Range Extension for Critically Endangered Sapajus xanthosternos, with Observations of Stone Tool Use at the Lower Limit of Habitat Suitability
摘要
Accurate knowledge of species distributions improves prioritization of conservation actions. Where the distributional limits of a species are poorly known, climatic and geographic characteristics for known species sites can be leveraged to model its fundamental niche and potential geographic range and to focus fieldwork to validate the species presence. Sapajus xanthosternos is a Critically Endangered platyrrhine endemic to Brazil, which occurs in both Atlantic Forest and in Mata Seca (Dry Forest) regions. We aimed to determine the southwestern distributional limit of S. xanthosternos, in a drier region in northern Minas Gerais. We used niche modeling to identify municipalities in northern Minas Gerais state to target fieldwork based on predicted habitat suitability and forest patch size. We interviewed local experts in 11 municipalities to determine fragments to visit. We used capuchin playback vocalizations in ten fragments and added camera traps to improve our sampling effort in three of those locations. We found S. xanthosternos at six new sites, which increased the species distribution by ~19,210 km2; we also found wild S. nigritus in Santo Hipólito municipality in Minas Gerais, farther north than its currently recognized distribution. We found evidence for S. xanthosternos stone tool use at five new sites, including two sites within the range expansion. Our study reinforced previous evidence that stone tool use by S. xanthosternos occurs exclusively in Mata Seca habitats, and our ecological niche modeling results showed that this habitat has the least suitable climate that still sustains this species. This led us to hypothesize that tool use allows S. xanthosternos to subsist in this relatively hostile region. We used the updated ecological niche modeling data to compare niche suitability at sites with and without evidence for tool use (including those from the literature and our newly discovered sites) and found that stone tool use was restricted to populations in the most unsuitable environments, supporting our hypothesis. Our study provides evidence that cultural innovation might expand ecological niche limits for a primate that uses tools only in the part of its range that is drier, hotter, and has longer dry seasons.