Diet Composition and Body Condition of Northern Continental Divide Grizzly Bears, Montana

From 2009–2013, we documented apparent population health by investigating food use and physiological condition of grizzly bears (Ursus arctos) in the Northern Continental Divide Ecosystem (NCDE), Montana.  We used stable isotope analysis upon hair and blood tissue to obtain information on percent terrestrial meat and plant matter in the diets of NCDE bears.  We also assessed body fat content of grizzly bears via bioelectrical impedance analysis.  Adult females used less meat compared to subadults and adult males (P < 0.0001).  Bears within regions on the southwestern, southern, and eastern periphery of the ecosystem consumed a significantly higher proportion of meat than those in the interior or northwestern periphery (P < 0.0001).  Diets of bears in the Whitefish Mountains and North and South Fork of the Flathead River were, on average, composed of 70% less meat than those on the East Front.  Adult males had significantly higher den entrance body fat contents than adult females and subadults (P < 0.0001).  Average body fat of adult females varied significantly between those in areas of high consumption of meat and those otherwise.  However, we find adult females across all regions enter dens at mean fat levels above those thought to be critical for cub production (i.e., > 20%).  We conclude that, within each region, the quantity and quality of foods appear adequate to meet the needs of reproductively-active adult females.  As truly opportunistic omnivores, grizzly bears in each region of the NCDE exploit diverse combinations of food items to arrive at productive body conditions

Conservation of Threatened Canada-USA Trans-border Grizzly Bears Linked to Comprehensive Conflict Reduction

Mortality resulting from human–wildlife conflicts affects wildlife populations globally. Since 2004, we have been researching conservation issues and implementing a comprehensive program to reduce human–bear conflicts (Ursus spp.; HBC) for 3 small, fragmented, and threatened grizzly bear (U. arctos) populations in the trans-border region of southwest Canada and northwest USA. We explored the temporal and spatial patterns of conflict mortality and found that HBC contributed significantly to the threatened status of these populations by causing decline, fragmentation, and decreased habitat effectiveness. Our program to reduce HBCs primarily included strategic private lands purchased to reduce human density in wildlife corridors, the reduction of bear attractants where human settlement and agriculture exists, and the nonlethal management of conflict bears. Attractant management strategies encompassed public education, cost-share electric fencing, bear-resistant garbage containers, and deadstock containment. We taught bear safety courses and bear spray training to increase tolerance and give people tools to avoid negative encounters with bears. We radio-collared and used nonlethal management on potential conflict bears and have a ~75% success rate in that the bear was alive and out of conflict situations over the life of the radio-collar. We identified important backcountry grizzly bear foraging habitat for motorized access control to reduce conflict and mortality and provide habitat security to reproductive females. Ongoing monitoring has demonstrated that our comprehensive HBC program has resulted in a significant reduction in human-caused mortality, increased inter-population connectivity, and improved habitat effectiveness. Several challenges remain, however, including an increase in the numbers of young grizzly bears living adjacent to agricultural areas. Herein we discuss strategies for how to integrate conservation vision into future HBC reduction programs

The bear circadian clock doesn’t ‘sleep’ during winter dormancy

Most biological functions are synchronized to the environmental light:dark cycle via a circadian timekeeping system. Bears exhibit shallow torpor combined with metabolic suppression during winter dormancy. We sought to confirm that free-running circadian rhythms of body temperature (Tb) and activity were expressed in torpid grizzly (brown) bears and that they were functionally responsive to environmental light. We also measured activity and ambient light exposures in denning wild bears to determine if rhythms were evident and what the photic conditions of their natural dens were. Lastly, we used cultured skin fibroblasts obtained from captive torpid bears to assess molecular clock operation in peripheral tissues. Circadian parameters were estimated using robust wavelet transforms and maximum entropy spectral analyses

American Black Bear Population Fragmentation Determined Through Pedigrees in the Trans-Border Canada-United States Region

Fragmentation of species with large numbers of individuals in adjacent areas can be challenging to detect using genetic tools as there often is no differentiation because genetic drift occurs very slowly. We used a genetic-based pedigree analysis to detect fragmentation in the American black bear (Ursus americanus) across 2 highways with large adjacent populations. We used 20 locus microsatellite genotypes to detect parent-offspring and full sibling pairs within a sample of 388 black bears. We used the spatial patterns of capture locations of these first order relatives relative to US Highway 2 in northwest Montana and Highway 3 in southeast British Columbia to estimate the number of close relatives sampled across the highways (migrants/km of highway length) as an index of fragmentation. We compared these values to an expected migrant/km rate derived from the mean values of simulated fractures in the Highway 2 and Highway 3 region. We found evidence that these highway corridors were fragmenting black bear populations, but not completely. The observed migrant/km rate for Highway 2 was 0.05, while the expected rate was 0.21 migrants/km. Highway 3 had an observed migrant/km rate of 0.09 compared to the expected rate of 0.26. None of the 16 bears carrying GPS radio collars for 1 year crossed Highway 2, yet 6 of 18 crossed Highway 3. Pedigree and telemetry results were more closely aligned in the Highway 2 system evidencing more intense fragmentation than we found along Highway 3. Our results demonstrate that pedigree analysis may be a useful tool for investigating population fragmentation in situations where genetic signals of differentiation are too weak to determine migration rates using individual-based methods, such as population assignment

