ABSTRACT
We investigated the spatial distribution of native and invasive marmoset species (Callithrix), as well as their hybrids, in the Serra dos Órgãos National Park (PARNASO) and surrounding area in Rio de Janeiro state, Brazil. To estimate occupancy and the detection probability, we surveyed 56 sites within the park and 52 sites outside its limits using vocal playbacks, as well as by interviewing local residents in the surrounding area. We estimated the occupancy and detection probability of Callithrix aurita and the observed groups composed of Callithrix jacchus, Callithrix penicillata, and their hybrids. We also recorded the presence or absence of mixed groups of native and exotic species, and their hybrids. We recorded similar occupancy rates and detection probabilities for both native and invasive species within the national park. C. aurita was found more often within the areas of the park located furthest from access roads and with the least human interference, while invasive species were more likely to be found along the edge of the park and in areas with greater human interference. In the area surrounding the park, invasive marmosets were recorded at seven sites, and a mixed group of native and invasive marmosets was observed at one site, but non-hybrid C. aurita groups were not recorded. The occupancy probability of C. aurita in the study area is relatively low, which may indicate a low population density, with groups restricted to a small region within the PARNASO in the proximity of groups of invasive marmosets.
