Bactrian camel

Bactrian camel
A Bactrian camel in the Shanghai Zoo

Critically endangered, possibly extinct in the wild  (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Camelidae
Genus: Camelus
Species: C. bactrianus
Binomial name
Camelus bactrianus
Linnaeus, 1758
Geographic range
Synonyms[2]

The Bactrian camel (Camelus bactrianus) is a large, even-toed ungulate native to the steppes of Central Asia. Of the two species of camels, it is by far the rarer. The Bactrian camel has two humps on its back, in contrast to the single-humped dromedary camel.[3] Its population of two million exists mainly in the domesticated form.[4] Some authorities, notably the International Union for Conservation of Nature (IUCN), use the binomial name Camelus ferus for the wild Bactrian camel and reserve Camelus bactrianus for the domesticated Bactrian camel.[1] Their name comes from the ancient historical region of Bactria.[5]

The domesticated Bactrian camel has served as a pack animal in inner Asia since ancient times. With its tolerance for cold, drought, and high altitudes, it enabled the travel of caravans on the Silk Road.[6] The wild form has dwindled to a population estimated at 800 in October 2002 and has been classified as critically endangered on the IUCN Red List of Threatened Species.[1] Its range in the wild is restricted to remote regions of the Gobi and Taklamakan Deserts of Mongolia and China. A small number of wild Bactrian camels still roam the Mangystau Province of southwest Kazakhstan and the Kashmir Valley in India. Feral herds of Bactrian camels are found in Australia.[7]

Taxonomy

Lamini

Alpaca

Vicuña

Llama

Guanaco





Camelini

Dromedary

Bactrian camel





Phylogenetic relationships of the dromedary from combined analysis of all molecular data.[8]

The Bactrian camel shares the genus Camelus with the dromedary (C. dromedarius) and the wild Bactrian camel (C. ferus). The Bactrian camel belongs to the family Camelidae.[2][9] The ancient Greek philosopher Aristotle (4th century BC) was the first to describe the species of Camelus. He named two species in his History of Animals: the one-humped Arabian camel and the two-humped Bactrian camel.[10][11] The Bactrian camel was given its current binomial name Camelus bactrianus by Swedish zoologist Carl Linnaeus in his 1758 publication Systema Naturae.[12]

In 2007, Peng Cui (of the Chinese Academy of Sciences) and colleagues carried out a phylogenetic study of the evolutionary relationships between the two tribes of Camelidae: Camelini - consisting of the three Camelus species (the study considered the wild Bactrian camel as a subspecies of the Bactrian camel) - and Lamini - consisting of the alpaca (Vicugna pacos), the guanaco (Lama guanicoe), the llama (L. glama) and the vicuña (V. vicugna). The study revealed that the two tribes had diverged 25 million years ago (early Miocene), notably earlier than what had been previously estimated from North American fossils. Speciation began first in Lamini as the alpaca came into existence 10 million years ago (late Pleistocene). Nearly two million years later, the Bactrian camel and the dromedary emerged as two independent species.[8]

The Bactrian camel and the dromedary often interbreed to produce fertile offspring. Where the ranges of the two species overlap, such as in northern Punjab, Persia and Afghanistan, the phenotypic differences between them tend to decrease as a result of extensive crossbreeding between them. The fertility of their hybrid has given rise to speculation that the Bactrian camel and the dromedary should be merged into a single species with two varieties.[13] However, a 1994 analysis of the mitochondrial cytochrome b gene revealed that the species display 10.3% divergence in their sequences.[14]

Subspecies

Bactrian camels in Nubra Valley, India

The wild Bactrian camel (Camulus ferus) was first described by Nikolay Przhevalsky in the late 19th century.

Zoological opinion nowadays tends to favour the idea that C. bactrianus and C. dromedarius are descendants of two different subspecies of C. ferus (Peters and von den Driesch 1997: 652) and there is no evidence to suggest that the original range of C. ferus included those parts of Central Asia and Iran where some of the earliest Bactrian remains have been found.[15]

In particular, a population of wild Bactrian camel has been discovered to live within a part of the Gashun Gobi region of the Gobi Desert. This population is distinct from domesticated herds both in genetic makeup[16] and in behavior.

