Ecology and Conservation of Bears

Contributed Oral Presentations

SESSION NUMBER: 89

Contributed paper sessions will be available on-demand for the duration of the conference, then again at the conclusion of the conference.

 

Assessing Population Viability of Black Bears Using Spatial Capture-Recapture Models
Richard Chandler; Michael J. Hooker; Bobby T. Bond; Michael J. Chamberlain
The Central Georgia Bear Population (CGP) is the least abundant and most isolated of Georgia’s 3 American black bear (Ursus americanus) populations. Beginning in 2011, changes to harvest regulations resulted in an increase in female bear harvest, creating concern that future harvest could be an important influence on population viability. Hence, our objective was to assess viability of the CGP under various levels of female mortality. During 2012-2016, we used barbed-wire hair snares to collect bear hair samples from within the range of the CGP. We used microsatellite genotyping to identify individual bears and created robust-design, spatial detection histories for all female bears detected. We fit open population spatial capture-recapture (SCR) models, and we forecast dynamics of the CGP 50 years into the future under various levels of female mortality. The top model included density-dependent per-capita recruitment, annual variation in detection probability, and a trap-level behavioral response. Abundance increased from 106 (95% CI: 86-132) females in 2012 to 136 (113-161) females in 2013 and remained relatively stable thereafter. Annual female survival was 0.75 (0.69-0.82) and did not vary among years. The per-capita recruitment rate decreased over time as density increased, being 0.49 (0.33-0.66) during the first time interval, and 0.29 (0.20-0.38) during the final time interval. Forecasts indicated continuation of the female mortality levels experienced from 2012-2016 were sustainable over 50 years, with the estimated extinction risk being <0.001%. Increasing annual harvest by 5 females introduced a negligible increase in the 50-year probability of extinction, but harvesting an additional 10 females/yr caused extinction risk to rise to 1.15%, which we consider high for a relatively small and genetically distinct population. We recommend that harvest regulations remain at current levels or do not increase by more than an annual average of 5 females above levels observed during our study.
Natal Den Selection by Parturient Female Louisiana Black Bears in Louisiana
Christopher D. Stelly; Heidi L. Adams
Despite being removed from the Federal List of Endangered and Threatened Wildlife in 2016, efforts persist to increase Louisiana black bear (Ursus americanus luteolus) occupation throughout their historical range. Reproductive habitat is an imperative component of these efforts due to the philopatric nature of the Louisiana black bear and its role in range expansion. Our objectives were to determine which land cover variables are important predictors of natal den site selection among female Louisiana black bears and how forest type influences the type of established natal den in the four subpopulations in Louisiana. Using natal den data from 1993 to 2017, land cover data from the National Land Cover Database (NLCD), and road data from the United States Census Bureau, we conducted Moran’s I Spatial Autocorrelation analyses and logistic regression to generate models describing the natal den site selection and den type establishment. Land cover types frequently represented in these models were woody wetlands, agricultural land, and deciduous forests. The amount of woody wetlands around an area increased the likelihood of a site being selected as a natal den by female Louisiana black bears and most often resulted in the establishment of a natal tree den. Agricultural land also tended to increase the likelihood of natal den site selection, possibly due to the availability of a food resource. The amount of deciduous forests increased natal den site selection likelihood in the Upper Atchafalaya River Basin subpopulation but decreased likelihood in the Tensas River Basin subpopulation. Results from our study may be used to manage habitats in and around the four Louisiana black bear subpopulations, as well as increase habitat connectivity between the subpopulations within the state of Louisiana and nearby states.
Statewide Home Ranges of American Black Bears in Florida Using 30 Years of Historic Data
Erin E. Poor; Brian Scheick; Jennifer M. Mullinax
