs in Hewitt [22]). Other sea turtle species inhabiting the eastern Pacific, specifically leatherback (Dermochelys coriacea) [21] and green turtles (Chelonia mydas) [23], also show stark behavioural, morphological and reproductive differences to their conspecifics in other ocean basins, suggesting environmental variability in the area may lead to the development of novel biological traits.…”

Identification of distinct movement patterns in Pacific leatherback turtle populations influenced by ocean conditions

“…Furthermore, the apparent lack of diversity in migration routes in EP leatherbacks is believed to make them more vulnerable to adverse anthropogenic impacts and environmental perturbations in the marine environment than WP and Atlantic leatherback populations (Saba et al 2008b, Wallace andSaba 2009). Additionally, underlying oceanographic features that influence sea turtle foraging and migratory behavior are poorly understood, yet these dynamic features have been linked to changes in the probability of fisheries interaction (Ž ydelis et al 2011).…”