Each piece of land has a specific carrying capacity. The carrying capacity for a piece of land is the number of animals that the land can sustain without damage to the habitat or the animals, during the least favorable time of the year. As in the illustration above, imagine the carrying capacity as a lake - the annual reproduction of wildlife (the rain) continuously replenishes the habitat.
However the habitat can only hold so much wildlife. The runoff from the dam indicates the different factors that will affect the wildlife population in a habitat. In North America, these factors are greater during the winter, when food sources diminish and cover is at a premium. During this time, competition between animals increases and the weaker ones die, thus bringing the animals in equilibrium with their habitat.
Disease spreads through wildlife populations especially when populations are very high. Examples of this are chronic wasting disease, Hemorrhagic fever and parasites.
Drought conditions dry up watering holes, and snow and ice cover food sources. Too much rain can damage nesting sites.
Predators prey on the very young, old and sick animals for food. Their population numbers are linked to their prey. If there are not enough prey, the predators will starve.
When animals compete for food, the weaker ones will generally lose out and starve.
Loss of habitat to development increases the occurrences of wildlife being hit by vehicles.
Hunting regulations allow hunters to tap into the surplus of wildlife in a given area. These are the animals that would die in some other way to reach the habitat's carrying capacity. If wildlife numbers are already below an area's carrying capacity, hunting is not permitted in that area.