Wildlife Encounters - 9th - 12th grade
Lesson 2: Wildlife Populations
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Adaptations: Population Movements

Animal populations are not static. The number and distribution of animals in the population is constantly changing. Populations grow in size due to births or immigration. Immigration is the movement of individual animals to a new area. This may be due to a higher availability of resources in that area. When natural habitat is cleared for human developments, the native wildlife that originally lived in the area is often removed. After development is complete, generalist species like raccoons will immigrate to the area to make use of new resources, such as birdfeeders and waste in garbage cans.

Deaths and emigration decrease population size. Emigration is the movement of individuals out of a population. This can result when resources like food or nesting sites become scarce in an area. When deer populations grow too large due to a lack of natural predators, deer will emigrate from natural habitat to adjacent urban and agricultural areas where landscape plants and agricultural crops can be used as food resources.

emigration Migration is when whole populations of animals move from one area to another, usually on a seasonal basis. This movement is often to follow resource availability, or for breeding purposes. The actual cue for migratory behavior may be due to changes in day-length, temperature, or local availability of food. Migratory behavior is largely due to genetics, though some species also rely on learned migration routes.

Whooping cranes are an endangered species that is being raised in captivity and later released to help prevent extinction of these birds. The cranes learn the migration routes from their parents, but captive-bred cranes must taught where to migrate by humans. Ultralight plane pilots wearing a crane costume will lead the young cranes on their migration routes.