Scavenger

Sarcophaga nodosa, a species of flesh fly feeding on decaying meat.

Scavenging is both a carnivorous and a herbivorous feeding behavior in which the scavenger feeds on dead animal and plant material present in its habitat.[1] Scavengers play an important role in the ecosystem by consuming the dead animal and plant material. Decomposers and detritivores complete this process, by consuming the remains left by scavengers.

Etymology

Scavenger is an alteration of scavager, from Middle English skawager meaning "customs collector", from skawage meaning "customs", from Old North French escauwage meaning "inspection", from schauwer meaning "to inspect", of Germanic origin; akin to Old English scēawian and German schauen meaning "to look at", and modern English "show" (with semantic drift).

Animals

Vultures eating the carcass of a red deer in Spain

Obligate scavenging is rare among vertebrates, due to the difficulty of finding enough carrion without expending too much energy. In vertebrates, only vultures and possibly some pterosaurs are obligate scavengers, as terrestrial soaring flyers are the only animals able to find enough carrion.[2]

Well-known invertebrate scavengers of animal material include burying beetles and blowflies, which are obligate scavengers, and yellowjackets.

Most scavenging animals are facultative scavengers that gain most of their food through other methods, especially predation. Many large carnivores that hunt regularly, such as hyenas and jackals, but also animals rarely thought of as scavengers, such as African lions, leopards, and wolves will scavenge if given the chance. They may also use their size and ferocity to intimidate the original hunters (the cheetah is a notable exception). Almost all scavengers above insect size are predators and will hunt if not enough carrion is available, as few ecosystems provide enough dead animals year-round to keep its scavengers fed on that alone. Scavenger wild dogs and crows frequently exploit roadkill.

Scavengers of dead plant material include termites that build nests in grasslands and then collect dead plant material for consumption within the nest. The interaction between scavenging animals and humans is seen today most commonly in suburban settings with animals such as opossums, polecats and raccoons. In some African towns and villages, scavenging from hyenas is also common.

In the prehistoric eras, the species Tyrannosaurus rex may have been an apex predator, preying upon hadrosaurs, ceratopsians, and possibly juvenile sauropods,[3] although some experts have suggested the dinosaur was primarily a scavenger. The debate about whether Tyrannosaurus was an apex predator or scavenger was among the longest ongoing feud in paleontology; however, most scientists now agree that Tyrannosaurus was an opportunistic carnivore, acting mostly as a predator but scavenging when it could.[4] Recent research also shows that while an adult Tyrannosaurus rex would energetically gain little though scavenging, smaller theropods of approximately 500 kg may have potentially gained levels similar to that of hyenas, though not enough for them to rely on scavenging.[5]

Animals which consume feces, such as dung beetles, are referred to as coprovores. Animals that collect small particles of dead organic material of both animal and plant origin are referred to as detritivores.

In humans

Men scavenging a dead horse during World War II (at the end of the Battle of Berlin), on Manfred-von-Richthofen-Straße in Tempelhof borough, 1945

In the 1970s Lewis Binford suggested that early humans primarily obtained meat via scavenging, not through hunting.[6] 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.[7]

In modern humans, necrophagy (eating of dead/decaying flesh) occurs rarely in most societies. This is likely an adaptation to the risk of disease, due to humans having lower levels of protective acids in the digestive tract, compared to species that are dedicated scavengers.[8] Many instances have occurred in history, especially in times of war, where necrophagy and cannibalism can emerge as a survival behavior.

Occupation

"Scavenger" appears as an occupation in the 1911 Census of England and Wales. This job title applied to someone who cleans the streets and removes refuse, generally a workman (a modern-day garbage collector, janitor, or street cleaner) employed by the local public-health authority.

Young people in developing countries can revert to scavenging and thus develop entrepreneurship skills in order to operate in hostile economic contexts.[9]

In India, the term "manual scavenging" is used to describe the removal of raw (fresh and untreated) human excreta from buckets or other containers that are used as toilets or from the pits of pit latrines. The workers pile the excreta into baskets and may carry these on their heads to locations sometimes several kilometers from the latrines.[10] India has officially prohibited the employment of manual scavengers since 1993, but the practice continues as of 2014.[11][12]

The term "scavenger" originated as "scavager" or "scaveger", an official concerned with the receipt of custom duties and the inspection (scavage) of imported goods. The "scavagers" are found with such officials of the City of London as an aleconner or beadle. These officials seem to have been charged also with the cleaning of the streets, and the name superseded the older rakyer for those who performed this duty.[13] These professions are essential to urban settings operating at the highest capacity. The garbage-collection jobs and scavenging professions allow urban populations to continue unhindered by outbreaks of disease most commonly caused by the build-up of physical waste. These jobs had great importance before the times of functional sewer systems and of indoor plumbing.

