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The fossa (Cryptoprocta ferox) lurks in the shadows of Madagascar’s forests and is the island’s largest carnivorous mammal. This elusive hunter has the body shape of a small cougar but belongs to a Malagasy carnivore family more closely related to mongooses.

Appearance and Evolution

An adult fossa has a head-and-body length of 70 to 80 cm (28 to 31 in), with a tail adding 65 to 70 cm (26 to 28 in), bringing total length to nearly 1.5 m (almost 5 ft). Males usually weigh 5.5 to 8.6 kg (12 to 19 lb), and large individuals can reach 10 to 12 kg (22 to 26 lb).

The fur is short and dense, typically reddish-brown to chocolate, sometimes darker. It has a dog-like snout, rounded ears, and forward-facing eyes that give good depth perception for moving between branches. Sensitive whiskers act like feelers, helping it detect obstacles and prey in dim light. The tail works as a counterbalance while climbing and sprinting through the canopy.

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Fossas belong to Eupleridae, a carnivore family found only in Madagascar. Genetic studies suggest all Malagasy carnivores descended from a single ancestor that reached the island about 18 to 20 million years ago and then diversified into different ecological roles. Madagascar once had a larger, now-extinct relative, the giant fossa (Cryptoprocta spelea), about 20% bigger than today’s species.

When and How It Hunts

Night stalker or day prowler? The fossa doesn’t follow the usual predator rules; it is cathemeral, active by day or night. It races along branches and climbs head-first down trees thanks to flexible ankle joints and semi-retractable claws. That agility matters because lemurs are its preferred prey. In many areas, lemurs make up a large share of its diet, and few predators can consistently catch these quick, tree-dwelling primates.

Mouse lemur

Coquerel's sifaka

Ruffed lemur

Smaller lemurs, like mouse lemurs, can be snatched in a single pounce. Bigger species such as sifakas or ruffed lemurs take more effort: the fossa grabs hold, wrestles for control, and then finishes the hunt with a powerful bite. Beyond lemurs, fossas hunt rodents, birds, reptiles, amphibians, and insects. They also raid ground nests for eggs and hunt tenrecs (hedgehog-like mammals) in the underbrush. Strong jaws and teeth let a fossa tackle prey close to its own size. If the first hunt fails, no problem. This tireless hunter can roam up to 25 km (15 miles) in a single day’s foraging rounds.

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Courtship, Cubs, and Care

For most of the year, fossas live alone and avoid others of their species, each patrolling its own territory. Encounters are uncommon except during the breeding season. In Madagascar’s spring, around September to October, a female enters estrus, the brief fertile period when she is ready to mate. She often stations herself high in a large tree and signals her readiness with distinctive calls and scent marks.

Multiple males converge below, drawn from far and wide. What follows mixes competition and courtship: males may snarl and tussle for a chance to climb up and approach the female. Over the next week or so, the female often mates with several of the strongest suitors, one after another. A single mating can last 90 to 165 minutes (nearly three hours) as the pair balances on a tree limb. The high-branch setting gives the female some control and safety because only the most agile males can follow her into the canopy. After this intense week, the female leaves, and another female may use the same “mating tree” with a different set of males.

Scientists call this system polyandry. Here’s why it helps: fossa litters usually come from several eggs released around the same time. If the female mates with multiple males over those days, different eggs can be fertilized by sperm from different fathers. In other words, one litter can have more than one dad. This boosts genetic variety in the cubs, increases the odds that all eggs are fertilized (a kind of “fertility insurance”), and lets the best sperm win through natural competition.

Gestation lasts about three months, with births often in December or January. The mother chooses a secluded den such as a cave, hollow log, or abandoned termite mound. Litters usually contain 2 to 4 cubs, occasionally up to 6. Newborns are altricial, meaning helpless. They arrive blind and toothless at about 100 g (3.5 oz) each. Unlike many carnivores, they are born with a thin fur coat, but their eyes do not open for 2 to 3 weeks. In the den, the mother nurses and guards the cubs; males do not help raise them.

Cubs remain in the den for 4 to 5 months, nursing until they are nearly half their mother’s size. After weaning, they make short trips outside under their mother’s supervision, learning to climb and hunt through play. Independence comes late: juveniles stay with their mother for 15 to 20 months before moving out on their own, and sexual maturity typically arrives at 3 to 4 years of age. In captivity, a fossa may live about 20 years; in the wild, life expectancy is likely shorter.

The species reproduces slowly. A female produces at most one small litter per year, and not all cubs survive to adulthood. This extended upbringing and low birth rate mean populations recover slowly and are vulnerable to threats that remove breeding adults or destroy denning areas.

Habitat and Ecological Role

Fossas live only on Madagascar. They occupy most forest types on the island, from eastern rainforests to western dry deciduous forests, and even montane forests up to about 2,000 m (6,560 ft). Their distribution is widespread but sparse: they need extensive, connected forests and do not thrive in treeless landscapes or open farmland.

As the island’s apex terrestrial predator, the fossa helps regulate prey populations, especially lemurs, which are key seed dispersers. At many sites, lemurs make up more than half of the diet, which helps keep browsing pressure in check and maintain ecological balance. Adults have no regular natural predators; rare risks include crocodiles at waterholes, and large raptors may take juveniles. Removing fossas would send ripples through Madagascar’s food webs.

Saving the Fossa

The fossa is listed as Vulnerable on the IUCN Red List, and populations are declining. Estimates suggest roughly 2,600 to 8,600 adults remain in the wild. The main threat is deforestation and fragmentation from agriculture (including slash-and-burn, locally called tavy), grazing, timber harvest, and charcoal production, which isolates small populations and reduces prey and gene flow.

The species is legally protected in Madagascar and listed on CITES Appendix II. Populations persist in parks and reserves such as Kirindy Forest and Masoala National Park. Priorities include safeguarding and reconnecting forests, curbing illegal logging, improving coexistence around farms and poultry, and continuing research and education so this predator can endure.

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