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26 Mouse Deer Mouse deer (Tragulus spp. and Hyemoschus aqua- ticus) are among the smallest ruminants known. The lesser mouse deer of Southeast Asia is probably the smallest; an adult stands only 20 cm high and weighs a mere 1-2.5 kg. Although they look vaguely like tiny deer, mouse deer differ in several particulars. The stomach is simpler and (like the camel's) has three instead of four effective compartments. Rumination occurs, but mouse deer are the most primitive of all ruminants. Indeed, they share a number of characteristics with nonruminants, including lack of horns or antlers; continually growing, tusklike upper canines in males; sharp-crowned premolars; and four fully developed toes. Virtually unchanged in 25 million years of evolution, these are solitary, nocturnal, retiring animals that have seldom received detailed research. Whether they might make suitable microlivestock is un- known. However, they seem to be tractable, and people in Southeast Asia (Sarawak, for instance) have traditionally kept at least one of the species as backyard pets. Moreover, mouse deer are indigenous to tropical lowland regions and withstand the heat and humidity that are stressful to most conventional livestock species. They probably also are resistant to many diseases of those torrid regions. In the United States, mouse deer are being raised as laboratory animals for basic research on ungulates. This is because the animals are easier to handle than large deer or goats.2 11 APPEARANCE AND SIZE Mouse deer are graceful, lithe, and look somewhat like large rodents. ' Also known as chevrotains. These animals are not true deer; their common name is a misnomer. Although they resemble deer, they also have some features of pigs. Zoologists classify them as a separate family, the Tragulidae. There are three Asian species: the lesser Malayan mouse deer Tragulus javanicus, the Indian mouse deer T. meminna, and the larger Malayan mouse deer T. napu. There is one African species, the water chevrotain Hyemoschus aquaticus. 2 Information from I. Muul. 291
~,- 292 MICROLIVESTOCK The Asian species are the shape and size of an agouti (see page 1981; the African species is more like the pace (see page 262~. All have short legs, a small head, and a pointed snout. Adults weigh from 1 to 5 kg, depending on species. The head and body are only 0.~1 m long, and the shoulder height is merely 2~36 cm. Males are generally smaller than females. In most species the body is a rich brown with white spots and stripes. The belly is usually white. The animals stand on the middle toes, so that the lateral ones do not touch the ground. Neither sex bears antlers. In males the upper canines form long tusks that may extend outside the lips and even to below the line of the jaw. DISTRIBUTION Twenty-five million years ago, early forms of mouse deer existed throughout Asia, Africa, and Europe. Today's species are restricted to tropical forests and mangrove thickets of Southeast Asia and Central Africa. Of the three Asian species, the Indian mouse deer occurs in southern India and Sri Lanka; the larger Malayan mouse deer occurs on the mainland of Southeast Asia and the lesser Malayan mouse deer occurs on Java as well. The water chevrotain, a related African animal, is found from eastern Zaire to the Atlantic coast. ~ Hi. ~ ~ '~ Range of Asian mouse deer: (1) Indian mouse deer; (2) larger and lesser Malayan mouse deer.
MOUSE DEER ( Range of water chevrotain. STATUS 293 t \: \ ~ \ In recent years, human encroachment into the forest has caused the destruction of the mouse deer habitats and has put various mouse deer species under a pressure that is causing their populations to decline. HABITAT AND ENVIRONMENT These animals inhabit equatorial forests and mixed secondary tropical forest. They generally live among undergrowth on the edges of dense lowland rainforests. They especially haunt rivers and swampy bush areas, seeking escape by water when in danger. BIOLOGY Little about these animals is recorded. Essentially vegetarians, they feed chiefly on fruits, supplemented by leaves. They also eat insects (for instance, ants), if available. They do not seem to eat grassy The premolars of the mouse deer are designed for piercing and chopping food rather than for chewing. As noted, the stomach consists of three functional compartments: the rumen, the reticulum, and the abomasum. (The omasum of ruminants is represented only by a rudimentary area.) The stomach occupies almost the whole of the 3 Information from G. Dubost.
