A female deer has little need of a monopolized male. He cannot produce milk or bring grass to the young. So the mating system of a deer is determined by the battle among males, which in turn is determined by how females decide to distribute themselves. Where females live in herds (for example, elk), males can be harem masters. Where females live alone (white-tailed deer), males are territorial and mostly monogamous. Each species has its own pattern, depending on the behavior of the females.
