The fossa is a cat-like, carnivorous mammal endemic to Madagascar. It is a member of the Eupleridae, a family of carnivorans closely related to the mongoose family (Herpestidae). Its classification has been controversial because its physical traits resemble those of cats, yet other traits suggest a close relationship with viverrids.

The fossa is the largest mammalian carnivore on the island of Madagascar and has been compared to a small cougar. Adults have a head-body length of 70–80 cm (28–31 in) and weigh between 5.5 and 8.6 kg (12 and 19 lb), with the males larger than the females. It is found solely in forested habitat, and actively hunts both by day and night. Over 50% of its diet consists of lemurs, the endemic primates found on the island; tenrecs, rodents, lizards, birds, and other animals are also documented as prey.

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