Biology:Omnivore

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Short description: Animal that can eat and survive on both plants and animals
Examples of omnivores. From left to right: humans,[1] dogs,[2] pigs, channel catfish, American crows, gravel ant
Among birds, the hooded crow is a typical omnivore.

An omnivore (/ˈɒmnɪvɔːr/) is an animal that has the ability to eat and survive on both plant and animal matter.[3] Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutrients and energy of the sources absorbed.[4] Often, they have the ability to incorporate food sources such as algae, fungi, and bacteria into their diet.[5][6][7]

Omnivores come from diverse backgrounds that often independently evolved sophisticated consumption capabilities. For instance, dogs evolved from primarily carnivorous organisms (Carnivora) while pigs evolved from primarily herbivorous organisms (Artiodactyla).[8][9][10] Despite this, physical characteristics such as tooth morphology may be reliable indicators of diet in mammals, with such morphological adaptation having been observed in bears.[11][12]

The variety of different animals that are classified as omnivores can be placed into further sub-categories depending on their feeding behaviors. Frugivores include cassowaries, orangutans and grey parrots;[13][14][15] insectivores include swallows and pink fairy armadillos;[16][17] granivores include large ground finches and mice.

All of these animals are omnivores, yet still fall into special niches in terms of feeding behavior and preferred foods. Being omnivores gives these animals more food security in stressful times or makes possible living in less consistent environments.[18]

Etymology and definitions

The word omnivore derives from Latin omnis 'all' and vora, from vorare 'to eat or devour', having been coined by the French and later adopted by the English in the 1800s.[19] Traditionally the definition for omnivory was entirely behavioral by means of simply "including both animal and vegetable tissue in the diet.[20]" In more recent times, with the advent of advanced technological capabilities in fields like gastroenterology, biologists have formulated a standardized variation of omnivore used for labeling a species' actual ability to obtain energy and nutrients from materials.[21][22] This has subsequently conditioned two context-specific definitions.

  • Behavioral: This definition is used to specify if a species or individual is actively consuming both plant and animal materials.[22][23][24][25] (e.g. "vegans do not participate in the omnivore based diet.") In the fields of nutrition, sociology and psychology the terms “omnivore” & “omnivory” is often used to distinguish prototypical highly diverse human diet patterns from restricted diet patterns that exclude major categories of food.[26][27][28][29][30]
  • Physiological: This definition is often used in academia to specify species that have the capability to obtain energy and nutrients from both plant and animal matter.[31][page needed][6][21][32] (e.g. "humans are omnivores due to their capability to obtain energy and nutrients from both plant and animal materials.")

The taxonomic utility of omnivore's traditional and behavioral definition is limited, since the diet, behavior, and phylogeny of one omnivorous species might be very different from that of another: for instance, an omnivorous pig digging for roots and scavenging for fruit and carrion is taxonomically and ecologically quite distinct from an omnivorous chameleon that eats leaves and insects. The term "omnivory" is also not always comprehensive because it does not deal with mineral foods such as salt licks and the consumption of plant and animal material for medical purposes which would not otherwise be consumed (i.e. zoopharmacognosy) within non-omnivores.

Classification, contradictions and difficulties

Though Carnivora is a taxon for species classification, no such equivalent exists for omnivores, as omnivores are widespread across multiple taxonomic clades. The Carnivora order does not include all carnivorous species, and not all species within the Carnivora taxon are carnivorous. (The members of Carnivora are formally referred to as carnivorans.)[33] It is common to find physiological carnivores consuming materials from plants or physiological herbivores consuming material from animals, e.g. felines eating grass and deer eating birds.[34][35] From a behavioral aspect, this would make them omnivores, but from the physiological standpoint, this may be due to zoopharmacognosy. Physiologically, animals must be able to obtain both energy and nutrients from plant and animal materials to be considered omnivorous. Thus, such animals are still able to be classified as carnivores and herbivores when they are just obtaining nutrients from materials originating from sources that do not seemingly complement their classification. For instance, it is well documented that animals such as giraffes, camels, and cattle will gnaw on bones, preferably dry bones, for particular minerals and nutrients.[36] Felines, which are usually regarded as obligate carnivores, occasionally eat grass to regurgitate indigestibles (e.g. hair, bones), aid with hemoglobin production, and as a laxative.[37]

Occasionally, it is found that animals historically classified as carnivorous may deliberately eat plant material. For example, in 2013, it was considered that American alligators (Alligator mississippiensis) may be physiologically omnivorous once investigations had been conducted on why they occasionally eat fruits. It was suggested that alligators probably ate fruits both accidentally and deliberately.[38]

