Scavenger

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

Scavengers are animals that consume dead organisms that have died from causes other than predation. [1] While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding behavior. [2] Scavengers play an important role in the ecosystem by consuming dead animal and plant material. Decomposers and detritivores complete this process, by consuming the remains left by scavengers.

Contents

Scavengers aid in overcoming fluctuations of food resources in the environment. [3] The process and rate of scavenging is affected by both biotic and abiotic factors, such as carcass size, habitat, temperature, and seasons. [4]

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).

Types of scavengers

Vultures eating the carcass of a red deer in Spain Buitres leonados (Gyps fulvus) 0.jpg
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.

Well-known invertebrate scavengers of animal material include burying beetles and blowflies, which are obligate scavengers, and yellowjackets. Fly larvae are also common scavengers for organic materials at the bottom of freshwater bodies. For example, Tokunagayusurika akamusi is a species of midge fly whose larvae live as obligate scavengers at the bottom of lakes and whose adults almost never feed and only live up to a few weeks.

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 victim, rather than a perpetrator). 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. Scavenging 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, [5] 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 feuds in paleontology; however, most scientists now agree that Tyrannosaurus was an opportunistic carnivore, acting mostly as a predator but scavenging when it could. [6] Recent research also shows that while an adult Tyrannosaurus rex would energetically gain little though scavenging, smaller theropods of approximately 500 kg (1,100 lb) may have potentially gained levels similar to that of hyenas, though not enough for them to rely on scavenging. [7] There are also an info that Otodus megalodon, Ceratosaurus, Andrewsarchus and some more prehistoric animals were scavengers. 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.

Ecological function

Scavengers play a fundamental role in the environment through the removal of decaying organisms, serving as a natural sanitation service. [8] While microscopic and invertebrate decomposers break down dead organisms into simple organic matter which are used by nearby autotrophs, scavengers help conserve energy and nutrients obtained from carrion within the upper trophic levels, and are able to disperse the energy and nutrients farther away from the site of the carrion than decomposers. [9]

Scavenging unites animals which normally would not come into contact, [10] and results in the formation of highly structured and complex communities which engage in nonrandom interactions. [11] Scavenging communities function in the redistribution of energy obtained from carcasses and reducing diseases associated with decomposition. Oftentimes, scavenger communities differ in consistency due to carcass size and carcass types, as well as by seasonal effects as consequence of differing invertebrate and microbial activity. [4]

Competition for carrion results in the inclusion or exclusion of certain scavengers from access to carrion, shaping the scavenger community. When carrion decomposes at a slower rate during cooler seasons, competitions between scavengers decrease, while the number of scavenger species present increases. [4]

Alterations in scavenging communities may result in drastic changes to the scavenging community in general, reduce ecosystem services and have detrimental effects on animal and humans. [11] 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. [4] Likewise, the reduction of vulture species in India lead to the increase of opportunistic species such as feral dogs and rats. The presence of both species at carcasses resulted in the increase of diseases such as rabies and bubonic plague in wildlife and livestock, as feral dogs and rats are transmitters of such diseases. 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. An increase of disease transmission has been observed in mammalian scavengers in Kenya due to the decrease in vulture populations in the area, as the decrease in vulture populations resulted in an increase of the number of mammalian scavengers at a given carcass along with the time spent at a carcass. [8]

Disease transmission

Scavenging may provide a direct and indirect method for transmitting disease between animals. Scavengers of infected carcasses may become hosts for certain pathogens and consequently vectors of disease themselves. An example of this phenomenon is the increased transmission of tuberculosis observed when scavengers engage in eating infected carcasses. [12] Likewise, the ingestion of bat carcasses infected with rabies by striped skunks (Mephitis mephitis) resulted in increased infection of these organisms with the virus.

