OK, here is a little bit of info about treeshrews:
Treeshrew - Wikipedia, the free encyclopedia
and some more here:
Tupai
This is very important - it explains how treeshrews are different from squirrels and that they eat different things (mostly soft fruits, not really nuts or plants):
The fruit-eating behavior of
Tupaia differs sharply from that of squirrels. Treeshrews feed mainly on the soft, edible fruit parts “designed” as rewards for dispersers and eject large, hard seeds before consumption. My observations in Sabah suggest that treeshrews and squirrels feed on different fruit species, as well as on different parts of the fruit. Only one squirrel (
Callosciurus prevosti) largely overlaps treeshrews in fruit preference, and this squirrel is a large, high-canopy species that directly competes for fruit only with
T. minor, and which was never seen insect foraging. Treeshrews lack both the dentition to open hard nuts and the digestive apparatus to process much plant material. They profit from the abundant energy, and likely calcium, available in fruit crops by a batlike fruit-feeding pattern apparently geared to rapid digestion of readily assimilated nutrients during high-speed passage.
Apparently treeshrews also eat insects. I hope this helps!