Occupying an area of 485.2 km2, it is bordered on the southwest by the Periyar Tiger Reserve and is one of the best preserved forests south of the Palghat Gap.

Water sources for the sanctuary are the Kallar and Mullaperiyar Dams and the Periyar, Naragaiar, Pachaiar, Mangar, Kovilar and Pairakudraiar rivers.

[citation needed] In addition to grizzled giant squirrels, other animals seen here are Bengal tiger, bonnet macaque, common langur, elephants, flying squirrels, gaur, Indian giant squirrel, leopard, lion-tailed macaques, mouse deer, Nilgiri langur, Nilgiri Tahrs, palm civets, porcupine, sambar, slender loris, sloth bear, spotted deer, tree shrews, wild boar and wild cats.

Nilgiri Tahr have been sighted in the entire division starting from Kottamala in Rajapalayam to Perumal Malai in Sathuragiri Hills near Sundara Mahalingam temple in Saptoor.

A bird survey in 2013 observed in the sanctuary rare endemic species including Sri Lankan frogmouth, mountain and rufous-bellied hawk-eagles, great Indian and Malabar pied hornbills, mountain and green imperial pigeons which are all species found only in the higher altitudes of Western Ghats.

[6] The sanctuary has numerous reptiles including king cobras, Indian rock python and many endemic species namely pit vipers, ornate flying snake, Draco or gliding lizard, large-scaled calotes and Monilesaurus ellioti and amphibians including endemic ones like Micrixalus, Indirana, Nyctibatrachus, Ramanella, Rhacophorus malabaricus, Raorchestes and Pseudophilautus.

Some of the rare butterflies spotted here include Evershed's ace, silver royal, orange awlet, and Hampson's hedge blue.

[2] 69 plant species belonging to 58 taxa and 42 families are used by the Paliyan tribal people, living in the sanctuary, to treat 15 ailments.

[8] The conservation problems affecting the sanctuary are human-elephant conflict, human encroachment, cattle grazing and forest fire.