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Black Bears (black + bear)
Selected AbstractsComputed Tomographic, Magnetic Resonance Imaging, and Cross-Sectional Anatomic Features of the Manus in a Normal American Black Bear (Ursus americanus)ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 3 2010C. P. Ober With 11 figures and 1 table Summary The purpose of this study was to provide a detailed description of cross-sectional anatomic structures of the manus of a black bear cadaver and correlate anatomic findings with corresponding features in computed tomographic (CT) and magnetic resonance (MR) images. CT, MR imaging, and transverse sectioning were performed on the thoracic limb of a cadaver female black bear which had no evidence of lameness or thoracic limb abnormality prior to death. Features in CT and MR images corresponding to clinically important anatomic structures in anatomic sections were identified. Most of the structures identified in transverse anatomic sections were also identified using CT and MR imaging. Bones, muscles and tendons were generally easily identified with both imaging modalities, although divisions between adjacent muscles were rarely visible with CT and only visible sometimes with MR imaging. Vascular structures could not be identified with either imaging modality. [source] Predicting the distribution of Sasquatch in western North America: anything goes with ecological niche modellingJOURNAL OF BIOGEOGRAPHY, Issue 9 2009J. D. Lozier Abstract The availability of user-friendly software and publicly available biodiversity databases has led to a rapid increase in the use of ecological niche modelling to predict species distributions. A potential source of error in publicly available data that may affect the accuracy of ecological niche models (ENMs), and one that is difficult to correct for, is incorrect (or incomplete) taxonomy. Here we remind researchers of the need for careful evaluation of database records prior to use in modelling, especially when the presence of cryptic species is suspected or many records are based on indirect evidence. To draw attention to this potential problem, we construct ENMs for the North American Sasquatch (i.e. Bigfoot). Specifically, we use a large database of georeferenced putative sightings and footprints for Sasquatch in western North America, demonstrating how convincing environmentally predicted distributions of a taxon's potential range can be generated from questionable site-occurrence data. We compare the distribution of Bigfoot with an ENM for the black bear, Ursus americanus, and suggest that many sightings of this cryptozoid may be cases of mistaken identity. [source] Historical and contemporary distributions of carnivores in forests of the Sierra Nevada, California, USAJOURNAL OF BIOGEOGRAPHY, Issue 8 2005William J. Zielinski Abstract Aim, Mammalian carnivores are considered particularly sensitive indicators of environmental change. Information on the distribution of carnivores from the early 1900s provides a unique opportunity to evaluate changes in their distributions over a 75-year period during which the influence of human uses of forest resources in California greatly increased. We present information on the distributions of forest carnivores in the context of two of the most significant changes in the Sierra Nevada during this period: the expansion of human settlement and the reduction in mature forests by timber harvest. Methods, We compare the historical and contemporary distributions of 10 taxa of mesocarnivores in the conifer forests of the Sierra Nevada and southern Cascade Range by contrasting the distribution of museum and fur harvest records from the early 1900s with the distribution of detections from baited track-plate and camera surveys conducted from 1996 to 2002. A total of 344 sample units (6 track plates and 1 camera each) were distributed systematically across c. 3,000,000 ha area over a 7-year period. Results, Two species, the wolverine (Gulo gulo) and the red fox (Vulpes vulpes), present in the historical record for our survey area, were not detected during the contemporary surveys. The distributions of 3 species (fisher [Martespennanti], American marten [M. americana], and Virginia opossum [Didelphisvirginiana]) have substantially changed since the early 1900s. The distributions of fishers and martens, mature-forest specialists, appeared to have decreased in the northern Sierra Nevada and southern Cascade region. A reputed gap in the current distribution of fishers was confirmed. We report for the first time evidence that the distribution of martens has become fragmented in the southern Cascades and northern Sierra Nevada. The opossum, an introduced marsupial, expanded its distribution in the Sierra Nevada significantly since it was introduced to the south-central coast region of California in the 1930s. There did not appear to be any changes in the distributions of the species that were considered habitat generalists: gray fox (Urocyon cinereoargenteus), striped skunk (Mephitis mephitis), western spotted skunk (Spilogale gracilis), or black bear (Ursus americanus). Detections of raccoons (Procyon lotor) and badgers (Taxidea taxus) were