Responses of Primates to Landscape Change in Amazonian Land‐bridge islands—a Multi‐scale Analysis

Large hydroelectric dams are one of the current drivers of habitat loss across Amazonian forests. We investigated how the primate community at a hydroelectric dam in Brazilian Amazonia responded to changes in the landscape and local habitat structure of land‐bridge islands after 21 yr of post‐isolation history. The Balbina Dam, constructed in 1986, inundated 3129 km² of primary forests and created more than 3500 variable‐sized islands. We conducted primate and habitat structure surveys on 20 islands from 5 to 1815 ha, and extracted forest patch and landscape metrics for each island. The number of primate species per island varied between 0 and 7 species. Primate composition varied substantially according to both island area and forest cover remaining within the landscape, whereas island area alone was the most significant predictor of richness. Locally, tree density and vertical stratification were the most significant explanatory variables of primate composition and richness. A model containing area effects had the most explanatory power regarding site occupancy for most species. Individually, each species responded differently, with howler and brown capuchin monkeys showing greater tolerance to cope with habitat changes. Body size was also an important predictor of primate occupancy. We recommend protecting large fragments and enhancing the suitability of surrounding habitats to ensure primate conservation in most Neotropical fragmented landscapes. Given the flat topography of hydroelectric reservoirs, which mainly favors the formation of small islands, and the escalating hydropower development plans in Amazonia, our findings provide evidence for pervasive detrimental impacts of dams on primate communities.     

Synergistic and antagonistic effects of land use and non‐native species on community responses to climate change

Climate change, land‐use change and introductions of non‐native species are key determinants of biodiversity change worldwide. However, the extent to which anthropogenic drivers of environmental change interact to affect biological communities is largely unknown, especially over longer time periods. Here, we show that plant community composition in 996 Swedish landscapes has consistently shifted to reflect the warmer and wetter climate that the region has experienced during the second half of the 20th century. Using community climatic indices, which reflect the average climatic associations of the species within each landscape at each time period, we found that species compositions in 74% of landscapes now have a higher representation of warm‐associated species than they did previously, while 84% of landscapes now host more species associated with higher levels of precipitation. In addition to a warmer and wetter climate, there have also been large shifts in land use across the region, while the fraction of non‐native species has increased in the majority of landscapes. Climatic warming at the landscape level appeared to favour the colonization of warm‐associated species, while also potentially driving losses in cool‐associated species. However, the resulting increases in community thermal means were apparently buffered by landscape simplification (reduction in habitat heterogeneity within landscapes) in the form of increased forest cover. Increases in non‐native species, which generally originate from warmer climates than Sweden, were a strong driver of community‐level warming. In terms of precipitation, both landscape simplification and increases in non‐natives appeared to favour species associated with drier climatic conditions, to some extent counteracting the climate‐driven shift towards wetter communities. Anthropogenic drivers can act both synergistically and antagonistically to determine trajectories of change in biological communities over time. Therefore, it is important to consider multiple drivers of global change when trying to understand, manage and predict biodiversity in the future.     

From savannah to farmland: effects of land‐use on mammal communities in the Tarangire–Manyara ecosystem,Tanzania

Land‐use change is considered a major driver of biodiversity loss. In the western part of the Tarangire–Manyara ecosystem, we assessed large mammal species richness along a land‐use gradient (national park, uninhabited pastoral area and settled pastoral‐ and farmland). We found the highest species richness in the national park and in the pastoral area and lowest species richness in the settled and farmed area. There was little evidence of seasonal changes in species diversity. Except for top‐order carnivores, all functional feeding guilds were still represented in pastoral and settled areas. Although we did not find significant differences in body mass distributions and species’ representation of feeding guilds between the study sites, there was a trend that omnivores, mesopredators and top‐order carnivores tended to occur at lower species richness in agricultural areas than in the pastoral and fully protected areas. These results indicate that areas used for livestock keeping can maintain high wildlife species richness and that direct and indirect effects of agricultural and settlement expansions are the main drivers of species richness loss in the Tarangire–Manyara ecosystem and possibly other African savannah ecosystems. These results are useful for informed land‐use planning that aims to maintain species diversity and ecological connectivity between protected areas.     

Behavioral “bycatch” from camera trap surveys yields insights on prey responses to human‐mediated predation risk

Human disturbance directly affects animal populations and communities, but indirect effects of disturbance on species behaviors are less well understood. For instance, disturbance may alter predator activity and cause knock‐on effects to predator‐sensitive foraging in prey. Camera traps provide an emerging opportunity to investigate such disturbance‐mediated impacts to animal behaviors across multiple scales. We used camera trap data to test predictions about predator‐sensitive behavior in three ungulate species (caribou Rangifer tarandus; white‐tailed deer, Odocoileus virginianus; moose, Alces alces) across two western boreal forest landscapes varying in disturbance. We quantified behavior as the number of camera trap photos per detection event and tested its relationship to inferred human‐mediated predation risk between a landscape with greater industrial disturbance and predator activity and a “control” landscape with lower human and predator activity. We also assessed the finer‐scale influence on behavior of variation in predation risk (relative to habitat variation) across camera sites within the more disturbed landscape. We predicted that animals in areas with greater predation risk (e.g., more wolf activity, less cover) would travel faster past cameras and generate fewer photos per detection event, while animals in areas with less predation risk would linger (rest, forage, investigate), generating more photos per event. Our predictions were supported at the landscape‐level, as caribou and moose had more photos per event in the control landscape where disturbance‐mediated predation risk was lower. At a finer‐scale within the disturbed landscape, no prey species showed a significant behavioral response to wolf activity, but the number of photos per event decreased for white‐tailed deer with increasing line of sight (m) along seismic lines (i.e., decreasing visual cover), consistent with a predator‐sensitive response. The presence of juveniles was associated with shorter behavioral events for caribou and moose, suggesting greater predator sensitivity for females with calves. Only moose demonstrated a positive behavioral association (i.e., longer events) with vegetation productivity (16‐day NDVI), suggesting that for other species bottom‐up influences of forage availability were generally weaker than top‐down influences from predation risk. Behavioral insights can be gleaned from camera trap surveys and provide complementary information about animal responses to predation risk, and thus about the indirect impacts of human disturbances on predator–prey interactions.