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USGS at The Wildlife Society: From Safe Road Passage for Wildlife to Dogs and Tortoises


Roads, wildlife, and people: How do we make the roaded landscape more permeable for wildlife? Until now, few, if any, decision guides for wildlife crossings are readily available and written for highway engineers and wildlife biologists. In this talk, researchers present the results of a 3-year research project intended to help make the North American roaded landscape safer and more permeable for wildlife while also increasing road safety for motorists by reducing the risk of wildlife-vehicle collisions. Through individual ecological and engineering projects, USGS, Utah State University, and colleagues conducted research concerning the state of the practice and science of wildlife crossings, how to best collect, map and analyze wildlife-vehicle collision data, the use of data to place wildlife crossings, and North American priorities for research and the practice concerning wildlife movement in roaded landscapes. The researchers brought these projects together to formally assist professionals and citizens in a decision guide to help mitigate the adverse effects of roads and railways on wildlife. The guide promotes landscape permeability by helping users assess a transportation plan or project for its potential effects on wildlife and ecosystems, identify mitigation techniques that could allow wildlife to move more freely over and under the road or railway, information on how to plan for and install that mitigation, and information on how to adaptively monitor and manage the situation over time. The Web site with the wildlife crossing guide also provides a search engine that accesses a literature database, database of wildlife crossings in North America, related websites, selected literature files, and wildlife-crossings pictures. The website will be updated through 2008 and possibly longer. Patricia Cramer and John Bissonette, Session 12, Sunday, Sept. 23, 2007, 4:30 p.m. (Contact:; 435-797-2511;

Impacts to the threatened desert tortoise from dogs: a growing threat at the urban interface in the Mojave Desert, California. Desert tortoise (Gopherus agassizii) populations have declined for numerous reasons in recent decades to the point where populations north and west of the Colorado River were federally listed as threatened in 1990. One important issue identified in the tortoise recovery plan is attack by domestic or feral dogs. USGS research reveals that attacks from dogs are likely to be a growing threat to recovery of the species. USGS scientists developed a method of grading trauma to live tortoises using 35-mm slides and data sheets, and then retrospectively created a database that includes more than 6,000 tortoises from more than 30 long-term and specialized research plots in California. The data set, collected between 1977 and 2005, includes potential source and severity of trauma. The objectives of this research were to characterize types of trauma affecting live tortoises by size, sex, and location; determine if signs of attacks by domestic or feral dogs could be separated from those of wild canids; determine if types and amounts of trauma differ in tortoise populations living near towns and settlements versus remote areas; and prepare a risk model. The scientists found that, in general, attacks by dogs differed from attacks by wild canids in the amount and type of scute (scale covering of the tortoise shell) removed and bone exposed, especially to the gular horn (on the underside of the tortoise shell), which is critical for courtship, aggression and protection. Tortoise populations most likely to be affected by dogs occur within 2-6 kilometers of settlements and towns. The percent of tortoises with moderate to severe trauma from predators was significantly higher at sites near settlements than in remote areas. One tortoise population, under study since 1980 and near a settlement, also showed significantly increased frequency in moderate to severe trauma over time Since 1994, when the Desert Tortoise Recovery Plan was published by the U.S. Fish and Wildlife Service, urban pressures have increased on critical habitat boundaries in several areas. Kristin Berry, Session 19, Monday, Sept. 24, 4:30 pm. (Contact:; 951-697-6361)

Effects of feeding and watering birds on nuisance rattlesnakes in National Parks. In Arizona, nuisance rattlesnakes are often found in human-modified habitats within or on the edges of National Parks during the summer. The generally accepted hypothesis is that human-modified habitats are attractive to rattlesnakes due to the presence of increased prey (rodent and bird) populations or to the availability of free water. USGS researcher Erika Nowak conducted the first field research to experimentally test these potential reasons, as well as the effects of human-modified habitats on rattlesnake life history, growth, reproduction, movements and behavior. Following two years of separate baseline data collection, Nowak fed and watered birds in a replicated design at two National Monuments over a two-year period. She trapped small mammals, assessed bird use of the grids, and recorded opportunistic use by other species using motion-detecting cameras and videography. At the same time, Nowak monitored western diamond-backed rattlesnake (Crotalus atrox) activity and movements at the monuments using radio-telemetry. Her preliminary results suggest that prey and predator responses varied depending on environmental conditions. Prey numbers, for example, may have been influenced by the availability of free water during drier periods. Most importantly, the study found that several individual rattlesnakes shifted established foraging ranges to encompass the experimental grids, a phenomenon not previously reported for these long-lived, predators that are known for being loyal to specific sites. Erika Nowak, Session 25, Monday, Sept. 24, 1:20 p.m. (Contact:; 928-556-7219)