"Life-history omnivores" is a specialized classification given to organisms that change their eating habits during their life cycle.[39] Some species, such as grazing waterfowl like geese, are known to eat mainly animal tissue at one stage of their lives, but plant matter at another.[40] The same is true for many insects, such as beetles in the family Meloidae,[41] which begin by eating animal tissue as larvae, but change to eating plant matter after they mature. Likewise, many mosquito species in early life eat plants or assorted detritus, but as they mature, males continue to eat plant matter and nectar whereas the females (such as those of Anopheles, Aedes and Culex) also eat blood to reproduce effectively.[42]

Omnivorous species

General

Although cases exist of herbivores eating meat and carnivores eating plant matter, the classification "omnivore" refers to the adaptation and main food source of the species in general, so these exceptions do not make either individual animals or the species as a whole omnivorous. For the concept of "omnivore" to be regarded as a scientific classification, some clear set of measurable and relevant criteria would need to be considered to differentiate between an "omnivore" and other categories, e.g. faunivore, folivore, and scavenger.[43] Some researchers argue that evolution of any species from herbivory to carnivory or carnivory to herbivory would be rare except via an intermediate stage of omnivory.[44]

Omnivorous mammals

Various mammals are omnivorous in the wild, such as species of hominids, pigs,[45] badgers, bears, foxes, coatis, civets, hedgehogs, opossums, skunks, sloths, squirrels,[46] raccoons, chipmunks,[47] mice,[48] hamsters and rats.[49][7][50][51]

Most bear species are omnivores

Most bear species are omnivores,[52] but individual diets can range from almost exclusively herbivorous (hypocarnivore) to almost exclusively carnivorous (hypercarnivore), depending on what food sources are available locally and seasonally. Polar bears are classified as carnivores, both taxonomically (they are in the order Carnivora), and behaviorally (they subsist on a largely carnivorous diet). Depending on the species of bear, there is generally a preference for one class of food, as plants and animals are digested differently. Canines including wolves, dogs, dingoes, and coyotes eat some plant matter, but they have a general preference and are evolutionarily geared towards meat.[53] However, the maned wolf is a canid whose diet is naturally 50% plant matter.

Like most arboreal species, squirrels are primarily granivores, subsisting on nuts and seeds.[54] However, like virtually all mammals, squirrels avidly consume some animal food when it becomes available. For example, the American eastern gray squirrel has been introduced to parts of Britain, continental Europe and South Africa. Its effect on populations of nesting birds is often serious because of consumption of eggs and nestlings.[55][56]

Other species

Various birds are omnivorous, with diets varying from berries and nectar to insects, worms, fish, and small rodents. Examples include cranes, cassowaries, chickens, crows[57] and related corvids, kea, rallidae, and rheas. In addition, some lizards (such as Galapagos Lava Lizard), turtles, fish (such as piranhas and catfish), and invertebrates are omnivorous.

Quite often, mainly herbivorous creatures will eagerly eat small quantities of animal food when it becomes available. Although this is trivial most of the time, omnivorous or herbivorous birds, such as sparrows, often will feed their chicks insects while food is most needed for growth.[58] On close inspection it appears that nectar-feeding birds such as sunbirds rely on the ants and other insects that they find in flowers, not for a richer supply of protein, but for essential nutrients such as cobalt/vitamin b12 that are absent from nectar. Similarly, monkeys of many species eat maggoty fruit, sometimes in clear preference to sound fruit.[59] When to refer to such animals as omnivorous, or otherwise, is a question of context and emphasis, rather than of definition.

