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Chevrotains (Tragulidae)

Chevrotains

(Tragulidae)

Class Mammalia

Order Artiodactyla

Suborder Ruminantia

Family Tragulidae


Thumbnail description
The most ancient living representatives of early ruminants; rabbit-sized ungulates, among the smallest of the even-toed ruminants; resembles a diminutive hornless deer; slender legs, stocky body, and arching back; reddish brown to brown pelage (coat) may be striped or spotted

Size
Head and body length: 17–19 in (44–85 cm); weight 4.4–29 lb (2–13 kg)

Number of genera, species
2 genera; 4 species

Habitat
Rainforests, secondary forests, and mangrove forests and thickets

Conservation status
Data Deficient: 1 species

Distribution
Genus Hyemoschus (true chevrotain) indigenous to eastern Africa; genus Tragulus (mouse deer) indigenous to south and southeastern Asia

Evolution and systematics

Chevrotains (genera Hyemoschus and Tragulus) are regarded as living fossils, the most ancient living representatives of early ruminants. Traditional classifications place the family Tragulidae between non-ruminating ungulates such as pigs and hippos and ruminating artiodactyls like deer antelope and cattle. Two genera are recognized: true chevrotain is represented by one species in Africa (Hyemoschus aquaticus); the mouse deer by three species in Asia (Tragulus napu, T. javanicus, and T. meminna).

Throughout the Eocene, some 54–38 million years ago (mya), Artiodactyls radiated into diverse families. Today's chevrotains are descendants of early Tragulids (Archaeotraguludus krabiensis) that appeared in Eocene. Based on fossil records, chevrotains similar to modern species did not appear until the Miocene (beginning 15 mya).

Like all ruminant artiodactyls, chevrotains evolved features that are adaptive for life on open grasslands. Global climate changes during the Miocene resulted in widespread cooling and drying, leading to the transition of many forest habitats to extensive grasslands. Ruminants such as chevrotains evolved specialized digestive systems and dentition that enabled them to use the nutrients in grasses and leaves—nutrients not available to non-ruminants that lack the ability to breakdown/digest cellulose and silica in the grasses and leaves. The multi-chambered ruminant gut is capable of digesting/breaking down cellulose and silica that are indigestible for non-ruminant mammals.

However, chevrotain feeding patterns and stomach structure differ from those of larger ruminants. Although they eat plants, chevrotains and other small ungulates tend to be more selective feeders than their larger grazing and browsing cousins. Since they do not need to gather large quantities of food daily, they can afford the time to carefully pick more digestible leaves, shoots, flowers, and fruits. Like all ungulates, they have a multi-chambered stomach in which the first two chambers, named the rumen and reticulum, mainly function as microbial fermentation vats for cellulose-rich plant cell-wall material that their own enzymes cannot breakdown. But, because more of their food is easy to digest, relative to the diet of the larger ruminants, their multi-chambered stomach structure permits easy-to-digest material to slip past the rumen and reticulum through a special groove and proceed directly into their conventional stomach, called the abomasum. In chevrotains, the chamber that connects the first two chambers to the abomasum, called the omasum, is absent.

A second adaptation that permits artiodactyls to thrive on grasslands is the evolution of molar teeth with crescent-shaped ridges (selenodont molar teeth) for more efficient grinding of plants. Like all Artiodactyl ruminants, chevrotains lack incisors and canines in the upper jaw as well. Their dentition resembles that of higher ruminants.

Modern-day chevrotains share many features with ancestral primitive ruminants. These small animals never developed antlers or horns. Instead, they grow tusk-like upper canines that are used by males in interspecific combat.

Of the four chevrotain species, the water chevrotain (Hyemoschus aquaticus) is regarded as the most primitive, due to several anatomical features that resemble pigs more than modern cervides. For example, the forelimbs lack a cannon bone and skin on the rump is especially tough, making it difficult for predators to bite into.

