Modelling leatherback biphasic indeterminate growth using a modified Gompertz equation

Damien Chevallier (1) , Baptiste Mourrain (2) , Marc Girondot (2)

1 DEPE-IPHC - Département Ecologie, Physiologie et Ethologie
2 ESE - Ecologie Systématique et Evolution

Leatherback turtles (Dermochelys coriacea) are the largest extant marine turtle, with some individuals measuring more than 1.80 m carapace length. Given the exceptional size of this species and that females only return to land every few years to nest, it is difficult to investigate its ontogeny from hatchling to adulthood. Distinct chondro-osseous (cartilage and bone) tissue morphology has led to some speculation that sexual maturity may be reached as early as 3 years, while other studies suggest this could take as long as 25 years. Using a combination of longitudinal measurements obtained from nesting females in French Guiana as well as a reanalysis of the growth trajectories of juveniles maintained in captivity and the age-size relationship of individuals in the wild, we demonstrated that leatherback turtles exhibit a biphasic indeterminate growth pattern and continue to grow as adults. Using the fitted model, we showed that some individuals can reach maturity at 7 years in natural conditions, while others require 28 years or more. This extreme plasticity in age at sexual maturity was already demonstrated in loggerheads in natural conditions and in green turtles in captivity. This could be a general feature of marine turtles.

Mots clés: Dermochelys coriacea; Biphasic indeterminate growth; Gompertz; Maturity; Leatherback; Marine turtles

Domaines: Sciences de l'environnement

Damien Chevallier, Baptiste Mourrain, Marc Girondot. Modelling leatherback biphasic indeterminate growth using a modified Gompertz equation. Ecological Modelling, 2020, 426, pp.109037. ⟨10.1016/j.ecolmodel.2020.109037⟩. ⟨hal-02573730⟩