Factors influencing food resources, use of wetlands, and foraging behavior of lesser scaup migrating throughout the upper-Midwest during spring. The continental lesser scaup (Aythya affinis) population has declined precipitously over the past 25 years. Historically a large proportion of the scaup population likely relied on nutrients for breeding that were acquired while staging on wetlands in the upper-Midwest (Iowa, Minnesota, and North Dakota) during spring. However, female scaup migrating throughout the upper-Midwest in spring currently are known to have low lipid (fat) reserve levels. USGS researchers, along with numerous state, federal and non-government partners, examined factors influencing food abundance, patterns of wetland use and foraging behavior of scaup on randomly selected wetlands in this region during springs 2004 and 2005. Their research found that in the upper Midwest, scaup used wetlands that were higher in amphipod numbers (aquatic crustaceans known as freshwater shrimp or scuds) than in chironomids (midges and other nonbiting two-winged flies), indicating that lesser scaup prefer a diet rich in amphipods. Amphipod densities currently are low throughout the upper Midwest (regional averages ranged from 1 to 12 individuals per square meter) in relation to historical records (typically ranging 90 to 2000 individuals per square meter). Feeding probability of scaup was associated with amphipod densities up to 26 individuals per square meter and then declined, suggesting that foraging efficiency increases at amphipod densities over 26 individuals per square meter (mean across the landscape). At the same time that amphipod and scaup densities have significantly decreased, the presence of fish in wetlands has substantially increased in the upper Midwest. This research revealed that amphipod densities were much lower in wetlands with higher densities of fish and more agricultural sedimentation. The researchers conclude that the decrease in amphipod densities throughout the upper Midwest is likely causing the decreases in lipid reserves of scaup. These results indicate that one step to conserve scaup could be to provide abundant populations of amphipods by restoring wetlands throughout the upper Midwest, but especially in Iowa and southern Minnesota. Michael J. Anteau, Session 25, Monday, Sept. 24, 3:50 p.m. (Contact:; 701-253-5507)

Effects of climate on annual survival of northern spotted owls in the Pacific Northwest. Declines in northern spotted owl (Strix occidentalis caurina) populations have been documented through extensive field surveys and range-wide demographic analyses. Although loss of late-successional forest habitat is credited as the primary cause for spotted owl population declines, environmental variation has also been shown to influence many avian species, including spotted owls. Climate, or the long-term average of weather, is one component of environmental variation that affects annual survival rates. This study identified components of weather and climate that affect spotted owl annual survival rates to determine how much variation in survival can be explained by these factors. Researchers monitored and examined 6 populations of northern spotted owls in Oregon and Washington using mark-recapture techniques for 12-20 years. For 4 of the 6 populations, drought conditions or high summer temperatures were negatively related to survival rates. t the 3 highest elevation study areas, survival was also negatively affected by winter, nesting season, and dispersal period temperature and precipitation as well as by the frequency of storm events; however, the relation of survival to these weather factors varied by study area. Increased numbers of storms negatively affected survival at 3 of 6 areas. The findings of this study suggest that spotted owl populations may face additional challenges if the climate in the Pacific Northwest follows the current predictions of year-round warming with warmer, wetter winters and hotter, drier summers in the 21st century. Elizabeth M. Glenn and Bob Anthony, Session 23, Monday, Sept. 24, 2007, 1:40 p.m. (Contact:;; 541 737-1938)

