The African buffalo (Syncerus caffer) is a large sub-Saharan African bovine.[2] There are five subspecies that are recognized as valid by most authorities:
- Syncerus caffer caffer, the Cape buffalo, is the nominotypical subspecies, as well as the largest, found in Southern and East Africa.
- S. c. nanus, the forest buffalo, is the smallest subspecies, common in forest areas of Central and West Africa
- S. c. brachyceros, the Sudan buffalo, a smaller version of the Cape buffalo, found in the drier, northern areas of Central and West Africa.
- S. c. aequinoctialis, the Nile Buffalo, sometimes considered identical to the Sudan buffalo, found in the drier, northern areas of East and Central Africa.
- S. c. mathewsi, the mountain buffalo, a disputed subspecies from the Virunga Mountains in Central Africa.
African buffalo Temporal range: Middle Pleistocene-Holocene
| |
---|---|
Cape buffalo (S. c. caffer) at Chobe National Park, Botswana with a cattle egret atop it | |
Forest buffalo (S. c. nanus) at Réserve Africaine de Sigean, France | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Artiodactyla |
Family: | Bovidae |
Subfamily: | Bovinae |
Genus: | Syncerus |
Species: | S. caffer
|
Binomial name | |
Syncerus caffer (Sparrman, 1779)
| |
Subspecies | |
S. c. caffer | |
Range of the commonly accepted forms of the African buffalo |
The adult African buffalo's horns are its characteristic feature: they have fused bases, forming a continuous bone shield across the top of the head, referred to as a "boss".
The African buffalo is more closely related to other buffalo species than it is to other bovids such as American bison or domestic cattle, with its closest living relative being the Asian water buffalo.[3] Its unpredictable temperament may be part of the reason that the African buffalo has never been domesticated, which would also explain why the African buffalo has no domesticated descendants, unlike the wild yak and wild water buffalo which are the ancestors of the domestic yak and water buffalo. Natural predators of adult African buffaloes include lions, African wild dogs, spotted hyenas, and Nile crocodiles. As one of the Big Five game animals, the Cape buffalo is a sought-after trophy in hunting.
Description
editThis section needs additional citations for verification. (March 2014) |
The African buffalo is a very robust species. Its shoulder height can range from 1.0 to 1.7 m (3.3 to 5.6 ft) and its head-and-body length can range from 1.7 to 3.4 m (5.6 to 11.2 ft). The tail can range from 70 to 110 cm (28 to 43 in) long.[4] Compared with other large bovids, it has a long but stocky body (the body length can exceed the wild water buffalo, which is heavier and taller) and short but thickset legs, resulting in a relatively short standing height. Cape buffaloes weigh 425 to 870 kg (937 to 1,918 lb) (males weigh about 100 kg (220 lb) more than females).[5] In comparison, African forest buffaloes, at 250 to 450 kg (600 to 1,000 lb), are only half that size.[6] Its head is carried low; its top is located below the backline. The front hooves of the buffalo are wider than the rear, which is associated with the need to support the weight of the front part of the body, which is heavier and more powerful than the back.
Savannah-type buffaloes have black or dark brown coats with age. Old bulls often have whitish circles around their eyes and on their face. Females tend to have more reddish coats. Forest-type buffaloes are 30–40% smaller, reddish brown in colour, with much more hair growth around the ears and with horns that curve back and slightly up. Calves of both types have red coats.
A characteristic feature of the horns of adult male African buffalo (southern and eastern populations) is that the bases come very close together, forming a shield referred to as a "boss". From the base, the horns diverge downwards, then smoothly curve upwards and outwards and in some cases inwards and or backwards. In large bulls, the distance between the ends of the horns can reach upwards of one metre (the record being 64.5 inches 164 cm). The horns form fully when the animal reaches the age of 5 or 6 years old, but the bosses do not become "hard" until it reaches the age of 8 to 9 years old. In cows, the horns are, on average, 10–20% smaller, and they do not have a boss. Forest-type buffalo horns are smaller than those of the savanna-type buffaloes from Southern and East Africa, usually measuring less than 40 cm (16 in), and are almost never fused.
Unlike other large bovines, African buffalo have 52 chromosomes (for comparison, American bison and domestic cattle have 60). This means domestic cattle and bison are unable to create hybrid offspring with cape buffalo.
