Meet the fossa

Photo by Mathias Appel. Retrieved from Flickr on 07/06/2022.

When I was in 7th grade, I had to do a social studies project on a country. The country I picked was Madagascar. It was here that I learned about the majestic fossa, and I’ve loved them ever since.

These mammals are exclusive to the island of Madagascar. Fossa look like small cougars – sleek and cat-like. They’re also pretty big; from tip to tail, a fossa can be up to 72 inches long (in comparison, an average bed is 74 inches). The tail makes up almost half of this length.

Also: fossa are cute!!

Long boi. Photo by Ran Kirlian. Retrieved from Wikipedia on 07/06/2022.

What’s in a name

Like many animals, we can learn a lot about fossa from their scientific name, Cryptoprocta ferox. The first part, Cryptoprocta, refers to a specific part of the fossa’s anatomy: their butt. Crypto means “hidden” in Ancient Greek, while procta means “anus.” That’s right – the fossa’s anus is hidden by their anal pouch.

Which leads to the question: what is an anal pouch?

Anal pouches, or anal sacs, are the part of the body that contains the anal glands. Fossa mark their territory by releasing a liquid from their anal glands and rubbing it on things like trees and rocks. This scent is primarily how the usually solitary fossa communicates – they can keep track of each other through this scent marking. Fossa will also release scent when they are scared or irritated.

Oh, and the second part of the fossa’s name, ferox? It’s the Latin adjective for “fierce” or “wild.”

So fierce. Photo by Cloudtail the Snow Leopard. Retrieved from Flickr on 07/06/2022.

Cat? Dog? Weasel?

What type of animal is a fossa, exactly? They do look a lot like a cougar, and they have some dog- and weasel-type features. For a while, it was an open question about where exactly to classify fossa. They’ve been placed over the years in the civet family (Viverridae), the cat family (Felidae), and the mongoose family (Herpestidae).

We now have the molecular tools available to categorize the fossa based on their genetics. Today, fossa are part of the family Eupleridae. This family contains all 10 living species of carnivorous mammals in Madagascar, like the Malagasy civet and brown-tailed mongoose. We think based on molecular evidence that all of these species evolved from a mongoose-like ancestor that rafted over from Africa 18 – 24 million years ago.

Every time is hunting time

Fossa are what is known as “cathemeral.” This was a new word for me – organisms that are cathemeral may be active in the day or night (unlike nocturnal animals that are active mostly at night or diurnal animals that are active mostly in the day). Cathemeral animals include lions, coyotes, and lemurs, and cathemerality may be driven by things like the availability of food and the ambient temperature.

This means that fossa can be active at really any time of the day; however, they tend to be most active in the morning, in the late afternoon, and late at night. In between these hunting periods, fossa will sleep and rest.

Nap time. Photo by Yinan Chen. Retrieved from Wikipedia on 07/06/2022.

Top of the food chain

Fossa are the top terrestrial predator in Madagascar. They are the largest terrestrial predator, and the only predator capable of hunting all species of lemurs living on the island. This is impressive, because the largest lemur species (the Indri) can weigh up to 90% of the fossa’s weight.

Part of the fossa’s hunting success has to do with their adaptations to being in trees. Their long tail provides them balance as they jump from tree to tree. Their claws are semi-retractable, so they are always somewhat out and ready to grip on tree branches or prey. Fossa ankles are super flexible, so they can quickly move headfirst down a tree trunk if needed.

Because of their ease in the trees, fossa can easily chase prey like lemurs through the trees and force them to the ground. While fossa are generally solitary, they sometimes hunt in groups during the breeding season – one individual will force the prey to the ground from the trees where the others will attack.

Temporary psuedo-penises

Remember the psuedo-penis that female spotted hyenas have? The enlarged clitoris that looks like a male penis? Well, spotted hyenas aren’t the only species to have them; fossa do, too.

But unlike the spotted hyena, a female fossa’s psuedo-penis is temporary. During adolescence, female fossa undergo what is known as transient masculinization. Their clitoris grows larger and spiky, resembling a male’s penis. However, as they continuing growing up and reach sexual maturity, this psuedo-penis disappears and becomes a regular clitoris in adulthood.

Fossa are the only species that undergo this transient masculinization and have their psuedo-penis diminish in size. We think that having this psuedo-penis as an adolescent may help females avoid unwanted sexual attention and aggression from males and/or territorial aggression from adult females.

The Mating Tree

Fossa mating is interesting. They have a mating tree. And I mean that literally. Females will sit in a tree while males will compete for mating rights among themselves on the ground. These mating trees are used year after year.

The female watches the competition and choses a male to mate with. She may mate with him multiple times and then pick another male to mate with her next. This mating process of picking males takes place over about a week. Because the female is choosing and mating with multiple different males, fossa are classified as being polyandrous.

The actual copulation is actually quite a lengthy process and can last for several hours. You see, male fossa have backward-facing spines on their penis. These spines reinforce the copulatory tie between males and females. A copulatory tie is most often seen in canines and is when the male and female are “tied” together until the penis becomes flaccid and can be removed. However, unlike canines, fossa can break the copulatory tie with some effort if needed.

After a week or so of mating, the female fossa leaves the mating tree and the next female takes residence.

Oh, and one other place you may remember seeing fossa? The 2005 film Madagascar. Fossa are the main antagonists in the film! But for some reason, the film didn’t go into all the details about fossa that you just learned here…



San Diego Zoo


Animal Diversity Web

Leave a Reply

%d bloggers like this: