The word scavenger once meant a medieval customs inspector
Scavenger comes from a Middle English word for a customs collector, a person who looked things over. Today it names the animals that clear away the dead, from vultures to hagfish. Even lions and wolves take free meals when offered, and palaeontologists argued for decades over whether T. rex did too.
Scavengers eat dead and decaying organic matter, most famously carrion from animals that died naturally or were killed by someone else, but also rotting plants and human refuse. Carrion specialists are called necrophages. The word itself drifted a long way: it comes from scavager, from Middle English skawager, a customs collector, ultimately from a Germanic root meaning to look at, the same one behind English show.
Living entirely on carrion is rare among vertebrates because finding enough bodies costs so much energy. Black vultures in the Americas and griffon, white-backed and lappet-faced vultures in the Old World manage it, helped by sharp eyesight, strong immune defences, toxin resistance, stretchy guts for gorging and energy-saving gliding flight. Far more common are opportunists: hyenas and jackals, but also lions, leopards and wolves, which may bully original hunters such as cheetahs off their kills. Gulls, crows and magpies work roadsides, and hagfish, great white sharks, alligators and otters take carrion in water.
Among invertebrates, burying beetles, vulture bees and bone skipper flies depend on carcasses as larvae, whereas blow flies and yellowjackets eat carrion without relying on it. Stag beetle larvae of the species Lucanus cervus spend 4 to 7 years chewing through dead oak, ash, elm and other woods, and termites and woodlice also feed on dead plants. In cities, refuse eaters include pigeons, raccoons, rats, baboons and ants, and at dumps polar bears, elephants and foxes have been seen foraging; in some prey-poor parts of East Africa hyenas raid rubbish tips.
Scavengers act as a sanitation service, keeping carcass energy in the upper food web and carrying nutrients farther than decomposers do, while bringing together species that otherwise rarely meet. In cool seasons carcasses rot slowly, competition eases and more species share each body. The long feud over Tyrannosaurus has largely settled on an opportunist that mostly hunted but scavenged when it could; one study suggests smaller theropods of about 500 kg could have gained as much from carrion as hyenas do.
Source: Scavenger
