Fossa Mammal

Fossa which is also commonly known and spelt as Foussa is scientifically known as Cryptoprocta ferox which is the largest native mammal carnivore of Madagascar. They are more cat-like in appearance and are active hunters of both days as well as nights. They are usually small and secretive dwellers and thus solely found in the forests or dense vegetative locations.  They belong to the family of civet, Viverridae that comprises 35 species of small world mammals. They are also considered in the family of carnivorans known as Eupleridae. They are also closely related to the family of mongoose known as Herpestidae. 

Mostly because of its cat-like structure its classification was quote controversial and couldn’t be recognized under one particular family. Due to its cat-like resemblance, it is also treated in close relation with Viverrides. There were many hypotheses about the number of times the carnivorous mammals have colonized Madagascar that has been primarily influenced by the fossa mammal species and other such relative carnivores. All the carnivorous mammals of the Madagascar forests are related closely to each other and often form clads and are recognized in the family of Eupleridae. According to the study it has been established that the carnivorous mammals have colonized the island once around 18 to 20 million years ago. 

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Taxonomy

Based on a specimen of Madagascar that was sent in the year 1833 by Charles Telfair, the fossa was then named Edward Turner Bennett. Through the name of the fossa is the same as that of the generic name of Malagasy Civet (Fossa fossana) but they are different species altogether. As they share the same physical characteristics as that of mongoose, viverrids and Felidae, their classification under one particular family or order is still controversial. Many of the taxonomists for a long period have classified fossa mammals as civets of the Viverridae. But because of its retractable claws, large eye sockets, compact brain and specially designed teeth for carnivores have made many of the taxonomists relate it with the felids. During the very initial years of the taxonomy study of this species, in the year 1939, William King Geoey and Milo Hellem placed the fossa mammal within its subfamily felida, the Cryptoproctinae. But in the year 1945, another taxonomist named Gayloard Simpson classified it back to Viverridae which is also its subfamily but also closely related to mammals with cat-like characteristics. 

The study published by the DNA hybridization of the fossa mammal species by a scientist named Geraldine Veron and Francois Catzflies suggested that the species must belong to the family of Herpestidae along with mongoose as it has more DNA resemblance with the same rather than any cats or civets. However, in the year 1995, the morphological study of Veron once again classified it into the group of Felidae. Finally, in the year 2003, the molecular phylogenetic study was carried out with the help of nuclear and mitochondrial genes by one of the taxonomists named Anne Yoder and the study clearly stated that all the Malagasy Carnivorous share a common ancestral trait or background that excludes the other carnivores. They have been seen as closely related to Asian and African Herpestidae. In order to put all of these into place, all Malagasy carnivores are now treated as a Eupleridae family. Within this family, Mossa is particularly classified in the subfamily Euplerinaealong with the Madagascar civet and Falanouc but the relationship between them is still faintly clear.

Description

They are the smaller form of the wild cat-like cougar but with a more muscular and slender body with a tail as long as its body. They usually have a head that is mongoose-like structure and much longer than that of a cat. They usually have a broad and short muzzle with large rounded ears. The eyes are round and separated apart from each other. The colour of their eyes is light brown with the pupil in the eye contract to a slit. Like many other carnivores that hunt at night, even the fossa mammals reflect light from eyes that are of orange hue. Its head to body length ranges from 70 to 80cm and the tail length ranging from 67 to 70 cms. There is a sexual dimorphism that can be witnessed among these mammals where the males are larger and heavier than the females. The weight of the male is around 6.2 to 8.6 kgs whereas the females are 5.5 to 6.8 kgs. The smaller species of the fossa are inhabitants of north and east Madagascar and the larger ones prefer the south and west Madagascar. Some of the individuals have even weighed around 20 kgs but their length measurements are not conformed in any study.

Both the sexes have reddish-brown fur that is quite short, straight and prevalently dense without any sports or pattern on them. During their mating season, the fur of the abdomen changes from reddish-brown to orange. It is probably due to the secretion of a chemical from a gland in their chest though the study is inconsistent song the researchers. The tail is relatively lighter in colour than the side of the species. The juvenile fossas are either grey or pure white in colour.

They are also expert tree climbers where they use their tails to strike a balance and possess semi-retractable claws that help them to climb efficiently to hunt down prey. During the arboreal locomotion, it keeps switching between the plantigrade-like walking manner but when they are terrestrial (on the ground0 they walk with all their toes and digits flat on the ground. Thus it is referred to as semi-plantigrade. Their paws are bare (that is without any fur on them) and highly cushioned and strongly padded. The ankle of fossas are very flexible that allows them to climb up and down the trees with head first position and leap from one tree to the another with much ease. The juvenile mammals that are under captivity are often seen hanging upside down from a rope with the help of their hind feet. 

Fossas have various scent glands that are developed more in males than in females. The anus skin gland is built inside a membranous sac that surrounds the anus. The pockets open with a horizontal slit to the exterior just below the tail. The other glands are located near the external genitalia. The penile glands emit a stronger odour. 

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Habit and Distribution

Though fossa has a wide range in the Madagascar islands, their density is very less in the remaining traces of forests in the islands. They mostly prefer to dwell in an undisturbed pristine forest habitat. Normally they can be seen in all the known forests of Madagascar starting from dry deciduous forests, eastern rainforest, to western and south spiny forests but they are mostly seen in humid areas than the dry ones. It is because fossa seems to travel easily in the humid forest as they provide more canopy than in dry forests. They like to dwell in most of the faunas that are from the central high plateau of Madagascar. They usually cannot survive in areas that have high habitat disturbances.

