Coastal leatherback turtles reveal conservation hotspot

Abstract

Previous studies have shown that the world’s largest reptile – the leatherback turtle Dermochelys coriacea – conducts flexible foraging migrations that can cover thousands of kilometres between nesting sites and distant foraging areas. The vast distances that may be travelled by migrating leatherback turtles have greatly complicated conservation efforts for this species worldwide. However, we demonstrate, using a combination of satellite telemetry and stable isotope analysis, that approximately half of the nesting leatherbacks from an important rookery in South Africa do not migrate to distant foraging areas, but rather, forage in the coastal waters of the nearby Mozambique Channel. Moreover, this coastal cohort appears to remain resident year-round in shallow waters (<50 m depth) in a relatively fixed area. Stable isotope analyses further indicate that the Mozambique Channel also hosts large numbers of loggerhead turtles Caretta caretta. The rare presence of a resident coastal aggregation of leatherback turtles not only presents a unique opportunity for conservation, but alongside the presence of loggerhead turtles and other endangered marine megafauna in the Mozambique Channel, highlights the importance of this area as a marine biodiversity hotspot.

A Comprehensive Survey of Pelagic Megafauna: Their Distribution, Densities, and Taxonomic Richness in the Tropical Southwest Indian Ocean

“…Similarly, the distribution of hard-shelled sea turtles observed during our survey is consistent with breeding sites in the area (Dalleau et al, 2012;Bourjea, 2015) or satellite tracking showing transit across the open ocean with clear preferences for foraging sites in shallow, euphotic coastal waters (Hays et al, 2014). By comparison, the sizeable densities of the critically endangered leatherback turtle encountered in the shelf strata of West coast of Madagascar confirm its coastal occurrence as observed along South African coast and Mozambique (Robinson et al, 2016). If individuals nesting in South Africa forage in the study area (Robinson et al, 2016) their relationships with known nesting sites need to be explored.…”

“…By comparison, the sizeable densities of the critically endangered leatherback turtle encountered in the shelf strata of West coast of Madagascar confirm its coastal occurrence as observed along South African coast and Mozambique (Robinson et al, 2016). If individuals nesting in South Africa forage in the study area (Robinson et al, 2016) their relationships with known nesting sites need to be explored.…”

Realignment of sea turtle isotope studies needed to match conservation priorities

“…Critically Endangered hawksbill turtles, and Data Deficient flatback turtles have not been the subject of any geographic isotope studies while the also Critically Endangered Kemp's ridley turtles have only recently received attention in their first isotope study (Reich et al 2017;see Table S3 in the Supplement). Similarly, until recently, no geographic isotope studies had been conducted in the Indian Ocean, with the first (focused on leatherback turtles) published in early 2017 (Robinson et al 2016). The Atlantic is the most studied ocean (particularly the northwest; Fig.…”

Satellite tracking and stable isotope analysis highlight differential recruitment among foraging areas in green turtles

“…Nevertheless, satellite telemetry is expensive and can entail direct costs to the study animals, and therefore, sample size is often limited (Wilson & McMahon 2006, Godley et al 2008. However, the satellite data from a few individuals can be scaled-up to infer habitat use at a population level through the use of forensic chemical techniques such as stable isotope analysis (Hobson 2007, Jaeger et al 2010, Zbinden et al 2011, Robinson et al 2016.…”