Covariates streamline age‐specific early life survival estimates of two chelonian species

International audienceDelayed maturity and high survival rates of immatures and adults characterizelong-lived species’ life histories. Understanding how these traits interact in stochasticenvironments is essential to understand early life in long-lived species and toassist conservation planning. Unfortunately, available information of demographictraits in immatures are often fragmentary and the logistical difficulties of capturingand recapturing this cohort leave little room for improvement. Published immaturechelonian survival estimates vary broadly, are often not age-specific, and lack precision.In an attempt to overcome this issue, we developed a novel modellingapproach based on Capture-Recapture data to obtain robust age-specific survivalprobabilities in two chelonian species (the freshwater European pond turtle, Emysorbicularis, and the terrestrial Hermann’s tortoise, Testudo hermanni). More specifically,we show that implementing a linear relationship between survival probabilitiesand age does not distort survival estimates and improves precision. Bothspecies display a progressive increase in survival with age, reaching a plateau atthe ages of four to five. As maturity occurs later in both species (8–12 years-old),the survival plateau might be governed by the final hardening of the carapace,which brings obvious survival benefits. Taking advantage of the flexibility of multieventmodels we encourage a systematic field approach even when very large samplesfrom immatures cannot be amassed. Only so can demographic traits inchelonians, and more generally in long-lived species, be properly explored