The district has been the habitat, from times immemorial, of a large variety 0f mammals, birds, reptiles and fish. Besides monkeys, longurs, wild-cats, goats, pigs, foxes and dogs, the district is noted for its black bears which are found in the Tehri forest division at lower altitudes and the brown and white bears which are found at higher altitudes. Panthers abound almost throughout the district, The flying squirrel, locally known as rinoola, is found largely in the Yomuna forest division. Tigers and elephants are not found in the district except when they enter the district from the Terai forests of Dehradun.
Among mammals, the chief carnivora found in the district are safed bagh (snow leopard) and baghera (leopard). The snow leopard is a rare species and is found near the snow regions (between 3.050 m. and 5,400 m.) in rocky areas. It preys on thar, bharal, sheep and goat. The leopard, which is quite common in rocky forests, carries away sheep, goats, mules and sometimes bullocks and rows also. The black bear lives generally in oak forests. It attacks unprovoked and lives on roots, acorn of oaks, grains, fruits and bark trees and rarely kills for flesh. It hibernates in winter though stray cases of mauling of human beings even during winter are known. The brown and white bear is found mostly in the snow regions.
Besides domesticated cattle, other animals generally met with here are bharal (Himalayan blue sheep), Himalayan thar, goral, kastura (musk-deer) and sambar. The Himalayan blue sheep or bharal is generally found above 4,270 m. in summer and is seldom seen at below 3,000 m. It is shy, quick and speedy and prefers undulating open ground. The Himalayan thar prefers moist rugged mountain terrian with little cover and lives under bushes or trees. In summer it is seldom found below 3,000 m. but in winter comes down to as low as 1,800 m. It is dark brown to almost black in colour, the older male being darker. The goral, a goat-like animal with pale brown colour (which turns to almost grey in summer), haunts the rocky hills in the middle of the forests 1,200 m. and 2,500m, It usually live in herds of 2 to 6. The kastura (musk-deer) which is famous for its musk pod, frequents steep hills with cover and is usually found above 2,700 m. The female deer has no musk. The musk doe begets 2 fawns at a time and, strangely enough, never keeps them together. Both sexes are devoid of horns. It is becoming extinct as it has been ruthlessly killed in the past for the valuable musk which is of high therapentic value in Ayurveda and is also used in the production of perfumes. The sambar is found up to the height of 2,700 m. and prefers moist dense forests. The young ones are greyish brown in colour but the elder males are much darker. It is locally known as jarao. It is said that it drops its horns in May and regrows them in October. The monkey is not seen above the altitude of 2,150 m. but langurs are found up to a higher level. The wild-dog which is found between 1,800 and 2,200 m. (above sea-Ievel) , lives chiefly on deer, sambar being its favourite prey. It lives in herds of 5 to 10. The hathi or Indian elephant may occasionally be seen in the forests between the Bhagirathi and the Yamuna on straying into the area from adjacent forests of the Dehradun district, It causes considerable damage to the cultivation on the border of the forest and destroys the young trees. Cheetal and panda are found largely in herds near Rishikesh forests on the roads to Devaprayag. Kakar-the barking deer-avoids moving about in herds and is usually found in dense forests.
