The Eastern Himalayas comprise the tracts of the Darjeeling Hills or North Bengal, Sikkim, Arunachal Pradesh, and eastern Bhutan. The region is drained by the Brahmaputra river and its tributaries: the Teesta drains Sikkim and the Darjeeling areas, and the Manas drains part of Bhutan and Arunachal Pradesh. The Kamang and the Subansiri are the other important rivers that drain the eastern Himalayas.
The Eastern Himalayas can be divided into the following climatic regions: arctic, sub-arctic, temperate, subtropical, and warm tropical. The forests are moist, dense, evergreen, semi-evergreen, or temperate. Precipitation is very high and the forest region is very humid. Sal forests and evergreen trees are found extensively all along the foothills of the Eastern Himalayas. Subtropical forests cover the hills up to an elevation of about 2000 m.
The temperate mixed forests are found up to a height of about 3000 m followed by the alpine forests, which consist mainly of fir, juniper, and rhododendron . This region is the home of a large variety of animals and birds including slow loris, rhinoceros, the golden languar, tiger, the Indian civet, clouded leopard, the golden cat. The birds include heron, the white-winged wood duck, and the snow cock. A number of wildlife sanctuaries and biosphere reserves have been set up in this region to protect the species from poachers and human encroachments. Jaldapara, in the Bhutan foothills of Bengal, is famous for the one-horned rhinoceros, hog deer, and tiger floricans. Buxa Sanctuary at the junction of Assam, northern West Bengal, and Bhutan is a tiger reserve under the Project Tiger and serves as a vital corridor for the elephants migrating between the forests of Assam and Bhutan. It has dense deciduous forest and is the home of the swamp deer, and leopard and many species of birds.
The Kangchendzonga national park in Sikkim is the home of many high-altitude mammals and birds such as the clouded leopard, red panda, musk deer, snow cock, and pheasants. The principal forest types found here are the coniferous and Alpine scrub. The Manas sanctuary, which lies on either side of the Manas river in Bhutan and Assam has very dense semi-evergreen and deciduous forests and swamps and marshes. It is famous for the golden languar which is found only in this area. Other animals found here include the barking deer, sambar, and golden cat. It is also a tiger reserve under the Project Tiger.
The Namdapa national reserve in Arunachal Pradesh is perhaps the only protected area where all the four major predators of the Himalayas, namely the tiger, leopard, clouded leopard, and the snow leopard are found. It has a wide variety of flora and fauna as the altitude ranges from 200 m to 4500 m. There are evergreen, sal, deciduous, oak, coniferous and sub-alpine forests. It is the home of the slow loris, leopard, red panda, hoolock, musk deer, and hornbilled duck.
The Namdapa biosphere reserve, located in the Lohit and Tirap districts in south-eastern Arunachal Pradesh, is considered one of the richest biotic areas in India. It is partly drained by the Brahmaputra river system and has a typical tropical to subtropical monsoon climate receiving very heavy rainfall. The vegetation consists of moist mixed deciduous forests, subtropical wet hill forests, wet temperate forests, and alpine forests. There are a very large variety of animals and birds such as the tiger, leopard, civet, red panda, heron, hornbill, and thrush.
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