Colours of Wildlife: Fossa
Created | Updated Jun 7, 2015
Fossa
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
Having had much fun in painting the Falanouc, I decided to bring you yet another of Madagascar's unique carnivores. This is indeed the most famous of them all, the Fossa, Cryptoprocta ferox. Its genus names 'Cryptoprocta' means 'hidden anus' because it has a pouch concealing that particular part of its body, while 'ferox' means 'ferocious'. It is indeed a fierce predator, the biggest on the entire island, and it eats pretty much everything else! The present-day fossa reaches an overall length of 1.5 m/5' and a bodyweight of 8.6 kg/19 lbs. Occasionally, much larger fossas are reported, up to 20 kg/44 lbs, but this is questionable. The giant fossa, a close relative that became extinct recently, did indeed grow that large. It went extinct likely due to the arrival of humans. Apart from the giant fossa, there were other giants on the island, such as gorilla-sized lemurs, giant flightless birds more than twice the size of ostriches, and several species of hippo. Some of these at least would have been prey for the giant fossa. With the arrival of humans, all the giant endemic animals were driven extinct. Today, the fossa is the largest remaining Madagascan mammal, and the Indri, which can reach a bodyweight of 10 kg/22 lbs, the largest remaining lemur.
Fossa Peculiarities
Taxonomists have in the past had difficulties classifying the fossa. It was considered a cat, then as a member of the civet and genet family, the Viverridae. Genetic studies now indicate that it belongs with all the other Madagascar carnivores in a family of their own, the Eupleridae. The falanouc is a fairly close relative. It seems all the Madagascan carnivores are descended from a handful of mongoose-like animals that reached the island from the east coast of Africa, perhaps floating there on vegetation uprooted by a storm or flood, about 18 to 20 million years ago, since when they've diversified into several quite different species, the fossa included.
The fossa is also unique in its reproductive equipment. The male is extremely well-endowed and his equipment bears some similarity to that of cats as well as mongooses. Interestingly, the female for a brief period of her life becomes masculinized, her feminine parts in her 'teenage' years resembling those of the male. This also happens in hyenas. But in them it is a permanent feature, while in the fossa it goes away again as the female grows older. The idea is that this temporary masculinity helps protect young females from the attentions of males, or that it makes them less of rivals for adult, territorial females.
Cat-like Lemur Hunter
Just looking at it, most people would consider the fossa to be a kind of cat. It most resembles the large American cat variously known as the puma, cougar, or mountain lion. It has a short, uniformly coloured, reddish brown coat. Its face is just slightly longer than that of most cats, and it has cat-like slit pupils. It is somewhat longer and lower than most cats, though, with quite a long tail. It has a peculiar carriage: it can walk flat on the soles of its feet, like a bear, or on its toes, like a cat. It uses the flat-footed mode when climbing or walking around in trees, but the toe-tip walk when it's on the ground. This switchability is called a semiplantigrade gait.
The feet of the fossa are indeed very well adapted to climbing. It has retractile claws on all four paws. Unlike cats, though, the claws don't fully retract into sheaths that cover them, but they're lifted well of the ground while the fossa walks, so keeping them sharp. When extended, they provide an excellent grip on bark. The fossa also has very flexible ankles, and it can climb down from trees head downward. It can even hang from branches from its hind feet!
All of this dexterity is vitally necessary when the fossa pursues its favourite prey, lemurs! Lemurs are monkey-like primates that only occur on Madagascar and the nearby Comoro Islands. They are all very adept climbers, having monkey-like grasping hands and feet, and long hind legs by which they can jump great distances. Fossas, pursuing these lemurs through the forest canopy, also frequently need to jump from branch to branch. Their chief tactic, however, is to try to force the lemurs to the ground, where they can catch them much more easily. Fossas sometimes hunt together in pairs, or parents together with their recent offspring, or occasionally a few males will hunt cooperatively.
Lemurs come in a huge variety of shapes and sizes, from the tiny mouse-lemurs to the indri. Fossas can kill the largest of the lemurs, but often takes the smaller ones also. Apart from lemurs, they also eat some other Madagascan mammals like tenrecs and rodents. They also eat reptiles, like the wonderful chameleons and geckoes of the island, birds, and invertebrates like insects and crabs. They ingest a small amount of plant material, probably as the stomach contents of their prey. Fossas hunt by day and by night. They're therefore quite adaptable, diet-wise, a factor that has enabled them to survive until today in spite of the many ways humans have changed the island and its environments.
Making Baby Fossas
Fossa reproduction has not been much studied in the wild, most of what we know coming from the fossas in western Madagascar rather than those of the moist, eastern rainforests. They apparently mate in trees, which is a bit of a balancing act! They're rather promiscuous. Several males will gather around a receptive female, and she might chose more than one of them to mate with. The mating act can go on for three hours! The male's remarkable equipment causes them to be locked together for a time.
The female fossa gives birth to a litter of one to six babies in a den, situated in a natural hollow or one she digs herself. Newborn fossas are blind and helpless. Their eyes open at the age of two weeks, at which point they are adorable and very much like kittens. Their fur starts out grey and turns reddish as they grow towards adulthood. Fossas are physically adult at about two years, but sexually mature at around four. They can live for twenty years.
Fossas are fairly endangered. They have lost much habitat because of the forests of the island having been cut down or burnt to make way for human villages and farms. They are occasionally killed by people because they prey on chickens, goats, piglets and other domestic animals. But they're also protected by some traditional ideas. Fossas are thought to scavenge on dead human bodies, and this makes them taboo to eat. Today fossas are also conserved in some of Madagascar's national parks, but since they occur at low densities, this may not be sufficient to ensure the survival of all populations. They're also present in a few zoos, where they are bred to boost their numbers.
