Quolls are carnivorous marsupials native to Australia and New Guinea. They are primarily nocturnal and spend most of the day in a den. Of the six species of quoll, four are found in Australia and two in New Guinea. Another two species are known from fossil remains in Pliocene and Pleistocene deposits in Queensland. Genetic evidence indicates that quolls evolved around 15 million years ago in the Miocene, and that the ancestors of the six species had all diverged by around four million years ago. The six species vary in weight and size, from 300 g (11 oz) to 7 kg (15 lb). They have brown or black fur and pink noses. They are largely solitary, but come together for a few social interactions such as mating which occurs during the winter season. A female gives birth to up to 18 pups, of which only six survive because she only has six teats with which to feed them. They have a life span from 2 to 4 years.
Quolls eat smaller mammals, small birds, lizards, and insects. Their natural lifespan is between two and five years. All species have drastically declined in numbers since Australasia was colonised by Europeans, with one species, the eastern quoll, becoming extinct on the Australian mainland, now found only in Tasmania. Major threats to their survival include the toxic cane toad, predators such as feral cats and foxes, urban development, and poison baiting. Conservation efforts include breeding programs in captivity, one of which is taking place in Tasmania with support from Rewilding Australia and Conjour.
Quolls are indigenous to mainland Australia, New Guinea, and Tasmania. The six species were once widely distributed across the three land masses, but are now restricted to only a few areas. Although primarily ground-dwelling, the genus has developed secondary arboreal characteristics. Each species of quoll lives in distinct geographical areas. The tiger quoll and eastern quoll are exclusively mesic zone species, that is they inhabit moister habitats. The western quoll also inhabits mesic habitat, but has adapted to arid regions across inland Australia, while the northern quoll inhabits tropical habitat of high rainfall.