Population recovery changes population composition at a major southern Caribbean juvenile developmental habitat for the green turtle, Chelonia mydas.

Understanding the population composition and dynamics of migratory megafauna at key developmental habitats is critical for conservation and management. The present study investigated whether differential recovery of Caribbean green turtle (Chelonia mydas) rookeries influenced population composition at a major juvenile feeding ground in the southern Caribbean (Lac Bay, Bonaire, Caribbean Netherlands) using genetic and demographic analyses. Genetic divergence indicated a strong temporal shift in population composition between 2006-2007 and 2015-2016 (ϕST = 0.101, P < 0.001). Juvenile recruitment (<75.0 cm straight carapace length; SCL) from the north-western Caribbean increased from 12% to 38% while recruitment from the eastern Caribbean region decreased from 46% to 20% between 2006-2007 and 2015-2016. Furthermore, the product of the population growth rate and adult female abundance was a significant predictor for population composition in 2015-2016. Our results may reflect early warning signals of declining reproductive output at eastern Caribbean rookeries, potential displacement effects of smaller rookeries by larger rookeries, and advocate for genetic monitoring as a useful method for monitoring trends in juvenile megafauna. Furthermore, these findings underline the need for adequate conservation of juvenile developmental habitats and a deeper understanding of the interactions between megafaunal population dynamics in different habitats.

Mixed-stock analysis in green turtles Chelonia mydas: mtDNA decipher current connections among west Atlantic populations.

The green turtle Chelonia mydas undertakes wide-ranging migrations between feeding and nesting sites, resulting in mixing and isolation of genetic stocks. We used mtDNA control region to characterize the genetic composition, population structure, and natal origins of C. mydas in the West Atlantic Ocean, at one feeding ground (State of Rio de Janeiro, Brazil), and three Caribbean nesting grounds (French Guiana, Guadeloupe, and Suriname). The feeding ground presented considerable frequency of common haplotypes from the South Atlantic, whereas the nesting sites presented a major contribution of the most common haplotype from the Caribbean. MSA revealed multiple origins of individuals at the feeding ground, notably from Ascension Island, Guinea Bissau, and French Guiana. This study enables a better understanding of the dispersion patterns and highlights the importance of connecting both nesting and feeding areas. Effective conservation initiatives need to encompass these ecologically and geographically distinct sites as well as those corridors connecting them.

Dispersal and Diving Adjustments of the Green Turtle Chelonia mydas in Response to Dynamic Environmental Conditions during Post-Nesting Migration.

In response to seasonality and spatial segregation of resources, sea turtles undertake long journeys between their nesting sites and foraging grounds. While satellite tracking has made it possible to outline their migration routes, we still have little knowledge of how they select their foraging grounds and adapt their migration to dynamic environmental conditions. Here, we analyzed the trajectories and diving behavior of 19 adult green turtles (Chelonia mydas) during their post-nesting migration from French Guiana and Suriname to their foraging grounds off the coast of Brazil. First Passage Time analysis was used to identify foraging areas located off Ceará state of Brazil, where the associated habitat corresponds to favorable conditions for seagrass growth, i.e. clear and shallow waters. The dispersal and diving patterns of the turtles revealed several behavioral adaptations to the strong hydrodynamic processes induced by both the North Brazil current and the Amazon River plume. All green turtles migrated south-eastward after the nesting season, confirming that they coped with the strong counter North Brazil current by using a tight corridor close to the shore. The time spent within the Amazon plume also altered the location of their feeding habitats as the longer individuals stayed within the plume, the sooner they initiated foraging. The green turtles performed deeper and shorter dives while crossing the mouth of the Amazon, a strategy which would help turtles avoid the most turbulent upper surface layers of the plume. These adjustments reveal the remarkable plasticity of this green turtle population when reducing energy costs induced by migration.

Implications of an individualistic lifestyle for species conservation: lessons from jealous beasts.

Polecat populations show a very low genetic diversity and a high inbreeding coefficient. Furthermore, the estimate of effective population size is alarmingly low. Polecats Mustela putorius populations are structured into scattered breeding sub-units usually made up of one male and two females, according to a polygynous mating system. Because a strict spatio-temporal segregation was observed between males and females, we propose to call individualistic such species. We suggest that the solitary habits of individualistic species may result in or worsen a high inbreeding and exacerbate their conservation issue, a crucial perspective for critically endangered species such as the European mink.