too rare to evaluate. Contemporary surveys indicated that weasels (M. frenata and M. erminea) were distributed throughout the study area, but historical data were not available for comparison. Main conclusions, Two species, the wolverine and Sierra Nevada red fox, were not detected in contemporary surveys and may be extirpated or in extremely low densities in the regions sampled. The distributions of the mature forest specialists (marten and fisher) appear to have changed more than the distributions of the forest generalists. This is most likely due to a combination of loss of mature forest habitat, residential development and the latent effects of commercial trapping. Biological characteristics of individual species, in combination with the effect of human activities, appear to have combined to affect the current distributions of carnivores in the Sierra Nevada. Periodic resampling of the distributions of carnivores in California, via remote detection methods, is an efficient means for monitoring the status of their populations. [source] Computed Tomographic, Magnetic Resonance Imaging, and Cross-Sectional Anatomic Features of the Manus in a Normal American Black Bear (Ursus americanus)ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 3 2010C. P. Ober With 11 figures and 1 table Summary The purpose of this study was to provide a detailed description of cross-sectional anatomic structures of the manus of a black bear cadaver and correlate anatomic findings with corresponding features in computed tomographic (CT) and magnetic resonance (MR) images. CT, MR imaging, and transverse sectioning were performed on the thoracic limb of a cadaver female black bear which had no evidence of lameness or thoracic limb abnormality prior to death. Features in CT and MR images corresponding to clinically important anatomic structures in anatomic sections were identified. Most of the structures identified in transverse anatomic sections were also identified using CT and MR imaging. Bones, muscles and tendons were generally easily identified with both imaging modalities, although divisions between adjacent muscles were rarely visible with CT and only visible sometimes with MR imaging. Vascular structures could not be identified with either imaging modality. [source] Landscape linkages and conservation planning for the black bear in west-central FloridaANIMAL CONSERVATION, Issue 1 2004Jeffery L. Larkin The Greater Chassahowitzka black bear population is the smallest documented in North America with fewer than 20 individuals. Its future depends on landscape linkages with other bear populations that are separated by denatured habitat. We used a Geographic Information System (GIS) to identify potential landscape linkages between this isolated population and six others in Florida. Pathway lengths ranged from 60,194 km with varying potentials for facilitating black bear dispersal. Each pathway incorporated 35,88% conservation land and encountered at least 11 dispersal bottlenecks. Even pathways that incorporated extensive conservation land encountered bottlenecks that make these linkages potentially unviable. All six pathways, however, passed through ,95% core black bear habitat. Thus, the infrastructure for a conservation network is still largely intact. The Suwannee pathway provides the best opportunity to restore connectivity between the Greater Chassahowitzka Ecosystem (GCE) and a southward colonising bear population in the Big Bend region. However, intensification of development poses an immediate threat to maintaining connectivity between the GCE and other bear populations in Florida. Through immediate strategic planning and active conservation and restoration measures, many of the generated pathways can provide long-term connectivity. Least-cost path analyses can aid in the conservation of wide-ranging animals by providing managers with a science-based, empirically derived blueprint of potential landscape linkages. [source] Representing genetic variation as continuous surfaces: an approach for identifying spatial dependency in landscape genetic studiesECOGRAPHY, Issue 6 2008Melanie A. Murphy Landscape genetics, an emerging field integrating landscape ecology and population genetics, has great potential to influence our understanding of habitat connectivity and distribution of organisms. Whereas typical population genetics studies summarize gene flow as pairwise measures between sampling localities, landscape characteristics that influence population genetic connectivity are often continuously distributed in space. Thus, there are currently gaps in both the ability to analyze genotypic data in a continuous spatial context and our knowledge of expected of landscape genetic structure under varying conditions. We present a framework for generating continuous "genetic surfaces", evaluate their statistical properties, and quantify statistical behavior of landscape genetic structure in a simple landscape. We simulated microsatellite genotypes under varying parameters (time since vicariance, migration, effective population size) and used ancestry (q) values from STRUCTURE to interpolate a genetic surface. Using a spatially adjusted Pearson's correlation