A major vector of transmission of diseases are various bird species, with outbreak being influenced by such carrier birds and their environment. An avian cholera outbreak from 2006 to 2007 off the coast Newfoundland, Canada resulted in the mortality of many marine bird species. The transmission, perpetuation and spread of the outbreak was mainly restricted to gull species who scavenge for food in the area. [13] 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 scavenging of ducks in rice paddy fields in particular resulted in increased contact with other bird species feeding on leftover rice, which may have contributed to increased infection and transmission of the avian influenza virus. The domestic ducks may not have demonstrated symptoms of infection themselves, though were observed to excrete high concentrations of the avian influenza virus. [14]

Threats

Many species that scavenge face persecution globally.[ citation needed ] Vultures, in particular, have faced incredible persecution and threats by humans. Before its ban by regional governments in 2006, the veterinary drug Diclofenac has resulted in at least a 95% decline of Gyps vultures in Asia. Habitat loss and food shortage have contributed to the decline of vulture species in West Africa due to the growing human population and overhunting of vulture food sources, as well as changes in livestock husbandry. Poisoning certain predators to increase the number of game animals is still a common hunting practice in Europe and contributes to the poisoning of vultures when they consume the carcasses of poisoned predators. [8]

Benefits to human well-being

Highly efficient scavengers, also known as dominant or apex-scavengers, can have benefits to human well being. Increases in dominant scavenger populations, such as vultures, can reduce populations of smaller opportunistic scavengers, such as rats. [15] These smaller scavengers are often pests and disease vectors.

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 Bundesarchiv Bild 183-R77871, Berlin, Einwohner zerlegen ein Pferd.jpg
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. [16] 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. [17]

In modern humans, necrophagy (eating of dead/decaying flesh) occurs rarely in most societies. Many instances have occurred in history, especially in times of war, where necrophagy and cannibalism can emerge as a survival behavior.

See also

Related Research Articles

Vulture Common name for several types of scavenging birds of prey.

A vulture is a scavenging bird of prey. The New World vultures include the California condor and the Andean condor; the Old World vultures include the birds that are seen scavenging on carcasses of dead animals on African plains. Some traditional Old World vultures are not closely related to the others, which is why the vultures are to be subdivided into three taxa rather than two. New World vultures are found in North and South America; Old World vultures are native to Europe, Africa, and Asia, meaning that between the two groups, vultures are found on every continent except Australia and Antarctica.

Old World vulture informal group of birds, use Q13428438 for the Aegypiinae

Old World vultures are vultures that are found in the Old World, i.e. the continents of Europe, Asia and Africa, and which belong to the family Accipitridae, which also includes eagles, buzzards, kites, and hawks.

Hooded vulture species of bird

The hooded vulture is an Old World vulture in the order Accipitriformes, which also includes eagles, kites, buzzards and hawks. It is the only member of the genus Necrosyrtes, which is sister to the larger Gyps genus, both of which are a part of the Aegypiinae subfamily of Old World vultures. It is native to sub-Saharan Africa, where it has a widespread distribution with populations in southern, East and West Africa. It is a scruffy-looking, small vulture with dark brown plumage, a long thin bill, bare crown, face and fore-neck, and a downy nape and hind-neck. Its face is usually a light red colour. It typically scavenges on carcasses of wildlife and domestic animals. Although it remains a common species with a stable population in the lower region of Casamance, some areas of The Gambia, and Guinea-Bissau, other regions such as Dakar, Senegal, show more than 85% losses in population over the last 50 years. Threats include poisoning, hunting, loss of habitat and collisions with electricity infrastructure, and the International Union for Conservation of Nature has rated its conservation status as "critically endangered" in their latest assessment (2017). The highest current regional density of hooded vultures is in the western region of The Gambia

White-backed vulture species of bird

The white-backed vulture is an Old World vulture in the family Accipitridae, which also includes eagles, kites, buzzards and hawks. It is closely related to the European griffon vulture, G. fulvus. Sometimes it is called African white-backed vulture to distinguish it from the Oriental white-backed vulture — nowadays usually called white-rumped vulture — to which it was formerly believed to be closely related.

Turkey vulture Most widespread New World vulture

The turkey vulture, also known in some North American regions as the turkey buzzard, and in some areas of the Caribbean as the John crow or carrion crow, is the most widespread of the New World vultures. One of three species in the genus Cathartes of the family Cathartidae, the turkey vulture ranges from southern Canada to the southernmost tip of South America. It inhabits a variety of open and semi-open areas, including subtropical forests, shrublands, pastures, and deserts.

