Secret Life of the Mouse Deer

Some images remain etched in our mind for a lifetime. For me, one such image was of a mouse deer taken by my favourite natural history writer and photographer, the late M. Krishnan, published with his remarkable article in the 1960s. Krishnan’s fortnightly column Country Notebook in The Statesman, printed from Kolkata at that time, was a staple mental nourishment during my teenage years. All his articles and photographs were excellent but I do not know why the mouse deer photograph has stuck in my mind. It was perhaps the first photograph taken in the wild of this elusive, tiny deer that spends all its life in the undergrowth of a forest.

Among the 12 species of deer found in India, the mouse deer is the smallest. Actually, the ten species of the mouse deer in Asia (a single species in West Africa) are the smallest hoofed ungulates of the world. My interest in this species was ignited when in November 2019 I heard that a lost species, Vietnam mouse deer Tragulus versicolor has been seen (camera trapped) after 30 years. They live such a reclusive life that it is easy to miss them.

The Indian mouse deer, also called Indian chevrotain (Moschiola indica) is endemic to the Indian subcontinent. It is mainly found in peninsular India with some old records from Nepal. Sri Lanka has a separate species called spotted chevrotain (Moschiola meminna). The Indian mouse deer is small, 25-30 cm at shoulder height, and weighs from two to four kg. A unique feature of this group is that instead of four-chambered stomach like in other ruminants, they have a three-chambered stomach. Ruminants are animals that have a digestive system where a plant-based diet is digested in a large stomach compartment called rumen. Of the four compartments, the rumen is the largest section and the main digestive centre. It is seen in sheep, goats, cattle, antelopes, deer, chevrotains, giraffes and a few others.

The Indian mouse deer is found in deciduous, semi-evergreen and evergreen forests, and may be in thick old plantations with good undergrowth, never very far from water. Riverine forests are its preferred habitat. It is also occasionally found in tall, wet grasslands but its thin pointed hooves make it difficult to walk on soft ground. Perhaps due to its life in the undergrowth, this is the only group of deer without antlers as antlers would get entangled in the thick vegetation. Instead, males have large canines protruding below the lip-line. Like antlers, canines are the secondary sexual organs for male mouse deer; females do not have long canines, instead they have small stubs.

Not much is known about the sexual life of the mouse deer as they are very difficult to study in the wild. They live a solitary life so it is presumed that males have territories where other males are excluded but females are welcomed for mating. In all such mating systems, females move from territory to territory and select a male of her choice for mating. Once mating is over, she again leads a solitary life and gives birth to one or two kids in a secluded place. Another unique behaviour of the mouse deer is that they make a den, generally in a hollow of a large tree trunk or in thick entangled ground foliage to hide when predators threaten them.

As expected, such a small animal has many predators such as eagles, pythons, jackals, wild cats, and monitor lizards. Therefore, it prefers to live a quiet, secretive life. Mouse deer go in the darkness of the night to search for fresh grass, leaves, fruits, and flowers. They have been around for almost 34 million years so they can take care of themselves rather well if we leave them alone.

Hunting and trapping by tribals and frequent forest fires are the biggest threats to these small deer. During traditional tribal hunts, called mahashikar, nets are laid in a large section of the forest to chase wildlife, sometimes with the help of trained dogs, to trap them. Dogs also help to ferret out the mouse deer from their dens. Their tiny pointed legs are made to skitter around in the undergrowth, not to run long distance. They are no match to trained dogs, so many are killed.

Most zoos would like to exhibit mouse deer but many do not know how to keep them. Caging them in a large enclosures without proper undergrowth results in most animals perishing due to stress and exposure. They need thick undergrowth and low ceilings — similar to the sort of habitat that they live in nature. They need a claustrophobic tunnel-shaped habitat that gives them a feeling of security. Large enclosures with wide open areas make them uncomfortable. Fortunately, the authorities and scientists of the Nehru Zoological Park, Hyderabad where a very successful conservation breeding programme of the Indian mouse deer is going on are doing the right things.

The Central Zoo Authority, New Delhi, has identified 73 endangered species for conservation breeding, and the mouse deer is one of them. The Hyderabad zoo started the Mouse Deer Conservation Breeding Programme in 2010 with a founder stock of two males and four females. Later, some more mouse deer were brought in from other zoos to improve the genetic diversity. As the breeding started and numbers increased, animals were kept in three blocks of 60 small cages. The cages were enriched with bamboo, palm, shrubs and bushes. Hollow wooden pipes were placed in the cages so that the deer could hide. By 2017, the captive population had increased to 230. Some animals were released in a very scientific and systematic way in the Amrabad Tiger Reserve, Kinnerasani Wildlife Sanctuary, and Mrugavani National Park. Before release they were kept in pre-released enclosures in Amrabad Tiger Reserve where food was provided. As the animals became acclimatised to their new environment, food was reduced so they started foraging natural food. After a few weeks, the cages were opened to release the animals in the wild. All animals were fitted with micro-chips and ear tags. The programme appears to be successful as a mating pair and a fawn was photographed in the released area.

We all agree that conservation breeding is the last option when it comes to saving a species. Habitat protection and curtailment of hunting have to be the first options. However, I think that conservation breeding should be attempted on many critically endangered species as a safety measure and also to know more about their biology to take proper in situ conservation measures.