White-tailed deer graze mornings and evenings. They are herbivores and feed on green plants and nuts. Deer live in small groups, usually only the mother and its calves. The males have magnificent antlers and live in small groups of three or four animals. Both the male deer and doe have a red-brown coat in the summer and a grey one in the winter. As they now have almost no natural enemies, deer populations are sometimes so large that they cannot find enough to eat. Deer are ruminant animals like cows, which means they have four stomachs and ruminate half-digested food. This complicated procedure allows the deer to eat twigs for example, which most animals cannot digest.