Carrion Dead and decaying flesh of an animal

Carrion is the decaying flesh of dead animals, including human flesh.

Brown hyena species of mammal

The brown hyena, also called strandwolf, is a species of hyena found in Namibia, Botswana, western and southern Zimbabwe, southern Mozambique and South Africa. It is currently the rarest species of hyena. The largest remaining brown hyena population is located in the southern Kalahari Desert and coastal areas in Southwest Africa. The global population of brown hyena is estimated by IUCN at a number between 4,000 and 10,000 and its conservation status is marked as near threatened in the IUCN Red List.

Spotted hyena Species of hyena

The spotted hyena, also known as the laughing hyena, is a hyena species, currently classed as the sole extant member of the genus Crocuta, native to sub-Saharan Africa. It is listed as being of least concern by the IUCN on account of its widespread range and large numbers estimated between 27,000 and 47,000 individuals. The species is, however, experiencing declines outside of protected areas due to habitat loss and poaching. The species may have originated in Asia, and once ranged throughout Europe for at least one million years until the end of the Late Pleistocene. The spotted hyena is the largest known member of the Hyaenidae, and is further physically distinguished from other species by its vaguely bear-like build, its rounded ears, its less prominent mane, its spotted pelt, its more dual purposed dentition, its fewer nipples and the presence of a pseudo-penis in the female. It is the only mammalian species to lack an external vaginal opening.

Pack hunter

A pack hunter or social predator is a predatory animal which hunts its prey by working together with other members of its species. Normally animals hunting in this way are closely related, and with the exceptions of chimpanzees where only males normally hunt, all individuals in a family group contribute to hunting. When hunting cooperation is across two or more species, the broader term cooperative hunting is commonly used.

An emergent virus is a virus that is either newly appeared, notably increasing in incidence/geographic range or has the potential to increase in the near future. Emergent viruses are a leading cause of emerging infectious diseases and raise public health challenges globally, given their potential to cause outbreaks of disease which can lead to epidemics and pandemics. As well as causing disease, emergent viruses can also have severe economic implications. Recent examples include the SARS-related coronaviruses, which have caused the 2002-2004 outbreak of SARS (SARS-CoV-1) and the 2019–20 pandemic of COVID-19 (SARS-CoV-2). Other examples include the human immunodeficiency virus which causes HIV/AIDS; the viruses responsible for Ebola; the H5N1 influenza virus responsible for avian flu; and H1N1/09, which caused the 2009 swine flu pandemic. Viral emergence in humans is often a consequence of zoonosis, which involves a cross-species jump of a viral disease into humans from other animals. As zoonotic viruses exist in animal reservoirs, they are much more difficult to eradicate and can therefore establish persistent infections in human populations.

White-headed vulture species of bird

The white-headed vulture is an Old World vulture endemic to Africa. Populations have been declining steeply in recent years due to habitat degradation and poisoning of vultures at carcasses. An extinct relative was also present in the Indonesian island of Flores, indicating that the genus was more widespread in the past.

Lesser yellow-headed vulture Species of bird

The lesser yellow-headed vulture also known as the savannah vulture, is a species of bird in the New World vulture family Cathartidae. It was considered to be the same species as the greater yellow-headed vulture until they were split in 1964. It is found in Mexico, Central America, and South America in seasonally wet or flooded lowland grassland, swamps, and heavily degraded former forest. It is a large bird, with a wingspan of 150–165 cm (59–65 in). The body plumage is black, and the head and neck, which are featherless, are pale orange with red or blue areas. It lacks a syrinx, so therefore its vocalizations are limited to grunts or low hisses.

Greater yellow-headed vulture Species of bird

The greater yellow-headed vulture, also known as the forest vulture, is a species of bird in the New World vulture family Cathartidae. It was considered to be the same species as the lesser yellow-headed vulture until they were split in 1964. It is found in South America in tropical moist lowland forests. It is a fairly large bird, with a wingspan of 166–178 cm (65–70 in), a weight of 1.65 kilograms (3.6 lb) and a body length of 64–75 cm (25–30 in). The body plumage is black, and the head and neck, which are featherless, range in color from deep yellow to pale orange. It lacks a syrinx, and its vocalizations are therefore limited to grunts or low hisses.

