Reproductive energetics in primates: how costly are babies?

International audienceOur recent studies of infant captive baboons (Garcia et al., 2008; 2009) found that infant to maternal mass was positively associated with reproductive parameters, e.g. duration of postpartum amenorrhea and interbirth interval. Baboon mothers resumed cycling and reconceived when their infants attained a relatively consistent threshold mass, as predicted from interspecific life history theory. We suggested that the duration of investment acted as a facultative adjustment to infant growth rates, and depended on maternal physical and social characteristics, such as size and dominance rank. What was surprising was the relatively low energetic costs associated with reproduction; mothers' intake and energy expenditure measured by the DLW method (Rosetta et al., 2011) did not closely predict the time to resumption of cycling. Energy expenditure was correlated with maternal body mass both during early lactation and after the resumption of cycling and there was a relationship between maternal energy expenditure and infant growth rates; mothers with rapidly growing infants had higher energy expenditure than did those with slowly growing infants. Here we place these results on infant growth and reproductive energetics into a broader primate life history perspective, and explore the question of how costly are non-human primate infants? I partition expenses into time costs and energy costs and look at each of these over the early phase of growth, using the baboon model