We studied sexual segregation in an endangered alpine ungulate, Sierra Nevada bighorn sheep (Ovis canadensis sierrae) in the Sierra Nevada, California, U.S.A., during winter 2005-2006. We tested hypotheses for sexual segregation to better understand that phenomenon and to obtain information critical for the conservation of these rare mammals. Females foraged in larger groups that were closer to escape terrain than did males. Areas used by males had higher biomass of vegetation and were less open than areas used by females. Males foraged more efficiently in larger groups, whereas females foraged more efficiently when close to escape terrain. Females exhibited a higher bite rate than did males. Males traveled farther per day and in more open terrain than did females. Sexes of bighorn sheep also differed in their dietary niches. Those niches differed most where sexes of bighorn sheep overlapped more in spatial distribution, and differed less where spatial separation was more pronounced. These outcomes are most parsimoniously explained by the gastrocentric and predation hypotheses. In addition, sexes of bighorn sheep behaved as if they were separate species by exhibiting avoidance on one niche axis (space) when there was overlap on another axis (diet). Management and conservation plans must consider the disparate requirements of males and females to help assure the viability of these endangered mountain ungulates.

Maintenance of movement corridors is a fundamental component of the conservation of biological diversity, and is especially critical for terrestrial species that migrate extended distances. Highways and interstate freeways fragment corridors and often result in increased mortality of terrestrial migrants from collisions with vehicles. Wildlife crossing structures are an important tool in multiple ecosystems to allow safe passage for wildlife across roadways. Indeed, crossing structures have been used extensively in Europe and with increasing frequency in North America to reconnect fragmented habitats for numerous species. Few projects, however, have documented responses to >1 structure type simultaneously that are close to one another. We used mule deer (Odocoileus hemionus), a widespread species across diverse bioregions in western North America, to test hypotheses about efficacy of 2 different types of crossing structures for ungulates. We documented behavioral responses and use of overpasses and underpasses by mule deer. Our metrics to evaluate success included passage rates and the number of animals that crossed each structure. Crossing structures were used by mule deer immediately following construction and although all of the crossing structures were used, we observed greater passage rates at overpasses than underpasses. Wildlife crossing structures reduced habitat fragmentation and enhanced connectivity by allowing safe passage across US 93. More importantly, those structures succeeded in removing a large number of mule deer from the roadway making US 93 safer for wildlife and motorists. Ó

Evidence for bovine viral diarrhea virus (BVDV) infection was detected in 2009–2010 while investigating a pneumonia die-off in Rocky Mountain bighorn sheep (Ovis canadensis, canadensis), and sympatric mountain goats (Oreamnos americanum) in adjacent mountain ranges in Elko County, Nevada. Seroprevalence to BVDV-1 was 81% (N = 32) in the bighorns and 100% (N = 3) in the mountain goats. Serosurveillance from 2011 to 2015 of surviving bighorns and mountain goats as well as sympatric mule deer (Odocoileus hemionus), indicated a prevalence of 72% (N = 45), 45% (N = 51), and 51% (N = 342) respectively. All species had antibody titers to BVDV1 and BVDV2. BVDV1 was isolated in cell culture from three bighorn sheep and a mountain goat kid. BVDV2 was isolated from two mule deer. Six deer (N = 96) sampled in 2013 were positive for BVDV by antigen-capture ELISA on a single ear notch. Wild ungulates and cattle concurrently graze public and private lands in these two mountain ranges, thus providing potential for interspecies viral transmission. Like cattle, mule deer, mountain goats, and bighorn sheep can be infected with BVDV and can develop clinical disease including immunosuppression. Winter migration patterns that increase densities and species interaction during the first and second trimester of gestation may contribute to the long term maintenance of the virus in these wild ungulates. More studies are needed to determine the population level impacts of BVDV infection on these three species.

Abstract. Loss of migratory corridors has been identified as an important ecological issue among species that exhibit long-distance migration worldwide. Increased mineral exploration and development has raised the level of concern over the protection of terrestrial migration routes for ungulates. Mineral exploration and other types of development may adversely affect migratory corridors for large herbivores, but little is known about functional effects on migratory behavior and resource selection. To address these important questions we examined movement patterns and resource selection to understand the effects of an operating gold mine on migratory pathways of mule deer (Odocoileus hemionus). We captured and applied radio collars to female mule deer (n ¼ 43) on the migratory pathway and in the proximity of an active mine in the Ruby Mountains of eastern Nevada. We used Brownian Bridge Movement Models to delineate stopover sites for each individual during both the autumn and spring migrations. We calculated linear efficiency of movement along the migration path and movement rate between stopover locations outside and within the mining area to determine the effects of the mine on movement patterns. We also used resource selection functions to determine if mule deer avoided areas with extensive excavation and disturbance of the land surface when navigating through the mine complex. Our results indicated greater linear efficiency of movement along the migration path and movement rates between stopover locations outside the mine when compared with movement through the mine complex. Additionally, mule deer that migrated through the mine complex avoided the highest disturbance levels by spending the majority of their time in undisturbed habitat patches. These results suggest an increase in energy expenditure of mule deer navigating through highly disturbed areas, which may have fitness consequences for migratory animals. Such increases in energy expenditure during migration may decrease survival or productivity of migratory populations of large, terrestrial mammals.