Valley of the T. rex is a Discovery Channel documentary, featuring paleontologist Jack Horner, that aired on September 10, 2001. The program shows Horner with his digging team as they travel to Hell Creek Formation in search for dinosaur fossils, while also following Horner as he presents his view of the theropod dinosaur Tyrannosaurus rex as a scavenger rather than a predator, as it is often portrayed in popular culture.

Mesocarnivore animal whose diet consists of 50–70% meat

A mesocarnivore is an animal whose diet consists of 50–70% meat with the balance consisting of non-animal foods which may include insects, fungi, fruits, other plant material and any food that is available to them. Mesocarnivores are from a large family group of mammalian carnivores and vary from small to medium sized, which are less than fifteen kilograms. Mesocarnivores are seen today among the Canidae, Viverridae (civets), Mustelidae, Procyonidae, Mephitidae (skunks), and Herpestidae. The red fox is also the most common of the mesocarnivores in Europe and has a high population density in the areas they reside.

Consumer–resource interactions are the core motif of ecological food chains or food webs, and are an umbrella term for a variety of more specialized types of biological species interactions including prey-predator, host-parasite, plant-herbivore and victim-exploiter systems. These kinds of interactions have been studied and modeled by population ecologists for nearly a century. Species at the bottom of the food chain, such as algae and other autotrophs, consume non-biological resources, such as minerals and nutrients of various kinds, and they derive their energy from light (photons) or chemical sources. Species higher up in the food chain survive by consuming other species and can be classified by what they eat and how they obtain or find their food.

Indian vulture crisis

Nine species of vulture can be found living in India, but most are now in danger of extinction after a rapid and major population collapse in recent decades. As recently as the 1980s there were up to 80 million white-rumped vultures in India, but today the population numbers only several thousand.

Social facilitation in animals

Social facilitation in animals is when the performance of a behaviour by an animal increases the probability of other animals also engaging in that behaviour or increasing the intensity of the behaviour. More technically, it is said to occur when the performance of an instinctive pattern of behaviour by an individual acts as a releaser for the same behaviour in others, and so initiates the same line of action in the whole group. It has been phrased as "The energizing of dominant behaviors by the presence of others."

Feeding behaviour of <i>Tyrannosaurus</i>

The feeding behaviour of Tyrannosaurus rex has been studied extensively. The well known attributes of T. rex are often interpreted to be indicative of either a predatory or scavenging lifestyle, and as such the biomechanics, feeding strategies and diet of Tyrannosaurus have been subject to much research and debate.

Agelaia multipicta is a swarm-founding, highly eusocial wasp that lives in Mexico, Argentina, Trinidad and southern Brazil. It nests in natural cavities such as hollow trees and aggressively defends the nest from ants, who are brood predators. The workers and queens are morphologically distinguished by ovarian development as well as external features such as a larger petiole and gaster in the queen. Like other carrion-eating (necrophagous) wasp species, A. multipicta plays a scavenging role in the ecosystem. Agelaia multipicta was described by the Irish entomologist Alexander Henry Haliday in 1836.