The district is rich in avifauna and in particular pheasants, partridges, pigeons and doves of various kinds which are the chief game birds. The bird life has a zonal distribution according to the altitude. The pheasants generally seen in the district are kaleej, koklas, cheers, and monal. The kareej, a common bird, occurs below 2,600 m. in heavy undergrowth of forests. The koklas is found in the fir zone and prefers moist woody forests. The prized monal is generally found at over 2,700 m. in the fir forests and comes down to the deodar forests during the winter. Wild fowls (locally called kukas) , harials, parrots, chatak, papiha, haldu, nilkanth, pigeons, partridges are found in varied colours and in abundance. Among partridges, the most common are kala titar, chakor and neora. The kala titar is found at up to 2,130 m. and frequents the grass and shrub patches near cultivated land, The chakor loves barren and open hill slopes dotted with bush and grasses and is found between the altitude of 1,300 m. and 3,600 m. It regularly visits the cultivated fields in search of grain or tender shoots of crop and lives in parties of 6 to 20 but is found in pairs in the summer. The neora or- hill partidge which is a dweller of evergreen forests, is found at heights between 1,300 m. and 2,700 m. and prefers broad-leafed forests. The pigeons found in the district are harial or wedge-tailed green pigeon, malyo or blue rock pigeon and snow pigeon of safed malyo. The hariyal is seen mostly in banj forests and is found in flocks. It is essentially a fruitarian bird. Its colour is yellowish-green with maroon markings on the middle of the back. The malyo has a slaty-grey colour with glistening metallic and purple round neck and the head is washed with steel-blue. It lives gregariously on cliffs and precipices, visits the cultivated fields in large flocks in search of food. The sated malyo or snow pigeon is a beautiful pigeon with a white under body, black head, a white cross bar on tail and three white bars on grey wings and completely replaces the blue rock pigeon in the higher altitudes. In habits, it closely resembles the blue rock pigeon. Among doves more numerous are the ghugti, or rufous turtle dove and the fakhta or ringed dove. The ghugti, a large dove, which is found at heights of up to 3,000 m. likes well-wooded forests and is generally seen in pairs or flocks. The fakhta is also a large dove which is found at heights up to 2,700 m, and is usually seen in the outhouses of bungalows in the forests. The shyam karka (woodcock) is also a game bird which dwells in moist fir forests and is nocturnal in habits. It looks like an outsized snipe and has dirty grey and brown markings. The eyes are placed farther back in the head than in other birds. It migrates to comparatively warmer areas during winter.
The non-game birds generally found in the district are magpies, jays, thrushes babblers, laughing thrushes and wood-peckers. These are common in the Yamuna division.
The birds found along the water-courses are brown dipper, spotted forktail, white-capped redstart and various wagtails. Murgabis and teels are also found in the Bhillangana.
The other birds found in the district are the paradise fly catcher, the great Himalayan barbet, the grosbeak, the parakeet, the golden oriole, the hedge sparrow, the sunbird, the flower peckers, the mor (peacock) , robins and the minivet. Out of the preying birds, vultures, falcons, ookav, basa, sikra, dhania, machmar (fish-killer) are foun. Besides, a number of fly catchers, the warblers, bulbuls and the myna, various swifts, sky- larks, bush chats, swallows and the buntings are the other birds which add to the rich bird life of the district.
Among the animal wealth of the district, noteworthy are the musk-deer (male only) that provides the famous and costly kasturi (musk) and the barad and white tutariyal species of deer that provide soft skin and tail for manufacturing mufflers and caps.
Among the avifauna wealth of the district monal provides costly and beautiful feathers which are put to several commercial uses.
Snakes are not numerous in the district but the cobra and the Russel’s viper are commonly found up to 1,800 m. The only hill- snake found above the altitude of 2,400 m. is Ancistrodon himalayanus which attains a length of about 65 cm. and is venomous though its bite is not fatal. Among the non-venomous snakes, the python is most notable. It grows to a length of about 9 m. though specimens over 6 m. are rare. The rat-snake, which attains a length of about 3 m., is also seen in the district. The leech is particularly active during the rains and prefers oak forests. The frog and the toad, both amphibians, are met with through out the district. Several species of lizards are frequently to be seen on rocks basking in the sun. The blood-sucker lizard, in spite of its name, is perfectly harmless and grows to a length from 25 cm. to 40 cm.
Fish is found in almost all the rivers, streams and lakes. The Jalkur, the Aglar, the Bhillangana, the Bhagirathi (the Ganga) and the Alaknanda abound in the larger fish. Some of these known as Gidhi, Gyoonri, Ghoonla weigh from 1 to 3 kg. while bara khasra weighs about 10 kg.