Grizzled giant squirrels are the smallest of the giant squirrels found in the Indian subcontinent They are named for the white flecks of hair that cover their greyish-brown bodies, giving them a grizzled look. There are two recognized subspecies which differ slightly in coloration. One subspecies is dorsally brown grizzled with white. Ventrally light brownish cream. The tail is frosted with white fur. Forehead and feet are black in color. Whereas upper parts of the other subspecies are jet black which contrast brownish cream to orange-yellow ventral surface. Tail frosted with black fur. The snout of both subspecies is pinkish in color.
Grizzled giant squirrels occur in south Asia. They are found in the Central and Uva provinces of Sri Lanka, along the Kaveri River and in the Karnataka, Tamil Nadu and Kerala states of southern India. In India, these squirrels have been recorded from Grizzled Squirrel Wildlife Sanctuary, Theni Forest Division, Palni Hills, Chinnar Wildlife Sanctuary, Anaimalai Tiger reserve, Sirumalai, Thiruvannamalai Forest Division of the Eastern Ghats, Hosur Forest Division and Cauvery Wildlife Sanctuary. Grizzled giant squirrels inhabit highlands, dry deciduous forest, patches of riparian forest along riverine habitat and the hill forests.
Grizzled giant squirrels are diurnal and arboreal creatures. They rarely come to the ground to escape from predators, to flee from an intruder, attack males of the territory, and connecting with females. They have a good vision, which aids them in detecting predators. However, their sense of hearing is relatively poor. During the day these squirrels are often seen sleeping in a spread-eagle like position on a branch. They are generally solitary and seen alone or in pairs. They are very territorial. Grizzled giant squirrels are very vocal and have a very distinct voice. Their call is staccato and loud with repeated shrill cackle. It is usually uttered in morning and evening. A low "churr" is also used to communicate with nearby groups. When these squirrels are disturbed, they usually flee or freeze. They can also flatten themselves against a branch and stay this way motionless when frightened. In general, Grizzled giant squirrels are very careful and hide well in the dense vegetation.
Little is known about the mating habits and reproductive behavior of Grizzled giant squirrels. During the breeding season, they construct a large nest, which reminds an eagle's nest. Females give birth to 1 or 2 kittens after the gestation period that lasts around 28 days. Young are nursed and remain in the nest approximately two or three months.
One of the main threats to Grizzled giant squirrels is habitat loss and its degradation through farm industry, logging, increase in human settlements, forest fire and local hunting for meat. Domestic predators pose another major threat for this species in South Asia. In India, hybridization between Grizzled giant squirrels and Indian giant squirrels is thought to be a big threat to remaining populations.
According to the IUCN Red List, the total population size of the Grizzled giant squirrel is unknown. However, the Indian population of this species has been estimated to be fewer than 500 mature individuals. Currently, Grizzled giant squirrels are classified as Near Threatened (NT) on the IUCN Red List and their numbers today are decreasing.