They are heavily found in the areas that are in solidarity and under high protection, that is, in most of the elevated gradients. The clear pieces of evidence of the fossas dwelling at four sites of the Reserve Naturelle Integrale d’Andringitra ranging from 810 to 1625 meters of the entire area. But the highest dwelling in the area reported is about 2000m. Similar pieces of evidence of the presence of fossas in the extreme elevation of the Andohahela National park and the dwelling area ranging from 440 to 1875 meters of the total area. With the consistency of its distribution reports throughout Madagascar, it is clear that they are easy adopters of various elevations. 

Behaviour and Diet

They are considered as cathemeral as they are equally active in both daytime and nighttime but their peak activity starts from early morning, in the late afternoon and at late night. Though they do not prefer to repeat their sleeping sites the mother fossa with her youngs often returns to her same den. In the Kirindy Forests, the home range of the males extends up to 26 Km2 whereas the females have a home range of 13 Km2. though the female home range is known to be separate from the males, the data and reports of the eastern forest claim that their habitat overlaps by 30%. Their home range usually exceeds beyond their actual range in the dry weather as there is a scarcity of the availability of food.

They are solidarity animals by nature and very rarely the pair of males or females are seen together except the mother with their cubs. Though a report that was published in the year 2009 claimed to have documented the cooperative hunting of 3 kg of sifaka by three male fossas that lasted for 45 minutes and then the prey were shared among the hunter fossas. Thus it can be derived that the cooperative hunting behaviour has diminished over time and are only used to hunt down bigger mammals. 

They usually use scents, voices and visual signals for communicating that includes loud cry as threatening calls, purring and a call of fear that is more of repeated loud course of inhalation and exhalation of breath. Fossa uses high long yelp to attract other fossas. While mating the female fossa mew while the male fossa sighs to communicate that he has found the female. They also communicate by face and body signals. Throughout the year they leave behind their sents on the rocks, trees and grounds they dwelled in. the fossas in captivity is not aggressive in nature but if disturbed the male fossa tends to bite. They are most aggressive in the wild during mating where the two males fight each other and the loser flees while the latter chase it to a short distance.

Diet of Fossa

The fossa is a carnivore that preys on small to medium-sized animals. It is known to be one of Madagascar’s largest surviving endemic as terrestrial as well as tree species. The fossas are the only known mammal that is capable of hunting down the adults of all the species that are endemic to Madagascar. They are experts in hunting down an animal that is 90% above weight compared to an average weighing fossa. They exhibit a wide range of diets that includes selective and specialized preying that depends on its habitat and season. Their diet doesn’t vary among the sexes. The population of the eastern Andringitra has been recorded preying on the widest range of animals including both the vertebrates and the invertebrates. The vertebrate preys include rodents, a wide range of birds including ground birds, reptiles, insectivores and lemures. Whereas the vertebrate preys that are consumed by fossas include insects and crabs of the high mountain zone of Andringitra. The normal diet of fossa mammal species comprises 90% of the vertebrates, 50% of lemures and the rest 9% lizards, 5% seeds and 2% birds. They also prey on domestic animals like goats, small calves and especially chickens.       

Reproduction

Fossas follow the polyandrous mating system where one female mates with multiple males of her choice. They prefer to stay in solidarity until they are in mating season that starts from September to November. During the mating season, the males and females identify the location or come in close vicinity by the scent released from their penile gland. In fossas, the female gets to choose the male where she invites them by mewing and then the males fight with each other with several vocalizations and antagonised portrayals. The female fossa mates with several males in the clad for over six weeks and the choice are not based upon the physical appearance of the male fossa. Once the process is over the female leaves for the other female to take over the cycle.

The gestation period of the female fossa lasts for three months that is approximate 90 days and they give birth to litters that may vary from 1 to 6. And 2 to 4 pups are born per litter. During the gestation period, the female fossa takes shelter in an enclosed and concealed area such as a den. The pups are finally born in December or January. The newborns are blind and toothless with weight, not more than 100 grams and thus are helpless. Their fur is thin grey-brown in colour. they open their eyes after 15 days and gradually their fur darkens to pearl-brown. The cubs are incapable of taking solid food for three months and their teeth gradually appear in 18 to 20 months. But in a year they become juvenile but till 3 to 4 months they do not leave their den.     

Fun Facts

Some of the fun facts about Fossa mammals are as follows

1. Their scientific name refers to the hidden anus.

2. Fossa mammals are the top predator of Madagascar.

3. Female fossas are more masculine than the male fossas.

Summary At a Glance

1. The classification of Fossas are very complexed due to their appearance relates to the cat family but their DNA study signifies the trait of Herpestidae

2. Their fur is straight small and brown in colour

3. Their body and tail are almost in the same ratio

4. They are the top predators of the Madagascar island where they prey both on the vertebrates and invertebrates as well as domestic animals

5. They have sexual dimorphism as the females are smaller and lighter in weight.

6. They are solitary and like to dwell in an undisturbed environment and prefers humid forests.

7. They are agile climbers and can jump from one tree to another and are also terrestrial.

8. They have unusual breeding habits where females choose to mate with different males for six weeks and then replaced them with the latter female.

9. Their breeding period is September to November with a gestation period of 90 days.

10. The cubs are born toothless and blind and cannot feed on solid food till three months.

11. They leave the den and the mother at about a year when they are juvenile.