Creature Feature: Fossa

When we think about top predators around the world, several iconic species come to mind: mountain lions, great white sharks, leopards, jaguars, tigers, and the list goes on. Yet, in Madagascar, the 4th largest island in the world that has been isolated from other landmasses for the past 80 million years, the top predator is, well…maybe not as seemingly ferocious. Looking like a cross between a dachshund and a cat, the fossa (Cryptoprocta ferox) is most closely related to the mongoose family. Although most mongoose species are relatively small, fossa can weigh up to 6.8 kg for females or 9.9 kg for males, with a body length of 70 – 80 cm and a tail that’s about as long (up to 70 cm) [1]. While this may seem relatively small for a top predator, up until recently there existed a much larger fossa species (Cryptoprocta spelea) on Madagascar which is thought to have hunted the now-extinct subfossil lemurs [1].

Fossa are rather atypical looking carnivorous top predators. Although they resemble cats, these mammals are more closely related to mongooses. [Photo taken by: Rod Waddington, Source]

As apex predators in their forest habitats, fossa will prey on a variety of animals including lemurs, birds, rats, snakes, lizards, tenrecs, and insects. They appear to have a relatively flexible diet, sometimes specializing on lemurs [2, 3], sometimes on birds [4]. Their diet can also change seasonally [5-7], meaning that predation risk for various prey species is also seasonally-dependent. Prey species are captured based on their abundance, meaning that predation risk for tenrecs and fat-tailed dwarf lemurs is lower during their hibernation periods in the austral winter and higher when they emerge in the austral summer. (Note: Since Madagascar is in the southern hemisphere, the seasons are reversed compared to landmasses in the northern hemisphere; i.e., austral summer occurs during winter in the northern hemisphere). Correspondingly, predation pressure on diurnal lemurs such as Verreaux’s sifaka is higher in the austral winter [3].

Fossa are endemic to Madagascar. Here’s a coarse view of their spatial distribution (in red) on the island, at a 10 km resolution. [Adapted from Di Marco et al. (2016) Journal of Applied Ecology].

Fossa frequently prey on lemurs as large as sifaka (some species can grow up to 6-7 kg), quite a feat for a relatively small-bodied predator! Fossa can consume a considerable proportion of their prey population each year. In fact, in western Madagascar, fossa are annually estimated to eat 13% of the Verreaux’s sifaka population (which includes 33% of the infants born) [3,8] and 18% of the mouse lemur population [3]. Since fossa are capable of hunting both on the ground and in the trees, thanks to their long tail and retractable claws which provide balance, prey such as Verreaux’s sifaka often sleep together in the tallest trees. These sleep site trees can only be accessed by leaping onto them from nearby trees, which helps to protect sifaka from fossa on the prowl. Despite such behavioral defenses, fossa still capture lemurs like the Milne Edwards sifaka in the rainforest at night, particularly during the dark phases of the moon [7].

Sifaka, like many lemur species, have a peculiar mode of locomotion that involves vertical clining and leaping from tree to tree. When they move on the ground, they resemble cautious and comical ballet dancers [Source: BBC Earth]

Fossa are often described as cathemeral, meaning they tend to be active throughout the 24-hour cycle; however, there seem to be peaks in their activity around dawn and dusk. This means they are important predators for both diurnal (day-living) and nocturnal (night-living) animals. In fact, this cathemeral activity pattern is thought to have partially driven the evolution of cathemerality in the Lemuridae family [9], particularly in brown lemurs and bamboo lemurs [10-11].

Like many carnivores, fossa are generally thought to be solitary outside of the mating season. Females defend individual territories, and males patrol areas that overlap with multiple female territories [12]. However, recent research has demonstrated that fossa are more social than previously thought. While females are generally solitary, a subset of males associate in stable dyads or pairs, share a territory, and often maintain close spatial proximity with each other [13]. In rare cases, male fossa have been observed to be hunting together [14]. While the exact cause of this social strategy isn’t fully understood, the social males are often related to each other and may be able to jointly defend females during mating season [15]. Fossa have a highly unusual mating system in which females occupy mating trees and mate with multiple males over the course of several days [16]. This bizarre mating ritual means that males are highly competitive; so two male fossa together may be able to defend a female from other solitary males, increasing their own chances passing on their genes.

This is a female fossa. Note how well camouflaged she is against the dry leaf litter on the ground. No doubt this dull coloration helps fossa sneak up on unsuspecting prey [Photo taken by Damien Caillaud, Kirindy-Mitea National Park]

Due to their elusive nature and low population densities, studying these creatures in the wild has historically been challenging. Previous studies have relied on indirect evidence (such as scat samples) to understand their diet and ranging patterns. Increasingly, scientists are using a variety of telemetry techniques to track individual animals to learn about their ranging behaviors, associations with other fossa, and more. Scientists have also co-opted camera trap technology to monitor fossa populations across Madagascar. Originally used by hunters, camera traps are automatically triggered to take picture or video whenever anything passes in front of them. From these images, scientists and conservationists can monitor animal population sizes, ranging behaviors, and much more.