As many as three regions in the genetic makeup are distinctly different from domesticated camels, with up to a 3% difference in the base genetic code. However, with so few wild camels, what the natural genetic diversity within a population would have been is not clear.

Another difference is the ability of these wild camels to drink saltwater slush, although whether the camel can extract useful water from it is not yet certain. Domesticated camels are unable to drink such salty water.[17]

Description

Detail of feet

The Bactrian camel is the largest mammal in its native range and rivals the dromedary as the largest living camel. Shoulder height is from 180 to 230 cm (5.9 to 7.5 ft), head-and-body length is 225–350 cm (7.38–11.48 ft), and the tail length is 35–55 cm (14–22 in). At the top of the humps, the average height is 213 cm (6.99 ft). Body mass can range from 300 to 1,000 kg (660 to 2,200 lb), with males often being much larger and heavier than females.[18][19] Its long, wooly coat varies in colour from dark brown to sandy beige. A mane and beard of long hair occurs on the neck and throat, with hairs measuring up to 25 cm (9.8 in) long. The shaggy winter coat is shed extremely rapidly, with huge sections peeling off at once, appearing as if sloppily shorn off. The two humps on the back are composed of fat (not water as is sometimes thought). The face is typical of a camelid, being long and somewhat triangular, with a split upper lip. The long eyelashes, along with the sealable nostrils, help to keep out dust in the frequent sandstorms which occur in their natural range. The two broad toes on each foot have undivided soles and are able to spread widely as an adaptation to walking on sand. The feet are very tough, as befits an animal of extreme environments.

Natural habitat

These camels are migratory, and their habitat ranges from rocky mountain massifs to flat arid desert, stony plains, and sand dunes. Conditions are extremely harsh – vegetation is sparse, water sources are limited and temperatures are extreme, ranging from as low as −40 °C in winter to 40 °C in summer. The camels’ distribution is linked to the availability of water, with large groups congregating near rivers after rain or at the foot of the mountains, where water can be obtained from springs in the summer months, and in the form of snow during the winter.

Life history

Bactrian camels are exceptionally adept at withstanding wide variations in temperature – ranging from freezing cold to blistering heat. They have a remarkable ability to go without water for months at a time, but when water is available they may drink up to 57 liters at once. When well fed, the humps are plump and erect, but as resources decline, the humps shrink and lean to the side. When moving faster than a walking speed, they pace, by stepping forwards with both legs on the same side (as opposed to trotting, using alternate diagonals as done by most other quadrupeds). Speeds of up to 65 kilometres per hour (40 mph) have been recorded, but they rarely move this fast. Bactrian camels are also said to be good swimmers. The sense of sight is well developed and the sense of smell is extremely good. The lifespan of Bactrian camels is estimated at up to 50 years, often 20 to 40 in captivity.

Diet

Bactrian camels are diurnal, sleeping in the open at night and foraging for food during the day. They are primarily herbivorous. They are able to eat plants that are dry, prickly, salty and/or bitter, and can ingest virtually any kind of vegetation. When other nutrient sources are not available, these camels may feed on carcasses, gnawing on bones, skin, or various different kinds of flesh. In more extreme conditions, they may eat any material they find, which has included rope, sandals, and even tents. Their ability to feed on a wide range of foods allows them to live in areas with sparse vegetation. With tough mouths that can withstand sharp objects such as thorns, the digestion process begins. The first time food is swallowed, it is not fully chewed. The partly masticated food (called cud) goes into the stomach and later is brought back up for further chewing.

Bactrian camels belong to a fairly small group of animals that regularly eat snow to provide their water needs. Any animals living above the snowline are obliged to do this, as snow and ice are the only forms of water during winter, and by doing so, their range is greatly enlarged. The latent heat of snow and ice is enormous compared with the heat capacity of water, demanding a large sacrifice in heat energy and forcing animals to eat only small amounts at a time.[20]

Group organisation

The population density of wild Bactrian camels is calculated to be five animals per 100 square kilometers. Wild camels generally appear to live in groups of up to 30 individuals, though most groups contain six to 20 individuals. A mature male acts as the leader of the group. Typically, Bactrian camels seen alone are postdispersal young individuals which have just reached sexual maturity.