Physical characteristics

As their common name suggests, mouse deer (chevrotain) resemble diminutive hornless deer with their small heads, tapered snouts, pencil-thin legs, and stocky bodies. Yet, these rabbit-sized ungulates are in a separate family. The chevrotain family (Tragulidae) has all of the following distinguishing features, including short, slender legs; even toes; a small, pointed head; a tapered snout; large eyes; slit-like nostrils; and medium-sized rounded ears covered with a thin layer of hair. Their backs are rounded and rise toward the rear quarters. This slipper body-shape facilitates moving through dense forest undergrowth. Chevrotains also bear a strong physical resemblance to the South American agouti.

The pelage is short and thick, reddish brown to brown, with contrasting patterns of white and brown spots and stripes on the neck, chest, sides, and underbelly, depending on the species. In three of the four species, females are larger than males.

Unlike true deer, chevrotains lack horns or antlers. Male chevrotains fight with tusk-like teeth—enlarged upper canines that protrude downward from the mouth. These upper canines are only small studs in females. Beyond the canines, most chevrotain dentition resembles that of higher ruminants. They lack upper incisors; the lower canine resemble incisors; and the cheek teeth have crescent-shaped ridges (seledontic). The dentition pattern is: (I0/3; C1/1; P3/3; M3/3) × 2 = 34.

Another distinct chevrotain feature is its less-specialized ruminant gut. The chevrotain has only three fully developed stomach chambers, as compared with the four-chambered stomach of larger ruminants. The omasm, the chamber that connects the first two chambers to the fourth chamber, is absent.

The female has four mammae, leading some researchers to suggest that chevrotains may be capable of larger litters than the small litters usually observed (one to two young). The chevrotain male's penis is spiral-shaped. Chevrotains have a gallbladder.

The skull is similar to true deer, except that the chevrotains have a unique ossified plate. There are four digits on each foot, but the second and fifth digits are short and slender.

Distribution

Distribution of the Tragulidae family was worldwide during the Oligocene and Miocene. At present, tragulids are restricted to the Old World. The three species of mouse deer (genus Tragulus) are endemic to Southeast Asia, while the single true chevrotain species (genus Hyemoschus) is found along east central Africa.

Habitat

Chevrotains inhabit rainforests, lowland forests, mangrove forests, and thickets. The three Asiatic species are found in dense vegetation during the day, occasionally frequenting open areas at night. These small mammals flee from disturbances by darting into dense vegetation or water. The African chevrotain is found in tropical rainforests, underbrush, and thick growth almost always along water courses where it can escape predators by diving into water.

Behavior

Chevrotains are extremely difficult to observe due to a timid behavior, have primarily nocturnal sleeping patterns and a preference for dense forests. These shy animals are flighty, easily excited, and prone to jumping in response to the slightest disturbance. They escape predators by darting into dense vegetation or water.

Chevrotains are regarded as extremely solitary, when compared with other forest species. Most chevrotains live alone, except during brief social periods when mating occurs or while raising young. One exception is the lesser Malay mouse deer, which is monogamous. Chevrotains are territorial. Even when

home ranges are densely populated, chevrotains rarely come into contact with one another.

Chevrotains communicate through scent marks and vocalizations. When frightened, mouse deer make soft bleating sounds. Vocalizations are used to signal intent to approach, followed by answer calls.

Chevrotains mark their home territory with scent marks of urine, feces, or glandular secretions. The male water chevrotain has anal and preputial glands. Male water chevrotains and male and female greater Malay mouse deer mark objects by rubbing their chins over a leaf branch end or a tree root.

Males fight with sharp canines, although fighting between males is brief and infrequent. Fighting between females is rare. Some researchers suggest that the lack of more frequent fighting patterns may indicate a lack of social hierarchy.

Early observations suggest that all chevrotains are nocturnal, or crepuscular; however, more recent observations of the lesser Malay mouse deer indicate that some mouse deer may be diurnal.

