Abstract
Research on relative brain size in mammals suggests that increases in brain size may generate benefits to survival and costs to fecundity: comparative studies of mammals have shown that interspecific differences in relative brain size are positively correlated with longevity and negatively with fecundity. However, as yet, no studies of mammals have investigated whether similar relationships exist within species, nor whether individual differences in brain size within a wild population are heritable. Here we show that, in a wild population of red deer (Cervus elaphus), relative endocranial volume was heritable (h2 = 63%; 95% credible intervals (CI) = 50–76%). In females, it was positively correlated with longevity and lifetime reproductive success, though there was no evidence that it was associated with fecundity. In males, endocranial volume was not related to longevity, lifetime breeding success or fecundity.
Highlights
Across mammalian species, brain size varies widely, both in absolute terms and in relative terms
We investigated selection on endocranial volume by models of longevity, fecundity and lifetime fitness, where fitness was estimated as lifetime breeding success (LBS) and or lifetime reproductive success (LRS; the total number of offspring surviving past 1 year of age)
We found that individual differences in endocranial volume in red deer were substantial, with coefficients of variation in the range of 7–12
Summary
Brain size varies widely, both in absolute terms (e.g. in weight or volume) and in relative terms (brain size accounting for overall body size, hereafter referred to as ‘relative brain size’; see [1] for a review). This variation is thought to be a consequence of interspecific differences in the relative benefits and costs of a larger brain size.
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