The Sunderbans offer a unique ecosystem and a rich wildlife habitat. As per the 2011 tiger census, the Sunderbans had around 270 tigers. Frequent tiger attacks take place in the Sunderbans. Other than the star highlight of the Sunderbans, the endangered Royal Bengal Tiger, there is more wildlife found. Surrounded by mangroves, the Sunderbans offer habitat to a variety of species like crabs, small fishes, crabs, shrimps and more. Other than these, one can spot fauna like wild boars, fishing cats, macaques, common grey mongooses, foxes, jungle cats, flying foxes, pangolins, and spotted deer at the Sunderbans.
After a study in the year 1991, it was discovered that the Bangladeshi part of the Sunderbans supports diverse biological resources that includes 150 species of commercially important fishes, 270 species of birds, 42 species of mammals, 35 reptiles and 8 amphibian species. This further represents that there is a significant proportion of the species in Bangladesh (around 30% of the reptiles, 37% the birds and 34% of the mammals). Sunderbans thus, houses a number of species that are now extinct elsewhere.
The Sunderbans is an important wintering area which attracts migrant water birds. The area of the Sunderbans is very suitable for watching and studying avifauna.
Most part of the Sunderbans has been taken over for human use which has left just some area of the forests. However, with the mangroves and remaining forests, Sunderbans form an important habitat for the endangered Bengal tiger (Panthera tigers). Other than the tigers, the forest is also home to leopard (Panthera pardus fusca) and many more small predators like the jungle cats (Felis chaus), fishing cats (Prionailurus viverrinus), and leopard cats (Prionailurus bengalensis).
The Sunderbans is the only place where the largest predator of the Indo- Pacific region is found, the Bengal Tiger. There are around 500 Bengal Tigers and 30,000 spotted dears in the area.
Two species of crocodiles, the saltwater crocodile (Crocodylus porosus) and mugger crocodile (Crocodylus palustris) are also predators. Other predators include gharial (Gavialis gangeticus) and the water monitor lizards (Varanus salvator), which hunt on both land and water.
The forests of Sunderbans are home to numerous species of birds. One can spot around 170 species of endemic brown-winged kingfishers (Pelargopsis amauroptera) and lesser adjutants (Leptoptilos javanicus), masked finfoots (Heliopais personata), ospreys (Pandion haliaetus), white-bellied sea eagles (Haliaeetus leucogaster) and grey-headed fish eagles (Ichthyophaga ichthyaetus).
There are many more famous birds found in the Sunderban region including Caspian terns, open billed storks, black-headed ibis, water hens, coots, pheasant-tailed jacanas, jungle babblers, pariah kites, brahminy kites, marsh harriers, swamp partridges, red junglefowls, spotted doves, common mynahs, whimbrels, jungle crows, cotton teals, herring gulls, gray herons, brahminy ducks, spot-billed pelicans, great egrets, night herons, common snipes, paradise flycatchers, wood sandpipers, green pigeons, rose-ringed parakeets, cormorants, white-bellied sea eagles, seagulls, common kingfishers, curlews, peregrine falcons, woodpeckers, black-tailed godwits, little stints, eastern knots, golden plovers, pintails, white-eyed pochards and lesser whistling ducks.
Common toads, silver carp, sawfish, butter fish, electric ray, common carp, barb, river eels, starfish, king crab, fiddler crab, hermit crab, prawn, shrimps, Gangetic dolphins, skipping frogs, and tree frogs are some amphibians and fishes found in the Sunderbans. The main attraction of the aqua fauna is the mudskipper, a gobioid which climbs out of the water into mudflats and can also climb trees.
The Sunderbans National Park has a wide variety of reptiles including green vine snake, olive ridley turtles, dog faced water snakes, green turtles, hard shelled batgun terrapins, estuarine crocodiles, chameleons, king cobras, salvator lizards, Russels vipers, mouse gekkos, monitor lizards, curviers, hawks bill turtles, pythons, sea snakes, common kraits, checkered keelbacks and rat snakes. Native species of the national park include river terrapin (Batagur baska), Indian flap-shelled turtles (Lissemys punctata), yellow monitors (Varanus flavescens), water monitors (Varanus salvator), peacock soft-shelled turtles (Trionyx hurum), Indian pythons (Python molurus).