Die another day; Growth model reveals high natural survival rates in loggerhead sea turtles

Abstract

Accurate survival estimates are essential to sea turtle conservation but difficult to estimate due to anthropogenic mortality and confounding factors such as tag loss and emigration. The Lester Growth Model allows for the estimation of sex-specific adult natural survival rates (the rate that a population would experience independent of human influence) from length-at-age and maturity data. I applied this model to individual loggerheads of the Northwest Atlantic subpopulation. Both male and female annual natural survival rates were estimated to be 96-97%; ~0.14 higher than published total survival values. This result was corroborated by a population model designed to estimate a range of possible adult survival rates. These natural survival rates, in conjunction with published rates, allow for the estimation of anthropogenic mortality and assessment of the impact of confounding factors on mark-recapture studies. It is likely that this technique can be leveraged for other loggerhead populations and sea turtle species.