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Significance. Primates from the Americas and Madagascar are predominantly arboreal but occasionally descend to the ground. This increased ground use was associated with multiple ecological drivers, including increased temperature and a decrease in canopy cover, as well as species-specific traits, including a dietary shift away from fruits and larger group size. As anthropogenic impacts to habitats and climate worsen, our results suggest that diurnal species already inhabiting hot, sparsely canopied sites, and exhibiting more generalized diets, are more likely to shift toward greater ground use., Among mammals, the order Primates is exceptional in having a high taxonomic richness in which the taxa are arboreal, semiterrestrial, or terrestrial. Although habitual terrestriality is pervasive among the apes and African and Asian monkeys (catarrhines), it is largely absent among monkeys of the Americas (platyrrhines), as well as galagos, lemurs, and lorises (strepsirrhines), which are mostly arboreal. Numerous ecological drivers and species-specific factors are suggested to set the conditions for an evolutionary shift from arboreality to terrestriality, and current environmental conditions may provide analogous scenarios to those transitional periods. Therefore, we investigated predominantly arboreal, diurnal primate genera from the Americas and Madagascar that lack fully terrestrial taxa, to determine whether ecological drivers (habitat canopy cover, predation risk, maximum temperature, precipitation, primate species richness, human population density, and distance to roads) or species-specific traits (body mass, group size, and degree of frugivory) associate with increased terrestriality. We collated 150,961 observation hours across 2,227 months from 47 species at 20 sites in Madagascar and 48 sites in the Americas. Multiple factors were associated with ground use in these otherwise arboreal species, including increased temperature, a decrease in canopy cover, a dietary shift away from frugivory, and larger group size. These factors mostly explain intraspecific differences in terrestriality. As humanity modifies habitats and causes climate change, our results suggest that species already inhabiting hot, sparsely canopied sites, and exhibiting more generalized diets, are more likely to shift toward greater ground use.

Human impacts on the natural world are increasing and are generally considered a threat to wildlife conservation and the persistence of species. However, not all human activities are antithetical to conservation and not all taxa are impacted in the same ways. Understanding how wildlife respond to human activities at the population and individual level will help inform management of landscapes where humans and wildlife can coexist. We examined the effects of anthropogenic activities on a critically endangered primate, Verreaux’s sifakas (Propithecus verreauxi), at a multiple-use reserve in southwest Madagascar. Specifically, we sought to determine which activities the sifakas perceived as disturbances, using the framework of the risk disturbance hypothesis (RDH). The RDH holds that animals will respond to perceived disturbances as they do to predation threats. We therefore predicted that sifakas would be more vigilant, spend more time in high forest strata, reduce their daily feeding time, and occur at lower densities in response to high levels of perceived disturbance. Using data on sifaka behavior and spatial distribution, and the frequencies of anthropogenic activities, we found that sifakas increased vigilance and their height above the ground in response to certain human-related activities, notably those of domestic dogs. Contrary to our predictions, however, we did not find a negative effect of anthropogenic activities on daily activity budgets or population density. The relationship between the occurrence of sifakas and the intensity of tree cutting was actually positive. Our results indicate that sifakas perceive certain anthropogenic activities as threats and respond with immediate behavioral shifts, but that these activities do not have a discernible negative impact on the reserve’s population at this time. These results suggest that lemur conservation can be successful even in areas that are subject to moderate human use.

The chameleon Furcifer voeltzkowi (Boettger, 1893) from northwestern Madagascar was considered to be a synonym of Furcifer rhinoceratus for many decades and was resurrected only recently based on studies of the morphology and osteology of a few male specimens, which were collected more than 100 years ago. However, basic data on this species remain unavailable, including its conservation status, life history, colouration in life, morphology of the female, genital morphology of the male, phylogenetic affinities, and genetic differentiation from F. labordi and other congeners. During a targeted expedition, we rediscovered F. voeltzkowi in its natural habitat close to its type locality, allowing us to fill some gaps of knowledge. Furcifer voeltzkowi is a sexually dimorphic species. The life colouration of males is largely green, whereas that of females is highly variable and can be extremely colourful. Both, morphology and life colouration of males and females show close similarities to F. labordi from west and southwest Madagascar, but also a number of distinct differences (e.g. a larger size of F. voeltzkowi and a smaller rostral appendage in both sexes), enabling a clear distinction of the two species in both sexes. DNA sequences of the nuclear CMOS gene and two mitochondrial markers (16S rRNA and ND4) also confirm that F. voeltzkowi is a distinct species and sister to F. labordi (pairwise differences in the 16S gene 3.5–3.6%). We estimate the distribution range (extent of occurrence) of F. voeltzkowi to comprise ca. 1.000 km2 and suggest that it qualifies as Endangered B1ab(iii) under the IUCN Red List Criteria as its populations are expected to be severely fragmented, and there is continuing decline in the extent and quality of its habitat. Similar to F. labordi, F. voeltzkowi might be an extremely short-living chameleon with a post hatching life span of only several months in the rainy season. The assumed short life might also partly explain why this splendid species got “lost” for many decades, since most roads in its habitat are not accessible in the wet season.