The American black bear in Florida (Ursus americanus floridanus) was classified as Threatened by Florida in 1974, with an estimated population of ~300 individuals. After extensive research and active, on-going management, the population is expanding and exists in disparate subpopulations throughout an ecologically diverse state. Growing bear and human populations require up-to-date, accurate information to manage populations and mitigate conflict. Some home ranges have not been updated since the 1980’s and creating statewide home ranges with newer methods could allow comparisons among subpopulations – not before possible with differing methods across studies. We analyzed 3 decades of VHF and GPS collar data to create kernel density estimate home ranges across Florida and tested differences in proportion of land cover within home ranges. We found significant differences in home range size among subpopulations and amount of land cover types within home ranges. We encourage researchers to create standardized methods in the future, and hope this information will aid in management decisions for this unique black bear population.
Characteristics of Tree Damage and Black Bear Space Use in Intensively Managed Conifer Forests of the Pacific Northwest
Jimmy Taylor
Black bear (Ursus americanus) damage to forest resources is well documented and the magnitude of economic damage varies with spatial scale. Yet, the causal mechanism for why bears select some stands over others remains unknown. The goal of this study was to identify emergent factors or relationships that could be used to improve management plans to reduce black bear peeling in intensively managed forests. We collected GPS locations at 15 minute intervals from 49 black bear in western Oregon and Washington and generated 95% contour spring home ranges using a dynamic Brownian Bridge Movement Model. Using tools in ArcGIS, we randomly selected bear locations for damage assessments. Mean spring home ranges for female bears (µ= 6.9 ± 4.9 (SD) km2) were smaller than male bears (µ= 17.0 ± 13.7 (SD) km2, W = 683, p = 0.006). Spring home ranges of bears with access to feeders were 16% smaller but not statistically different than bears with no feeders present (W = 546, p = 0.442). Spring home ranges for females with cubs contracted an average of 61% during the cubs’ first year. Female bears damaged 3.5 times the number of trees damaged by males (χ21 = 7.2, p < 0.001). Bear age did not influenced peeling (χ23 = 5.8, p = 0.1) nor did the amount of time a bear spent in a stand (χ24= 6.2, p = 0.1). There was strong evidence stand age influenced tree peeling (χ21 = 21.1, p < 0.001) and the occurrence of fresh peeling was strongly associated with the combined presence of old bear peeling and stand age in both states. Thus far, our findings lend no silvicultural recommendations to foresters to decrease peeling damage. Ongoing efforts are further exploring these data with logistic regression and step selection function models.
Integrating Old and New Technologies to Investigate Polar Bear Energetics
Todd Atwood; Anthony Pagano
Since the late 1950’s, transmitter tags have been an important tool for understanding wildlife spatial ecology. Advances in tag technology, like the launching of the Argos satellite system in the 1970’s and development of the global positioning system (GPS) in the 1990’s, have made the collection of data more efficient while also improving the precision of point locations. Recent technological advances provide opportunities to create accessorized tags that allow for the simultaneous collection of spatial and behavioral data that, when integrated with other data, allow biologists to develop a more nuanced understanding of how animals interact with their environment. Here, we discuss the development and application of a tag and sensor platform to investigate the behavioral and physiological responses of polar bears (Ursus maritimus) to changes in sea ice habitat. We used GPS satellite collars with tri-axial accelerometers, conductivity sensors, and video cameras to measure the location, behavior, and energy expenditure of adult female polar bears from Alaska’s southern Beaufort Sea. We calibrated accelerometer and conductivity data collected from collars with behaviors observed from video-recorded captive polar bears and with video from camera collars deployed on free-ranging polar bears on sea ice and on land. Analyses suggested a strong ability to discriminate common polar bear behaviors using a combination of accelerometer and conductivity sensor data. This approach provides a method to quantify polar bear behavior and energetics in order to evaluate the impacts of further declines in Arctic sea ice.
Using Stable Isotopes to Measure the Impact of Corn on Mammalian Omnivores
John Hopkins