Camera traps are increasingly being used by scientists and conservationists all over the world to monitor elusive top carnivores like fossa (picture in inset k). [Image taken from Rich et al. (2017) Global Ecology & Biogeography]

As with much of Malagasy wildlife (and particular mammals), fossa are threatened by anthropogenic change and considered vulnerable by the IUCN. As Madagascar’s forests disappear, fossa and other wildlife are brought closer and closer to human settlements. Fossa are known to kill livestock and raid eggs from local villages, causing conflict with local people who depend on these resources [17]. Besides this direct conflict, fossa are generally found at low densities throughout the eastern rainforests and western dry forests of Madagascar [18]. As the forests become more fragmented, there are fewer habitats large enough to maintain  genetically-viable fossa populations. Based on captures of fossa in western Madagascar, it is estimated that none of Madagascar’s 46 protected areas support a large enough fossa population [18]. While more studies need to be conducted to confirm these conclusions— particularly in the rainforests—this is certainly alarming for conservationists.Yet, all is not lost for fossa. Fossa in northern Madagascar are easily able to cross human-settled areas that are up to 15 km wide and their densities are relatively similar across degraded and pristine forest [19]. This means that they may be more resilient than their lemur prey, which often suffer in fragmented landscapes [20-21]. Thus, although they do not resemble what we often think of as classic top predators, fossa may continue to rule the forests they inhabit for the foreseeable future.


This Creature Feature comes to us from ABGG graduate student Meredith Lutz, who is currently in the field in Madagascar chasing after lemurs, which she studies for her dissertation research.


References:

Main featured image taken by Damien Caillaud in Kirindy-Mitea National Park.

1. Goodman et al. (2012) Les Carnivora de Madagascar. Association Vahatra Guides Dur La Diverstié Biologique de Madagascar.

2. Rasoloarison, R.M., Rasoloandrasana, B.P.N., Ganzhorn, J.U., & Goodman, S.M. (1995). Predation on vertebrates in the Kirindy Forest, western Madagascar. Ecotropica, 1, 59-65.

3. Hawkins, C.E., & Racey, P.A. (2008). Food habits of an endangered carnivore, Cryptoprocta ferox, in the dry deciduous forests of western Madagascar. Journal of Mammology, 89, 64-74.

4. Goodman, S.M., Langrand, O., & Rasolonandrasana, B.P.N., (1997). The food habits of Cryptoprocta ferox in the high mountain zone of the Andringitra Massif, Madagascar (Carnivora, Viverridae). Mammalia, 61, 185-192.

5. Goodman, S.M., O’Connor, S., & Langrand, O. (1993). A review of predation on lemurs: Implications for the evolution of social behavior in small, nocturnal primates. In: Lemur social systems and their ecological basis, pp. 51066. Springer.

6. Dollar, L., Ganzhorn, J.U., & Goodman, S.M. (2007). Primates and other prey in the seasonally variable diet of Cryptoprocta ferox in the dry deciduous forest of western Madagascar. In Primate anti-predator strategies (eds. S.L. Gursky, & K.A.I. Nekaris), pp. 73-76. Springer US: New York.

7. Wright, P.C., Heckscher, S.K., & Dunham, A.E. (1997). Predation on Milne Edward’s sifaka (Propithecus diadema edwardsi) by the fossa (Cryptoprocta ferox) in the rain forest of southeastern Madagascar. Folia Primatologica, 68, 34-43.

8. Ganzhorn, J.U. & Kappeler, P.M. (1996). Lemurs of the Kirindy forest. Primate Report, 46, 257-274.

9. Colquhoun, I.C. (2006). Predation and cathemerality. Folia Primatologica, 2, 143–165.

10. Donati, G., Baldi, N., Morelli, V., Ganzhorn, J.U., & Borgognini-Tarli, S.M. (2009). Animal Behavior, 77, 317–325.

11. Eppley, T.M., Ganzhorn, J.U., & Donati, G. (2015). Behavioural Ecology and Sociobiology, 69, 991–1002.

12. Hawkins, C.E. (1998). The behaviour and ecology of the fossa, Cryptoprocta ferox, (Carnivora: Viverridae) in a dry deciduous forest in western Madagascar. PhD thesis, University of Aberdeen.

31. Luhrs, M.L. (2012). Social organisation and mating system of the fosa (Cryptoprocta ferox). PhD thesis, University of Gottingen.

14. Luhrs, M.L., & Dammhahn, M. (2010). An unusual case of cooperative hunting in a solitary carnivore. Journal of Ethology, 28, 379-383.

15. Hawkins, C.E., & Racey, P.A. (2009). A novel mating system in a solitary carnivore: the fossa. Journal of Zoology, 277, 196-204.

16. Albignac, R. (1970). Notes ethologiques sur quelques carnivores malgaches : le Cryptoprocta ferox (Bennett). Terre et Vie. 24, 395-402.

17. Merson, S. D. (2017). Bushmeat hunting, retaliatory killing, habitat degradation and exotic species as fossa (Cryptoprocta ferox) conservation. Ph.D. thesis, University of Oxford.

18. Hawkins, C. E., & Racey, P. A. (2005). Low population density of a tropical forest carnivore Cryptoprocta ferox: Implications for protected area management. Oryx, 39, 35-43.

19. Gerber, B., Karpanty, S.M., Crawford, C., Kotschwar, M., & Randrianantenaina, J. (2010). An assessment of carnivore relative abundance and density in the eastern rainforests of Madagascar using remotely-triggered camera traps. Oryx, 44, 219-222.

20. Irwin, M.T. (2008). Feeding ecology of Propithecus diadema in forest fragments and continuous forest. International Journal of Primatology, 29, 95–115.21. Irwin, M.T., Junge, R.E., Raharison, J.L., & Samonds, K.E. (2010). Variation in physiological health of diademed sifakas across intact and fragmented forest at Tsinjoarivo, eastern Madagascar. American Journal of Primatology, 72, 1013-1025.

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