Following a gestation of 28 days, the grizzled giant squirrel gives birth to one or two young in a large nest high in the trees. The young are looked after for several months before dispersing. It is thought that the grizzled giant squirrel raises more than one litter each year, but this is unconfirmed (2).
The grizzled giant squirrel is highly territorial and is very vocal upon encountering an intruder. It is usually found alone or occasionally in pairs. When frightened it will either flee, leaping up to six metres between trees, or will flatten itself against a branch, remaining motionless. It is diurnal, spending the day eating fruit, nuts, insects, bird eggs and the bark of some trees. At midday, the squirrel rests; sleeping spread-eagled on a branch (2).