See also

References

  1. ↑ Beasley, DeAnna; Koltz, Amanda; Lambert, Joanna; Fierer, Noah; Dunn, Rob (29 July 2015). "The Evolution of Stomach Acidity and Its Relevance to the Human Microbiome". PLOS ONE 10 (7): e0134116. doi:10.1371/journal.pone.0134116. PMID 26222383. Bibcode: 2015PLoSO..1034116B. 
  2. ↑ "Canis lupus familiaris". Animal Diversity Web. 2002. http://animaldiversity.ummz.umich.edu/site/accounts/information/Canis_lupus_familiaris.html. 
  3. ↑ Biology. McGraw-Hill. 2008. p. 1326. ISBN 978-0072956207. https://archive.org/details/biology00geor. 
  4. ↑ Encyclopedia of Animal Science - (Two-Volume Set). McGraw-Hill. 2018. p. 1350. ISBN 978-0072956207. https://books.google.com/books?id=mSJWDwAAQBAJ&pg=PT1350. 
  5. ↑ Bradford, Alina (25 January 2016). "Reference: Omnivores: Facts About Flexible Eaters". Livescience. http://www.livescience.com/53483-omnivores.html. 
  6. ↑ 6.0 6.1 "Omnivore". National Geographic Education. National Geographic Society. 2011-01-21. http://education.nationalgeographic.com/education/encyclopedia/omnivore/?ar_a=4&ar_r=3. 
  7. ↑ 7.0 7.1 McArdle, John. "Humans are Omnivores". Vegetarian Resource Group. http://www.vrg.org/nutshell/omni.htm. 
  8. ↑ "Why Your Dog's Pedigree Goes Back 40 Million Years". http://dinosaurs.about.com/od/otherprehistoriclife/a/Prehistoric-Dogs-The-Story-Of-Dog-Evolution.htm. 
  9. ↑ "Evolutionary History of Pigs – Domesticating Wilbur". http://blogs.lt.vt.edu/pigdomestication/category/evolutionary-history-of-pigs/. 
  10. ↑ "Order Cetartiodactyla - Even-toed ungulates (and whales)". http://www.ultimateungulate.com/Cetartiodactyla.html. 
  11. ↑ Evans, Alistair R.; Pineda-Munoz, Silvia (2018), Croft, Darin A.; Su, Denise F.; Simpson, Scott W., eds., "Inferring Mammal Dietary Ecology from Dental Morphology" (in en), Methods in Paleoecology: Reconstructing Cenozoic Terrestrial Environments and Ecological Communities, Vertebrate Paleobiology and Paleoanthropology (Springer International Publishing): pp. 37–51, doi:10.1007/978-3-319-94265-0_4, ISBN 978-3-319-94265-0 
  12. ↑ Sacco, Tyson; Valkenburgh, Blaire Van (2004). "Ecomorphological indicators of feeding behaviour in the bears (Carnivora: Ursidae)" (in en). Journal of Zoology 263 (1): 41–54. doi:10.1017/S0952836904004856. ISSN 1469-7998. 
  13. ↑ "Diet and metabolism", Parrots of Africa, Madagascar and the Mascarene Islands (Wits University Press): pp. 159–191, 2012, doi:10.18772/22012125522.13, ISBN 9781868145911, http://dx.doi.org/10.18772/22012125522.13, retrieved 2023-06-05 
  14. ↑ "Cassowary". 2022. https://animals.sandiegozoo.org/animals/cassowary. 
  15. ↑ Galdikas, Biruté M. F. (1 February 1988). "Orangutan diet, range, and activity at Tanjung Puting, Central Borneo" (in en). International Journal of Primatology 9 (1): 1–35. doi:10.1007/BF02740195. ISSN 0164-0291. 
  16. ↑ McCarty, John P.; Winkler, David W. (1 January 1999). "Foraging Ecology and Diet Selectivity of Tree Swallows Feeding Nestlings". The Condor 101 (2): 246–254. doi:10.2307/1369987. 
  17. ↑ Superina, Mariella (1 March 2011). "Husbandry of a pink fairy armadillo (Chlamyphorus truncatus): case study of a cryptic and little known species in captivity" (in en). Zoo Biology 30 (2): 225–231. doi:10.1002/zoo.20334. ISSN 1098-2361. PMID 20648566. 
  18. ↑ Shute, Nancy (20 April 2012). "For Most Of Human History, Being An Omnivore Was No Dilemma". NPR. https://www.npr.org/sections/thesalt/2012/04/20/150817741/for-most-of-human-history-being-an-omnivore-was-no-dilemma. 
  19. ↑ "omnivore: definition of omnivore in Oxford dictionary (American English) (US)". http://www.oxforddictionaries.com/us/definition/american_english/omnivore. 