References

  1. TAN, CEDRIC K. W.; CORLETT, RICHARD T. (2011-03-30). "Scavenging of dead invertebrates along an urbanisation gradient in Singapore". Insect Conservation and Diversity. 5 (2): 138–145. doi:10.1111/j.1752-4598.2011.00143.x. ISSN   1752-458X.
  2. Getz, W (2011). "Biomass transformation webs provide a unified approach to consumer–resource modelling". Ecology Letters. 14 (2): 113–124. doi:10.1111/j.1461-0248.2010.01566.x. PMC   3032891 . PMID   21199247.
  3. Castilla, A.M.; Richer, R.; Herrel, A.; Conkey, A.A.T.; Tribuna, J.; Al-Thani, M. (July 2011). "First evidence of scavenging behaviour in the herbivorous lizard Uromastyx aegyptia microlepis". Journal of Arid Environments. 75 (7): 671–673. Bibcode:2011JArEn..75..671C. doi:10.1016/j.jaridenv.2011.02.005. ISSN   0140-1963.
  4. 1 2 3 4 Turner, Kelsey L.; Abernethy, Erin F.; Conner, L. Mike; Rhodes, Olin E.; Beasley, James C. (September 2017). "Abiotic and biotic factors modulate carrion fate and vertebrate scavenging communities". Ecology. 98 (9): 2413–2424. doi: 10.1002/ecy.1930 . ISSN   0012-9658. PMID   28628191.
  5. 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.
  6. Hutchinson, John (July 15, 2013). "Tyrannosaurus rex: predator or media hype?". What's in John's Freezer?. Retrieved August 26, 2013.
  7. Kane; et al. (2016). "Body Size as a Driver of Scavenging in Theropod Dinosaurs" (PDF). The American Naturalist. 187 (6): 706–16. doi:10.1086/686094. hdl:10023/10617. PMID   27172591.
  8. 1 2 3 Ogada, Darcy L.; Keesing, Felicia; Virani, Munir Z. (16 December 2011). "Dropping dead: causes and consequences of vulture population declines worldwide". Annals of the New York Academy of Sciences. 1249 (1): 57–71. Bibcode:2012NYASA1249...57O. doi:10.1111/j.1749-6632.2011.06293.x. ISSN   0077-8923. PMID   22175274.
  9. Olson, Zachary H.; Beasley, James C.; Rhodes, Olin E. (2016-02-17). "Carcass Type Affects Local Scavenger Guilds More than Habitat Connectivity". PLOS ONE. 11 (2): e0147798. Bibcode:2016PLoSO..1147798O. doi:10.1371/journal.pone.0147798. ISSN   1932-6203. PMC   4757541 . PMID   26886299.
  10. Dunlop, Kathy M.; Jones, Daniel O. B.; Sweetman, Andrew K. (December 2017). "Direct evidence of an efficient energy transfer pathway from jellyfish carcasses to a commercially important deep-water species". Scientific Reports. 7 (1): 17455. Bibcode:2017NatSR...717455D. doi:10.1038/s41598-017-17557-x. ISSN   2045-2322. PMC   5727084 . PMID   29234052.
  11. 1 2 Olson, Z. H.; Beasley, J. C.; DeVault, T. L.; Rhodes, O. E. (31 May 2011). "Scavenger community response to the removal of a dominant scavenger". Oikos. 121 (1): 77–84. doi:10.1111/j.1600-0706.2011.19771.x. ISSN   0030-1299.
  12. Carrasco-Garcia, Ricardo; Barroso, Patricia; Perez-Olivares, Javier; Montoro, Vidal; Vicente, Joaquín (2 March 2018). "Consumption of Big Game Remains by Scavengers: A Potential Risk as Regards Disease Transmission in Central Spain". Frontiers in Veterinary Science. 5: 4. doi:10.3389/fvets.2018.00004. ISSN   2297-1769. PMC   5840163 . PMID   29552564.
  13. Wille, Michelle; McBurney, Scott; Robertson, Gregory J.; Wilhelm, Sabina I.; Blehert, David S.; Soos, Catherine; Dunphy, Ron; Whitney, Hugh (October 2016). "A Pelagic Outbreak of Avian Cholera in North American Gulls: Scavenging as a Primary Mechanism for Transmission?". Journal of Wildlife Diseases. 52 (4): 793–802. doi: 10.7589/2015-12-342 . ISSN   0090-3558. PMID   27455197.
  14. Henning, Joerg; Wibawa, Hendra; Morton, John; Usman, Tri Bhakti; Junaidi, Akhmad; Meers, Joanne (August 2010). "Scavenging Ducks and Transmission of Highly Pathogenic Avian Influenza, Java, Indonesia". Emerging Infectious Diseases. 16 (8): 1244–1250. doi:10.3201/eid1608.091540. ISSN   1080-6040. PMC   3298304 . PMID   20678318.
  15. O'Bryan, Christopher J.; Holden, Matthew H.; Watson, James E. M. (2019). "The mesoscavenger release hypothesis and implications for ecosystem and human well-being". Ecology Letters. 0 (9): 1340–1348. doi:10.1111/ele.13288. ISSN   1461-0248. PMID   31131976.
  16. 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.
  17. 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.

Further reading