834 S. D. Merson et al.
impact of dogs on Madagascar’s ecosystem is still being investigated. Disease transmission from cats and dogs is a significant
threat to the long-term health of endemic species. Fatal cases of Toxoplasma gondii infection have been recorded in captive fosas (Corpa et al., 2013) and lemurs (Juan-Sallés et al., 2011; Siskos et al., 2015), highlighting their vulnerability to lethal infections. Field studies of exotic carnivores in Ankarafantsika NationalPark have identified the occurrence of multiple viruses and parasites, including canine parovirus, feline calicivirus and T. gondii (Pomerantz et al., 2016), the latter prevalent in .93% of captured wild fosas. The detri- mental impact of disease on Madagascar’s wild fosa popula- tions could be significant, reflecting disease-related species population declines elsewhere (Pedersen et al., 2007).
Habitat degradation impact on fosa occupancy
PLATE 1 Wild cats Felis sp. preying on (a) a red-fronted brown lemur Eulemur rufus and (b) a speckled hognose snake Leioheterodon geayi in Andranomena Special Reserve, Madagascar (Fig. 1).
Masoala–Makira (Murphy et al., 2018a); negative associations have also been recorded between cats and the rainforest- dwelling euplerids Galidia elegans and Fossa fossana (Gerber et al., 2012a; Farris et al., 2015b). Collectively these results sug- gest that cats are probably having a negative impact on the fosa and other endemic species, at the very least through direct pre- dation and competition for prey. In concordance with previous studies in rainforest, dogs
did not have a negative association with fosa occupancy (Gerber et al., 2012a; Farris et al., 2015b). This is in contrast with the reported impact of dogs on the euplerid Galidictis fasciata (Gerber et al., 2012a) and incongruous with the damaging effects of dogs globally (Hughes & Macdonald, 2013). However, activity pattern analyses have indicated fosas display temporal activity shifts towards greater noctur- nality (Farris et al., 2015a; Merson, 2018), and/or absence from sites with higher frequency of dog detections (Gerber et al., 2012a; Farris et al., 2015b). The sociality and size of dog packs (L.J. Dollar, unpubl. data) may be a source of interference competition for fosas, but the predatory
Fosa occupancy was higher in Andranomena Special Reserve, possibly because of greater forest cover, and lower dog and human presence. However, within ourmodels fosa occupancy was not influenced by any habitat degradation parameters, with results similar to those reported for Madagascar’srainfor- ests (Gerber et al., 2012a; Farris et al., 2015b). Despite this, sur- veys have not recorded fosas in areas.5 km from the nearest contiguous forest (Kotschwar Logan et al., 2015)orinforest fragments .2.5 km from the nearest contiguous forest (Gerber et al., 2012a). This suggests that despite their resilience to habitat degradation within contiguous forest, fosas are un- able to persist far fromintact
forest.ConsideringMadagascar’s highly fragmented forests (Vieilledent et al., 2018), it is likely that most forest areas are of insufficient size to support fosa populations in the long term (Hawkins & Racey, 2005). Cat occupancy was higher in the Reserve, positively asso-
ciated with higher vegetation cover and weakly associated with narrow trails. This could be attributed to their avoidance of larger carnivores (dogs, fosas) andpeople.Farris et al. (2015b) found similar positive associations with forest cover, possibly confirming theirpreference forareasofgreater preyabundance. Dogs had the highest occupancy in the Park. They had
a positive association with large trails, and civets, and a negative association with old-growth forest, and savannah, possibly explained by dogs accompanying people during forest-related activities. This was apparent in the Park, where the forest surrounding rural villages encompassed a mixture of savannah and degraded forest, with high pres- ence of people and exotic species (e.g. zebu, civet).
Long-term implications
Looking beyond the snapshot view of single-season occu- pancy models, recent multi-year studies in north-eastern Madagascar recorded occupancy of endemic and exotic
Oryx, 2020, 54(6), 828–836 © 2019 Fauna & Flora International doi:10.1017/S003060531800100X
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