Developmental habitat is critical for understanding population structure and resiliency, especially for critically endangered species. In long-lived, oceanic, migratory species such as sea turtles, elucidating developmental grounds is even more difficult. When data are difficult to acquire or deficient, scientists often lean towards traditional quantitative methods when a social-economic systems approach could provide crucial baseline data and guiding information. Fishers’ ecological knowledge, the combination of experiential and culturally transmitted knowledge, is expert knowledge and should be treated as such. In 2008, this knowledge led to the “rediscovery” of the Eastern Pacific (EP) hawksbill sea turtle population, which was previously thought to be ecologically extirpated. Since then, research has shown that >70% of the approximately 800 nesting females in this population (ranging from Mexico to Peru) nest within two mangrove estuaries in El Salvador and Nicaragua, respectively. Genetics and limited satellite tracking studies demonstrate that adults also forage within these two mangrove estuaries, but we do not know how extensively EP hawksbills use these habitats throughout ontogeny. To answer this question, we use a social-ecological systems approach, integrating the social (interactive interviews to capture fishers’ ecological knowledge) and natural (stable isotope ecology) sciences, to find that mangrove estuary habitat is crucial developmental habitat for immature critically endangered EP hawksbills.
Results/Conclusions
Interactive interviews with 68 fishers sparked the invention of a new sampling tool and generated 301 baseline data points for EP hawksbill habitat use near the population's two primary mangrove estuary rookeries. These baseline data guided opportunistic sampling of 154 immature sea turtles: skin samples from each turtle were run for bulk δ13C and δ15N stable isotope analysis. Here we combined fishers’ ecological knowledge with accepted ecological tools, corroborated the knowledge, and in the process revealed novel information: immature hawksbills begin an estuarine developmental stage around 37 cm curved carapace length, and from then on increase their reliance on mangrove estuarine resources by c.4% per cm increase in their curved carapace length, on average. This work reveals that mangrove estuary habitat is critical for the development of this critically endangered population, and highlights the effectiveness of a social-ecological systems approach. Further, we demonstrate that collaborative social science is a valuable first step towards identifying baseline information to guide natural science studies, especially in areas where habitat of the species being studied and human presence overlap.