See also

References

  1. ↑ Getz, W. (2011). Biomass transformation webs provide a unified approach to consumer–resource modelling. Ecology Letters, doi:10.1111/j.1461-0248.2010.01566.x.
  2. ↑ Kane, Adam; Healy, Kevin; Guillerme, Thomas; Ruxton, Graeme D.; Jackson, Andrew L. (2017-02-01). "A recipe for scavenging in vertebrates – the natural history of a behaviour". Ecography. 40 (2): 324–334. doi:10.1111/ecog.02817. ISSN 1600-0587.
  3. ↑ Switeck, Brian (April 13, 2012). "When Tyrannosaurus Chomped Sauropods". Journal of Vertebrate Paleontology. 25 (2): 469–472. doi:10.1671/0272-4634(2005)025[0469:TRFTUC]2.0.CO;2. Retrieved August 24, 2013.
  4. ↑ Hutchinson, John (July 15, 2013). "Tyrannosaurus rex: predator or media hype?". What's in John's Freezer?. Retrieved August 26, 2013.
  5. ↑ Kane; et al. (2016). "Body Size as a Driver of Scavenging in Theropod Dinosaurs" (PDF). The American Naturalist.
  6. ↑ Binford, Lewis R. (1985). "Human ancestors: Changing views of their behavior". Journal of Anthropological Archaeology. 4 (4): 292–327. doi:10.1016/0278-4165(85)90009-1.
  7. ↑ Lieberman, Daniel; Bramble, Dennis (2007). The Evolution of Marathon Running: Capabilities in Humans. Adis Data Information BV. p. 288. doi:10.2165/00007256-200737040-00004. Retrieved 2017-03-15. Human endurance running performance capabilities compare favourably with those of other mammals and probably emerged sometime around 2 million years ago in order to help meat-eating hominids compete with other carnivores. [...] [S]mall teeth, larger bodies and archaeological remains suggest that hominids started to incorporate meat and other animal tissues in the diet at least 2.5Ma, probably by hunting as well as scavenging. [...] [Endurance running] might have enabled hominids to scavenge carcasses from lions after they were abandoned but before hyenas arrived, as modern hunter-gatherers still do in East Africa.
  8. ↑ Beasley, D. E; Koltz, A. M; Lambert, J. E; Fierer, N; Dunn, R. R (2015). "Evolution of stomach acidity". PLOS ONE. 10 (7): e0134116. Bibcode:2015PLoSO..1034116B. doi:10.1371/journal.pone.0134116. PMC 4519257. PMID 26222383.
  9. ↑ Patwary, O'Hare, Karim, Sharker (2012). "The Motivation into Young People Moving into Medical Waste Scavenging as a 'Street Career'". Journal of Youth Studies. 5 (15): 591–604.
  10. ↑ "Human rights and manual scavenging" (PDF). Know Your Rights Series. National Human Rights Commission. Retrieved September 16, 2013.
  11. ↑ "Cleaning Human Waste: "manual scavenging", Caste and Discrimination in India" (PDF). Human Rights Watch. 2014. Retrieved 23 June 2015.
  12. ↑ "Human rights and manual scavenging" (PDF). Know Your Rights Series. National Human Rights Commission. Retrieved September 16, 2013.
  13. ↑ 1911 Encyclopædia Britannica

Further reading

  • Merriam-Webster's Dictionary
  • Smith TM, Smith RL (2006) Elements of Ecology. Sixth edition. Benjamin Cummings, San Francisco, CA.
  • Chase, et al. The Scavenger Handbook. Bramblewood Press, Santa Barbara, CA.
  • Rufus, Anneli and Lawson, Kristan. The Scavengers' Manifesto. Tarcher, New York.
  • "Tasmanian devil". Britannica Concise Encyclopedia. Chicago: Encyclopædia Britannica, 2009. Credo Reference. Web. 17 September 2012.
  • Kruuk, H. Hunter and Hunted: Relationships between Carnivores and People. Cambridge, UK: Cambridge University Press, 2002. Print.
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