Twenty-six species of mammals have been recorded in the park, including the largest regional population of Nilgiri tahr (Nilgiritragus hylocrius),[3] a rare highland ungulate related to sheep and goats, estimated at 750 individuals.

Other local mammal species include chital, Nilgiri langur, lion-tailed macaques, gaur, red muntjac, wild boar and sambar.

Some of the smaller mammals include rodents, mustelids and viverrids, such as the dusky palm squirrel, Indian crested porcupine, ruddy, brown, grey and stripe-necked mongooses, Nilgiri marten and Asian small-clawed otter.

Endemic butterflies (largely confined to the shola grassland ecosystem) include the red disk bushbrown and Palani fourring, among 101 total Lepidopteran species in the park.

In 2010, a new bright-reddish-orange frog, with multiple glands and extremely short limbs, was discovered in Eravikulam National Park.

The newly-discovered species was said to be, apparently, restricted to less than 3 km2 on the peak of Anamudi, thus being deserving of immediate conservation priority, as reported by scientists S.D.

The government of Kerala resumed control in 1971 (Kannan Devan Hill Produce (Resumption of lands) Act, 1971), and declared the Eravikulam-Rajamala Wildlife Sanctuary in 1975 to protect the habitat of the endangered Nilgiri tahr.