It’s a lemur’s worst nightmare: Lithe, powerful, alert, and extraordinarily agile, the fossa is one of the world’s ultimate carnivores. But despite this animal’s physical attributes and hunting prowess—it can kill lemurs and other prey nearly as large as itself—until recently, most people had never heard of the fossa. That changed in 2005, thanks to the DreamWorks animated film Madagascar. In the movie, fossas strike fear into the lemurs and other native Malagasy wildlife—with good reason. In many areas, lemurs make up 50 percent or more of the fossa’s diet.
The largest mammalian carnivore in Madagascar, the fossa has a cat-like body, a dog-like muzzle, and prominent eyes and ears. An adult weighs 15 to 25 pounds and averages four and a half feet long. Its wonderfully long tail is nearly half the animal’s overall length and helps the fossa maintain balance in trees, where it spends a significant amount of time resting and hunting. Other adaptations for a partially arboreal lifestyle include semi-retractable claws, extended pads on large paws, and “reversible” ankles that enable this mammal to grasp small branches and hang from its hind feet or descend from trees headfirst.
In addition to lemurs, fossas eat tenrecs (shrew-like animals), rodents, snakes, and invertebrates. They will also take domestic poultry and other small livestock, which puts them into conflict with humans—their only predator other than perhaps, the Nile crocodile.
People often kill fossas because of the threat, largely perceived, they pose to livestock. But the most serious problem fossas face is habitat loss. Humans have inhabited Madagascar for more than 2,000 years. Currently, the population exceeds 19 million, nearly half of whom are under age 15. According to WCS-Madagascar director Helen Crowley, the livelihoods of most Malagasy depend heavily on forests. They clear and burn tracts for farming and harvest forest plants and animals for food. Meeting the basic needs of the increasing population has resulted in an alarming rate of deforestation. Today, only 10 to 15 percent of the island remains forested.
Fossas live in a variety of habitats, ranging from tropical humid forests to deciduous dry forests, from coastal lowlands to elevations of 6,500 feet. They probably exist at low population densities regardless of forest type.
Clare Hawkins and Paul Racey, both with Scotland’s University of Aberdeen, spent three years marking and recapturing fossas in Kirindy Forest, a dry deciduous landscape in southwestern Madagascar. They found fossas at a density of roughly one adult per two square miles. It is reasonable to assume that fossa densities are higher in humid forests because there is more prey and the protective cover is greater. However, WCS field biologist Christopher Holmes, who works in Makira in the northeastern part of the country, says the dense vegetation in humid forests makes studying this elusive predator and getting reliable population estimates very difficult.
Fossas appear to be solitary, except during the breeding season, and they can be active during the day and in the evening. Females have home ranges of approximately four square miles, and males are thought to have territories nearly twice as large. They roam smaller areas in the rainy season than during the dry season because there is more food and water available at that time.
The mating season lasts from October through December. Males apparently compete for a female in estrus, and she may copulate with more than one male. In the wild, scientists observed an estrous female sitting in a tree, with multiple males soliciting her. Mating in trees has been seen so infrequently that it’s difficult to say if it is the exception or the rule. But in zoos, fossas will mate above the ground.
After a gestation period of six to seven weeks, the female fossa delivers a litter of two to four, occasionally up to six, offspring. The pups are born in a den in a tree hollow or underground, and the female raises them alone. Pups weigh about three and a half ounces at birth, and their physical development is slow. They do not open their eyes for 16 to 25 days and do not begin eating meat until they are three months old. Weaning takes place at approximately four months, but the youngsters are not independent until at least one year of age. Fossas reach adult size at two years and are sexually mature when three to four years old. In zoos, fossas have lived to be more than 20.
The best chance for the fossa’s long-term survival in the wild is probably on the Masoala Peninsula in northeastern Madagascar. In the mid-1990s, WCS worked with Malagasy wildlife officials and the government to set aside an 840-square-mile region of tropical humid forest as Masoala National Park, the country’s largest national park. With dense vegetation and a healthy amount of prey, Masoala is ideal for fossas.
WCS also works in the adjoining Makira Forest—1,430 square miles of similar habitat (see “Makira,” December 2007). According to Holmes, the Makira-Masoala landscape, which covers more than 2,315 square miles, provides the last intact area that can support a viable fossa population. Crowley notes that more than 50 percent of Madagascar’s floral biodiversity occurs there. She also believes that Makira’s forests serve as a critical connection between Masoala National Park and the Anjanaharibe-Sud Special Reserve—a genetic corridor protecting the ecological integrity of one of the most diverse areas of Madagascar.
But even this vast landscape does not secure the fossa’s future. More than 100 villages and a mix of forested and agricultural lands surround Makira. Fossas require large tracts of undisturbed forest, so they move through homesteads and forest-edge villages, sometimes killing livestock. Supported by WCS, Christopher Golden investigated bushmeat hunting around Makira in 2004–’05 and found that villagers commonly targeted fossas. He concluded that hunting of fossa there is unsustainable.
Holmes and others at WCS-Makira are working with the Madagascar Ministry of Environment, Water, and Forest to improve conditions for villagers and help local communities sustainably use their natural resources. They are also studying the nature and extent of fossa-human encounters. Information from this research is critical to developing management policies that will reduce conflict. One strategy would be to compensate villagers for livestock losses proven to result from fossa predation. This would encourage tolerance of fossas around farms and bolster community support for conservation.
What is it like to come face to face with a fossa? Bronx Zoo visitors will be able to watch these magnificent predators prowl the Masoala exhibit in Madagascar!, which is scheduled to open on June 19. Their exhibit replicates Masoala’s humid forest, rocky cliffs, arboreal pathways, and dense vegetation. Fewer than 40 fossas live in 12 North American zoos, so plan a visit soon to see these conservation ambassadors and help us raise awareness of the plight of their wild cousins.
Patrick Thomas is general curator at WCS’s Bronx Zoo. He wrote about the zoo’s African wild dog exhibit in our June 2006 issue.