Embryos of different bird species differ considerably to their sensitivities to methylmercury. Avian embryos are especially sensitive to methylmercury, a very toxic form created by bacteria in nature, but few field and laboratory studies have been conducted to determine how much mercury must be in the eggs of a given species to cause toxicity to embryos. A USGS study led by Gary Heinz compared the sensitivities of the embryos of 26 different species (representing 8 different orders) of birds to different doses of methylmercury. The researchers found that the embryos of these species differed considerably in their sensitivity to methylmercury. Of particular note was the finding that mallard (Anas platyrhynchos) embryos were not particularly sensitive to injected methylmercury, although the toxic threshold of mercury in mallard eggs is often used as a default value for the sensitivity of embryos of wild birds for which no mercury toxicity data generally exist. Some species, such as the American kestrel (Falco sparverius), osprey (Pandion haliaetus), common grackle (Quiscalus quiscula), snowy egret (Egretta thula), and white ibis (Eudocimus albus), were more sensitive than the mallard, whereas other species, such as the double-crested cormorant (Phalacrocorax auritus), sandhill crane (Grus canadensis), and lesser scaup (Aythya affinis) were of roughly the same sensitivity as mallards. These findings will improve the ability of resource managers to judge the potential hazard of mercury to birds in their area. Gary Heinz and Jon D. Klimstra, Session 37, Tuesday, Sept. 25, 4:30 p.m. (Contact:; 301-497-5711;; 301-497-5754)

Potential effects of human recreation activity on bighorn sheep habitat use in Joshua Tree National Park, California. Moderate to high levels of human recreation activity may temporarily exclude bighorn ewes from their preferred habitat, according to research findings that USGS scientist Kathleen Longshore will present at The Wildlife Society’s annual conference. To study potential effects of recreation activities on desert bighorn sheep (Ovis canadensis nelsoni) habitat use, she and colleagues at USGS and the University of Nevada, Las Vegas, placed GPS collars on 10 bighorn ewes within the Wonderland of Rock/Queen Mountain region of Joshua Tree National Park, Calif., from 2002-2004. Recreation use was highest from March to April and during weekends throughout the year. The researchers compared the ewes’ habitat use (slope, ruggedness, distance to water and distance to trails) between weekdays and weekend days during months with high recreation and low recreation use at 5 a.m, noon and 8 p.m. During all months, ewes selected steeper, more rugged slopes during evening (8 p.m.) and early morning hours (5 a.m.). Ewes did not select for steeper, more rugged terrain during midday. During weekends of months with high recreation use, ewes avoided habitat near trails during midday but did not avoid habitat adjacent to trails during 5 a.m. or 8 p.m. during weekends or weekdays. The most probable cause of differences in habitat use during weekends is the increase in recreation activity. Kathleen Longshore, session 16: Conservation and Management of Mammals, Monday, Sept. 24, 8:40 a.m. (Contact:; 702-564-4505)

Choice of home range estimators can affect conservation and management decisions for the threatened desert tortoise. USGS scientists conducted a multi-year study of an undisturbed population of desert tortoises (Gopherus agassizii) in the central Mojave Desert, Calif. This species is federally listed as threatened in parts of the Southwest. Home-range size and shape are important conservation and management issues because the data affect designs of protected areas. Researchers evaluated factors affecting home-range sizes of adults, such as gender, dominance and locations of mates, using two estimators. Using one estimator, the means for home ranges of 11 females and 16 males were 13.5 hectares and 43.8 hectares, respectively. Using the second estimator, the home range sizes overall were smaller, but the pattern was similar. Dominance was an important factor in shape and location of home range among alpha males. Only small portions of home ranges for some alpha males overlapped, and core portions of their ranges were isolated from each other. Mean home-range size of alpha males was higher than that of lower-ranked males, but the differences were not significant. Within home ranges, locations of core use areas varied by season for both sexes. Areas used for winter differed from areas used during the hottest part of summer and may have been influenced by seasonal choices of cover sites. Other factors affecting home range are mates, foraging areas, topography, surface geology, and probably age. Jeremy Mack, Session 19, Monday, Sept. 24, 4:50 p.m. (Contact:; 951-697-5241)