Estimating Grizzly Bear Use of Large Ungulate Carcasses With GPS Telemetry Data

Ungulate meat is among the most calorie-rich food sources available to grizzly bears  (Ursus arctos) in the greater Yellowstone ecosystem (GYE). However, the ephemeral and unpredictable nature of carcasses makes them difficult to study and their influence on grizzly bear foraging and spatial ecology is poorly understood. We developed a spatial-clustering technique specifically for detecting grizzly bear use of large ungulate carcasses using Global Positioning System (GPS) telemetry locations (n = 54 bear years). We used the DBScan algorithm to identify GPS clusters of individual bears (n = 2,038) and intersected these clusters with an independent dataset of site  visits to recent bear movement paths based from randomly selected days (n = 732 site visits; 2004–2011) resulting in 174 clusters associated with field measured bear behavior. Using a suite of predictor variables derived from GPS telemetry locations, e.g., duration of cluster, area used, activity sensor values, re-visitation rate, we used multinomial logistic regression to predict the probability of belonging to  each of the five response classes (resting, multiple-use, low-biomass carcass, high-biomass carcass, old carcass). Focusing on the high-biomass carcass category, for which our top model correctly classified 88 percent of the carcasses correctly, we applied our approach to a larger dataset of GPS data to examine trends in large-ungulate carcass using of grizzly bears in the GYE from 2002-2011. We found quantitative support for a positive effect of year and mortality adjusted white bark pine cone counts on the carcass-use index during the fall months (Sep and Oct) from 2002-2011

Report from UCSF.

Table S1. Body weights (kg) of captive bears just prior to entering winter dormancy. (PDF 630 kb

Applied Investigations into Grizzly (Ursus arctos) and black bear (U. americanus) ecology and management

The following dissertation is composed of three stand-alone manuscripts. However all contribute to a working set of knowledge and techniques pertaining to the ecology and management of grizzly (Ursus arctos) and black (U. americanus) bears. In Chapter I, I studied the interaction of grizzly and black bear abundance with declining numbers of cutthroat trout along spawning stream reaches. We estimated numbers of grizzly bears and black bears visiting streams by 1) capturing hair from collection sites along 35 historically fished streams and 2) modeling individual DNA encounter histories. When compared to 1997-2000 levels, the number of spawning cutthroat trout per stream and the number of streams with cutthroat trout had decreased. We estimated that 48 (95% CI = 42-56) male and 23 (95% CI = 21-27) female grizzly bears visited the historically fished tributary streams during the 3-yr study. In any one year, 46 to 59 independent individuals (8-10% of estimated Greater Yellowstone Ecosystem [GYE] population) visited these streams. When compared with estimates from the 1997-2000 study and adjusted for equal effort, the number of grizzly bears using the stream corridors had decreased by 63%.In the second Chapter, I investigated the genetic consequences of management actions and genetic introgression on black bears. Due to changing management philosophies and policies in Yellowstone National Park (YNP), large numbers of black bears were removed (13 to 30% of population per annum) from the core of the ecosystem between 1930 and 1970. Using ancient DNA (aDNA) extraction techniques on historic specimens, we investigated whether these removals influenced genetic diversity of black bears within the GYE. While Ne values were found to be historically low (Ne point estimates of 19-87) since the early years of the Park, we observed only slight decreases in all diversity measures before and after the large-scale removal of black bears, likely due to gene flow from outside demes. However, the strength of genetic drift following removals may have been much more substantial without this outside introgression.Chapter III introduces a novel combination of anesthetics shown to be quite effective in immobilizing captive and wild grizzly bears. Fast induction of anesthesia, maintenance of healthy vital rates, and predictable recoveries are essential when immobilizing bears for research and management. We investigated these attributes in both captive and wild grizzly bears anesthetized with a combination of a reversible α2¬ agonist (dexmedetomidine) and a nonreversible glutamate agonist and tranquilizer (tiletamine and zolazepam, respectively). A smaller than expected dose of the combination (1.23 mg tiletamine, 1.23 mg zolazepam, and 6.04 µg dexmedetomidine per kg bear) produced reliable, fast ataxia (3.7 ± 0.5 min, ± SE) and workable anesthesia (8.1 ± 0.6 min) in captive adult grizzly bears. Contrary to previously published accounts of bear anesthesia with medetomidine, this combination produced less significant hypertension, hypoxemia, hypoventilation, or rectal temperatures, although mild bradycardia (< 50 beats per minute) occurred in most bears during the active season. With captive bears, effective dose rates during hibernation were approximately half those during the active season. The time to first signs of recovery after the initial injection of dexMTZ was influenced by heart rate (P < 0.001) and drug dose (P < 0.001). Field trials confirmed that the dexMTZ + atipamezole protocol is safe, reliable, and predictable when administered to wild grizzly bears during foothold snare, and helicopter capture operations