The main predators of deer are people and dogs. Deer are also subject to predation by coyotes, bobcats, mountain lions and wolves.
Deer populations are generally at peak capacity, which is why it is legal to hunt deer in most rural areas. Without hunting, deer populations often become too big for the environment, resulting in starvation, since competition for food becomes high with overpopulation.
In urban areas, deer populations often become unmanageable because hunting is not usually allowed and populations can get immense quickly. Even where hunting is allowed, overpopulation can affects some areas of the United States where the predatory threat to deer is low.