A scavenger is an animal that seeks out and feeds upon dead and/or decaying organic matter. Some scavengers specialize on feeding upon dead animals, or carrion, while others feed more generally on dead plants and animals.
Scavengers are part of the detrital food web of ecosystems. Scavengers provide a very important ecological service, because they help to rapidly reduce dead animals and plants to simpler constituents, and thereby prevent an excessive accumulation of dead biomass. Large quantities of dead animal biomass can represent a indirect health hazard to living animals, by enhancing the survival of pathogens. A similar effect can be caused to living plants by dead plant biomass. Excessive accumulations of dead plants can also bind up much of the nutrient capital of ecosystems, so that not enough is recycled for use by living plants, and ecosystem productivity becomes constrained by nutrient limitations. The valuable ecological service of recycling of dead biomass is not just performed by scavengers—other detritivores such as bacteria, and fungi are also important, and in fact are largely responsible for the final stages of the decomposition and humification process. However, scavengers are important in the initial stages of biomass decomposition and recycling.
There are many examples of scavengers. Invertebrates are the most abundant scavengers in terrestrial ecosystems, especially earthworms and insects such as beetles, flies, and ants. Many marine crustaceans are important scavengers, including most species of crabs and gammarids. Some birds are specialized as scavengers, most notably the New World vultures (family Cathartidae) and Old World vultures (family Accipitridae). The turkey vulture (Cathartes aura) of the Americas is one of the only bird species that has a sense of smell, which is utilized to find carrion. Some mammals are opportunistic
scavengers, eating dead animals when they can find them. Examples of such species in North America are black bear (Ursus americanus), grizzly bear (Ursus arctos), and wolverine (Gulo gulo).
See also Food chain/web.