ABOVE: Lesser Treeshrew Tupaia minor. The Lesser Treeshrew frequently climbs into the canopy to feed on fruit especially fruiting figs. Of the 9 treeshrews that occur in Borneo 8 species have been recorded feeding on fruit. The most preferred fruits are figs. Photo by Arlene Walshe in Temburong , Brunei.
According to Wells (2009) Seeds eaten by small mammals in Borneo examination of the feces of freshly trapped Plain Treeshrews showed that they could swallow and defecate seeds up to 5.8 mm diameter. The largest fig seed of any Bornean fig F. deltoidea is only 5.6 mm in diameter so potentially Plain Treeshrews could swallow and defecate the seeds of any Bornean fig. However studies by Emmons (1991) Frugivory in treeshrews found that when eating fibrous fruit such as figs the bulky fiber and seeds were pressed against the roof of the mouth with the tongue to create a wad of fiber which was then discarded rather than swallowed by the treeshrew. A similar technique of discarding the fiber and seeds and only swallowing the pulp is used by most fruit bats when eating figs. In these cases the fig seeds are dispersed only locally.
However, a study by Mike Shanahan and Stephen Compton of Ficus montana figs fed to captive Lesser Treeshrews, Shanahan & Compton (2000) Fig eating by Tupaia minor in the UK’ found that the treeshrews ate the ripe figs, swallowing and defecating the seeds which had a maximum diameter of 1.5 mm. There was no evidence that the treeshrews rejected the fiber and seeds so Lesser Treeshrews do appear to be effective dispersers of fig seeds.
Slender Treeshrew Tupaia gracilis looks similar to the more aboreal Tupaia minor and the two species are frequently mistaken. However Slender Treeshrew feeds mainly within 1.5 m of the ground on butterfly and moth larvae (caterpillars) and fallen fruit. Photo by Mike Gordon at Deramakot.
EMMONS (2000) FRUIT SPECIES EATEN BY TREESHREWS
“As soon as we began to follow treeshrews by radio tracking at Poring, we discovered that they often spent much of their day at fruit trees. I was able to watch Lesser treeshrews feeding on fruit, sometimes for hours.
At Poring, figs so completely dominated the list of fruits eaten by treeshrews (64%) that treeshrews might have been thought to be fig specialists. However, the next year at Danum figs were only 27% percent of species known to be eaten, and it was clear that fruiting fig trees were simply much more numerous on the study area at Poring than at Danum Valley, where other fruits were eaten more often. In both areas suitable fig trees. commanded intense interest from all species of treeshrews, in terms of both hours spent at them and the number of daily visits, so that figs can be said to be among the most preferred fruit.”
CONCLUSION: The majority of Borneo’s treeshrews are insectivores but all include a significant proportion of fruit in their diet. The most preferred fruit are figs. All types of ripe figs are eaten. The aboreal Lesser Treeshrew is the most frugivorous and climbs into fruiting fig trees to collect figs before they fall. Fig seeds are effectively dispersed by Lesser Treeshrews via swallowing and defecation. Terrestrial treeshrews also eat fallen figs but have been recorded ejecting a fiber wad without swallowing the seeds so are probably less effective dispersers. The impact of treeshrews on earth figs is unknown but because earth figs have such tiny seeds it is likely that they are dispersed by swallowing and defecation. See: Figs dispersed by rats in Borneo.