The effects of ecology on life history strategies and metabolic disturbances during development: an example from the African bovids

Abstract

Life history theory predicts environmental factors to affect changes in life history strategies. However, owing to the interrelationships between body mass and life history variables, it is difficult to discern causal relationships, especially in large-bodied mammals and using a comparative approach. The situation is exacerbated in palaeobiological studies, where many of the variables cannot be observed directly. Specifically, mortality risk has been identified as one of the most important factors determining life history strategies, but its assessment is difficult. This hampers analyses of life history evolution. This study thus explored the possibility to extract previously untapped information from hard tissue, i.e. teeth, which may be useful for life history reconstruction. Histological sections of 25 molars of bovids, representing all subfamilies and spanning a wide range of body masses, were analysed with regard to: (i) molar crown formation times in relation to female body mass and gestation length, and (ii) metabolic disturbances from early to late forming teeth in relation to habitat type occupied, diet consumed and habitual walking style employed. It was found that molar crown formation times in bovids are highly correlated with gestation length once the effects of body mass have been removed. This differs from primates and indicates similarities in pre- and postnatal growth rates in these mammals. Closed-habitat species exhibit relatively fewer disturbances during development than open-country species, but the reverse holds for adult specimens. This accords with what is known about the ecological and behavioural adaptations of the species and is predicted by life history theory. It could thus be confirmed that teeth may provide vital information about life history variables. Exploitation of this information will allow hypotheses to be tested regarding the evolutionary changes in life history strategies of extinct species. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 75, 271–279.