Sex-specific body mass aging trajectories in adult Asian elephants

In species with marked sexual dimorphism, the classic prediction is that
the sex which undergoes stronger intrasexual competition ages earlier or
quicker. However, more recently, alternative hypotheses have been put
forward, showing that this association can be disrupted. Here, we utilise
a unique, longitudinal dataset of a semi-captive population of Asian
elephants (Elephas maximus), a species with marked male-biased intrasexual
competition, with males being larger and having shorter lifespans, and
investigate whether males show earlier and/or faster body mass ageing than
females. We found evidence of sex-specific body mass ageing trajectories:
adult males gained weight up to the age of 48 years old, followed by a
decrease in body mass until natural death. In contrast, adult females
gained body mass with age until a body mass decline in the last year of
life. Our study shows sex-specific ageing patterns, with an earlier onset
of body mass declines in males than females, which is consistent with the
predictions of the classical theory of ageing.