The fossa is the largest carnivore in Madagascar and superficially resembles an elongate cat in appearance (2). The tail is almost as long as the slender, muscular body, and the fossa's coat is short and reddish-brown in colour (4). The head is fairly small, with a short muzzle and prominent ears (6). Unlike other members of the Viverridae family, the fossa walks on the soles of its feet; a method of locomotion known as 'plantigrade'. The short, retractable claws also enable efficient tree climbing (4). One of the more unique peculiarities of the fossa is the fact that adolescent females go through a 'masculinisation' phase during their development; the clitoris becomes enlarged and covered in spines thus resembling the male penis, and there is an orange secretion on their underbelly which is usually only seen in mature males (2).
Fossas are active during the day and night and, with the exception of the breeding season, they are generally solitary (6). Both males and females occupy territories, which are scent marked with anal gland secretions, and vary in size depending on the abundance of prey species (6). Fossas have an extremely unusual mating system, a receptive female will occupy a tree below which males congregate, fighting and calling to the female (2). Over the period of a week the female will mate with a number of different males, and copulation bouts can sometimes last for over 2.5 hours (4). A new female then arrives and replaces the original one, mating with the gathered males in her turn (2). The mating season runs from September to November, and between 2 and 4 young are born in a den three months after copulation (6). The young are initially blind and helpless, opening their eyes after 15 days; they remain with their mother until they are 15 to 20 months old (4).
Fossas feed on a wide variety of small mammals, birds and reptiles (4). In high mountain areas, small mammals such as tenrecs feature heavily in the diet, whilst in forest areas lemurs can make up more than 50 percent of prey items (7). The fossa's long tail provides balance for pursing this agile prey through the trees (2), and pairs may cooperate to catch larger prey (6).
Recent surveys have revealed the fossa population on Madagascar to be fewer than 2,500 individuals (1). Habitat loss is one of the main causes of decline, and fragmented populations become isolated in remaining forest patches (1). Probably the most important threat to survival however, comes from local farmers who regard fossas as serious predators of poultry (1).
Fossas are protected in a number of Madagascan reserves; they are found within the Ankarana and Analamera Special Reserves, and within the Ranomafana, Andasibe-Mantadia and Montagne d'Ambre National Parks (6). A successful captive breeding programme has also been established (1), and it is hoped that these measures will be sufficient to secure the future of one of Madagascar's most enigmatic and fascinating mammals.
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