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Habitat loss has major impacts on biodiversity. Yet, such impacts are not always linear, as there can be threshold values of habitat amount below which species become extirpated from human-modified landscapes (extinction thresholds). This may be particularly the case for species with high habitat spatial requirements, especially in regions with a long land-use history, which have a lower extinction debt. To address these issues, we evaluated the linear and non-linear effects of landscape-scale forest (habitat) loss on primate species richness in regions with relatively new (Amazon) and old (Atlantic Forest) histories of land-use change. We also evaluated the role of mean home range size in regulating species responses to forest loss. Extinction thresholds were higher in the Atlantic Forest (78% remaining forest cover) than in the Amazon (45%), but primate-landscape associations were stronger in the Amazon. Thus, despite its recent land-use history, Amazon primates are more sensitive to habitat loss. As predicted, mean home range size decreased with forest loss in both biomes. Our findings highlight the importance of stopping deforestation in both biomes to maintain habitat amount above these thresholds. Yet, as

Predicting potential habitat across a landscape for rare species is extremely challenging. However, partitioned Mahalanobis D² methods avoid pitfalls commonly encountered when surveying rare species by using data collected only at known species locations. Minimum habitat requirements are then determined by examining a principal components analysis to find consistent habitat characteristics across known locations. We used partitioned D² methods to examine minimum habitat requirements of Indiana bats (Myotis sodalis) in the Champlain Valley of Vermont and New York, USA, across 7 spatial scales and map potential habitat for the species throughout the same area. We radiotracked 24 female Indiana bats to their roost trees and across their nighttime foraging areas to collect habitat characteristics at 7 spatial scales: 1) roost trees, 2) 0.1-ha circular plots surrounding the roost trees, 3) home ranges, and 4-7) 0.5-km, 1-km, 2-km, and 3-km buffers surrounding the roost tree. Roost trees (n = 50) typically were tall, dead, large-diameter trees with exfoliating bark, located at low elevations and close to water. Trees surrounding roosts typically were smaller in diameter and shorter in height, but they had greater soundness than the roost trees. We documented 14 home ranges in areas of diverse, patchy land cover types that were close to water with east-facing aspects. Across all landscape extents, area of forest within roost-tree buffers and the aspect across those buffers were the most consistent features. Predictive maps indicated that suitable habitat ranged from 4.7-8.1% of the area examined within the Champlain Valley. These habitat models further understanding of Indiana bat summer habitat by indicating minimum habitat characteristics at multiple scales and can be used to aid management decisions by highlighting potential habitat. Nonetheless, information on juvenile production and recruitment is lacking; therefore, assessments of Indiana bat habitat quality in the region are still incomplete. [ABSTRACT FROM AUTHOR]

A major challenge facing conservation biologists and wildlife managers is to predict how fauna will respond to habitat loss. Different species require different amounts of habitat for population persistence, and species' reproductive rates have been identified as one of the major factors affecting these habitat-amount requirements. The purpose of this study was to test the prediction that species with higher reproductive rates require less habitat for population persistence than species with lower reproductive rates. We used 41 species of forest breeding birds to test for a relationship between the annual reproductive output and the amount of forest cover at which each species has a 50% probability of presence in the landscape. To look at the presence of species over landscapes with varying amounts of forest cover, we combined two large-scale independent data sets: the North American Breeding Bird Survey and the U.S. Geological Survey (USGS) Land Use and Land Cover (LULC) digital data. Species presence/absence information was determined over a 10-year window for 779 circular landscapes that surround each Breeding Bird Survey route in the central and eastern USA region. Annual reproductive rates were obtained from the literature. There was a significant negative (interspecies) relationship between the estimated minimum habitat amount at which there was a 50% probability of presence in the landscape and annual reproductive output (F[SUB]1,39[SUB] = 7.71, P = 0.008, r[SUP]2[SUP] = 0.16). This is the first direct test for a negative relationship between minimum habitat requirements and annual reproductive rates. [ABSTRACT FROM AUTHOR]