of the world population. The One-Horned rhinoceros, Royal Bengal Tiger, Asian elephant, wild water buffalo and swamp deer are collectively known as 'Big Five' of Kaziranga. Kaziranga is one of the few wild breeding areas outside Africa for multiple species of large cats, such as Bengal tigers and Indian leopard. Kaziranga was declared a Tiger Reserve in 2006 and has the highest density of tigers in the world (1 per 5 km2), with a population of 118, according to the latest census. Other felids include the jungle cat, fishing cat and leopard cat. Small mammals include the rare hispid hare, Indian gray mongoose, small Indian mongooses, large Indian civet, small Indian civets, Bengal fox, golden jackal, sloth bear, Chinese pangolin, Indian pangolins, hog badger, Chinese ferret-badger, and particoloured flying squirrel. Nine of the 14 primate species found in India occur in the park. Prominent among them are the Assamese macaque, capped and golden langur, as well as the only ape found in India, the hoolock gibbon. Kaziranga's rivers are also home to the endangered Ganges dolphin. Kaziranga has been identified by Birdlife International as an Important Bird Area. It is home to a variety of migratory birds, water birds, predators, scavengers, and game birds. Birds such as the lesser white-fronted goose, ferruginous duck, Baer's pochard duck and lesser adjutant, greater adjutant, black-necked stork, and Asian openbill stork migrate from Central Asia to the park during winter. Riverine birds include the Blyth's kingfisher, white-bellied heron, Dalmatian pelican, spot-billed pelican, Nordmann's greenshank, and black-bellied tern. Birds of prey include the rare eastern imperial, greater spotted, white-tailed, Pallas's fish eagle, grey-headed fish eagle, and the lesser kestrel. Kaziranga was once home to seven species of vultures, but the vulture population reached near extinction, supposedly by feeding on animal carcasses containing the drug Diclofenac. Only the Indian vulture, slender-billed vulture, and white-rumped vulture have survived. Game birds include the swamp francolin, Bengal florican, and pale-capped pigeon. Other families of birds inhabiting Kaziranga include the great pied hornbill and wreathed hornbill, Old World babblers such as Jerdon's and marsh babblers, weaver birds such as the common baya weaver, threatened Finn's weavers, thrushes such as Hodgson's bushchat and Old World warblers such as the bristled grassbird. Other threatened species include the black-breasted parrotbill and the rufous-vented grass babbler. Two of the largest snakes in the world, the reticulated python and Indian rock python, as well as