During my back and forth to Way Canguk, Lampung Sumatera from1997 to 2001, I noted that there were 7 species of squirrels and 3 species of treeshrews living in this lowland rain forest of Sumatra. The most common species was plantain squirrel Callosciurus notatus and the rarest were the giant Ratufa affinis and horse-tailed squirrels Sundasciurus hippurus (my favourite!). The different species of squirrel and treeshrew in Way Canguk have huge variation in their head to tail sizes, 25 cm up to 80 cm in length. Character and identification of each species can be found in “A field guide to the mammals of Borneo” by Payne et al. (1995).
Although they shared the same forest, squirrels and treeshrews did divide their home-forest, mainly to avoid resource competition. Tree species tended to be found in closed-canopy habitat while the ground-dwelling ones could be found in almost any type of forest habitat, whether it was closed or open canopy.
Vertically, different species were living in different heights. The most upper canopy occupied by two species of giant squirrels –Ratufa bicolor and R. affinis— and the most common plantain squirrels. Here in the upper-most canopy (15 to 25 meters above the ground), the black giant squirrels wandered in average height of 25 meters, followed by giant squirrels at around 16 meters and plantain squirrels at 14 meters.
Under 15 meters above the ground, we would mostly see horse-tailed S. hippurus , slender S. tenuis and Low’s squirrels S. lowii. One little tree shrew species, lesser treeshrews Tupaia minor, joined this middle canopy critters’ community. The mean height of slender squirrels’ stratum was 10 meters followed by the lesser treeshrews at 6 meters and Low’s squirrels at 4 meters.
At the ground level, one species of squirrel, the three-striped ground squirrels Lariscus insignis, and two species of tree shrews, the large Tupaia tana and common treeshrews T. glis, dwelled in Way Canguk forest. Closer to the ground, the tree-striped ground squirrels foraged at around 10 cm above the ground, while the tree shrews climbing the understorey a bit at an average of 40 cm. However, the large treeshrews was seen climbing up to 10 meters once.
Although not complete, I managed to note some of plants and animals eaten by these critters. The upper canopy species, the two giant squirrels and the plantain squirrels, were noted to eat various of plants. No animals were seen eaten by these squirrels.
In the middle canopy, the horse-taild squirrels (n=1) was seen eating paitan fruit (Hydnocarpus gracilis, Flacourtiaceae). It was quite difficult to observe this rare and shy animals thus very little information was collected on their behavior.
The Low’s squirrels (n=2) was seen feeding on fruit, insect and mollusk. This species foraged on dry leaves of gelam (Eugenia spp., Myrtaceae), and Aporosa sp. (Euphorbiaceae) and Popowia bancana trees(Annonaceae), possibly to find small animals. The slender squirrels (n=2) also ate insects and foraged on dead trees for insects. Like the middle canopy squirrels, lesser treeshrews (n=2) also seen eating and foraging on dry leaves and lianas for some insects.
On the ground, the tree-striped ground squirrels (n=15) was recorded eating fruit and/or seed of Antiaris sp. (Moraceae), Dracontomelum dao (Anacardiaceae), Canarium denticulatum (Burceraceae), stem of Zingiberaceae and some insects (unknown). While eating, this species found sitting on rocks or fallen branches at 5 to 50 cm above the ground. Search for food were mostly conducted on the ground. The ground tree shrews, Tupaia tana and T. glis, (n=9), on the contrary ate more animals such as insects, arthropods or mollusks than plants. These species foraged in various heights above the ground from 50 cm to 10 meters on fallen branches, logs, lianas, dead trees and dry lianas.