JCJC - Jeunes chercheuses & jeunes chercheurs

Migration et Reproduction chez les Tortues marines: Trajectoires Ecophysiologiques – MIRETTE

Submission summary

The spatio-temporal heterogeneity of the environment in which organisms evolve induces physiological, morphological, behavioural and ecological strategies (hereafter referred as ecophysiological trajectories) for facing the trade-offs between survival, growth and reproduction throughout life. Organisms compensate for the costs associated with reproduction either by storing before reproduction large amount of body reserves on which they rely during the breeding season (capital breeders) or by feeding during the breeding season (income breeders). Capital breeders are thus supposed to better face a limited decrease in food availability for a given reproductive event, but they should deteriorate their body reserves and their future reproductions when food is limited. Identifying the potential range of ecophysiological trajectories adopted by organisms for ensuring both survival and reproduction is a key step for understanding the mechanisms by which they respond to environmental conditions and to their potential changes. This point is particularly critical for endangered species for which survival depends on a better knowledge of their biology for implementing well-grounded conservation measures. This project focuses in the critically endangered leatherback turtle Dermochelys coriacea nesting in French Guiana. As all marine turtles, leatherbacks are commonly considered to be capital breeders and present the highest costs of reproduction among turtles. Yet recent results suggest that in French Guiana, they may adopt an intermediate strategy as they may feed during the nesting season. Leatherbacks are long distance migrating species and gravid females nesting in French Guiana have been reported to adopt two main nesting strategies (by nesting every 2 or 3 years) with potential differences in their subsequent reproductive effort in some years. In addition, leatherbacks from French Guiana have been reported to adopt at least two main migration strategies (North versus East). Yet to date, there has been no attempt to link the individual migration and nesting patterns, the potential determinants of these patterns, and their consequences in reproduction in marine turtles. MIRETTE aims to investigate the potential links between the MIgration and the REproductive patterns in marine Turtles and the range of Trajectoires Ecophysiologiques they can adopt for optimising their fitness during one nesting season and over successive reproductive cycles. Here we propose to monitor throughout consecutive reproductive cycles a population of gravid leatherbacks of known identity and known reproductive history nesting in French Guiana for assessing their individual morphological (body condition), hormonal and physiological status and their individual nesting (e.g. migration duration, number of eggs laid) and migration strategy (e.g. migration duration, foraging habitat and behaviour). This study population has been identified since 2005 and provides a unique opportunity for answer these questions by testing at least 3 hypotheses: - H1 leatherbacks nesting after 3 years of migration initiate their next nesting season with a better body condition, resulting in a higher reproductive effort, than after 2 years with nutritionally and/or hormonally mediation; - H2 the nesting pattern (2 versus 3 years) is related to the migration pattern (North versus East); - H3 leatherbacks may compensate for high reproductive costs by feeding during the nesting season, and may adjust the allocation of their endogenous (maternal) and exogenous (alimentary) resources depending on their nutritional and/or hormonal status and on their reproductive effort. We will test these hypotheses thanks to complementary expertises now available at IPHC thanks to the recent fusion of different laboratories. The expertises will be interconnected for developing an original multidisciplinary complete approach. We will test H1 through a population monitoring by capture-mark-recapture protocols, a monitoring of individual body condition and of the reproductive physiology by analysing plasmatic hormones and metabolites deriving from the fast. We will test H2 by investigating at the scale of the population the migration duration depending on the migratory patterns assessed by an original, cost-efficient, purpose-built ultra-miniaturised geolocation datalogger. We will test H3 by combining all approaches with stable isotopes techniques that will also be used as a cue of trophic transfers. This project aims to assess at the population level and for the first time in marine turtles the potential links between individual migratory pattern, environmental variability, individual nutritional and hormonal status and ultimately the individual reproductive quality. It thus provides original scientific-based data for supporting conservations actions developed on these endangered species.

Project coordination

Jean-Yves GEORGES (Organisme de recherche)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Help of the ANR 200,000 euros
Beginning and duration of the scientific project: - 48 Months

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