A scavenger is an organism that mostly consumes decaying biomass, such as meat or rotting plant material. Many scavengers are a type of carnivore, which is an organism that eats meat. While most carnivores hunt and kill their prey, scavengers usually consume animals that have either died of natural causes or been killed by another carnivore.
Scavengers are a part of the food web, a description of which organisms eat which other organisms in the wild. Organisms in the food web are grouped into trophic, or nutritional, levels. There are three trophic levels. Autotrophs, organisms that produce their own food, are the first trophic level. These include plants and algae. Herbivores, or organisms that consume plants and other autotrophs, are the second trophic level. Scavengers, other carnivores, and omnivores, organisms that consume both plants and animals, are the third trophic level.
Autotrophs are called producers, because they produce their own food. Herbivores, carnivores, and omnivores are consumers. Herbivores are primary consumers. Carnivores and omnivores are secondary consumers.
Scavengers play an important role the food web. They keep an ecosystem free of the bodies of dead animals, or carrion. Scavengers break down this organic material and recycle it into the ecosystem as nutrients.
Some birds are scavengers. Vultures only eat the bodies of dead animals.
Vultures have many biological adaptations that make them well-suited to being scavengers. Most have excellent eyesight and a strong sense of smell. They use these keen senses to locate rotting carrion while they are soaring high over land. Unlike raptors, or birds that hunt, vultures have weak talons and beaks. Raptors use sharp talons and beaks to kill, while vultures do not need to overpower or secure their prey. Many vultures are also bald, meaning they have no feathers on their head. This prevents bits of carrion, which can carry toxic bacteria, from sticking to feathers and infecting the bird.
Lammergeiers, or bearded vultures, have more specialized feeding habits than other vultures. Rather than eating meat, they survive almost entirely by eating bones. Lammergeiers drop the bones from great heights to break them into smaller pieces, then chew them up to get at the marrow, the soft tissue inside the bones.
Many insects are scavengers. Animals do not always have to be dead for these scavengers to feast on their decaying flesh. Blowflies often feed on the wounds in sheep, cattle, and other livestock. The dead flesh around the wound is eaten, while the animal itself remains relatively healthy.
Some mammals are scavengers. Hyenas are often thought of as scavengers, but are also traditional carnivores. A lone hyena feeds mostly on dead animals. Hyenas may consume an animal that has died of injuries, or it may steal meat from another carnivore, such as a lion. A pack of hyenas, however, will work together to hunt antelope and other creatures.
Like the hyena, few scavengers eat decaying flesh exclusively. In addition to the area around wounds of livestock, blowflies also feed on plant matter such as rotting garbage. Cockroaches feed on dead animals, but they also eat plants, paper, and other material.
Sea creatures such as crabs and lobsters will eat carrion and most anything else they find. Eels eat dead fish. In addition to hunting, great white sharks feast on dead whales, fish, and pinnipeds such as sea lions.
Scavengers in the Food Chain
Many animals will scavenge if they have the chance, even though carrion is not their preferred food source. Lions, leopards, wolves, and other predators—animals that hunt other animals—will eat carrion if they come across it. Black bears feed mostly on fruit, nuts, and berries, but they, too, will eat dead animals. Foxes and coyotes are more likely to eat carrion in the winter when they cannot find other food.
Because most scavengers are flexible about what they eat, they have an easier time finding food than creatures with more restricted diets. This sometimes makes scavengers better at adapting to new environments than other organisms.
Urban development, the process of clearing land for homes, businesses, and agriculture, destroys animal habitat, the places where animals live in the wild. Herbivores such as elephants cannot survive without a lot of trees and grasses to eat, for example. In developed areas, carnivores such as the mountain lion often do not have enough prey to survive.
Scavengers, however, can usually adapt well to an urban area or farmland. In the wild, the American crow will eat mice, eggs, seeds, and nuts. However, in developed areas, one of its most common meals is roadkill, or the remains of animals that have been hit by cars. Scavengers such as opossums, seagulls, and raccoons thrive on food in garbage cans.
Sometimes, scavengers can pose a danger to people or themselves. The polar bears around Churchill, Canada, for instance, adapted to life near a developed area by seeking out food from the town dump. These large carnivores became a major threat to the community. Some of the food the bears scavenged also poisoned them. In 2006, Churchill closed its dump to protect the bears and the community.