Greater Mouse-Deer

Greater mouse‑deer (Tragulus napu), commonly called the greater chevrotain, belongs to the family Tragulidae, the most primitive ruminants. It inhabits the lowland and hill forests of Southeast Asia, from southern Thailand and Peninsular Malaysia through Borneo, Sumatra, Java and the Philippines. The species prefers dense undergrowth in primary dipterocarp forest, peat swamp forest, and secondary regrowth where thick leaf litter provides cover. Adults are the largest of the mouse‑deer, weighing up to 7 kg and measuring 55–70 cm in head‑body length, with a short, reddish‑brown coat marked by a faint dorsal stripe. Both sexes possess small, backward‑curving horns that are concealed by fur. The greater mouse‑deer is primarily nocturnal, relying on its keen hearing and scent to avoid predators such as clouded leopards and large snakes. Although classified as Least Concern by the IUCN, populations are fragmented and declining in parts of its range due to habitat conversion to oil‑palm plantations and unsustainable hunting for meat and traditional medicine. Conservation actions focus on protecting remaining forest blocks, enforcing hunting regulations, and promoting community‑based monitoring programs. Genetic studies indicate low connectivity between isolated subpopulations, raising concerns about long‑term viability. The species plays a role in seed dispersal, especially of small fruits, and its foraging helps maintain understory diversity.

Greater mouse‑deer are solitary for most of the year, with males maintaining overlapping home ranges that are defended through scent marking and occasional vocalizations. Females occupy smaller, more exclusive territories, especially when caring for young. The species is crepuscular to nocturnal, becoming active at dusk and before sunrise to browse low vegetation while avoiding diurnal predators. Individuals communicate using a repertoire of soft whistles, snorts, and a characteristic “bark” produced when alarmed. Scent glands on the pre‑orbital region and the metatarsus deposit urine and secretions on vegetation, establishing territorial boundaries. Home‑range sizes vary with habitat quality, ranging from 0.5 ha in dense forest to over 2 ha in fragmented landscapes. Overlap between male and female ranges facilitates brief mating encounters, but prolonged social interaction is rare.

The greater mouse‑deer is a strict herbivore, feeding primarily on fallen leaves, young shoots, buds, fruits, and seeds found on the forest floor. Preferred plant families include Rubiaceae, Myrtaceae, and Euphorbiaceae, with seasonal shifts toward ripe figs (Ficus spp.) and palm fruits during the dry season. An adult consumes roughly 0.5–1 kg of vegetation daily, selecting high‑protein young leaves and avoiding mature, fibrous material. Foraging occurs close to the ground, and individuals use their elongated snout to pluck items while moving silently through leaf litter. Occasionally, they ingest fungi and small invertebrates to supplement mineral intake, but such opportunistic feeding represents less than 5 % of total diet. Their selective browsing helps control understory growth and contributes to seed dispersal for several tropical plant species.

Sexual maturity is reached at about 9–12 months for both sexes, although females in high‑quality habitats may breed earlier. Breeding can occur year‑round in equatorial zones, with peaks during the rainy season when food is abundant. After a gestation period of 150–155 days, females give birth to a single fawn in 70 % of cases, with twins occurring rarely in undisturbed forest. Newborns are precocial, standing within minutes and following the mother after a brief hiding period. The mother nurses the fawn for 8–10 weeks, during which time the young are concealed in dense underbrush to reduce predation risk. Weaning is complete by three months, after which juveniles disperse to establish their own territories. Longevity in the wild averages 10–12 years, allowing females to produce up to six litters in a lifetime under optimal conditions.

The IUCN classifies the greater mouse‑deer as Least Concern, yet regional assessments reveal declining trends in Indonesia and Malaysia. Primary threats include rapid deforestation for oil‑palm plantations, logging, and infrastructure development, which fragment habitat and reduce available foraging area. Hunting pressure remains significant; the species is hunted for meat, traditional medicine, and the pet trade, with estimated offtake of up to 15 % of local populations in some districts. Road mortality and predation by introduced feral dogs further exacerbate losses. Population surveys suggest a total of 500,000–800,000 mature individuals, but numbers are decreasing at an estimated rate of 10–15 % over the past decade. Conservation measures focus on protecting key forest corridors, strengthening anti‑poaching patrols, and engaging local communities in sustainable land‑use planning.

• The greater mouse‑deer is the largest species of the tiny chevrotains, yet it still fits on a human palm.
• Both sexes have tiny, backward‑curving horns that are hidden by fur and are rarely seen.
• It can run at speeds up to 30 km/h (19 mph) despite its small size.
• Its nocturnal vocalizations include a high‑pitched whistle that can travel over 200 m in dense forest.
• The species plays a crucial role in dispersing seeds of over 30 tropical plant species.