2. THEY CALL IT HOME
2.3 Geology
The geology of the Andamans has not yet been well studied. Mud volcanoes on Baratang Island and Middle Andamans have given rise to the hope that there might be petroleum deposits and this has lately spurred on the geological survey although so far no mineral deposits of economic value have been discovered.
The oldest rock formations represent deposits laid down in the deep, open sea from the Cretaceous period immediately preceding the Cenozoic to the middle Tertiary. The islands were born when the sea floor, consisting of a core of faulted sandstone and shale) was lifted and piled up into the present mountain chain during the Oligocene. Ritchie's archipelago, Little Andaman and the Nicobars rose from the sea at a somewhat later stage. Most of the islands are surrounded by coral reefs or extensive mangrove swamps. Behind these formidable coastal defenses is a deeply indented shore that provides many good and well-camouflaged anchorages. Throughout the ages, any captain keen-eyed and ad-venturous enough to take the risks could find valuable hiding places. Many un-doubtedly did.
The large main islands (apart from North Sentinel, Ritchie's archipelago and Little Andaman) are collectively called the Great Andamans. They are so close together - in places literally only a stone's throw - that for all practical purposes they form one large island.
Despite the abundant greenery, Andamanese soils are not very fertile, with a low capacity for holding moisture. They are mostly soft, deep sandy loams with acidic or slightly acidic reactions and rather deficient in calcium. Such soils are not con-ducive to the development of agriculture and this may have been one contributory reason why the aboriginal Andamanese stubbornly remained exclusive hunter-gatherers.
2.4 Fauna
There is little variety in mammal life. Most noticeable is the absence of large car-nivores with only 19 land-living species of small mammals sharing the islands with humans. The seas, on the other hand, teem with large mammals: there are sea cows (dugong, of the order Sirenia), dolphins and whales. Among non-mammalian groups there is rather more variety: there are 72 kinds of reptiles such as snakes, lizards, turtles and crocodiles and no less than 255 kinds of bird. It may be noted here that most of the land animals show more affinity to Burma rather than to Malaya or Sumatra.
The largest naturally occurring land mammal is the Andamanese pig (sus andamanensis, sometimes called sus scrofus andamanensis) which played and still plays a major part in traditional Andamanese life. There are also a civet cat, a wild cat as well as many types of small rodents, flying fox and bats. Among reptiles, the large turtles are important to the natives but there are also many species of snakes, lizards and a truly terrifying saltwater crocodile (crocodilus porosus) that can reach a length of up to 9 m (30 ft). The very common carrion-eating monitor lizard also can grow to impressive size. The monitors fill the role that the jackal and the vultures fill elsewhere, eating the cadavers and offal that even the dogs will not touch. Amphibians, mostly frogs and toads, abound.
There is a vast variety of life in the seas all around the islands, from sharks and sting rays to fish of all shapes and sizes, not forgetting an enormous variety of crustaceans in the water, on the beach and on dry land. A walk along or behind an Andamanese beach can be an odd experience as thousands of "stones," ranging from the size of sand grains to sizeable "rocks," scatter unhurriedly in all directions before one's approach. These are hermit crabs in their protective shells.
Just as fascinating but not always quite so agreeable, there is also a lot of insect life. The two species of honey bee whose product has always been of great importance to aboriginal Andamanese society are among the more agreeable ones. Much of the rest, unfortunately, shows a tendency towards the frankly obnoxious. The insect torturers are joined by legions of ticks, leeches, centipedes and other creatures. The lower animals of the archipelago have been studied and classified only superficially. Many new species are sure to be found once this work is systematically taken in hand but there is so much variety that it will be the life's work of more than just one person. The Andamanese jungle is not the place one could recommend, with a clear conscience, to people who feel bothered at a picnic by a lone wasp or a few ants.
The islands are well-known in diving circles for their coral reefs, most of them of the fringing type. Because there are so many large rivers emptying fresh water into the Bay of Bengal and there is such heavy rain in the area at times that salinity is rather low (usually less than 33 ppt around the Andamans), conditions for the growth of corals are not optimal but clearly sufficient. Two coral-building species dominate: Porites and Favia, with Acropora and Pocillopora also present to a lesser extent.
That the archipelago has long been isolated is documented by no less than 200 endemic species of animals, i.e. animals that occur only in these islands and no-where else, apart from the Nicobar Islands in some cases. It is well-known that evolutionary pressure on an island population and in a heavily forested habitat tends to produce dwarf forms. This seems to have happened in the Andamans: many indigenous land-living species are down-sized variants of rela-tives living on the mainland, including most remarkably Homo sapiens.
The best known and largest of the endemic forms is the Andamanese pig. Other special Andamanese forms include a civet cat (paguma larvata tytlerii), a water snake (xenochrophis melazostus andamanensis), a gecko (phelsuma anda-manensis), a monitor lizard (varanus salvator andamanensis) as well as several birds that are often known from the Nicobars also such as the Andaman dark serpent eagle (spilornis elgini), a teal (anas gibberifrons albogularis), a pigeon (ducula aenea andamanensis) and two parakeets (psittacula eupatrid magniros-tris and psittacula alexandri abbotti) as well as many others.
At least two forms of deer, the hog deer and the spotted deer, have been introduced from India after the 1920s. In the absence of large predators, they have become pests in some places. The traditional arch-conservative aboriginal Andamanese will not hunt and eat the new-fangled animals despite their perfectly edible meat. Another recent introduction to the island is the elephant. Many are used by the timber industry and they often swim in the sea when they are off-duty. Over the years, individual enterprising elephants have used their ability to swim up to 20 km (12 miles) to abandon their work and their employers to settle elsewhere. On Interview Island today, for example, there is a population of feral elephants that is not entirely harmless and that is actively hindering the exploration of that island.
