INTRODUCTION
Bhutan is a small kingdom covering an area of 46,500 square kilometres in the eastern part of the Himalayan Range between latitudes 260 40’ and 280 20’ north and longitude 880 45’ and 920 7’ east. It is surrounded by the Tibetan Plateau in the north, the Bengal and Assam Plains in the south, Arunachal Pradesh in the east and the Darjeeling and the Sikkim Himalaya in the west (see Figure 1).