Giant Squirrel (Ratufa affinis)
Rodents can be recognised by their dentition, with large, curved, chiselling incisors in both the upper and lower jaw, no canines and a wide diastema (= toothless gap) before the cheek. Unlike insectivores and treeshrews, all the Bornean rodents have only four long, clawed digits on each front foot, and a short thumb with a nail instead of a claw.
Many of the squirrels appear quite similar, but can usually be identified based on differences in colour patterns if they are seen clearly. Conditions are rarely ideal, though, and many ground squirrels are glimpsed only briefly in dim light, while tree squirrels are often obscured by leaves or silhouetted against the sky. Binoculars are helpful for viewing squirrels, and many species, with the exception of giant and pygmy squirrels, can be trapped fairly easily in cage traps for closer study.
The Shrew-faced Ground Squirrel, Rhinosciurus laticaudatus, could be mistaken at a distance for a Tupaia treeshrew because of its pointed muzzle, but can be distinguished by its shorter bushy tail.
Measurements:HB 320-380, T370-444, HF 67-86 (18 specimens). Wt 875-1500 kg.
Identification: The largest tree squirrel in Borneo. Coloration variable, but upper parts usually dark in the middle; underparts pale. Four subspecies are recognized, although there is some colour variation within each form, partly obscuring the differences. R.a. sandakanensis: upper parts very dark in the midline; underparts very pale, almost white; sides of body speckled with buff; normally no reddish tinge. R.a.baramensis: upper parts less dark along midline; underparts buff; thighs grizzled. The whole body with a reddish tinge, especially the sides. Giant Squirrels intermediate in coloration between these two forms have been collected from the Kelabit uplands and the Lawas district in northern Sarawak. R.a. cothurnata: resembles baramensis but thighs pale, not grizzled. R.a. ephippium: resembles cothurnata but upper parts with a very dark midline. Island forms variable, but one from P. Laut is entirely pale brown. Three colour forms have been reported (but not collected) from the upper Temburong of Brunei: one resembles baramensis, another is similar but with grey underparts and the third is entirely pale brown. When moving quickly through the tree canopy, the tail is held out horizontal but when sitting on a branch it hangs vertically. The loud call is a short, harsh chatter, often audible for several hundred metres. It also has a distinctive soft call, a series of "hgip......hgip...." audible from several tens of metres.
Ecology and Habitat: Diurnal, usually emerging from the nest well after dawn and retiring for the night before dusk. The nest, a neat rather globular array of twigs, is usually built in the crown of a tall tree. Mostly active in tall trees, descending to the ground only to cross gaps in the tree canopy. Diet mainly seeds with some leaves and bark. Occurs in dipterocarp and lower montane forests, also secondary forests. Rarely enters plantations.
Distribution: R.a. baramensis. Found in Sarawak between S. Baram and the Sabah-Sarawak border probably mixed. Recorded to the south of the Saribas region and S. Karangan, except in the extreme south-east.