Effects of habitat alteration and disturbance by humans and exotic species on fosa Cryptoprocta ferox occupancy in Madagascar's deciduous forests SAMUEL D. MERS O N,LUKE J. DOL LAR
CEDRI C KAI WEI TAN and DAV I D W. MAC D O N A L D
Abstract Anthropogenic habitat alteration and invasive species are threatening carnivores globally. Understanding the impact of these factors is critical for creating localized, effective conservation programmes. Madagascar’s Eupleridae have been described as the least studied and most threatened group of carnivores.We investigated the effects of habitat deg- radation and the presence of people and exotic species on the modelled occupancy of the endemic fosa Cryptoprocta ferox, conducting camera-trap surveys in two western deciduous forests, Ankarafantsika National Park and Andranomena Special Reserve. Our results indicated no clear patterns be- tween habitat degradation and fosa occupancy but a strong negative association between cats Felis sp. and fosas. Cat occu- pancy was negatively associated with birds and positively as- sociated with contiguous forest and narrow trails. In contrast, dog Canis lupus familiaris occupancy was best predicted by wide trails, degraded forest and exotic civets. Our results sug- gest fosas are capable of traversing degraded landscapes and, in the short term, are resilient to contiguous forest disturb- ance. However, high occupancy of cats and dogs in the land- scape leads to resource competition through prey exploitation and interference, increasing the risk of transmission of potentially fatal diseases. Management strategies for exotic carnivores should be considered, to reduce the widespread predation of endemic species and the transmission of disease.
Keywords Ankarafantsika, deforestation, Eupleridae, fosa, feral cat, habitat degradation, invasive species, Menabe
Supplementary material for this article is available at
https://doi.org/10.1017/S003060531800100X
Introduction
ecosystems across Madagascar as an apex predator of lemurs, small mammals, reptiles and birds (Dollar et al., 2007; Hawkins & Racey, 2008). Weighing 6–7 kg (Hawkins, 1998; Dollar, 2006), male fosas have been estimated to occupy large home ranges of up to 50 km2 (Lührs & Kappeler, 2013) at low densities of 0.18–0.26 per km2 in deciduous forests (Hawkins & Racey, 2005) and 0.20 per km2 in rainforests (Murphy et al., 2018b). Currently categorized as Vulnerable on the IUCN Red List (Hawkins, 2016), fosas are threatened by bushmeat hunting (Golden, 2009; Farris et al., 2015b;Merson, 2018), retaliatory killing in response to poultry predation (Hawkins, 2016; Merson, 2018), exotic species (Gerber et al., 2012b; Farris et al., 2015c) and habitat loss (Gerber et al., 2012a; Farris et al., 2015b). Deforestation has significantly reduced Madagascar’s
T
overall forest cover, and much of the remaining forest is severely degraded (Allnutt et al., 2013; Vieilledent et al., 2018). However, there has been little research on the effects of anthropogenic disturbance on Madagascar’s endemic species (Irwin et al., 2010). In addressing these empirical deficits, the fosa is a useful focal species because its innate biological characteristics (large body size and home range, low population density) make it potentially more suscep- tible to human-caused extinction (Ripple et al., 2014). Research documenting the fosa’s persistence in human-
SAMUEL
D.MERSON (Corresponding author,
orcid.org/0000-0003-1544-4790)
Zoological Society of London, Outer Circle, Regent’s Park, London,NW1 4RY, UK. E-mail
samuel.merson@
zsl.org
LUKE
J.DOLLAR* Nicholas School of the Environment, Duke University, Durham, North Carolina, USA
CEDRIC KAIWEI TAN and DAVID
W.MACDONALDWildlife Conservation Research Unit, Department of Zoology, University of Oxford, The Recanati–Kaplan Centre, Tubney House, Tubney, UK
*Also at: Department of Environment & Sustainability, Center for the Environment, Catawba College, Salisbury, North Carolina, USA
Received 15 January 2018. Revision requested 16 April 2018. Accepted 24 July 2018. First published online 21 May 2019.
disturbed landscapes is mostly limited to Madagascar’s east- ern rainforests. Camera-trap studies have reported broad patterns of lower native, and higher exotic carnivore occu- pancy in more degraded forests (Gerber et al., 2012a; Farris et al., 2014, 2015b; Murphy et al., 2017). However, despite these advances in the knowledge of anthropogenic distur- bance in eastern Madagascar, no similar research has yet been published from Madagascar’s deciduous forests, a glo- bally important, threatened ecoregion (Waeber et al., 2015). Deforestation inwestern Madagascar has reduced much of
its deciduous forest cover (Scales, 2012), with high annual rates of loss continuing (Zinner et al., 2014). Many narrow-ranged endemic taxa occupy these forests (Waeber et al., 2015), and are potentially capable of responding differently to anthro- pogenic change in rainforests compared to deciduous forests
Oryx, 2020, 54(6), 828–836 © 2019 Fauna & Flora International doi:10.1017/S003060531800100X
he fosa Cryptoprocta ferox is Madagascar’s largest endemic carnivore. The species plays a critical role in
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