Influence of Whitebark Pine Decline on Fall Habitat Use and Movements of Grizzly Bears in the Greater Yellowstone Ecosystem

Seeds of whitebark pine (WBP; Pinus albicaulis) are a major food item for grizzly bears (Ursus arctos) in the greater Yellowstone ecosystem. Higher rates of bear mortality and bear-human conflicts are linked with low WBP productivity. Recently, infestations of mountain pine beetle (Dendroctonus ponderosae) have killed many mature, cone-bearing WBP trees. We investigated whether this decline caused bears to reduce their use of WBP and increase use of areas near humans. We used 52,332 GPS locations of 72 individuals (89 bear-years) monitored during fall (15 Aug–30 Sep) to examine temporal changes in habitat use and movements during 2000–2011. We calculated a Manley-Chesson (MC) index for selectivity of mapped WBP habitats for each individual within its 100% local convex hull home range, and determined dates of WBP use. One third of sampled grizzly bears had fall ranges with little or no mapped WBP habitat. Most other bears (72%) had a MC index > 0.5, indicating selection for WBP habitats. Over the study period, mean MC index decreased and median date of WBP use shifted about 1 week later. We detected no trends in movement indices over time. Outside of national parks, 78 percent of bears selected for secure habitat (areas ? 500 m from roads), but mean MC index decreased over the study period during years of good WBP productivity. The foraging plasticity of grizzly bears likely allowed them to adjust to declining WBP. However, the reduction in mortality risk associated with use of WBP habitat may be diminishing for bears in multiple-use areas

Trends in Causes and Distribution, and Effects of Whitebark Pine Decline on Grizzly Bear Mortality in the Greater Yellowstone Ecosystem

Documented grizzly bear (Ursus arctos) mortalities have been increasing in recent years in the Greater Yellowstone Ecosystem (GYE), due, in part, to increases in bear numbers and range expansion. Previous research has documented that variable seed production of whitebark pine (WBP; Pinus albicaulis), an important fall food, is inversely related to grizzly bear fall mortality.  However, WBP has experienced widespread mortality during the last decade because of mountain pine beetle (Dendroctonus ponderosae) infestations. We investigated trends in causes and distribution of human-caused mortalities for independent-aged (? 2 yrs old) grizzly bears in the GYE during 1975–2012, and the effect of WBP cone production on numbers of fall (> 1 August) mortalities (n = 172) during the period of WBP decline (2000-2012) using Poisson regression. During 1975–1982, 91 percent of mortalities occurred within the Grizzly Bear Recovery Zone and primary causes were poaching/malicious killings and losses related to conflicts with livestock. During the two most recent decades most mortalities were associated with ungulate hunting, usually involving self-defense kills, or anthropogenic sites, and an increasing percentage of mortalities occurred outside the recovery zone. Using predictor variables of cone production, sex, location in or out of the Recovery Zone, and year suggests: 1) annual cone production was still predictive of human-caused fall mortalities, 2) no evidence of a difference in annual numbers of fall mortalities between males and females, and 3) an increase in annual mortalities over the study period, with most of this increase outside the Recovery Zone

A review of bat hibernacula across the western United States: Implications for white-nose syndrome surveillance and management

Efforts to conserve bats in the western United States have long been impeded by a lack of information on their winter whereabouts, particularly bats in the genus Myotis. The recent arrival of white-nose syndrome in western North America has increased the urgency to characterize winter roost habitats in this region. We compiled 4,549 winter bat survey records from 2,888 unique structures across 11 western states. Myotis bats were reported from 18.5% of structures with 95% of aggregations composed of ≤10 individuals. Only 11 structures contained ≥100 Myotis individuals and 6 contained ≥500 individuals. Townsend’s big-eared bat (Corynorhinus townsendii) were reported from 38% of structures, with 72% of aggregations composed of ≤10 individuals. Aggregations of ≥100 Townsend’s big-eared bats were observed at 41 different caves or mines across 9 states. We used zero-inflated negative binomial regression to explore biogeographic patterns of winter roost counts. Myotis counts were greater in caves than mines, in more recent years, and in more easterly longitudes, northerly latitudes, higher elevations, and in areas with higher surface temperatures and lower precipitation. Townsend’s big-eared bat counts were greater in caves, during more recent years, and in more westerly longitudes. Karst topography was associated with higher Townsend’s big-eared bat counts but did not appear to influence Myotis counts. We found stable or slightly-increasing trends over time in counts for both Myotis and Townsend’s big-eared bats from 82 hibernacula surveyed ≥5 winters since 1990. Highly-dispersed winter roosting of Myotis in the western USA complicates efforts to monitor population trends and impacts of disease. However, our results reveal opportunities to monitor winter population status of Townsend’s big-eared bats across this region