Sex-specific body mass ageing trajectories in adult Asian elephants

Abstract

Sex-specific life-histories are thought to shape senescence patterns differently for males and females. In species with marked sexual dimorphism and where one sex is undergoing stronger intrasexual competition, it is expected that this sex ages earlier or quicker. Here, we utilise a unique, longitudinal dataset of a semi-captive population of Asian elephants (Elephas maximus) to describe the body mass ageing trajectories in this species with marked sexual dimorphism in size and lifespan, with males being larger and living shorter. Our results show sex-specific ageing trajectories: males gained weight throughout their life, at a diminishing rate until natural death. In contrast, adult female body mass did not change significantly with age until an abrupt decline during the last year of life. Our study shows that sex-specific life-histories shape ageing patterns contrary to those predicted by classical theory and expands the previously described diversity of ageing dynamics.