Geology topics

Robert A. Long

Publications and source records attributed to Robert A. Long.

5 recordsLinked to original sources

USGS2026

Monitoring wolverine (Gulo gulo) distribution across the western United States for regional and national assessment

Population monitoring of at-risk species is fundamental to directing effective and timely conservation actions. For wide-ranging threatened species, such as the wolverine ( Gulo gulo ), monitoring across multiple jurisdictions is necessary to track their distribution to inform collaborative regional and national management and policy. We repeated a landscape-scale, multi-jurisdictional remote camera survey first completed in 2017 to evaluate wolverine occupancy throughout the western United States in 2022. Our objectives were to 1) expand the sampling frame to include areas of potential recolonization (Colorado, Oregon, Utah, USA), 2) evaluate whether overall and state-specific occurrence has changed from 2017 in the common sampling frame of Idaho, Montana, Washington, and Wyoming, USA, and 3) evaluate spatial drivers of wolverine occurrence in 2022. From a sampling frame of 770 sites (15 × 15-km cells) identified as potential wolverine habitat, 229 sites were surveyed in 2022; no wolverines were detected in Colorado, Oregon, or Utah. We predicted wolverine occupancy and 95% highest posterior density intervals (HPDI) in states with detections to be 0.47 (0.37–0.58) in Idaho, 0.35 (0.21–0.52) in Montana, 0.29 (0.09–0.54) in Washington, and 0.35 (0.27–0.47) in Wyoming. We found weak to moderate evidence of a small decline in overall occupancy ( 𝜓 ) from the common sampling frame (2017: 0.44 [0.37–0.52]; 2022: 0.39 [0.30–0.49]; P( 𝜓 2022 <𝜓 2017 ) = 0.81), driven by lower occurrences in Montana and Washington. However, this finding is complicated by a change in detection methodology that may have contributed to lower occurrences in Montana and Washington. Lastly, we found strong support (probability of an effect >0.95) that within areas of predicted wolverine habitat, increasing habitat connectivity and the proportion of a site that was previously burned (2001–2015) were associated with increased wolverine occupancy, while increasing normalized difference vegetation index (NDVI) was associated with decreased wolverine occupancy. Our expanded sampling frame provides the means to track wolverine occupancy and range extent—including recolonizations and contractions—across the western United States, providing insights at both the state and national scales.

Colorado, Idaho, Montana, Oregon, Utah, Washington↗

USGS2010

Effectiveness of scat detection dogs for detecting forest carnivores

We assessed the detection and accuracy rates of detection dogs trained to locate scats from free-ranging black bears (Ursus americanus), fishers (Martes pennanti), and bobcats (Lynx rufus). During the summers of 2003-2004, 5 detection teams located 1,565 scats (747 putative black bear, 665 putative fisher, and 153 putative bobcat) at 168 survey sites throughout Vermont, USA. Of 347 scats genetically analyzed for species identification, 179 (51.6%) yielded a positive identification, 131 (37.8%) failed to yield DNA information, and 37 (10.7%) yielded DNA but provided no species confirmation. For 70 survey sites where confirmation of a putative target species' scat was not possible, we assessed the probability that ???1 of the scats collected at the site was deposited by the target species (probability of correct identification; P ID). Based on species confirmations or PID values, we detected bears at 57.1% (96) of sites, fishers at 61.3% (103) of sites, and bobcats at 12.5%o (21) of sites. We estimated that the mean probability of detecting the target species (when present) during a single visit to a site was 0.86 for black bears, 0.95 for fishers, and 0.40 for bobcats. The probability of detecting black bears was largely unaffected by site- or visit-specific covariates, but the probability of detecting fishers varied by detection team. We found little or no effect of topographic ruggedness, vegetation density, or local weather (e.g., temp, humidity) on detection probability for fishers or black bears (data were insufficient for bobcat analyses). Detection dogs were highly effective at locating scats from forest carnivores and provided an efficient and accurate method for collecting detection-nondetection data on multiple species.

Journal of Wildlife Management↗

USGS2010

Comparing scat detection dogs, cameras, and hair snares for surveying carnivores

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.

Journal of Wildlife Management↗

USGS2010

Predicting carnivore occurrence with noninvasive surveys and occupancy modeling

Terrestrial carnivores typically have large home ranges and exist at low population densities, thus presenting challenges to wildlife researchers. We employed multiple, noninvasive survey methods—scat detection dogs, remote cameras, and hair snares—to collect detection–nondetection data for elusive American black bears ( Ursus americanus ), fishers ( Martes pennanti) , and bobcats ( Lynx rufus ) throughout the rugged Vermont landscape. We analyzed these data using occupancy modeling that explicitly incorporated detectability as well as habitat and landscape variables. For black bears, percentage of forested land within 5 km of survey sites was an important positive predictor of occupancy, and percentage of human developed land within 5 km was a negative predictor. Although the relationship was less clear for bobcats, occupancy appeared positively related to the percentage of both mixed forest and forested wetland habitat within 1 km of survey sites. The relationship between specific covariates and fisher occupancy was unclear, with no specific habitat or landscape variables directly related to occupancy. For all species, we used model averaging to predict occurrence across the study area. Receiver operating characteristic (ROC) analyses of our black bear and fisher models suggested that occupancy modeling efforts with data from noninvasive surveys could be useful for carnivore conservation and management, as they provide insights into habitat use at the regional and landscape scale without requiring capture or direct observation of study species.

Vermont↗

USGS1998

Mortality and survival of white-tailed deer Odocoileus virginianus fawns on a north Atlantic coastal island

Mortality and survival of white-tailed deer Odocoileus virginianus fawns (N = 29) were studied from birth to one year of age during 1991–95 on Mount Desert Island (MDI), Maine, where deer hunting is prohibited, coyotes Canis latrans have become recently established, and protected U.S. National Park lands are interspersed with private property. The rate of predator-caused mortality was 0.52, with coyote predation (N = 8) accounting for at least 47% of mortalities from all causes (N = 17). Mortality rate from drowning was 0.24 (N = 3), and from vehicles 0.14 (N = 3). For fawns radio-collared as neonates, 10 of 14 mortalities occurred during the first two months of life. Annual rate of fawn survival was 0.26. Survival rate from six months to one year was 0.65 and four mortalities (two predation, two drowning) were observed during this interval. A subgroup of fawns (N = 11) captured near a residential area and along the periphery of a coyote territory had a higher rate of survival to one year of age (S = 0.67) than did fawns from all other areas (N = 18, S = 0.00). Recruitment to one year of age was lower than that observed in other deer populations in the northeastern United States. Low recruitment associated with coyote predation and mortality sources associated with humans appears to be limiting white-tailed deer populations in some segments of this insular landscape.

Maine↗