The Andaman and Nicobar archipelago comprises of 572 islands extending around 912 km in Bay of Bengal. These islands were once a part of the Asian mainland but got detached some 100 million years ago during the Upper Mesozoic Period due to geological upheaval. The existing groups of islands constitute the physiographic continuation of the mountainous ranges of Naga and Lushai Hills and Arakan Yoma of Burma through Cape Negrais to the Andaman and Nicobar Islands and southeast of Achin Head in Sumatra. The chain of these islands are in fact the camel backs of the submerged mountain ranges projecting above the sea level running north to south between 6°45′ N and 13°30′ N latitudes and 90°20'E and 93°56′E longitudes. Andaman Islands are separated from Nicobar by a 160 km. wide channel known as Ten Degree Channel. Andaman and Nicobar Islands are an internationally acknowledged biodiversity hot spot, off the Indian mainland and lying isolated is 8249 sq. km. areas. These islands encompass a very high degree of endemism in especially plants, reptiles, insects, birds and mammals. Geographically these islands fall under Indo-Malayan biogeograhic regime in which Andaman bears close biogeographical affinities with Myanmar and Thailand while Nicobar has affinities with Indonesia and South-east Asia which signifies the close proximity of Sundaland Hotspot. The notified forest area of Andaman and Nicobar Islands is 7171 km2 in which 105 protected areas including 96 Sanctuaries, 9 National Parks (among these 2 are Marine National Parks) and one biosphere reserve have been declared. Andaman and Nicobar Regional Centre of Zoological Survey of India (ZSI) established at Port Blair on 21st April 1977 under the Sixth Five Year Plan of Government of India. It is one among the 16 Regional Centres of ZSI. The jurisdiction of the Centre covered entire Andaman and Nicobar Islands, and its territorial waters. The faunal communities of marine and terrestrial ecosystems of these islands are being inventorized by the Centre by conducting exploratory surveys. Expertise on several groups of animals such as sponges, all types of corals, sea anemones, molluscs, echinoderms, crustaceans, fishes, butterflies, moths, birds and mammals are available at the Centre. The studies on the faunal communities have been carrying out with the state-of-art facilities for undersea survey such as SCUBA diving equipments and marine sampling instruments, Leica M205A automated stereo-zoom microscope with DFC 500 camera attachment, compound microscopes with computer connectivity, high resolution cameras with tele-lens, and still and video cameras with underwater housing facility.
Andaman and Nicobar Islands are oceanic in nature and separated by mainland India by Bay of Bengal. As geosynclinals basin, tectonic movements have been helping to make change in the sedimentation pattern in the surrounding marine environment of these areas according to the time. Andaman and Nicobar Regional Centre was established in Andaman and Nicobar Islands to promote and explore the faunal diversity of these islands. The total areas of A & N Islands are about 8249 sq. km. where Andaman group comprises of 6,408 sq. km. and Nicobar group comprises of 1,841 sq. km. with a total coastline area of 1962 km. as a whole and account for 30% of the Indian Exclusive Zone. The islands are surrounded by Coco Channel on the northern side, Andaman Sea on eastern side, Great Channel on the southern side and Bay of Bengal on the western side. There are several channels which separated the islands in the form of groups. Among all the groups, Ritchie’s Archipelago and Labyrinth Archipelago of South Andaman are well known for the presence of two Marine National Parks (MNP) such as Rani Jhansi Marine National Park and Mahatma Gandhi Marine National Park. The capital of this Union Territory is Port Blair, located 1255 km. from Kolkata and 1190 km. from Chennai. In these areas, mountain terrain are with long ranges of hills and narrow valleys with a maximum altitude of 732 m (Mt. Saddle Peak near Diglipur) in Andaman group whereas 642 m (Mt. Thullier, Great Nicobar Island) in Nicobar group, where as only two rivers such as Kalpong and Galathea also situated in those areas respectively. Andaman and Nicobar Islands show tropical climate with the presence of two seasons i.e. Wet Season and Dry Season as with a humidity of 80% and temperature range of 23ºC to 32ºC. The region faces unequal rainfall due to usual North-East monsoon (arid) and South-West monsoon (dripping) with annual rainfall of 3180 mm.