Reproduction

Bactrian camels are induced ovulators - they ovulate after insemination of semen into the vagina; the seminal plasma, not the spermatozoa, induces ovulation. Ovulation occurs in 87% of females after insemination: 66% ovulate within 36 h and the rest by 48 h (the same as natural mating). The least amount of semen required to elicit ovulation is about 1.0 ml.[21]

The mating season occurs in the fall. Males during this time are often quite violent and may bite, spit, or attempt to sit on other male camels. The age of sexual maturity varies, but is usually reached at 3 to 5 years. Gestation lasts around 13 months, with most young being born from March through April. One or occasionally two calves are produced, and the female can give birth to a new calf every other year. Young Bactrian camels are precocial, being able to stand and run shortly after birth, and are fairly large at an average birth weight of 36 kg (79 lb). They are nursed for about 1.5 years. The young calf stays with its mother for three to five years, until it reaches sexual maturity, and often serves to help raise subsequent generations for those years. Wild camels sometimes breed with domesticated or feral camels, as well.

Threats

The only extant predators that regularly target wild Bactrian camels are gray wolves, which have been seen to pursue weaker and weather-battered camels as they try to reach oases.[22] Due to increasingly dry conditions in the species' range, the numbers of cases of wolf predation on wild camels at oases has reportedly increased.[23] Historically, the Caspian tiger was also known to prey on wild Bactrian camels, but this subspecies is almost certainly extinct.[24]

History

Two Bactrian camels

The Bactrian camel is thought to have been domesticated (independently of the dromedary) sometime before 2500 BCE,[25] in Northeast Afghanistan,[25] or southwestern Turkestan.[26] The dromedary camel is believed to have been domesticated between 4000 BCE and 2000 BCE[27] in Arabia. As pack animals, these ungulates are virtually unsurpassed, able to carry 170–250 kg (370–550 lb) at a rate of 47 km (30 miles) per day, or 4 km/h (2 mph) over a period of four days.

Bactrian camels have been the focus of artwork throughout history. For example, western foreigners from the Tarim Basin and elsewhere were depicted in numerous ceramic figurines of the Chinese Tang dynasty (618–907).

Evolutionary history

As of the 1980s, a complete range of fossils suggests the first camelids appeared in North America about 30 million years ago, had relatively small body masses, and were adapted to warm climates.[28] By the early Pleistocene (about 2 million years ago), they had already evolved into a form similar to the current Bactrian camel, and many individuals permanently migrated to the opposite end of the Bering Strait in an abrupt fashion, probably as a response to the advancing ice age. The remaining related types of American camelids are now only in South America.

Documentaries

Conservation

The Bactrian camel was identified as one of the top ten "focal species" in 2007 by the Evolutionarily Distinct and Globally Endangered (EDGE) project, which prioritises unique and threatened species for conservation.[29] Fewer than a thousand (around 600 individuals) are thought to survive in the wild and the population is decreasing. The immediate threats faced by the species are all human related. Firstly, habitat loss has been high due to development for mining and industrial complexes. Due to increasing human populations, wild camels are forced to share food and water sources with introduced domestic stock, thus are sometimes shot by farmers. Included in this stock are domesticated Bactrians, which freely mate with wild individuals. This has led to a concern of a loss of genetically distinct wild Bactrian camels.

Facilitated by the Wild Camel Protection Foundation, two wildlife preserves were founded by the governments of Mongolia and China to protect the Gobi desert, the Great Gobi Reserve A in Mongolia in 1982, and the Arjin Shan Lop Nur Nature Reserve in China in 2000. A small captive-breeding program has also been started, with the ultimate goal of reintroduction.

Gallery

See also

Wikimedia Commons has media related to Camelus bactrianus.

