Located in the Nilgiri Hills, Silent Valley is the second largest National Park in Kerala with an area of 90 sq.km. Plans for a hydroelectric project that threatened the park's rich wildlife started an environmentalist social movement in the 1970s, known as the Save Silent Valley movement. This movement led to the establishment of Silent Valley National Park in 1980. It is the core of the Nilgiri International Biosphere Reserve and is part of the Western Ghats World Heritage Site, recognised by UNESCO in 2007. Silent Valley is home to the largest population of lion-tailed macaques, an endangered species of primate, and 34 different species of mammals besides a majority of flora which are endemic to the Western Ghats. The rare bird species found here include the Ceylon frogmouth and great Indian hornbill, alongside 138 other species of birds including 17 species that were newly observed in the Silent Valley area. The Silent Valley Bush Frog, Raorchestes silentvalley, first discovered in 2016, is named after the park.