  20. ↑ Collocott, T. C., ed (1974). Chambers Dictionary of science and technology. Edinburgh: W. and R. Chambers. ISBN 978-0-550-13202-4. 
  21. ↑ 21.0 21.1 "Omnivore - Biology-Online Dictionary". http://www.biology-online.org/dictionary/Omnivore. 
  22. ↑ 22.0 22.1 "omnivore - definition of omnivore in English from the Oxford dictionary". http://www.oxforddictionaries.com/us/definition/english/omnivore. 
  23. ↑ "Definition of OMNIVORE". http://www.merriam-webster.com/dictionary/Omnivore. 
  24. ↑ "omnivore Definition in the Cambridge English Dictionary". http://dictionary.cambridge.org/us/dictionary/english/omnivore?q=Omnivore. 
  25. ↑ Clarys, Peter; Deliens, Tom; Huybrechts, Inge; Deriemaeker, Peter; Vanaelst, Barbara; De Keyzer, Willem; Hebbelinck, Marcel; Mullie, Patrick (24 March 2014). "Comparison of Nutritional Quality of the Vegan, Vegetarian, Semi-Vegetarian, Pesco-Vegetarian and Omnivorous Diet". Nutrients 6 (3): 1318–1332. doi:10.3390/nu6031318. ISSN 2072-6643. PMID 24667136. 
  26. ↑ Michel, Fabienne; Knaapila, Antti; Hartmann, Christina; Siegrist, Michael (2021-07-01). "A multi-national comparison of meat eaters' attitudes and expectations for burgers containing beef, pea or algae protein" (in en). Food Quality and Preference 91: 104195. doi:10.1016/j.foodqual.2021.104195. ISSN 0950-3293. 
  27. ↑ Valente, Martina; Syurina, Elena V.; Muftugil-Yalcin, Seda; Cesuroglu, Tomris (2020-11-01). ""Keep Yourself Alive": From Healthy Eating to Progression to Orthorexia Nervosa A Mixed Methods Study among Young Women in the Netherlands". Ecology of Food and Nutrition 59 (6): 578–597. doi:10.1080/03670244.2020.1755279. ISSN 0367-0244. PMID 32366121. Bibcode: 2020EcoFN..59..578V. 
  28. ↑ Norris, Catherine J.; Do, Elena; Close, Emma; Deswert, Sky (2019-09-01). "Ambivalence toward healthy and unhealthy food and moderation by individual differences in restrained eating" (in en). Appetite 140: 309–317. doi:10.1016/j.appet.2019.05.033. ISSN 0195-6663. PMID 31136805. https://www.sciencedirect.com/science/article/pii/S0195666318313448. 
  29. ↑ Schreiner, Philipp; Yilmaz, Bahtiyar; Rossel, Jean-Benoît; Franc, Yannick; Misselwitz, Benjamin; Scharl, Michael; Zeitz, Jonas; Frei, Pascal et al. (July 2019). "Vegetarian or gluten-free diets in patients with inflammatory bowel disease are associated with lower psychological well-being and a different gut microbiota, but no beneficial effects on the course of the disease". United European Gastroenterology Journal 7 (6): 767–781. doi:10.1177/2050640619841249. ISSN 2050-6406. PMID 31316781. 
  30. ↑ O'Malley, Keelia; Willits-Smith, Amelia; Aranda, Rodrigo; Heller, Martin; Rose, Diego (2019-06-01). "Vegan vs Paleo: Carbon Footprints and Diet Quality of 5 Popular Eating Patterns as Reported by US Consumers (P03-007-19)" (in en). Current Developments in Nutrition 3 (Supplement_1): nzz047.P03–007–19. doi:10.1093/cdn/nzz047.P03-007-19. PMC 6574879. https://academic.oup.com/cdn/article/3/Supplement_1/nzz047.P03-007-19/5517901. 
  31. ↑ Reece, Jane (10 November 2013). Campbell Biology (10th ed.). Boston: Pearson. pp. Chapter 55. ISBN 978-0321775658. 
  32. ↑ "Animals: Carnivore, Herbivore or Omnivore?" (in en-US). 2014-02-27. http://www.sciencemadesimple.co.uk/curriculum-blogs/biology-blogs/animalscarnivore_herbivore_or_omnivore. 
  33. ↑ Ewer, R. F. (1973). The Carnivores. London: Weidenfeld and Nicolson. ISBN 978-0-297-99564-7. 
  34. ↑ "Why Dogs Eat Grass ~ Dr. Richard Orzeck". http://www.worldsvet.com/dogseatgrass.html. 
  35. ↑ "White-tailed deer shown to raid nests, eat eggs and baby birds, USGS reports". http://www.nola.com/outdoors/index.ssf/2015/03/white-tailed_deer_shown_to_rai.html. 