In world that is rapidly changing, it is more important than ever to develop the appropriate quantitative tools to measure the impact people have on wildlife. In this study, we develop an integrative approach to measure the proportion of corn, a C4 plant, in the diets of free-ranging mammalian omnivores in C3-dominated ecosystems. We fed captive mice corn, C3 plants, and meat until carbon stable isotopes (δ13C) from each diet equilibrated in their hair. We then used carbon discrimination factors (Δ13C; offsets between stable isotope values of consumer tissues and their foods) for mice from these feeding trials and a simple carbon stable isotope mixing model to estimate the corn-based diets of free-ranging American black bears in Wisconsin and brown bears in Slovenia. We used Δ13C factors for mice to estimate the diets of bears because mice models are commonly used to study mammalian diet and health, including humans and bears, and body mass has little to no effect on carbon discrimination factors in mammals. In this study, we found that mice grew fastest, largest, and δ13C values equilibrated quickest in the hair of mice fed meat versus plant-based diets, and that Δ13C was highest and most variable in the hair, serum, and liver of mice fed a mixed diet of C3 plants. Lastly, we found that corn may have been a more important component of bear diets in Wisconsin than previously thought, and brown bears may have fed on 50% more corn in autumn during a year when beechnut availability was low. Here, we provide a quantitative tool to measure the impact people have on mammalian omnivores and encourage others researchers to do the same for other taxa of interest.
Movement and Habitat Selection of Black Bears within the Urbanized Context of Central Florida’S Wekiva River Basin
Dana L. Karelus; Daniel J. Smith; Crystal Gagne
Florida black bears (Ursus americanus floridanus) in central Florida’s Wekiva River Basin reside in an area where protected conservation lands abut high densities of residential and commercial development. Local area bear and human densities have increased in the past decade, and the number of human-bear conflicts has risen. Therefore, our objectives were to test for differences in bear movements between these suburban and natural areas and examine their habitat selection considering suburban neighborhood features (e.g. woodlots, golf courses) and temporal aspects (e.g. garbage day, rush hour) to better understand why bears frequented certain neighborhoods. We GPS collared 17 bears (9 females, 8 males) between 2014 and 2016. We fit hidden Markov models (HMMs) to hourly bear locations to determine behavioral states that described their movements and to estimate movement parameters defining those states. Then, for each step, we randomly selected alternate unused steps based on the corresponding assigned behavioral state and used step-selection functions to investigate habitat selection. Overall, females and males exhibited average hourly step lengths (± SE) of 125.73 ± 1.24 m and 193.55 ± 2.29 m, respectively. Based on sex and season specific 3-state HMMs, females in all seasons exhibited 2 states with short step lengths and sharp turning angles and a third state with long steps and wide turning angles. For males, the pattern was similar except the second state instead included moderate step lengths and wide turning angles. Overall, bears selected most for natural wooded land cover types and selected least for anthropogenic land covers, but males were more likely to use neighborhoods than females and both sexes were more likely to use them in the fall. Our results provide useful information for bear management and conflict mitigation in this sprawling suburban area of Orlando, Florida and for other bear populations at a wildland-urban interface.
Bear’s Eye View: Using ‘Critter Cams’ to Compare Male Versus Female Foraging and Activity of American Black Bears in the Appalachian Mountains
Brogan E. Holcombe; Robert S. Alonso; David M. McNitt; Marcella J. Kelly
Frequency of occurrence analyses of scat are traditionally used to understand diet and consumption patterns of carnivores. However, these methods are difficult to interpret for omnivorous species, such as American black bears (Ursus americanus), because large diet items like white-tailed deer (Odocoileus virginianus), are easily detected by indigestible parts, but the soft mast is usually digested and thus is underrepresented potentially leading to erroneous diet classification. We used critter-cams on 18 GPS-collared black bears in 2018 (4M, 4F) and 2019 (5M, 3F) in the central Appalachian Mountains of Virginia, to document and compare diet and foraging behavior of male versus female bears. We recorded 10-20 seconds of video every 20 minutes during daylight hours (15-20 minutes/day), for a maximum of 17.5 hours per bear over 2-4 months. The high-quality video enabled us to determine the plants, animals, fungi, and anthropogenic food bears consume. We