Order : RODENTIA
Family : Sciuridae
Species : Exilisciurus exilis

Head-Body Length : up to 7.5 cm
Tail Length : up to 5 cm
Weight : up to ~ 20 grams

This tiny squirrel inhabits tall forest in many parts of Borneo : the loss of such forests, due to logging and conversion to agriculture, means its range is becoming more restricted in lowland areas. Locally it occurs at montane elevations : on Gunung (= Mount) Pueh in Sarawak it is documented at 1700 metres.

Typically this species is active from eye-level to around 10 metres on the trunks of medium to large trees, and lianas. It is a bark gleaner, which means that it mainly consumes bark (and probably associated lichen). It sometimes appears to supplement its diet with small insects too.

Its body fur is mainly olive brown, grading to orange brown on the back of the neck and on top of the head. Its tail is grizzled brown and orange brown, and its underside is pinkish brown.

It typically weighs less than 20 grams, which makes it the world's smallest diurnal squirrel : it is  similar in size to Emily's Flying Squirrel Petaurillus emiliae which is nocturnal, and also occurs in Borneo.

The Bornean Pygmy Squirrel, or Least Pygmy Squirrel, is endemic to Borneo (including the island of Banggi off the northern tip of Sabah).

Fig 1 : Adult example on the trunk of a large streamside tree at Lambir Hills, Sarawak. The outermost layer of bark of this tree is extensively pock-marked as a result of the feeding habits of this species : typically no long-lasting damage is done to such favoured trees.

Fig 2 : The same adult (centre) accompanied by a single juvenile (left).

Fig 3 : Close-up of the juvenile, busy feeding on bark.

Fig 4 : These squirrels are easily overlooked : this example was spotted in lowland forest surrounding Niah Caves, Sarawak.


References : M2, M10