Only mothers with young clean their offspring with their tongues, otherwise there is no mutual licking. Female chevrotains are more active than males. To rest, they sit on their hind legs or crouch with folded forelegs and hind legs.

Feeding ecology and diet

As ruminants, chevrotains are able to digest grasses and leaves that are indigestible to most non-ruminants. However, small ungulates such as chevrotains can afford to eat more selectively because they need less food than their larger ruminant cousins that must consume large quantities of food daily. As a result, the chevrotain diet tends to favor young shoots, forbs, fruits that have fallen to the ground, and seeds, in addition

to occasional leaves and grasses. Some chevrotains have been observed eating arthropods and small animals.

Reproductive biology

The reproductive biology of most chevrotain species is poorly known, though most are polygamous. Chevrotains reach sexual maturity sometime between five to 26 months. When a female enters estrus, males seek out and follow her while making cry-like vocalizations. In the case of water chevrotains, the male's cry causes the female to stop moving, allowing the male to lick her genital area. Among greater and lesser Malay mouse deer, males also stroke females with a special gland located between the rami of the male's lower jaw. After repeating a pattern of cries and physical contact, copulation takes place. Female greater and lesser Malay mouse deer can mate 85–155 minutes after giving birth; as a result, they are capable of almost continuous pregnancy through most of their adult lives.

Gestation lasts six to nine months, depending on the species, and females give birth to one young a year. The female has four mammae, leading some researchers to suggest that chevrotains may be capable of larger litters. Females ingest the placenta after giving birth. Offspring are precocial, capable of standing within an hour after birth, yet the young remain hidden on the forest floor. Females do not stay with young, except for brief feeding/suckling periods. Young are weaned at three to six months and disperse from the mother's home range when they reach sexual maturity between nine to 26 months. Individuals live to an age of 11–13 years.

Conservation status

Knowledge concerning the status of the four chevrotain is far from satisfactory. The combination of their shy, flighty behavior, small size, and their nocturnal activity patterns makes these diminutive ungulates especially difficult to study. All four chevrotain species are threatened by hunting and habitat destruction. The IUCN Red List classifies only one subspecies as Endangered, and the water chevrotain as Data Deficient.

Significance to humans

In all parts of its range, chevrotains are hunted by indigenous people for food. Although there is interest in using chevrotain as pets and for basic research on ungulates, most chevrotain are difficult to breed and care for in captivity. Zoos have had some success in breeding water chevrotain in captivity.

Species accounts

List of Species

Water chevrotain
Lesser Malay mouse deer
Greater Malay mouse deer
Spotted mouse deer

Water chevrotain

Hyemoschus aquaticus

taxonomy

Hyemoschus aquaticus (Ogilby, 1841), Sierra Leone.

other common names

English: African chevrotain; French: Chevrotain aquatique; German: Afrikanisches Hirschferkel; Spanish Antilope amizclero enano de agua; cervatillo almizclero acuatico.

physical characteristics

Considerably larger than its Asian counterparts: head and body length: 28–31 in (70–80 cm); tail length: 4–5.5 in (10–14 cm); shoulder height: 14–16 in (35–40 cm); weight: 22–33 lb (10–15 kg). Males are slightly smaller than females. Males average 4.4 lb (9.7 kg); females average 5.1 lb (12 kg). The weight at birth is unknown.

The coat has an unmistakable pattern of spots and stripes that may provide camouflage in the shade of dense forests. The body is reddish brown with six or seven vertical rows of white spots along the back and a white line along each side from shoulder to rump. The head is covered with black and white bands.

distribution

Africa's single chevrotain species, it is endemic to lowland tropical forest zones of eastern Central Africa. While much of its range hugs the coast, this species has a disjointed distribution from Sierra Leone to western Uganda. The current range includes scattered regions of east Sierra Leone, Liberia, west Côte d'Ivoire, and south Ghana. There is a single record from southeast Nigeria.

habitat

Inhabit dense tropical rainforests and tropical scrub forests, always near water. These shy ungulates escape predators by diving into water. During the day, they hide in dense forest

undergrowth; at night, they have been observed along exposed clearings and river banks.

behavior

May be the only exclusively nocturnal member of the chevrotain family. It hides in dense forest vegetation during the day and forages at night. As its name suggests, it is a capable swimmer although it may not be capable of swimming for extended periods of time. It always lives within 820 ft (250 m) of water. When disturbed, it escapes by plunging into the water.