Subspecies
editImage | Subspecies | Description | Distribution |
---|---|---|---|
Syncerus caffer caffer (the Cape buffalo) | Nominate subspecies and the largest one, with large males weighing up to 870 kg (1,920 lb). The average weight of bulls from South Africa was 753 kg (1,660 lb).[7] In Serengeti National Park, eight bulls averaged similarly 751 kg (1,656 lb).[8] In one survey, mature bulls and cows from Kruger National Park averaged 590 kg (1,300 lb) and 513 kg (1,131 lb) respectively.[9] In both Kenya and Botswana, the average adult weight of this race was estimated as 631 kg (1,391 lb).[10][11] Buffaloes of this subspecies living in the south of the continent, notably tall in size and ferocity, are the so-called Cape buffalo. Color of this subspecies is the darkest, almost black. | Southern and East Africa. | |
S. c. nanus (the forest buffalo, dwarf buffalo or Congo buffalo) | The smallest of the subspecies; the height at the withers is less than 120 cm and average weight is about 270 kg (600 lb), or about the size of a zebra, and two to three times lighter in mass than the nominate subspecies.[8][12] The color is red, with darker patches on the head and shoulders, and in the ears, forming a brush. This subspecies is so different from the Cape buffalo that some researchers still consider it to be a separate species, S. nanus. Hybrids between the Cape and forest buffalo are not uncommon. | Forest areas of Central and West Africa. | |
S. c. brachyceros (the Sudan buffalo or West African savanna buffalo) | Intermediate between the first two subspecies. Its dimensions are relatively small, especially compared to other buffalo found in Cameroon, which weigh half as much as the Cape subspecies (bulls weighing 600 kg (1,300 lb) are considered to be very large). Adults average in weight up to 400 kg (880 lb).[13] | West Africa | |
S. c. aequinoctialis (the Nile buffalo) | It is similar to the Cape buffalo, but somewhat smaller, and its color is lighter. This subspecies is sometimes considered to be the same as the Western savanna buffalo.[14] | Central Africa. | |
S. c. mathewsi (the mountain buffalo or Virunga buffalo) | Not universally recognized by all authorities.[15] | mountainous areas of the Democratic Republic of the Congo, Rwanda and Uganda. |
Ecology
editThe African buffalo is one of the most successful grazers in Africa. It lives in savannas, swamps and floodplains, as well as mopane grasslands, and the forests of the major mountains of Africa.[16] This buffalo prefers a habitat with dense cover, such as reeds and thickets, but can also be found in open woodland.[17] While not particularly demanding in regard to habitat, they require water daily, and so they depend on perennial sources of water. Like the plains zebra, the buffalo can live on tall, coarse grasses. Herds of buffalo mow down grasses and make way for more selective grazers. When feeding, the buffalo makes use of its tongue and wide incisor row to eat grass more quickly than most other African herbivores. Buffaloes do not stay on trampled or depleted areas for long.
Other than humans, African buffaloes have few predators and are capable of defending themselves against (and killing) lions.[18] Lions kill and eat buffaloes regularly, and in some regions, the buffaloes are the lions' primary prey. It often takes several lions to bring down a single adult buffalo, and the entire pride may join in the hunt. However, several incidents have been reported in which lone adult male lions have successfully brought down adult buffaloes. On very rare occasions, buffaloes and white rhinos will fight over territory; due to the rhino's strength and size advantage, the rhino typically wins and the buffalo can die from injuries sustained during the encounter. Rhinos live solitary lives, whereas buffalo (excluding solitary adult bulls) primarily live social lives and thus they do not usually recognize each other as threats.[19] Hippopotamuses and buffalo also do not normally interact, but if the buffalo provokes the hippo or makes it feel threatened, a fight can break out, but this is also rare.[20] Adolescent bull African elephants may harass or kill Cape buffalo, either out of territorial aggression or while in musth; when they do this, the calves are most likely to be killed by the elephant attack as they are defenseless when facing an elephant alone, whereas adults will try to fight back and may survive (or succumb to injuries afterward).[21] The average-sized Nile crocodile typically attacks only old solitary animals and young calves, though they can kill healthy adults. Exceptionally large, old male crocodiles may become semi-habitual predators of buffaloes.[4][22][23] The cheetah, leopard, African wild dog and spotted hyena are normally a threat only to newborn calves, though larger clans of hyenas have been recorded killing cows (mainly pregnant ones) and, on rare occasions, full-grown bulls.[24][25][26] Large packs of wild dogs have been observed to hunt calves and sick adults.
