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.

The datasets have been anonymised. Please contact Prof. Virpi Lumma (virpi.lummaa at utu.fi) for information about Asian elephants datasets. Please open README file for a description of the dataset and R-scripts.Funding provided by: Academy of FinlandCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100002341Award Number: 292368Funding provided by: European Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000781Award Number: 648766Funding provided by: Ella ja Georg Ehrnroothin SäätiöCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100003502Award Number: