The fossa (Cryptoprocta ferox) is the largest carnivorous mammal on the island of Madagascar. They can reach nearly six feet in length, with half of that due to their long tails.

They look like a cross between a cat, a dog, and a mongoose. Fossas have slender bodies, muscular limbs, and short, reddish-brown coats. They have small, cat-like heads, short, dog-like muzzles, and large, rounded ears.

So what is a fossa? Read on to find out about Madagascar's top predator.

1. Their scientific name means "hidden anus." The fossa's genus name, Cryptoprocta, is inspired by how its anus is concealed by an anal pouch. It comes from the Greek for hidden (crypto) and anus (procta). The fossa's species name, ferox, refers to its exaggerated reputation for ferocity.

Photo: Ran Kirlian, via Wikimedia Commons. Distributed under a CC-BY-SA-4.0 license.

2. Fossas are the top predator in Madagascar. Fossas hunt during both day and night, and can take prey from both the ground and in trees. Lemurs make up a good deal of their diets, but they also eat small mammals, fish, lizards, birds, frogs, and insects.

3. Their classification has been complicated. The fossa has features in common with three different families of carnivores: Herpestidae (mongooses), Viverridae (civets and their relatives), and Felidae (cats). Recent molecular studies have put the fossa in the Eupleridae family, a group that consists of Malagasy carnivores. Members of this family are thought to have descended from mongoose-like ancestors that colonized Madagascar about 20 million years ago.

4. Fossas are mainly solitary. With the exception of mothers with young and brief pairings during the breeding season, fossas are solitary animals. They patrol and defend territories as large as four square kilometers.

An exception was recorded in 2009, when scientists observed three male fossas cooperatively hunting a sifaka for 45 minutes. After they caught the prey, they shared it. The scientists believe this behavior may be a vestige of the cooperative hunting that would have been necessary to take down larger lemurs that existed in the past on Madagascar.

5. Fossas communicate largely through scent glands. Both males and females occupy territories that they scent mark with secretions from glands on their chests and under the base of their tails. Fossas mark rocks, trees, and the ground to communicate and keep track of each other. Their glands also release a pungent smell when the animal is irritated or frightened.

6. They also make several kinds of sounds. Fossas mainly vocalize during the breeding season. Females mew to attract males, and males sigh when they have found a receptive female and yowl when competing for her affections.

Photo: Chad Teer, via Wikimedia Commons. Distributed under a CC-BY-2.0 license.

7. They are agile climbers. The fossa's long, slender tail provides balance as it moves through the trees, and its semiretractable claws and flexible ankles allow it to climb up and down trees head-first. The fossa walks flatfooted on the soles of its feet, like a bear, in a method of locomotion known as 'plantigrade.' This gives them extra balance and stability when leaping from branch to branch.

8. Fossas like forests. Fossas are widespread throughout forested areas of Madasgascar, although their population densities are usually low. They can be found at elevations above 2,000 meters.

9. Female fossas are temporarily masculine. The female fossa undergoes a strange developmental stage during adolescence known as transient masculinization, unique to fossas. She develops an enlarged, spiky clitoris that resembles the male's penis, and secretes an orange substance on her underbelly which is usually only seen in mature males. Adult females lack these features. It's unclear what purpose this transient masculinization serves, but scientists hypothesize that it protects juvenile females from either sexual harassment by adult males or aggression from territorial females.

10. Fossas have an unusual mating system. A receptive female occupies a site high in a tree, below which males will congregate and compete for mating rights. She may choose to mate with several of her suitors over the next week, and bouts of copulation may last for several hours. This lengthy mating is partly due to the backwards-pointing spines on the male's penis, which results in a copulatory tie that is difficult to break. Once the first female has left, a new female will take over the mating site. The same trees are frequently used year after year. This mating system, in which a female monopolizes a site and chooses her mates, seems to be unique among carnivores.

References and Other Resources:

Cryptoprocta ferox (Fossa). Encyclopedia of Life. Accessed December 13, 2014 at eol.org/pages/347438/overview.

Hawkins, C. E. and Racey, P. A. (2005). Low population density of a tropical forest carnivore, Cryptoprocta ferox: implications for protected area management. Oryx 39(1): 35-43. doi: 10.1017/S0030605305000074.

Hawkins, C.E. and Racey, P.A. (2009). A novel mating system in a solitary carnivore: the fossa. Journal of Zoology 277(3): 196–204. doi:10.1111/j.1469-7998.2008.00517.x.

Köhncke, M. and Leonhardt, K. (1986). Cryptoprocta ferox. Mammalian Species (254): 1–5. doi:10.2307/3503919.

Lührs, M.-L. and Dammhahn, M. (2009). An unusual case of cooperative hunting in a solitary carnivore. Journal of Ethology 28(2): 379–383. doi:10.1007/s10164-009-0190-8.

Lundrigan, B. and Zachariah, T. (2000). Cryptoprocta ferox. Animal Diversity Web. Accessed December 13, 2014 at animaldiversity.org/accounts/Cryptoprocta_ferox/.

Yoder, A. D., Burns, M. M., Zehr, S., Delefosse, T., Veron, G., Goodman, S. M. and Flynn, J. J. (2003). Single origin of Malagasy Carnivora from an African ancestor. Nature 421: 734-737. doi: 10.1038/nature01303.