Diseases
editThe African buffalo is susceptible to many diseases, including those shared with domestic cattle, such as bovine tuberculosis, corridor disease, and foot-and-mouth disease. As with many diseases, these problems remain dormant within a population as long as the health of the animals is good. These diseases do, however, restrict the legal movements of the animals and fencing infected areas from unaffected areas is enforced. Some wardens and game managers have managed to protect and breed "disease-free" herds which become very valuable because they can be transported. Most well-known are Lindsay Hunt's efforts to source uninfected animals from the Kruger National Park in South Africa. Some disease-free buffaloes in South Africa have been sold to breeders for close to US$130,000.[27]
Social behavior
editHerd size is highly variable. The core of the herds is made up of related females, and their offspring, in an almost linear dominance hierarchy. The basic herds are surrounded by subherds of subordinate males, high-ranking males and females, and old or invalid animals.
African buffaloes engage in several types of group behavior. Females appear to exhibit a sort of "voting behavior". During resting time, the females stand up, shuffle around, and sit back down again. They sit in the direction they think they should move. After an hour of more shuffling, the females travel in the direction they decide. This decision is communal and not based on hierarchy or dominance.[28]
When chased by predators, a herd sticks close together and makes it hard for the predators to pick off one member. Calves are gathered in the middle. A buffalo herd responds to the distress call of a threatened member and tries to rescue it.[29] A calf's distress call gets the attention of not only the mother, but also the herd. Buffaloes engage in mobbing behavior when fighting off predators. They have been recorded killing lions[30] and chasing lions up trees and keeping them there for two hours, after the lions have killed a member of their group. Lion cubs can get trampled and killed. In one videotaped instance, known as the Battle at Kruger, a calf survived an attack by both lions and a crocodile after intervention of the herd.
Males have a linear dominance hierarchy based on age and size. Since a buffalo is safer when a herd is larger, dominant bulls may rely on subordinate bulls and sometimes tolerate their copulation. The young males keep their distance from the dominant bull, which is recognizable by the thickness of his horns.[31]
Adult bulls spar in play, dominance interactions, or actual fights. A bull approaches another, lowing, with his horns down, and waits for the other bull to do the same thing. When sparring, the bulls twist their horns from side to side.[29] If the sparring is for play, the bull may rub his opponent's face and body during the sparring session. Actual fights are violent but rare and brief. Calves may also spar in play, but adult females rarely spar at all.
During the dry season, males split from the herd and form bachelor groups.[31] Two types of bachelor herds occur: ones made of males aged four to seven years and those of males 12 years or older.[32] During the wet season, the younger bulls rejoin a herd to mate with the females. They stay with them throughout the season to protect the calves.[33] Some older bulls cease to rejoin the herd, as they can no longer compete with the younger, more aggressive males. The old bachelors are called dagga boys ("mud covered"), and are considered the most dangerous to humans.[34]
Vocalizations
editAfrican buffaloes make various vocalizations. Many calls are lower-pitched versions of those emitted by domestic cattle. They emit low-pitched, two- to four-second calls intermittently at three- to six-second intervals to signal the herd to move. To signal to the herd to change direction, leaders emit "gritty", "creaking gate" sounds.[17] When moving to drinking places, some individuals make long "maaa" calls up to 20 times a minute. When being aggressive, they make explosive grunts that may last long or turn into a rumbling growl. Cows produce croaking calls when looking for their calves. Calves make a similar call of a higher pitch when in distress.[17] When threatened by predators, they make drawn-out "waaaa" calls. Dominant individuals make calls to announce their presence and location. A version of the same call, but more intense, is emitted as a warning to an encroaching inferior.[17] When grazing, they make various sounds, such as brief bellows, grunts, honks, and croaks.