294 MICROLIVESTOCK abdominal cavity, extending from the diaphragm to the pelvic inlet, which provides this small animal with large food-storage capacity. The blood has a very high erythrocyte (red blood corpuscle) count as well as the smallest erythrocyte size of any mammal. The flesh is ''white" and the muscles contain little myoglobin. Mature females reproduce almost continuously, and usually regard- less of season. In the female larger Malayan mouse deer, mating occurs within 2 days of giving birth. In the African species, many births are synchronized with the rainy seasons, when fruits are plentiful. The gestation period is about 5~ months, depending on the species. There is only one young per birth. Weaning normally occurs at 2-3 months, but can occur as early as 3 weeks, with sexual maturity achieved at =5 months (Asian species) and 10 months (African species). The young stay alone, hidden in vegetation during the first month or two. BEHAVIOR Mouse deer are shy, keeping to dense jungle and depending on concealment for protection. Although often present in large numbers, they are seldom seen. Preferring to be near lakes, rivers, or streams, they can nevertheless wander 1 km or more from water. They feed mostly at dusk or at night, sheltering in undisturbed areas or under shady bushes during the day. They utter weak, bleating sounds, and when frightened, jump a meter or more in the air. Communication is by scent and calls. The African species possess anal and preputial glands, with which, along with urine and feces, they mark their home ranges. Males of both Asian and African species possess a chin gland to mark either the vegetation or their mates. Mouse deer are among the most excitable, nervous, and jumpy animals. One must tread softly in their presence for fear of causing absolute pandemonium and mishap. USES Mouse deer are widely sought by native people for food, and their meat is highly regarded. Dressed carcasses have a high proportion of muscle (84 percent in Asian species), low proportion of bone (15 4 Information from G. Dubost. Opposite: Water chevrotain. (A.R. Devez, CNRS, Mission Biologique au Gabon)
296 MICROLIVESTOCK percent), and an insignificant amount of fat. The ratio of muscle to bone is large 5.6:1. The mean dressing percentage of 62.1 percent is greater than that reported for cattle, water buffalo, or goat.5 HUSBANDRY Adults are wild, generally intractable, and "flighty," but young animals (at least of the Asian species) tame readily and make good pets. Nevertheless, these are delicate creatures and must always be handled gently. Individuals caught in the wild tend to bash against the sides of cages. Despite an unpromising temperament, Asian mouse deer are regularly bred in zoos, including those in Amsterdam, New York, and Zurich. They also have been reared successfully in small enclosures at several research institutes, such as the I.R.E.T Institute, Makokou, Gabon; the Institute of Medical Research in Kuala Lumpur, Malaysia; and at Fort Detrick in the United States. Perhaps the best way to breed this animal is by using the battery system of small units comprising one male and two females per cage. The costs are mostly for obtaining suitable enclosures and for feeding and watering troughs.6 The cages must be covered with mesh because the mouse deer can jump. However, the covering must be sufficiently high to allow the male to stand with its body vertical during copulation.7 They can be fed a variety of foods and grow well on stems of bean plants. ADVANTAGES As noted, these are small, seemingly tractable creatures that are at home in the heat, humidity, and diseases of tropical lowlands. They might play a particularly important role as livestock for tropical rainforests; the forests could be left standing while the animal still produces meat. Today, in a widely condemned process, tropical rainforests are being felled in order to raise cattle for meat. 5 Information from M.K. Vidyadran. 6 Information from Roy A. Sirimanne. 7 Information from I. Muul.
MOUSE DEER LIMITATIONS 297 Small size makes mouse deer easy prey for various predators. In the wild, snakes, crocodiles, eagles, and forest cats feed on them. Mouse deer are among the most excitable, nervous, and jumpy animals. One must tread softly in their presence for fear of causing absolute pandemonium and mishap. The different species are solitary, and it is difficult to keep many individuals (especially males) in a restricted space. They must be kept in a quiet enclosure, with cover or good shelters. RESEARCH AND CONSERVATION NEEDS The survival of these four "living fossils" depends on conserving their rainforest habitat and restricting hunting, especially night hunting. But studies of their propagation and management are also imperative. In particular, research is warranted on various aspects of their husbandry, such as enclosure design, space requirements, and health. A special research need is to understand the animal's nutritional requirements and to develop diets for use in captivity. 1~
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