Natal foraging philopatry in eastern Pacific hawksbill turtles

Abstract

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.

Tracking movements and growth of post-hatchling to adult hawksbill sea turtles using skeleto+iso

“…Our study was conducted at two primary nesting and foraging areas for hawksbills in the EP (Gaos et al, 2012a(Gaos et al, , 2017Liles et al, 2017): Bahía de Jiquilisco (13 • 13 N, 88 • 32 W) and Punta Amapala (13 • 08 N, 87 • 55 W) in El Salvador (Figure 1). Small-scale, nearshore fisheries provide important livelihood support for coastal residents at both sites.…”

“…Punta Amapala (26 km 2 ), approximately 60 km east of Bahía de Jiquilisco, flanks the western border of the Gulf of Fonseca and is comprised primarily of submerged volcanic reef formations at depths ranging from 0 to 30 m. It hosts diverse marine communities, including corals, sponges, and fishes (Domínguez-Miranda, 2010), and constitutes one of the most important open-coast nesting beaches for hawksbills in the eastern Pacific (Liles et al, 2011;Gaos et al, 2017). Lobster gillnet fishing along the rocky reef is a major threat to hawksbills at Punta Amapala and represents the greatest single source of human-induced, in-water mortality of hawksbills in the eastern Pacific (Liles et al, 2017).…”

“…First, the non-estuary stable isotope signal, characterized by δ 13 C values greater than -18 , was found consistently in all the age 0-3 growth layers, regardless of where the turtle eventually stranded. Previous speculation on post-hatchling movement has questioned if some hatchlings from mangrove nests might have short-dispersal oceanic developmental periods (Gaos et al, 2017) or perhaps even remain within the estuary, growing rapidly and never undertaking an oceanic juvenile stage characteristic of most hard-shelled sea turtle species (Bolten, 2003). However, findings here strongly suggest that this is not the case-that hawksbills in this population do not immediately settle into the mangrove estuary, but instead spend at least a few years in an offshore, if not oceanic, habitat during their post-hatchling juvenile stage.…”

“…Turtles inhabiting these nearby mangrove habitats are known to have stable carbon isotope values similar to those in Bahía de Jiquilisco (Wedemeyer-Strombel et al, 2021), so it is possible that some mangrove-foraging turtles do move between different mangrove estuaries. However, currently, there is more evidence that hawksbills have fidelity to just one mangrove estuary, as demonstrated by genetic studies, longterm recapture, and nesting histories showing high levels of natal foraging philopatry (Gaos et al, 2017(Gaos et al, , 2018(Gaos et al, ). 10.3389/fevo.2022 Yet inspection of the SIA values of individual turtles also reveals more intricate patterns, including the potential for some individuals to undertake movements between the estuary and reef habitats.…”

Ecological vulnerability of two sea turtle species in the Gulf of Mexico: an integrated spatial approach

“…Variability in somatic and ethological conditions within the group was expected but did not affect the general representation of their spatial distribution and configuration. Additionally, as sea turtles are loyal to their nesting beaches (thus their internesting sites), feeding grounds (even overwintering) and migratory routes (philopatry) (Broderick et al 2007, Hulin & Guillon 2007, Lee et al 2007, Stiebens et al 2013, Gaos et al 2017, we assumed that the spatial configuration elucidated by the tracked individuals from several beaches in the study area was valid and representative of the nesting female populations in the study region, thus incorporating a connectivity element (migratory routes) as has been encouraged to enable better conservation plans (Mazor et al 2016).…”