Reproduction
editFemales reach sexual maturity at around five years of age while males are sexually matured at four to six.[35] African buffaloes mate and give birth only during the rainy seasons. Birth peak takes place early in the season, while mating peaks later. A bull closely guards a cow that comes into heat, while keeping other bulls at bay.[17][31] This is difficult, as cows are quite evasive and attract many males to the scene. By the time a cow is in full estrus, only the most dominant bull in the herd/subherd is there.[17]
Cows first calve at five years of age, after a gestation period of 11.5 months. Newborn calves remain hidden in vegetation for the first few weeks while being nursed occasionally by the mother before joining the main herd. Older calves are held in the centre of the herd for safety.[36] The maternal bond between mother and calf lasts longer than in most bovids. That bonding ends when a new calf is born, and the mother then keeps her previous offspring at bay with horn jabs. Nevertheless, the yearling follows its mother for another year or so. Males leave their mothers when they are two years old and join the bachelor groups. Young calves, unusually for bovids, suckle from behind their mothers, pushing their heads between the mothers' legs.[37]
In the wild African buffaloes have an average lifespan of 11 years but they've been recorded to reach 22 years of age. In captivity they can live for a maximum of 29.5 years though they only live 16 years on average.[35]
-
Two-week-old calf suckling
At Kazinga Channel in Uganda
Relationship with humans
editStatus
editThe current status of the African buffalo is dependent on the animal's value to both trophy hunters and tourists, paving the way for conservation efforts through anti-poaching patrols, village crop damage payouts, and CAMPFIRE payback programs to local areas.
The African buffalo is listed as Near threatened by the IUCN, with a decreasing population of 400,000 individuals. While some populations (subspecies) are decreasing, others will remain unchanged in the long term if large, healthy populations continue to persist in a substantial number of national parks, equivalent reserves and hunting zones in southern and eastern Africa."[1]
In the most recent and available census data at continental scale, the total estimated numbers of the three savanna-type African buffalo subspecies (S. c. caffer, S. c. brachyceros and S. c. aequinoctialis) are at 513,000 individuals.[38]
In the past, numbers of African buffaloes suffered their most severe collapse during the great rinderpest epidemic of the 1890s, which, coupled with pleuro-pneumonia, caused mortalities as high as 95% among livestock and wild ungulates.[39]
Being a member of the big five game group, a term used to describe the five most dangerous animals to hunt, the Cape buffalo is a sought-after trophy, with some hunters paying over $10,000 for the opportunity to hunt one. The larger bulls are targeted for their trophy value, although in some areas, buffaloes are still hunted for meat.
Attacks
editOne of the "big five" African game, it is known as "the Black Death" or "the widowmaker", and is widely regarded as a very dangerous animal. African buffaloes are sometimes reported to kill more people in Africa than any other animal, although the same claim is also made of hippopotamuses and crocodiles.[40] These numbers may be somewhat overestimated; for example, in the country of Mozambique, attacks, especially fatal ones, were much less frequent on humans than those by hippos, and especially, Nile crocodiles.[41] In Uganda, on the other hand, large herbivores were found to attack more people on average than lions or leopards and have a higher rate of inflicting fatalities during attacks than the predators (the African buffalo, in particular, killing humans in 49.5% of attacks on them), but hippos and even elephants may still kill more people per annum than buffaloes.[42] African buffaloes are notorious among big-game hunters as very dangerous animals, with wounded animals reported to ambush and attack pursuers.[43]
See also
editReferences
edit- ^ a b IUCN SSC Antelope Specialist Group (2019). "Syncerus caffer". IUCN Red List of Threatened Species. 2019: e.T21251A50195031. doi:10.2305/IUCN.UK.2019-1.RLTS.T21251A50195031.en. Retrieved 19 November 2021.
- ^ Grubb, P. (2005). "Order Artiodactyla". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. pp. 695–696. ISBN 978-0-8018-8221-0. OCLC 62265494.
- ^ Jirik, Kate. "LibGuides: Forest Buffalo (Syncerus caffer nanus) Fact Sheet: Taxonomy & History". ielc.libguides.com. Retrieved 2023-04-30.
- ^ a b Huffman, Brent (2010-05-24). "Syncerus caffer – African buffalo". Ultimateungulate.com. Archived from the original on 2012-03-19. Retrieved 2010-10-23.
- ^ Estes, Richard; et al. (2020). "Cape buffalo". Britannica. Retrieved 2023-02-16.