  36. ↑ Hutson, Jarod M.; Burke, Chrissina C.; Haynes, Gary (1 December 2013). "Osteophagia and bone modifications by giraffe and other large ungulates". Journal of Archaeological Science 40 (12): 4139–4149. doi:10.1016/j.jas.2013.06.004. Bibcode: 2013JArSc..40.4139H. 
  37. ↑ Negron, Vladimir (20 April 2009). "Why do cats eat grass?". petMD. http://www.petmd.com/cat/wellness/evr_ct_eating_grass. 
  38. ↑ Platt, S. G.; Elsey, R. M.; Liu, H.; Rainwater, T. R.; Nifong, J. C.; Rosenblatt, A. E.; Heithaus, M. R.; Mazzotti, F. J. (2013). "Frugivory and seed dispersal by crocodilians: an overlooked form of saurochory?" (in en). Journal of Zoology 291 (2): 87–99. doi:10.1111/jzo.12052. ISSN 1469-7998. 
  39. ↑ "Omnivore". http://www.eoearth.org/view/article/171414/. 
  40. ↑ Maclean, Gordon Lindsay (1993). Roberts' Birds of Southern Africa. Publisher: New Holland. ISBN:978-0620175838.
  41. ↑ Skaife, S. H. (1953). African Insect Life. Pub. Longmans, Green & Co., London.
  42. ↑ "Anopheles Male Vs. Female". http://animals.mom.me/anopheles-male-vs-female-7968.html. 
  43. ↑ Singer, Michael S.; Bernays, Elizabeth A. (2003). "Understanding Omnivory Needs: A Behavioral Perspective". Ecology 84 (10): 2532–2537. doi:10.1890/02-0397. Bibcode: 2003Ecol...84.2532S. 
  44. ↑ "Omnivores' ancestors primarily ate plants, or animals, but not both". 2012-04-17. http://www.dnaindia.com/scitech/report_omnivores-ancestors-primarily-ate-plants-or-animals-but-not-both_1677181. 
  45. ↑ Brent Huffman. "Family Suidae (Pigs)". UltimateUngulate.com. http://www.ultimateungulate.com/Cetartiodactyla/Suidae.html. 
  46. ↑ "Tree Squirrels". The Humane Society of the United States. http://www.hsus.org/wildlife/a_closer_look_at_wildlife/tree_squirrels.html. 
  47. ↑ "Eastern Chipmunk". Wonder Club. http://www.wonderclub.com/Wildlife/mammals/easternchipmunk.htm. 
  48. ↑ "Florida Mouse". United States Fauna. http://www.unitedstatesfauna.com/floridamouse.php. 
  49. ↑ "Brown Rat". Science Daily. https://www.sciencedaily.com/articles/b/brown_rat.htm. 
  50. ↑ Robert E. C. Wildman; Denis M. Medeiros (2000). Advanced Human Nutrition. CRC Press. p. 37. ISBN 978-0849385667. https://books.google.com/books?id=CXwylbbRXvAC&pg=PA37. Retrieved 6 October 2013. 
  51. ↑ Robert Mari Womack (2010). The Anthropology of Health and Healing. Rowman & Littlefield. p. 243. ISBN 978-0759110441. https://books.google.com/books?id=RqAraOMz. Retrieved 6 October 2013. 
  52. ↑ "Food and Diet". bearsmart.com. http://www.bearsmart.com/resources/north-american-bears/food-and-diet. 
  53. ↑ "About Wolves". http://wolfpark.org/oldsite/aboutwolves.shtml. 
  54. ↑ Halle, S. & Stenseth, N. (2000). Activity patterns in small mammals: an ecological approach. Berlin; Heidelberg, Germany; New York: Springer-Verlag. p. 131.
  55. ↑ Annex: Towards a Forestry Commission England Grey Squirrel Policy, UK: Forestry Commission, 22 January 2006, http://www.forestry.gov.uk/pdf/greysquirrel-annex.pdf/%24FILE/greysquirrel-annex.pdf, retrieved 15 May 2012 
  56. ↑ Moller, H. (1983). "Food and foraging behaviour of red (Scirus vulgaris) and grey (Scirus carolinensis) squirrels". Mammal Review 13: 81-98.
  57. ↑ Seattle Audubon Society. "Family Corvidae (Crows/Ravens)". BirdWeb.org. http://birdweb.org/birdweb/bird_details.aspx?id=318. 
  58. ↑ Capinera, John (2010). Insects and Wildlife. Publisher: Wiley-Blackwell. ISBN:978-1-4443-3300-8.
  59. ↑ Ewing, Jack (2005). Monkeys Are Made of Chocolate. Publisher: Pixyjack Press. ISBN:978-0-9658098-1-8.



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