The Princeton Guide to Ecology

Wildlife populations occur within both protected areas and human-dominated ecosystems. In both cases, populations are monitored to ensure they coexist with other species in their habitats in a stable way or are harvested as a resource in a sustainable fashion. Management may be limited to monitoring or it may involve active change in the ecosystem. Conditions that require active management include altering competition and predation effects, adjusting habitats, and counteracting effects of exotic species. Ecosystems exhibit complex behavior such as the rapid switch from one set of species to another when the environment changes gradually, a phenomenon called multiple states. Such rapid changes may require active management to ensure the persistence of valued species.

density dependence. The relationship of mortality or births to the size of a population, with proportional mortality increasing or births decreasing as numbers in the population increase.

ecosystem. The interaction of the biotic community, made up of all the species present, and the physical and chemical environment.

multiple states. Alternative composition of species that occurs when a threshold of environmental change is reached.

trophic cascade. The alternating changes in populations of each trophic level when a top level is perturbed.

trophic level. The position of a species in the chain of energy or nutrients. In a three-level chain, the top level is taken by predators, the next level below by herbivores, and the bottom level by plants.

wildlife. Typically refers to vertebrates such as mammals, birds, reptiles, and amphibians.

Wildlife, which generally refers to the higher land vertebrates such as mammals, birds, reptiles, and amphibians, is valued by society for social, economic, and esthetic reasons.

People enjoy observing wildlife and spend considerable income on feeding wildlife in their backyards or traveling to their natural habitats to view wildlife. In 2001 in the United States, more than 50 million Americans spent over $3.7 million feeding wild birds, and over 66 million people made trips primarily to view wildlife, spending $38.4 billion. Wildlife also is harvested for meat and other products and for sport hunting. Reindeer (Rangifer tarandus) husbandry provides livelihood for Lapps in Scandinavia, safari hunting accounts for the bulk of revenue earned in communal areas in Zimbabwe, and in the European Union, hunting generates about 100,000 jobs. Iguana meat and eggs are the traditional Easter substitute for red meat in Central America, and felt made from beaver fur is used to make wide-brimmed Stetson hats so often seen at rodeos in western North America.

Humans and wildlife do not always live in harmony. In North America and Europe, humans commonly lose crops to geese and rodents, plantation trees to bears (Ursus spp.) and pigs (Sus scrofa), and livestock to lynx (Lynx lynx) and wolves (Canis lupus). The European badger (Meles meles) has been implicated in the maintenance and transmission of tuberculosis (Mycobacterium bovis) to cattle in England. In the extreme, humans are killed by bears (Ursus spp.) in North America, lions (Panthera leo) in Africa, and tigers (P. tigris)in India. Management of wildlife is thereby motivated by a desire to (1) enjoy wildlife nonconsumptively, (2) obtain

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