Wow! Such a massive world, but apart from humans and the common animals that we know like cats, dogs and so on, there are many species or organisms distributed diversely across the globe. Just like a country consists of states further comprising of cities, towns, villages similarly the whole world is divided into ZOO-GEOGRAPHICAL REALMS, meaning having a characteristic fauna. This division of the world into SIX zoo-geographical realms was postulated first by ALFRED RUSSEL WALLACE, who is the father of bio-geography.

Let’s explore each of these realms or regions:

PALAEARTIC REGION

1. Biggest realm which is bounded by sea in west, north and east and by Sahara and Himalayas in the south.
2. This region shows wide range of temperature and rainfall fluctuations.
3. It is divided into four sub-regions:

• EUROPEAN: Includes northern and southern Europe, Black sea, Caucasus. This region is represented by 85 families of vertebrates. The peculiar mammal to this region is MYOGALE (Desmans). Birds like Tits, wagtails and some of the mammals like wolves and moles are common in this sub-region.

• MEDITERRANEAN: Includes south of Alps, Balkans and Caucasus, portion of Arabia, Afghanistan, Sahara desert and Baluchistan upto bank of Indus. This sub-region is characterised by 124 families of terrestrial vertebrates including birds like Upupa and Pastor and mammals like Wild ass, Porcupine and Hyaena.
• SIBERIAN: Includes Caspian sea to Kamchatka and Bahring’s starits from Arctic sea to Himalayas. It comprises of 94 vertebrate families. Mammals confined to this region are Antelopes, Reindeers, Seal (Phoca sibirica) inhabits the great fresh water lake BAIKAL.
• MANCHURIAN: Includes Korea, Japan, Manchuria upto Amur rivers and China upto Nanking mountain. Mammals like Tibetan Langur, Great Panda and Chinese water deer (Hydropotes) are unique to this region.

NEARCTIC REGION  

1. Region above the tropics of North America includes the Arctic Archipelago and the Greenland.
2. This region is known as the “Headquarters of urodela” because of the dominance of the tailed amphibians.
3. Nearctic region shows a great variations in climatic conditions and temperatures.
4. Like Palaearctic region, this region is also further divided into four sub-regions:

• CALIFORNIA: Includes a part of North America, Nevada, Cascade regions and part of British Columbia. Contains nearly 86 families of vertebrates. Vampire bats and free tailed bats are unique to this region.
• ROCKY MOUNTAIN: Includes mountain of East California. 107 families of terresterial vertebrates are present, American Bison and poisonous lizard (Heloderma) are characteristic animals of this sub-region.

• ALLEGHASY: Includes lakes of eastern parts of U.S.A. and rocky mountain sub-region as well. This sub-region is unique as it contains Star nosed moles and Opossums among mammals and Turkeys and Carolina parrots among birds.
• CANADIAN: Includes remaining parts of North America and Greenland. Characteristic vertebrates are Elk, Polar beer and Gluttons and Arctic fox.

ETHIOPIAN REGION

1. Includes whole of Africa, Southern Arabia and Madagascar.
2. This region shows extensive desert on north, thick forests on its western side and grassland in the rest of the Africa.
3. Divided into four sub-regions:

• EAST AFRICAN: Includes Sahara desrt, North-East Africa, Southern Arabia and upto Zambezi in the south. Comprises of 145 families of vertebrates among which the peculiar ones are Crested rats and Whale headed birds. Because of the high temperature Desert ostrich, Zebra, Giraffe and Camels are also common.

• WEST AFRICAN: Includes west Africa upto river Congo. This sub-region shows heavy rainfall with thick forests. Apes, Panthers, Lions and Elephants are common.
• SOUTH AFRICAN: Includes southern African valley. Peculiar fauna includes African moles, Bandicoots, Secretary birds and South African Lungfish (Protopterus).

• MALAGASY: Includes Madagascar and nearby islands. Among mammals Lemurs, among birds Helemt vanga and among reptiles Pipe snakes are common.

ORIENTAL REGION

1. This region is bounded by Himalayas in north and Indian and Pacific oceans in south.
2. No definite boundary in South East is present.
3. Divided into following sub-regions:

• INDIAN: Includes India along with Bhutan, Nepal and Maldives. Wide variation of temperature and rainfall including mountains, forests, deserts. Peculiar species are Indian bear, Peacock, Indian bison, Colubrine snake and Rhinoceros.

• CEYLONESE: Includes Ceylon (Sri Lanka). This sub-region shows tropical climate. Endemic species are Shield tail, Spring rat.
• INDO-CHINESE: Includes China, Myanmar, Thailand, Laos, Cambodia, Vietnam, Taiwan, Island of Andaman. Peculiar species includes Panda, Flying Lemur, Malayan Tapir, Disc tongued frog and salamander.
• INDO-MALAYAN: Includes Malaya peninsula and Malay Archipelago (Sumatra, Bali, Philippines, Nicobar). Shows tropical climate and the unique fauna includes Malayan Tapir, Broad bills, Proboscis monkey.

NEOTROPICAL REGION

1. Joined to Nearctic region by Central American Isthmus and separated from all the other regions by sea.
2. Known for the presence of luxurious forests (Amazon valley), Plains (Savanna), Mountain (Andes) and complete absence of desert.
3. The four sub-regions are:

• CHILLIAN: Includes Western coast of South America, Andes mountain ranges, Peru, Bolivia and Argentina. The unique species are 3 toed ostrich known as Rhea Americana, Llamas, Oil birds and Chinchillas.

• BRAZILLIAN: From Isthmus of Panama to La Plata in south. American monkeys, Armadillos, Spiny mice, Anaconda are common in this sub-region.
• MEXICAN: Includes Mexico and Guatemala. Comprises mainly of rocky mountains and this sub-region is also said to be the “Transition Zone” between Nearctic and Neotropical region. Terrapins are mostly found here.

• ANTILLEAN: Includes West Indies islands ( Cuba, Haiti, Jamaica, Porto Rico). This sub-region shows uniformly high temperature and rainfall. The vertebrate fauna is poor and hence no endemic mammals are found.

AUSTRALIAN REGION

1. This region includes whole Australia, New Zealand, New Guinea, Molucca and all Pacific islands.
2. Climate is hot and tropical in northern part, hot and arid in central part and temperate and cool in southern part.
3. Divided into four sub-regions as following:

• AUSTRALIAN: Includes Australian mainland and Tasmania. This sub-region is known as “HOME OF MARSUPIALS”. Wombats, Marsupial moles, Platypus, Scrub birds and Emus are endemic to this sub-region.

• NEW ZEALAND: Includes New Zealand and surrounding islands. Mammals present here are Bats and Murids. Birds common to this sub-region are Kiwi, Owl parrots, Nestor parrots. One interesting trait here is the absence of snakes.
• POLYNESIAN: Includes many Pacific islands like Hawaiian island, Samoa island, Fiji, Caroline island. Poor endemic fauna, mainly characterized by Tooth billed pigeons.
• AUSTRO-MALAYAN: Includes New Guinea and islands of Malay Archipelago. The endemic species are Crowned pigeon, Flying river turtle, Cassowaries, Bower birds, Tree frogs.