Robert A. Long

Comparing Scat Detection Dogs, Cameras, and Hair Snares for Surveying Carnivores

Abstract Carnivores typically require large areas of habitat, exist at low natural densities, and exhibit elusive behavior—characteristics that render them difficult to study. Noninvasive survey methods increasingly provide means to collect extensive data on carnivore occupancy, distribution, and abundance. During the summers of 2003–2004, we compared the abilities of scat detection dogs, remote cameras, and hair snares to detect black bears (Ursus americanus), fishers (Martes pennanti), and bobcats (Lynx rufus) at 168 sites throughout Vermont. All 3 methods detected black bears; neither fishers nor bobcats were detected by hair snares. Scat detection dogs yielded the highest raw detection rate and probability of detection (given presence) for each of the target species, as well as the greatest number of unique detections (i.e., occasions when only one method detected the target species). We estimated that the mean probability of detecting the target species during a single visit to a site with a detection dog was 0.87 for black bears, 0.84 for fishers, and 0.27 for bobcats. Although the cost of surveying with detection dogs was higher than that of remote cameras or hair snares, the efficiency of this method rendered it the most cost-effective survey method.

Focal species and landscape “naturalness” corridor models offer complementary approaches for connectivity conservation planning

ContextThe dual threats of habitat fragmentation and climate change have led to a proliferation of approaches for connectivity conservation planning. Corridor analyses have traditionally taken a focal species approach, but the landscape “naturalness” approach of modeling connectivity among areas of low human modification has gained popularity as a less analytically intensive alternative.ObjectivesWe compared focal species and naturalness-based corridor networks to ask whether they identify similar areas, whether a naturalness-based approach is in fact more analytically efficient, and whether agreement between the two approaches varies with focal species vagility.MethodsWe compared focal-species and naturalness-based connectivity models at two nested spatial extents: greater Washington State, USA, and, within it, the Columbia Plateau ecoregion. We assessed complementarity between the two approaches by examining the spatial overlap of predicted corridors, and regressing organism traits against the amount of modeled corridor overlap.ResultsA single naturalness-based corridor network represented connectivity for a large (>10) number of focal species as effectively as a group of between 3 and 4 randomly selected focal species. The naturalness-based approach showed only moderate spatial agreement with composite corridor networks for large numbers of focal species, and better agreed with corridor networks of large-bodied, far-dispersing species in the larger scale analysis.ConclusionsNaturalness-based corridor models may offer an efficient proxy for focal species models, but a multi-focal species approach may better represent the movement needs of diverse taxa. Consideration of trade-offs between the two approaches may enhance the effectiveness of their application to connectivity conservation planning.

Factors Influencing Occupancy Patterns of Eastern Newts across Vermont

Abstract Of the threats facing amphibian populations today, habitat transformation resulting from land use is among the most pressing. Although conservation of pond-breeding salamanders clearly requires protection of breeding ponds and their surrounding habitat, little is known about the effects of land use and other factors on the occurrence of salamanders in the dispersal/terrestrial phase of their life cycle. To determine these effects, we surveyed populations of Eastern Newts (Notophthalmus viridescens) at 551 stations across Vermont and modeled salamander distribution as a function of environmental variables hypothesized to influence site occupancy. We developed a set of 12 models based on seven a priori hypotheses of site occupancy. We hypothesized that occupancy was influenced by (1) amounts of available habitat types, (2) arrangement of these habitat types, (3) geographic position, (4) housing density, (5) road density, (6) short-term changes in habitat distribution, or (7) habitat structure at the stand level. We used a single-season occupancy model to rank and compare the 12 models. A total of 232 Eastern Newts was detected at 82 of 551 stations. Of the 12 models, amount of habitat within 0.5 km of the survey station best represented the field data. Strong effects were indicated for developed land (−), open water (+), and forest (+) cover. Given a survey station with average forest and open water characteristics, stations with >5% developed land classes within a 0.5-km buffer had a very low probability of occupancy. Further research is needed to determine the direct role of development on occupancy patterns.