These solitary forest animals are rarely seen together other than during mating and while females rear young. Few play behaviors have been observed. Males occasionally engage in brief fights consisting of short rushes and biting. Their population density ranges between 19.25–70 individuals per mi2 (7.7–28 individuals per km2). Females have small home ranges, approximately 32–34.5 acres (13–14 ha) in area, and may occupy the same range through their adult life. Male ranges often include the ranges of two or more females 49.4–74.1 ac (20–30 ha); males can be displaced from their home ranges several times in one year. Females are much more active than males. Lifespan is 10–14 years.

feeding ecology and diet

An herbivorous browser, primarily feeds on fallen fruit, along with occasional leaves, buds, trees, and shrubs. It has been observed eating insects, crustaceans, and small animals. Like all ruminants, it has a multi-chambered ruminating stomach that facilitates digestion of a low-nutrient diet.

reproductive biology

Polygamous. When a female enters estrus, males follow her movements while making vocalizations. The cry of the male causes the female to stop moving and hold still, while he licks her genital area. The pattern of movement, cries, and licking is repeated until the male mounts the female and copulation takes place.

Gestation lasts six to nine months, after which the female gives birth to one or two young. The youngster is precocial, capable of standing within an hour after birth. Young remain hidden on the forest floor with the mother. Females do not stay with the young except for brief feeding/suckling sessions. Lactation lasts three to six months and the young disperse from the mother's home range when they reach sexual maturity (between nine and 26 months). Individuals live to an age of 11–13 years.

conservation status

Overall numbers are currently decreasing due to hunting by humans and habitat destruction for timber resources. The 2000 IUCN Red List: Data Deficient. This is a change of status from 1996 Red List: Lower Risk/Near Threatened. This species is listed under Appendix III of CITES in Ghana.

significance to humans

Hunted by humans throughout its range.


Lesser Malay mouse deer

Tragulus javanicus

taxonomy

Tragulus javanicus (Osbeck, 1765), west Java, Indonesia.

other common names

French: Petit chrotain malais; German: Kleinkantschil.

physical characteristics

The name mouse deer refers to the diminutive size of this deer-like ungulate, although it is not a true deer or mouse. The smallest living artiodactyl, it weighs only 4.4 lb (2 kg). Head and body length: 18–22 in (45–55 cm); tail length 2 in (5 cm); shoulder height 8–10 in (20–25 cm); weight 3.3–5.5 lb (1.5–2.5 kg).

It has a delicate black nose and large eyes surrounded by a lighter ring. The ears are sparsely covered with black hair. The upper coat is brown with an orange tinge, while the underside (including the belly, inner legs, and chin) is white. The neck has a series of white vertical markings. Females are slightly smaller than males.

distribution

Malaysia (Peninsular Malaysia), Range Brunei Darussalam, Cambodia, southwestern China (Yunan province), Indonesia, Borneo, Laos, People's Democratic Republic, Malaysia, Myanmar, Singapore, and Thailand.

habitat

Primary and secondary lowland forests. Found near water in dense vegetation, hollow trees, or among rocks.

behavior

While it is more common than the other three chevrotain species, little has been published regarding its behavior and ecology. Previously it was assumed that it is nocturnal and solitary. However, recent studies suggest that at least some are diurnal and form monogamous pairs. Males are territorial, marking territory with urine feces and secretions from an intermandible gland under the chin; it fights with sharp canines, protecting itself and its mate against threatening rivals. When frightened, they beat their hooves on the ground as fast as seven times per second, creating a drum roll. Otherwise silent, a frightened mouse deer also makes a shrill cry.

