Fosas in Madagascar’s deciduous forests 829
FIG. 1 (a) Forest cover (shaded) and location of study sites in north-west and western Madagascar where the camera-trap surveys were conducted during 2014–2015, with location of camera traps in (b) north-west Ankarafantsika National Park and (c) western Andranomena Special Reserve.
(Gardner, 2009;Irwin et al., 2010).With these species now fa- cing greater anthropogenic disturbance, understanding this relationship is more important than ever. This study investigated the effects of anthropogenic dis-
turbance on fosas living in deciduous forest. Surveys were conducted in two forests, Ankarafantsika National Park and Andranomena Special Reserve, contrasting in degra- dation, forest cover and human occupation. Our objectives were to examine (1) the effects of human and exotic species presence on fosa occupancy, (2) the effects of various land- scape variables (measures of forest degradation) on fosa occupancy, and (3) differences in fosa occupancy between the two forests.
Study area
Ankarafantsika National Park is Madagascar’s largest continuous dry deciduous forest (1,350 km2; Fig. 1). The 37.73 km2 study site within the Park includeses four villages and is characterized by old-growth forest (defined as continuous forest that has experienced some human disturbance), savannah, raffia plantations and rice fields. It is used recurrently by local people and frequented by exotic species, including the zebu Bos primigenius indicus, free-ranging dogs Canis lupus familiaris and cats Felis sp., bushpig Potamochoerus larvatus, small Indian civet Viver- ricula indica, and another endemic carnivore, the western falanouc Eupleres major (Merson et al., 2018). Andranomena Special Reserve (64 km2) is located in the
central-western region of Menabe. The 35.45 km2 study site within the Reserve encompasses contiguous, mostly old- growth forest, with two villages on its boundary. The area is bisected by a grid system of trails established by the former
Forestry Commission (Fig. 1). Despite the cessation of commercial logging, widespread illegal logging was evident throughout the study site. The Reserve is home to another euplerid, the endemic bokiboky Mungotictis decemlineata.
Methods
Eighty pairs of camera traps (Cuddeback Ambush IR 1187, De Pere, USA) were placed along trails in Ankarafantsika National Park for 80 days during April–June 2014), and in Andranomena Special Reserve for 35 days during May– June 2015. Trails were chosen to maximize the detection of fosas and exotic species for occupancy analysis (O’Connell et al., 2010). Camera stations were c. 500mapart, improving the detection of E. major and M. decemlineata, which have smaller home ranges than C. ferox. Stations were set up fol- lowing the methodology of Gerber et al. (2012a). Pairs of in- dependently operated cameras were placed flanking trails, 20–30 cm above the ground, to improve detection and ac- count for potential camera-trap failure. Camera stations op- erated for 1–3months to ensure sufficient datawere collected, and to minimize violation of the assumption of population closure for occupancy modelling (MacKenzie, 2006).
Analysis
We used occupancy modelling to investigate the effects of camera-station level, landscape-level and species-level (i.e. species presence) variables on the probability of fosa presence (MacKenzie & Nichols, 2004). Photographic data were converted into detection histories (1, detection; 0, non- detection) for the fosa, and for key exotic species (Table 1)
Oryx, 2020, 54(6), 828–836 © 2019 Fauna & Flora International doi:10.1017/S003060531800100X
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