found males spent ~69% of events sleeping/resting and only 8% of events foraging/eating, while females spent fewer events sleeping/resting (26-54%) and more events foraging/eating (13-21%). Males spent a higher proportion of events foraging for food in tree logs (0.21) and mounds (0.29), while females displayed higher proportions of rock flipping (0.40) and leaf litter digging (0.29). Additionally, males ate soft mast in a lower proportion of events than females (0.44 vs. 0.79) and ate carcass meat, commonly white-tailed deer, more often than females (0.42 vs. 0.06). Furthermore, we did not document bears consuming anthropogenic food and rarely located them in residential areas. Our results highlight sex differences in foraging behavior, the importance of soft mast for females, and propensity for male bears to consume more deer. Our “critter-cam” data analyses provide better insight than scat sampling into black bear foraging ecology and provide information relevant to black bear management.
Pulling Hair: Estimating the Black Bear Population in Wisconsin Using Genetic Spatial Capture-Recapture
Jennifer L. Price Tack; Laura A. McMahon; Ben C. Augustine; Nathan M. Roberts; David M. MacFarland
Robust population estimates are paramount for informing management of harvested wildlife populations and populations of conservation concern. For example, while the Wisconsin Department of Natural Resources (DNR) relies on an age-at-harvest model to predict population responses to black bear (Ursus americanus) harvest rates, it still requires periodic calibration with a population point-estimate. We used traditional spatially-explicit capture-recapture (SCR) and the recently developed genetic spatial partial identity model (SPIM) to obtain bear population estimates in Wisconsin using hair samples. The genetic SPIM model utilizes all samples, regardless of whether they meet microsatellite matching requirements for individual detection, and accounts for genotyping errors. During the summer of 2019, we collected 6,396 hair samples at 844 barbed wire hair corrals across 34 counties during four weekly checks. Of the hair corrals set, 72.5% were visited by bear at least once. We estimated density of 30-40 bears/100 km2 across the state, with variation across management zones. The SPIM results increased the precision of our estimates relative to the traditional SCR model, but only slightly. Given the relatively large sample size of our study, our results indicate that genetic SPIM models may be most valuable for studies with small samples sizes, which may see increased payoff from including genetic samples that were previously discarded. We discuss the implications of our study for bear management in Wisconsin and of our approach to estimating abundance of other wildlife populations.
Validating a Gis Model of Black Bear Corridors in Alabama
Hannah Leeper; Todd Steury
Corridors are important for many species, especially for black bears (Ursus americanus), which use corridors for juvenile dispersal and connectivity between preferred habitat patches. Black bears are historically native throughout Alabama; however, historic populations have diminished as a result of (at least in part) habitat degradation and decreased connectivity. Now, there are only two small populations of black bears in Alabama. One is a newly recolonized population in northern Alabama that is growing quickly. The other is a remnant population in the Mobile River Basin that is genetically isolated from other black bear populations in the southeastern U.S. Neither population is exhibiting the spatial growth patterns typical of such small populations. One proposed explanation for the observed limited spatial growth and genetic isolation is a lack of corridors, resulting in decreased connectivity. Thus, this study had two main objectives: first, we created a Geographic Information System (GIS) model of corridor suitability for black bears in Alabama based on previously-published black bear corridor models. Higher quality corridors were designated as >800 meters from a road, <600 meters to a water body, having a low level of human development, and within preferred black bear land cover types. Second, we used ROC curves of actual black bear use locations and randomly generated locations fit to the model to validate our corridor suitability model. We hypothesized that physical barriers on the landscape inhibit black bear movement. We also hypothesized that actual black bear use locations would be in higher quality corridors, compared to random locations. Results indicated that the availability of corridors does not appear to be limiting spatial population growth or gene flow in Alabama black bear populations.

 

Virtual
Location: Virtual Date: Time: -