feeding ecology and diet

Primarily herbivorous; its diet consists primarily of leaves, buds, grass, and fruits that have fallen from trees. In captivity, they have been observed eating arthropods.

reproductive biology

Monogamous. Reach sexual maturity at five to six months. The female is able to conceive only 85–155 minutes after giving birth, so it has the potential to be constantly pregnant throughout its adult life. Gestation lasts 4.5–5 months and produces one fawn, occasionally two. Young are precocial, fully developed, and can stand within 30 minutes of birth. Fawns are exceptionally shy. Mothers nurse their young while standing on three legs. Offspring are weaned at 10–13 weeks. Lifespan is up to 12 years.

conservation status

Since 1975, its range and density have increased, due to conservation efforts to rehabilitate native ecosystems. However, it remains threatened by hunting and habitat destruction. Predators are carnivorous mammals, large birds, and snakes. IUCN: not listed; ESA: Threatened; CITES: Appendix II.

significance to humans

Hunted and traded for its smooth skin. Due to the ease of taming mouse deer, it is sometimes used as a pet.


Greater Malay mouse deer

Tragulus napu

taxonomy

Tragulus napu (F. Cuvier, 1822), south Sumatra, Indonesia.

other common names

French: Grand chevrotain malais; German: Grosskantschil.

physical characteristics

Similar to, but larger than its cousin, the lesser Malay mouse deer: head and body length: 2.3–2.5 ft (70–75 cm); tail length:3.2–4 in (8–10 cm); shoulder height: 12–14 in (30–35 cm); weight: 11–17.6 lb (5–8 kg). Upper coat is brown to orange-brown, and the underparts are white. The underside of the chin is white with a series of white markings. The hindquarters are lightly grizzled with black.

distribution

Southern Thailand and Indochina, Malay Peninsula, and several nearby islands, Sumatra, Borneo, North and South Natuna island, Balabac Island, Brunei Darussalem, Cambodia, Indonesia, Myanmar, Philippines, Singapore, and Vietnam.

habitat

In dense undergrowth at the edge of dense lowland forests, usually close to water.

behavior

Nocturnal and rarely seen, it travels through small tunnel-like trails through thick brush. Both males and females are territorial and regularly mark their territories with urine, feces, and

secretions from an intermandibular gland under the chin. Adult females with young occupy range of 32.5–35 ac (13–14 ha); adult males range is 50–75 ac (20–30 ha). When agitated, they drum on the ground with their hooves at a rate of four times per second.

feeding ecology and diet

Primarily herbivorous, choosing buds, leaves, and fruit that has fallen to the ground. Presumably, it also feeds on arthropods and other animals when available, based on observations of other chevrotains.

reproductive biology

Polygamous. Gestation lasts for about five months, after which the female generally gives birth to one or two young. Life expectancy is unknown. A single deer has lived for more than 16 years in captivity.

conservation status

Tragulus napu and its subspecies are threatened by habitat loss and hunting. Subspecies T. n. nigricans is classified as Endangered by the IUCN (2000). The subspecies occurs on Balabac Island in the southwest Philippines and is threatened by intense hunting pressure and habitat destruction.

significance to humans

Hunted for food. Although it is also easy to tame as a pet or for research, it may be too delicate to survive in captivity for any length of time.


Spotted mouse deer

Tragulus meminna

taxonomy

Tragulus meminna Hodgson, 1843. Very little is known about the Indian or spotted mouse deer. On the basis of its anatomical and morphological differences from the two other Asian mouse deer, systematists have placed it into its own subgenus (Moschiola, Erxleben, 1777, Sri Lanka).

other common names

English: Indian spotted chevrotain; French: Chevrotain tachete indien; German: Flecken kantschil.

physical characteristics

Head and body length: 20–23 in (50–58 cm); weight: 6.6 lb (3 kg). As its name suggests, the upper side of the coat is finely speckled. The flanks and rump have a pattern of spots and stripes: five to seven white lines on the throat, and the underparts are whitish. The male has a black coat with a red or orange shoulder-patch; females heavily barred below.

