Mammals
Fossa
Cryptoprocta ferox · also called Malagasy civet-cat (incorrectly)
The fossa is Madagascar’s answer to a leopard — a lithe, russet, cat-shaped hunter that runs through the canopy after lemurs. It is not a cat at all, but the largest member of a carnivore family that exists nowhere else on Earth.
Overview
Fossas live in forest across Madagascar — rainforest in the east, dry deciduous forest in the west, and spiny forest in the south — wherever there is enough continuous woodland and enough prey. They are solitary outside the brief mating season, active by day and night, and equally at home on the ground and high in the trees. Each animal ranges over a large area, and males in particular patrol territories of many square kilometres.
Madagascar’s own carnivore
When Madagascar broke away from the other continents, it had no cats, dogs, bears, or weasels. A single mongoose-like ancestor rafted over around 20 million years ago and gave rise to the family Eupleridae — a set of small carnivores unique to the island. The fossa is the biggest of them, and in the absence of any competition it evolved into the apex predator, taking on a strikingly cat-like form through convergent evolution: a rounded head, semi-retractable claws, a very long tail, and an ambush-and-pounce hunting style.
The lemur hunter
Over half the fossa’s diet is lemurs, and it is the only predator able to chase them through the canopy at the lemurs’ own game. Reversible ankle joints let it descend trunks head-first and grip while facing down; the long tail balances it through leaps; and its speed and agility let it corner prey among the branches. It takes lemurs of every size, and its predation has been a major force shaping how lemurs live — their group sizes, alarm calls, and vigilance.
An unusual breeding system
Fossa mating is one of the stranger events in the carnivore world. A receptive female claims a traditional mating tree and stays in it for about a week; males assemble below and mate with her one after another, high in the branches, in couplings that can last for hours. Juvenile females also pass through a temporary “masculinised” phase, with male-like genitals and scent, thought to shield them from adult males.
Threats and conservation
The fossa is Vulnerable and declining. The core problem is deforestation and forest fragmentation — the fossa needs big, connected forests, and Madagascar’s are shrinking and breaking apart, leaving small inbred populations. Persecution as a chicken thief, bushmeat hunting, and diseases from domestic dogs and cats add to the pressure. Protecting and reconnecting the island’s remaining large forest blocks is essential to keeping the fossa — and the lemur communities it regulates.
Fossa: common questions
Is the fossa a cat?
No, though it looks and behaves remarkably like one. The fossa belongs to Eupleridae, a carnivore family found only on Madagascar, whose members all descend from a single mongoose-like animal that reached the island around 20 million years ago and then diversified. With no cats, dogs, or bears present, the fossa evolved into the island's top predator, converging on a cat-like body — retractable claws, short face, long tail, ambush hunting — entirely independently of true cats.
How does the fossa hunt lemurs?
It is one of the few predators that can pursue lemurs through the trees. Its semi-retractable claws, long balancing tail, and flexible ankle joints — which rotate so the hind feet can grip a trunk while the fossa faces downward — let it run down vertical branches and leap between them at speed, something almost no other carnivore its size can do. It also hunts on the ground. Because it can take lemurs of every size, from mouse lemurs to the largest indri and sifaka, the fossa is the main non-human predator shaping lemur behaviour and evolution.
What is unusual about fossa mating?
A great deal. Females come into season one at a time and each takes up position in a specific "mating tree" that the local population uses year after year, staying there for about a week. Several males gather below and mate with her in turn, high in the tree, and a single copulation can last two to three hours because the male's anatomy locks the pair together. Young female fossas also go through a temporary phase of "masculinisation," developing an enlarged, spiny clitoris and male-like scent, which may protect them from harassment by adult males.
Why is the fossa endangered?
Its survival depends on large blocks of forest, and Madagascar has lost most of its forest cover, with what remains heavily fragmented. Small, isolated fossa populations then suffer from inbreeding and are easily wiped out. Fossas are also killed by farmers as poultry predators and hunted for bushmeat in some regions, and they catch diseases such as distemper and toxoplasmosis from village dogs and cats. Fewer than 2,500 breeding adults are thought to remain.