- ^ Boitani, Luigi, Simon & Schuster's Guide to Mammals. Simon & Schuster/Touchstone Books (1984), ISBN 978-0-671-42805-1
- ^ Cornélis, D., Melletti, M., Korte, L., Ryan, S. J., Mirabile, M., Prin, T., & Prins, H. H. (2014). African buffalo Syncerus caffer (Sparrman, 1779). In Ecology, Evolution and Behaviour of Wild Cattle: Implications for Conservation (pp. 326-372). Cambridge University Press, Cambridge.
- ^ a b Grubb, P. (1972). Variation and incipient speciation in the African buffalo. Zeitschrift für Säugetierkunde, 37, 121-144.
- ^ Visscher, D. R., Van Aarde, R. J., & Whyte, I. (2004). Environmental and maternal correlates of foetal sex ratios in the African buffalo (Syncerus caffer) and savanna elephant (Loxodonta africana) Archived 2017-08-09 at the Wayback Machine. Journal of Zoology, 264(2), 111-116.
- ^ Bonyongo, M. C., & Harris, S. (2007). Grazers species-packing in the Okavango Delta, Botswana. African Journal of Ecology, 45(4), 527-534.
- ^ Oindo, B. O. (2002). Body size and measurement of species diversity in large grazing mammals. African Journal of Ecology, 40(3), 267-275.
- ^ Korte, L. M. (2008). "Variation of group size among African buffalo herds in a forest-savanna mosaic landscape". Journal of Zoology. 275 (3): 229–236. doi:10.1111/j.1469-7998.2008.00430.x.
- ^ Brown, W. (1988). Age determination of the West African buffalo Syncerus caffer brachyceros and the constancy of tooth wear. African Journal of Ecology, 26(3), 221-227.
- ^ C. P. Groves, D. M. Leslie Jr. (2011) Family Bovidae (Hollow-horned Ruminants). pp. 585–588. In: Wilson, D. E., Mittermeier, R. A., (Hrsg.). Handbook of the Mammals of the World. Volume 2: Hooved Mammals. Lynx Edicions, 2009. ISBN 978-84-96553-77-4
- ^ "BioLib - Syncerus caffer matthewsi (Virunga Buffalo)". biolib.cz.
- ^ Hughes, Kristen; Fosgate, Geoffrey T.; Budke, Christine M.; Ward, Michael P.; Kerry, Ruth; Ingram, Ben (13 September 2017). "Modeling the spatial distribution of African buffalo (Syncerus caffer) in the Kruger National Park, South Africa". PLOS ONE. 12 (9): e0182903. Bibcode:2017PLoSO..1282903H. doi:10.1371/journal.pone.0182903. PMC 5597095. PMID 28902858.
- ^ a b c d e f Estes, R. (1991) The Behavior Guide to African Mammals, Including Hoofed Mammals, Carnivores, Primates. Los Angeles, The University of California Press. pp. 195–200 ISBN 0520080858
- ^ "Cape Buffalo". Canadian Museum of Nature. Retrieved 2010-10-23.
- ^ "'Extremely rare sighting' of rhino's head-to-head battle with buffalo caught on camera | Animal Behaviour | Earth Touch News". Earth Touch News Network. Retrieved 2023-04-30.
- ^ "Buffalo escapes pride of 15 lions and then 3 hippos". Getaway Magazine. 2023-03-31. Retrieved 2023-04-30.
- ^ bennostand (2015-10-06). "VIDEO: Why the elephant killed the buffalo - an expert's opinion". Lowvelder. Retrieved 2023-05-01.
- ^ Graham, A. D. (1968). The Lake Rudolf Crocodile (Crocodylus niloticus Laurenti) Population. Masters of Science Thesis, The University of East Africa.
- ^ Pienaar, U. D. V. (1969). "Predator-prey relationships amongst the larger mammals of the Kruger National Park". Koedoe. 12. doi:10.4102/koedoe.v12i1.753.
- ^ Kruuk, Hans (1979). The Spotted Hyena: A study of predation and social behaviour. University of Chicago Press. p. 335. ISBN 978-0-226-45508-2.
- ^ Trinkel, M. (11 December 2009). "Prey selection and prey preferences of spotted hyenas Crocuta crocuta in the Etosha National Park, Namibia". Ecological Research. 25 (2): 413–417. doi:10.1007/S11284-009-0669-3. ISSN 0912-3814. Wikidata Q105300095.
