The Indian subcontinent has varied physical and climatic conditions and types of vegetation, stretching from the northern temperate Zone to the equator and embracing such contrasting regions as the Himalayas in the north and tropical sea-coast in the south. The affinity of fauna of the Siwalik beds and that of present-day Africa and India suggest that they were derived from common species which migrated from Europe and Central Asia which enjoyed warm climate at that time. The advent of ice age in these regions must have forced many species to migrate southwards. Some of them reached India. Migration of fauna to India also took place from the eastern lands, which are now separated from  the Bay of Bengal and also from the west. Thus the wild life of India comprises the originally indigenous species as well as the species which migrated from elsewhere. It is really the admixture of Indian, Malayan, African and European elements. The respective species inhabited the areas adjacent to their original home lands.

For the systematic study of global distribution of wild life. The earth has been divided into six Zoogeographical regions.

1. The Neoartic region consisting of North America, Canada, Iceland and Green land

2. The Palaeartic region consisting of North Africa, Europe, North East and Central Asia.

3. The Neo-tropical region comprising southern peninsula of North America and South America.

4. The Ethiopian region consisting of three fourths of Africa and southern Arabia.

5. The oriental region including Indian Subcontinent and South East Asia.

6. The Australian region comprising mainly Australia.

India with south-east of Asia forms a part of the oriented region. Millions of years ago India was an Island continent it moved northwards joining the land mass of Asia across an ocean which has now vanished. On account of geological movements millions of years of ago India and Africa joined Asia and Europe establishing physical contact and scope for movement of fauna. Based on the distinctive types of flora and fauna the Indian subcontinent has been divided in to three sub regions though they do not form rigid boundaries. They are (a) Himalayan sub- region (b) Tropical rain forest (c) Indian Peninsular region. Certain species are widespread in the country and cover more than one region. Thus there is always an intermingling of species between these zones.