The forests are found on the eastern slopes of the Western Ghats. Only 6.3% of the total geographical area of the district is under forests. Many rare and endemic varieties of flora and fauna are found along the mountain slopes. A wildlife sanctuary, spread over 480 sq. kms. was established in 1989 at Shenbagathopu in Srivilliputtur taluk. This sanctuary is contiguous with the Periyar tiger reserve on the south-western side and the Megamalai reserve forest on the north-western side. The altitude varies from 100m to 2010 m above sea level. The sanctuary is home to the endangered, arboreal Grizzled giant squirrel Ratufa macrora. The home range of an individual is between 0.197 hectares and 0.611 hectares.
The sanctuary also hosts a variety of birds, mammals, reptiles and butterflies. Resident and migratory elephants are common. Other animals sighted are tiger, leopard, Nilgiri tahr, ( Hemitragus Hylocrius ) Spotted Deer, Barking Deer, Sambar, Wild Boar, Porcupine, Nilgiri langur, Lion-tailed macaque, common langur, slender loris, bonnet macaque, sloth bear and flying squirrel. Over 100 species of birds have been identified. The rare Great Indian horn bill is also found.
Special steps have been taken to conserve the forest areas in the sanctuary. The annual leases given for the collection of fruit and other minor forest produce has been stopped. Fruit bearing trees and other trees have been planted. This will increase the food sources as well as ensure continuity in the canopy. Soil conservation and water harvesting measures have been undertaken to improve the habitat. The best time to visit the sanctuary are throughout the year except for the months of March, April and May.
The forests of Alagarkoil valley in Srivilliputur taluk and Saduragiri are known for rare medicinal plants. The medicinal value of 275 plants has been recorded and reported. The forests host a rich variety of orchids and ferns.