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Pencil-Tailed Tree Mouse Breeders

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Note: I have occasionally seen specimens offered for sale as Pencil-tailed Dormice. This name is not generally used and is, in any case, misleading since the species is not closely related to the dormice (family: Myoxidae).

Introduction

Six species of Tree Mouse are generally recognised by most authorities although some reference sources give only five species. At one time a seventh species, Chiropodomys jingdongensis from Jingdong in Yunnan Province, SW China, was described, but this is no longer generally accepted as a separate species and is usually included in C. gliroides.

The Common Pencil-tailed Tree Mouse is the most widespread and best-known of the six species of Tree Mouse. Originally included with the true mice in the genus Mus and given the scientific name Mus gliroides (Blyth, 1856), it is now thought to be more closely related to the Asiatic Climbing or Marmoset Rats (Hapalomys spp.) and, possibly, the Pygmy Tree Mice (Haeromys spp.).

Being a relatively new species in captivity, there remains much we do not understand about it. This presents an opportunity for the amateur keeper to make a positive contribution to existing scientific knowledge simply by observing his/her animals and recording the findings.

Measurements

Head and body length 66-122 mm. Tail length 85-171 mm. Weight 15-43 grams.

Appearance

The pelage is soft, dense, and uniform in length without conspicuous guard hairs. The colour is a dull greyish brown, buffy brown or chestnut. Underparts are white to grey or orange red. The head and body are very mouse-like, but there is no mistaking this rodent as it has a distinctive, long and slender tail unlike any other species. The tail is brown and naked save for a thin covering of short hairs near the base. Feet are short and broad. Digit pads are large and the sole of the hind foot is naked. The first digit of the hands and feet is short, stumpy and opposable like a primate thumb, and the claw here has become a small, flat nail, whereas all the other digits still carry short, slightly curved claws. Females have just four mammae.

The thin, membrane-like ears are moderately large and hairless. Like radar dishes, they are constantly rotating, first one way and then another, as their owner listens out for the sibilant sounds of grubs and other insects. Watching their ears moving independently as they track each sound, I am reminded of the Aye-aye lemur.

Distribution

Assam to south-eastern China, Burma and the Malay Peninsula, Sumatra and the adjacent islands of Nias and Tujuh, Bali, Borneo, Java and the Natuna Islands.

Natural Habitat

Occupies both primary and secondary tropical forests. It has a preference for bamboo forests as this tall, treelike grass provides the animal with ideal sleeping and nesting refuges in the internodal hollows. Although most common in lowland forests, the Pencil-tailed Tree Mouse has been found at elevations of up to 1200 metres.

Social Structure

A sociable species, Pencil-tailed Tree Mice should be kept in breeding pairs or small groups.

Temperament

I have heard it said that some individuals can be quite fierce and difficult to tame even when reared in captivity. This I would refute. I have kept half a dozen at one time or another, and none was aggressive. They would venture quite close to my hand whenever I changed the food dish, but remained nervous and quick to retreat at any sudden movement. Pencil-tailed Tree Mice do, however, bite (and bite hard!) if held in the hand. I usually employ a glass jar if I need to catch or sex one.

Behaviour

As its name suggests, this is primarily an arboreal species. Almost exclusively nocturnal, it has, on very rare occasions, been known to have limited periods of activity during the day, but usually spends the hours of daylight resting in a small hollow within a tree branch or in the internodal space of a bamboo stalk.

The hollow, woody-walled stems of bamboo are extremely tough and in constant demand by the building industry, as well as being used to make poles, furniture, fences, etc. This same quality makes bamboo a secure home for any small rodent able to gain access. To reach the internodal space of standing bamboo, the Pencil-tailed Tree Mouse gnaws one, or more usually two, circular holes, 25 mm in diameter, in the side of the internode. The opening is then lined with leaves. One of the entrances is used as an emergency 'bolt' hole should a predator invade the other hole.

Diet

In the wild, this species appears to be mostly herbivorous, eating a wide variety of seeds, leaves and fruit, although insects are also taken. Captive individuals thrive on mixed roots, grains and fruits. They enjoy a standard rodent mixture with added small sunflower seed, as well as various millets such as a budgerigar or canary mixture. This basic diet should be supplemented several times a week with live insects, including locusts and locust hoppers, meal worms or crickets. Every other day, two or three varieties of fruit or vegetables can be offered, but should always include apple, which is a firm favourite with these rodents. Other preferences include banana, grape, peach, pear, and sweet potato. I never give much more than a slice or two of each variety, as an excess of soft fruit can result in diarrhoea. Millet sprays are relished and fresh branches of non-toxic trees are important for exercising teeth. Branches can be given complete with bark, as the bark is a source of valuable trace elements. Fresh bones and even raw meat can be offered as occasional treats.

Fresh, clean drinking water must be available at all times, given either in a bottle or a shallow metal or earthenware dish. Plastic bowls are invariably chewed.

Accommodation

Pencil-tailed Tree Mice are very destructive to anything made of wood or plastic, as is only to be expected from a species which habitually gnaws its way into the tough stems of bamboo. Do not make the mistake I once did of attempting to keep this species in a plastic tank. The next morning I was shocked to discover a neat circular hole had been gnawed in one corner of the plastic mesh lid and all four animals had disappeared.

In the light of my bitter experience, the only cage I now recommend for this species is a large glass tank with a ¼ or ½ inch wire mesh top. Provide plenty of well washed, non-toxic, tree branches and more slender twigs for climbing on and for gnawing. Give the animals a choice of sleeping and nesting locations by adding several nest boxes, wicker finch baskets or lengths of bamboo. The optimum daytime temperature in the tank is about 70° F, although normal room temperature is fine.

Reproduction

In common with many rodents, females are polyoestrous. The oestrous period lasts about one day and recurs at intervals of not less than seven days. In at least one part of its range (Malaysia) it breeds all year round, although breeding tends to peak in the months September to March. Hay, dry leaves or kapok are preferred nesting materials. The gestation period is 19-21 days. Litter size is small for a murid, averaging only 2-3 young (range: 1-4). Females give birth to several litters each year. One captive female produced four litters in ten months.

The new-born young cling persistently to their mother's nipples and will be dragged about if she is disturbed. They are partially independent at 17-18 days and completely weaned by four weeks.

The young can safely be left with the parental stock if necessary, although there is an obvious risk of inbreeding, or can be removed upon weaning. Sexual maturity is reached at 100-120 days.

Conservation Status

Throughout its extensive range, the Pencil-tailed Tree Mouse is one of the commonest forest animals, albeit little-seen and studied because of its small size and nocturnal habits. However, with persistent deforestation plaguing South-east Asia, it may not be too many more years before even this common and highly adaptable species joins the dismal list of endangered animals. Many undoubtedly perish in the widespread fires used in slash-and-burn agriculture all over the region. Two related species are already considered to be threatened. These are Koopman's Pencil-tailed Tree Mouse (Chiropodomys karlkoopmani), endangered due to intensive logging on the only two small islands – Siberut and North Pagi off Sumatra – on which it is found, and the Grey-bellied Pencil-tailed Tree Mouse (Chiropodomys muroides) of north-eastern Borneo. Hopefully the experience gained by breeding the Common Pencil-tailed Tree Mouse can eventually be applied to the rarer species, should these become available.

Life Span

The maximum life span in the wild is around 24 months. In captivity, in the absence of predators and with a dependable food supply, individuals can be expected to live much longer – up to 3½ to 4 years.