Midwinter bald eagle counts in the southwestern United States. Each January, several hundred observers count bald eagles (Haliaeetus leucocephalus) as part of the Midwinter Bald Eagle Survey. The annual survey represents a unique source of long-term, baseline data and unlike nesting surveys, it provides information on both breeding and nonbreeding segments of the population at a potentially limiting time of the year. Researchers assessed trends in numbers of bald eagles counted along survey routes in the contiguous United States from 1986 to 2005. Preliminary analyses suggest that counts of eagles increased 1.7 percent per year, nationwide, over the 20-year sampling period. However, counts in the Southwest portion of the country decreased 1.2 percent each year over the same period. These findings are consistent with results of other studies that have demonstrated that numbers of nesting pairs in the Southwest region have not increased as much as numbers of pairs in other parts of the contiguous United States. Within the Southwestern Bald Eagle Recovery Region, researchers evaluated 1,128 surveys conducted on 118 routes in five states to assess variation in count trends among biotic communities and across elevational gradients within the recovery region. Possible reasons for the decrease include increasingly warmer winters may mean that more eagles overwinter in the north; increases in counts may be inversely proportional to declines suffered in the DDT area (declines were more severe in the Northeast than in the Southwest), and more rapid rates of human population growth in the Southwest could be affecting eagle population trends. Karen Steenhof (USGS) and Wade L. Eakle (U.S. Army Corps of Engineers), Session 41, Tuesday, Sept. 25, 4:10 p.m. (Contact:; 415-503-6577; or after Sept 30,; 208-426-5206)

DNA-based density estimate for grizzly bears in Glacier National Park, Montana. Grizzly bear (Ursus arctos) population size in Glacier National Park (GNP) in northwestern Montana, USA, was last estimated in 1971 using sightings of unmarked bears. Researchers from the U.S. Geological Survey and their colleagues (University of Montana, University of Idaho, Integrated Ecological Research in Canada, and Wildlife Genetics International in Canada) estimated the number of grizzly bears living in a 2-million-acre area in and around GNP using hair sampling in conjunction with DNA analysis to identify individual bears. Researchers used two methods concurrently to collect bear hair. They distributed 625 baited barbed-wire hair corrals on an 8 x 8 kilometer grid to systematically sample the study area during 5 14-day sessions. The second sampling method collected hair at 2-4 week intervals from more than 1,000 unbaited bear rub trees along trails. From analysis of the 6,449 and 8,352 hair samples, we derived population estimates of 319 and 339 grizzly bears in 1998 and 2000 respectively. Grizzly bear density in the greater Glacier NP area is estimated at 3 bears/100 km2 although density is higher than this inside GNP and lower outside the park where the majority of mortality occurred. This study provides baseline information important for managing one of the few remaining populations of grizzlies in the contiguous United States. Katherine Kendall, Session 15, Monday, Sept. 24, 8:20 a.m. (Contact:; 406-888-7994)

Assessment of genetic diversity in the western shovel-nosed snake. The western shovel-nosed snake (Chionactis occipitalis) is distributed throughout much of the Sonoran and Mojave deserts. Four morphologically-based subspecies are currently recognized: Mohave shovel-nosed snake (C. o. occipitalis), Colorado Desert shovel-nosed snake (C. o. annulata), Nevada shovel-nosed snake (C. o. talpina), and Tucson shovel-nosed snake (C. o. klauberi). In December 2004, the U.S. Fish and Wildlife Service was petitioned to list C. o. klauberi under the Endangered Species Act. An important question in evaluating that petition is whether C. o. klauberi is a distinct subspecies. In 2006, USGS scientists and colleagues coordinated surveys for Chionactis occipitalis and collected samples from 32 Arizona specimens. These samples, along with 51 previously collected samples, were used in a phylogeographic assessment of this species, based on mitochondrial DNA sequences. The researchers assumed that subspecies should reflect some indication of evolutionary history. Thus, the current morphologically-based subspecies of Chionactis occipitalis should, if valid, exhibit exclusive or near-exclusive distinctions within their mitochondrial DNA. The analysis revealed none of the currently defined subspecies form an exclusive group by themselves. Instead, the data suggest 2 evolutionary lineage groups, which would be formed by combining eastern populations of C. o. occipitalis with C. o. annulata and C. o. klauberi, and western populations of C. o. occipitalis with C. o. talpina. Mitochondrial DNA sequences suggest specimens currently recognized as C. o. klauberi are embedded in a larger geographic clade whose range has expanded from western Arizona populations, and these data are concordant with longitudinal variation in morphology. The researchers also include data from surveys of 2006, which involved extensive collaborative effort and included more than100 hours and more than 2,000 miles of road surveys, walking surveys, and pit fall traps. Dustin Wood, Session 26, Monday, Sept. 24, 3:50 p.m. (Contact:; 619-225-6432)


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