distribution

Southern India, Nepal, and Sri Lanka.

habitat

Equatorial tropical rainforests, including rocky sites.

behavior

Little information is available. This timid, nocturnal animal is extremely difficult to observe in the wild; even slight disturbances cause it to disappear into dense vegetation. Solitary, except for the mating period and when raising young.

feeding ecology and diet

Has a highly varied diet that includes both plants and small animals.

reproductive biology

Polygamous. Gestation lasts for about five to six months, after which the female generally gives birth to one or two young.

conservation status

Possibly endangered, though not listed by the IUCN. Both heavy hunting and habitat loss threaten its survival.

significance to humans

Hunted by indigenous people for food.


Resources

Books

Geist, V., and F. Walther, eds. The Behavior of Ungulates and Its Relation to Management. Gland, Switzerland: IUCN, 1974.

Kingdon, Jonathan. East African Mammals. Vol. 3. New York: Academic Press, Inc., 1979.

Lydekker, R. Catalogue of the Ungulate Mammals in the British Museum (Natural History). London: Trustees of the British Museum of Natural History, 1913–1916.

Putman, R. The Natural History of the Deer. Ithaca, NY: Cornell University Press, 1988.

Robin, Klaus. "Chevrotains." In Grzimek's Encyclopedia of Mammals. New York: McGraw-Hill Publishing Company, 1990.

Van Soest, P. J. Nutritional Ecology of the Ruminant. 2nd ed. Ithaca, NY: Cornell University Press, 1994.

Vrba, E. S., and G. B. Schaller, eds. Antelopes, Deer and Relatives: Fossil Record, Behavioral Ecology, Systematics and Conservation. New Haven: Yale University Press, 2000.

Wemmer, C. M., ed. "The Comparative Behavior and Ecology of Chevrotains, Musk Deer, and Morphologically Conservative Deer." In Biology and Management of Cervidae. Washington, DC: Smithsonian Institution Press, 1987.

Wilson, D. E., and DeeAnn M. Reeder, eds. Mammal Species of the World. 2nd ed. Washington, DC: Smithsonian Institution Press, 1993.

Periodicals

Coley, P. D., J. P. Bryant, and F. S. Chapin. "Resource Availability and Plant Antiherbivore Defense." Science 230 (1985).

Dubost G. "Comparison of the Diets of Frugivorous Forest Ruminants of Gabon." Journal of Mammalogy 65, no. 2(1984): 298–316.

Hofmann, R. "Evolutionary Steps of Ecophysiological Adaptation and Diversification of Ruminants: A Comparative View of Their Digestive System." Oecologia 78, no. 4 (1989).

Janis, C. M. "A Climatic Explanation for Patterns of Evolutionary Diversity in Ungulate Mammals." Paleontology 32 (1989): 463–481.

Matsubayashi, H., E. Bosi, and S. Kohshima. "Activity and Habitat Use of Lesser Mouse Deer (Tragulus javanicus)." Journal of Mammalogy 84, no. 1 (2003): 234–242.

Metais, G., Y. Chaimanee, and J. J. Jaeger, "New Remains of Primitive Ruminants from Thailand: Evidence of the Early Evolution of Ruminants." Zoological Scripta 30, no. 4 (2001): 231–248.

Murphy, W. J., et al. "Molecular Phylogenetics and the Origins of Placental Mammals. Home Range, Activity Patterns and Habitat Relations of Reeves Muntjacs in Taiwan." Journal of Wildlife Management (June 2002).

Vidyadaran, M. K., R. S. Sharma, S. Sumita, I. Zulkifli, and Mazlan Razeem. "Male Genital Organs and Accessory Glands of the Lesser Mouse Deer, Tragulus javanicus." Journal of Mammalogy 80, no. 1 (1999): 199–204.

Corliss Karasov

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