References

  1. 1 2 3 Hare, J. (2008). Camelus ferus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 31 January 2008. Database entry includes justification for why this species is critically endangered
  2. 1 2 Grubb, P. (2005). "Order Artiodactyla". In Wilson, D.E.; Reeder, D.M. Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 645-6. ISBN 978-0-8018-8221-0. OCLC 62265494.
  3. ↑ The mnemonic that allows one to remember the correct English word for each is: "Bactrian" begins with "B", and "Dromedary" begins with "D" – and "B" on its side has two humps, whilst "D" on its side has only one hump.
  4. ↑ "Bactrian Camel." EdgeofExistence.org. EDGE, 2010.
  5. ↑ "Camels – Old World Camels". Science Encyclopedia. Net Industries. Retrieved 29 November 2012.
  6. ↑ Potts, Daniel (June 2005). "Bactrian Camels and Bactrian-Dromedary Hybrids". The Silk Road Foundation Newsletter. The Silk Road Foundation. Retrieved 13 January 2013.
  7. ↑ Edwards, G. P.; Saalfeld, K.; Clifford, B. (2005). "Population trend of feral camels in the Northern Territory, Australia". Wildlife Research 31 (5): 509–517.
  8. 1 2 Cui, P.; Ji, R.; Ding, F.; Qi, D.; Gao, H.; Meng, H.; Yu, J.; Hu, S.; Zhang, H. (2007). "A complete mitochondrial genome sequence of the wild two-humped camel (Camelus bactrianus ferus): an evolutionary history of Camelidae". BioMed Central Genomics 8 (1): 241. doi:10.1186/1471-2164-8-241.
  9. ↑ Groves, C.; Grubb, P. (2011). Ungulate Taxonomy. Johns Hopkins University Press. p. 32. ISBN 978-1-4214-0093-8.
  10. ↑ de Buffon, C. (1791). Natural History, General and Particular. London, UK: Alexander Strahan. p. 121.
  11. ↑ Smith, W.; Anthon, C. (1870). A Dictionary of Greek and Roman Antiquities (3rd ed.). New York, USA: Harper and Brothers Publishers. p. 204.
  12. ↑ Linnaeus, C. (1758). Systema Naturæ Per Regna Tria Naturae (10th ed.). Stockholm, Sweden: Laurentius Salvius. p. 65.
  13. ↑ Mukasa-Mugerwa, E. (1981). The Camel (Camelus dromedarius): A Bibliographical Review (PDF). Addis Ababa, Ethiopia: International Livestock Centre for Africa. pp. 1–147.
  14. ↑ Stanley, H.F.; Kadwell, M.; Wheeler, J.C. (1994). "Molecular evolution of the family Camelidae: a mitochondrial DNA study". Proceedings of the Royal Society B: Biological Sciences 256 (1345): 1–6. doi:10.1098/rspb.1994.0041.
  15. ↑ Potts (2004), p. 145.
  16. ↑ "Wild camels 'genetically unique'". Earth News (BBC). 22 July 2009. Retrieved 22 July 2009.
  17. ↑ Wild Camel Protection Foundation. "Wild Camels". Retrieved 7 December 2012.
  18. ↑ EDGE :: Mammal Species Information. Edgeofexistence.org (2010-11-12). Retrieved on 2012-12-19.
  19. ↑ Bactrian Camel- Ultimate Ungulate Species Account
  20. ↑ Replacing Water with Snow. (PDF) . Retrieved on 2012-12-19.
  21. ↑ Chen, B.X., Yuen, Z.X. and Pan, G.W. (1985). "Semen-induced ovulation in the bactrian camel (Camelus bactrianus)". J. Reprod. Fert. 74 (2): 335–339.
  22. ↑ Kara Rogers. The Last Wild Camels. Encyclopedia Britannica Blog. (Posted: February 18, 2010). Britannica.com. Retrieved on 2012-12-19.
  23. ↑ Camelus ferus (Bactrian Camel, Wild Bactrian Camel). Iucnredlist.org. Retrieved on 2012-12-19.
  24. ↑ tabaristan: Caspian Tiger. Enmazeroni.blogspot.com. Retrieved on 2012-12-19.
  25. 1 2 "camel", Encyclopædia Britannica. 2007. Encyclopædia Britannica Online. accessed 11 February 2007.
  26. ↑ Myths About Camels, The Hatch Report.com.
  27. ↑ Al-Swailem, et al. Classification of Saudi Arabian camel (Camelus dromedarius) subtypes based on RAPD technique., Journal of Food, Agriculture and Environment, Vol.5 (1) : 143–148. 2007.
  28. ↑ Ferguson, K. "Agricultural Landscape: Invented Tradition of the Mesa Verde World". Cortez: University of Cortez, in press).
  29. ↑ "Protection for 'weirdest' species". BBC. 2007-01-16. Retrieved 2007-05-22.

External links

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