Antlers, body size and breeding group size in the Cervidae

Abstract

The tendency for large deer species to have relatively big antlers for their body size has been explained as the result of an inevitable evolutionary trend leading to increased antler size1–4, of linkage between genetic factors influencing body size and relative antler size5, of the increased need for larger deer to lose heat6 and of an increased reliance of larger deer species on displays to avoid fighting7. Here we test an alternative hypothesis: that large deer species tend to be more polygynous than smaller ones and that intense inter-male competition in large species has led to the development of relatively large antlers. Analysis of comparative data8–42 confirms two predictions based on this hypothesis: (1) that large deer species form bigger breeding groups than small ones; and (2) that deer which form large breeding groups have relatively larger antlers for their body size than those that form smaller ones. However, antler size is not proportional to body size among species that form breeding groups of similar size, indicating that other factors must also be involved.