Silent Valley National Park A dense rain forest and the habitat of rare species 80 km from Palakkad. It is popularly known as the evergreen forest and noted for its eerie silence because of the lack of cicadas.[citation needed] It is an important biosphere reserve in the Western Ghats and home of the tribal people. The valley is known for the rare Lion-Tailed Macaque. This National Park is a protected area for tigers also.