- ^ Hayward, M. W. (December 2006). "Prey preferences of the spotted hyaena (Crocuta crocuta) and degree of dietary overlap with the lion (Panthera leo)". Journal of Zoology. 270 (4): 606–614. doi:10.1111/J.1469-7998.2006.00183.X. ISSN 1469-7998. Wikidata Q55951239.
- ^ Laing, Aislinn (24 April 2016). "Why is this buffalo worth £8.5 million?". The Telegraph. The Telegraph. Archived from the original on 2022-01-12. Retrieved 25 June 2019.
- ^ Wilson, D. S. (1997). "Altruism and Organism: Disentangling the Themes of Multilevel Selection Theory". The American Naturalist. 150: S122–S134. doi:10.1086/286053. JSTOR 2463504. PMID 18811309. S2CID 23390199.
- ^ a b Sinclair, A. R. E. (1977) The African Buffalo. Chicago, The University of Chicago Press.
- ^ YouTube. youtube.com.
- ^ a b c Turner, W. C.; Jolles, A. E.; Owen-Smith, N. (18 October 2005). "Alternating sexual segregation during the mating season by male African buffalo (Syncerus caffer)". Journal of Zoology. 267 (03): 291. doi:10.1017/S095283690500748X. ISSN 1469-7998. Wikidata Q56338562.
- ^ Ryan, S. J.; Knetchtel, Christiane U.; Wayne, M. (2006). "Range and habitat Selection of African Buffalo in South Africa" (PDF). Journal of Wildlife Management. 70 (3): 764–776. doi:10.2193/0022-541X(2006)70[764:RAHSOA]2.0.CO;2. S2CID 356110.
- ^ Main, M. B.; Coblentz, Bruce E. (1990). "Sexual Segregation among Ungulate: A Critique". Wildlife Society Bulletin. 18 (2): 204–210. JSTOR 3782137.
- ^ "Buffalo - Godfather of the African bushveld". Africa Geographic. 5 August 2020. Archived from the original on 6 August 2021.
- ^ a b Ng, Christoph. "Syncerus caffer (African buffalo)". Animal Diversity Web. Retrieved 2022-12-15.
- ^ "African Buffalo". British Broadcasting Corporation. Archived from the original on 27 October 2010. Retrieved 2010-10-23.
- ^ Prins, H.H.T (1996). Ecology and Behaviour of the African Buffalo: Social Inequality and Decision Making. Springer. p. 118. ISBN 978-0-412-72520-3. Retrieved 31 July 2013.
- ^ Melletti M. and Burton J. (eds). 2014. Ecology, Evolution and Behaviour of Wild Cattle: Implications for Conservation. Cambridge University Press
- ^ Winterbach, H. E. K. (1998). "Research review: the status and distribution of Cape buffalo Syncerus caffer caffer in southern Africa". South African Journal of Wildlife Research. 28 (3): 82–88.
- ^ Stumpf, Bruce G. "Africa on the Matrix: The Cape Buffalo". Archived from the original on 2002-12-20. Retrieved 2010-10-23.
- ^ Dunham, K. M., Ghiurghi, A., Cumbi, R., & Urbano, F. (2010). Human–wildlife conflict in Mozambique: a national perspective, with emphasis on wildlife attacks on humans. Oryx, 44(2), 185-193.
- ^ Treves, A., & Naughton-Treves, L. (1999). Risk and opportunity for humans coexisting with large carnivores. Journal of Human Evolution, 36(3), 275-282.
- ^ "African Animals Hunting facts and tips – Buffalo Hunting". safariBwana newsletter. Archived from the original on 2013-07-08. Retrieved 2010-10-23.
Further reading
edit- Melletti M. and Burton J. (eds). 2014. Ecology, Evolution and Behaviour of Wild Cattle. Implications for Conservation (Cambridge University Press). http://www.cambridge.org/us/academic/subjects/life-sciences/animal-behaviour/ecology-evolution-and-behaviour-wild-cattle-implications-conservation
- Ecology and Behaviour of the African Buffalo – Social Inequality and Decision Making (Chapman & Hall Wildlife Ecology & Behaviour)
- Huffman, B. 2006. The ultimate ungulate page. UltimateUngulate.com. Retrieved January 9, 2007.
- Nowak, R.M. and Paradiso, J.L. 1983. Walker's Mammals of the World. Baltimore, Maryland, USA: The Johns Hopkins University Press. ISBN 978-0-8018-2525-5