The Sanctuary was named after the Mehao Lake. The terrain of the Sanctuary is hilly, clothed with Tropical Evergreen Forests. The under-storey is also thickly covered with undergrowth. There are two major lakes inside the Sanctuary, Mehao and Sally. The Mehao lake (<200 ha) is situated at an altitude of 1,640 m and Sally (2 ha) is at 520 m. The Mehao Lake originated as a result of the 1950 earthquake. Mehao WLS is thinly populated and most of the areas have not yet been named. There is only one fair-weather jeepable road passing through the Sanctuary from Roing to Hunli (Chakraborty and Sen 1991). Topographically, the terrain is entirely hilly, varying in altitude from 400 m to 3,560 m. A number of perennial fast flowing streams drain the Sanctuary, notably the Iphipani, Eje, Eme, Aba and Difu. The Sanctuary forms a part of the catchment area of the Brahmaputra river. Peaks above 2,000 m experience above snowfall. The Sanctuary is located on the windward side of the Eastern Himalayas so it receives heavy rainfall both from the southwest and the northeast monsoons. It rains nearly half of the year (Chakraborty and Sen 1991). Areas converted due to jhum cultivation earlier, are being covered with bamboo and other secondary vegetation. Cane is common in humid areas.
AVIFAUNA: At least 175 bird species have been recorded in this IBA (Katti et al. 1992). Among the threatened birds, Spotbill Pelican Pelecanus philippensis was recorded just outside the Sanctuary in 1994 (Choudhury 2000). White-winged Duck Cairina scutulata was also recorded from Mehao lake (Choudhury 1995).
The Wedge-billed Wren-Babbler Sphenocichla humei, a Restricted Range species, and one of the least known Indian species, has been recorded from this Sanctuary (Katti et al. 1992). It has been collected only three times in the last century, in 1905 by Stevens (1914), in 1938 by Lightfoot (1940) and in 1988 by Ripley et al. (1991). It occurs in two races: humei and roberti. Rasmussen and Anderton (in press) have elevated these races to full species: Sphenocichla humei and Sphenocichla roberti. This would qualify one or both for threatened status (BirdLife International 2001). Ali and Ripley (1987) have also considered both subspecies as very rare residents.
Stattersfield et al. (1998) have identified endemic bird areas EBA) of the world and listed Restricted Range species found in each EBA. In the Eastern Himalayas EBA, 21 species are found in India, out of which 10 have been reported from this IBA. There are not many IBAs in this EBA where so many Restricted Range species are found.
Due to altitudinal variation from 400 m to 3,560 m, this site has three biomes: Biome 7 (Sino-Himalayan Temperate Forest), Biome-8 (Sino-Himalayan Subtropical Forest), Biome-9 (Indo-Chinese Tropical Moist Forest). A total of 60 biome species are found in this IBA but they are too many to list here.
OTHER KEY FAUNA: Chakraborty and Sen (1991) have recorded 66 mammals from this IBA site. Five primates have been recorded, of which Capped Langur Trachypithecus pileatus and Slow Loris Nycticebus coucang are uncommon (Chakraborty and Sen 1991). Red Panda Ailurus fulgens is found at higher elevations only. Seven species of Felids are reported, including the Snow Leopard Uncia uncia, which is only a winter visitor. Sinha (1984) has reported the Clouded Leopard Neofelis nebulosa, but Chakraborty and Sen (1991) could not confirm it during their survey. Marbled Cat Pardofelis marmorata is extremely rare in this IBA. Not much information is available on reptiles and amphibians.
BirdLife International (2019) Important Bird Areas factsheet: Mehao Wildlife Sanctuary. Downloaded from http://www.birdlife.org on 22/05/2019.