Scavenger

[3] The process and rate of scavenging is affected by both biotic and abiotic factors, such as carcass size, habitat, temperature, and seasons.

Obligate scavenging (subsisting entirely or mainly on dead animals) is rare among vertebrates, due to the difficulty of finding enough carrion without expending too much energy.

In the prehistoric eras, the species Tyrannosaurus rex may have been an apex predator, preying upon hadrosaurs, ceratopsians, and possibly juvenile sauropods,[5] although some experts have suggested the dinosaur was primarily a scavenger.

As a result of this resource oversupply, it is possible that some theropods evolved to get most of their calories by scavenging giant sauropod carcasses, and may not have needed to consistently hunt in order to survive.

[8][9] The same study suggested that theropods in relatively sauropod-free environments, such as tyrannosaurs, were not exposed to the same type of carrion oversupply, and were therefore forced to hunt in order to survive.

Scavengers play a fundamental role in the environment through the removal of decaying organisms, serving as a natural sanitation service.

[11] Scavenging unites animals which normally would not come into contact,[12] and results in the formation of highly structured and complex communities which engage in nonrandom interactions.

[13] The reintroduction of gray wolves (Canis lupus) into Yellowstone National Park in the United States caused drastic changes to the prevalent scavenging community, resulting in the provision of carrion to many mammalian and avian species.

Furthermore, the decline of vulture populations in India has been linked to the increased rates of anthrax in humans due to the handling and ingestion of infected livestock carcasses.

[16] Similarly, an increase of transmission of avian influenza virus to chickens by domestic ducks from Indonesian farms permitted to scavenge surrounding areas was observed in 2007.

The domestic ducks may not have demonstrated symptoms of infection themselves, though were observed to excrete high concentrations of the avian influenza virus.

[19] In 2010, Dennis Bramble and Daniel Lieberman proposed that early carnivorous human ancestors subsequently developed long-distance running behaviors which improved the ability to scavenge and hunt: they could reach scavenging sites more quickly and also pursue a single animal until it could be safely killed at close range due to exhaustion and hyperthermia.

[21] A similar funerary practice that features excarnation can be found in Zoroastrianism; in order to prevent the pollution of the sacred elements (fire, earth, and water) from contact with decomposing bodies, human cadavers are exposed on the Towers of Silence to be eaten by vultures and wild dogs.