coefficient to test the significance of landscape variable(s) on genetic structure we were able to detect landscape genetic structure on a contemporary time scale (,5 generations post vicariance, migration probability ,0.10) even when population differentiation was minimal (FST,0.00015). We show that genetic variation can be significantly correlated with geographic distance even when genetic structure is due to landscape variable(s), demonstrating the importance of testing landscape influence on genetic structure. Finally, we apply genetic surfacing to analyze an empirical dataset of black bears from northern Idaho USA. We find black bear genetic variation is a function of distance (autocorrelation) and habitat patch (spatial dependency), consistent with previous results indicating genetic variation was influenced by landscape by resistance. These results suggest genetic surfaces can be used to test competing hypotheses of the influence of landscape characteristics on genetic structure without delineation of categorical groups. [source] Black bear femoral geometry and cortical porosity are not adversely affected by ageing despite annual periods of disuse (hibernation)JOURNAL OF ANATOMY, Issue 2 2007Meghan E. McGee Abstract Disuse (i.e. inactivity) causes bone loss, and a recovery period that is 2,3 times longer than the inactive period is usually required to recover lost bone. However, black bears experience annual disuse (hibernation) and remobilization periods that are approximately equal in length, yet bears maintain or increase cortical bone material properties and whole bone mechanical properties with age. In this study, we investigated the architectural properties of bear femurs to determine whether cortical structure is preserved with age in bears. We showed that cross-sectional geometric properties increase with age, but porosity and resorption cavity density do not change with age in skeletally immature male and female bears. These findings suggest that structural properties substantially contribute to increasing whole bone strength with age in bears, particularly during skeletal maturation. Porosity was not different between skeletally immature and mature bears, and showed minimal regional variations between anatomical quadrants and radial positions that were similar in pattern and magnitude between skeletally immature and mature bears. We also found gender dimorphisms in bear cortical bone properties: females have smaller, less porous bones than males. Our results provide further support for the idea that black bears possess a biological mechanism to prevent disuse osteoporosis. [source] Maintenance of bone mass and architecture in denning black bears (Ursus americanus)JOURNAL OF ZOOLOGY, Issue 4 2004Connor K. Pardy Abstract Bone mass is dramatically compromised during periods of weightlessness, inactivity, or bed rest. Animals that hibernate reduce their body temperature, heart rate and metabolic activity, and likewise lower bone turnover activity during their immobile state. Black bears Ursus americanus, however, do not hibernate, but rather overwinter by denning during which they maintain a nearly normal functional heart rate, cardiac output and temperature. Furthermore, markers of bone turnover in black bears are maintained during denning periods. Thus, the purpose of this work was to determine if the denning state of relative immobility in black bears results in changes in bone mass and bone architectural structure. Harvested forelimbs (ulna and radius) were compared between pre- and post-denning black bears using X-ray imaging, dual energy X-ray absorptiometry, and micro-computed tomography to quantify total distal forelimb bone mineral density, cancellous bone mineral density, bone mineral content, bone volume fraction, degree of anisotropy, structure model index, and trabecular thickness. No significant differences in any of the measured parameters were found in comparing radius and ulna from autumn and spring bears in this cross-sectional sample, suggesting that black bears did not experience a significant change in bone mass or architecture during denning. The statistical power for detecting a significant difference (P, 0.05) for this sample was 0.8. The specific mechanism by which the preservation of bone was attained may be related to skeletal muscle interaction or circulating systemic hormones. [source] Sex-biased natal dispersal and inbreeding avoidance in American black bears as revealed by spatial genetic analysesMOLECULAR ECOLOGY, Issue 21 2008CECILY M. COSTELLO Abstract We tested the hypothesis that sex-biased natal dispersal reduces close inbreeding in American black bears, a solitary species that exhibits nearly complete male dispersal and female philopatry. Using microsatellite DNA and spatial data from reproductively mature bears (, 4 years old), we examined the spatial genetic structure of two distinct populations in New Mexico from 1993 to 2000. As predicted, relatedness (r) and the frequency of close relationships (parent,offspring or full siblings) decreased with distance among female dyads, but little change was observed among male or opposite-sex dyads. Neighbouring females were more closely related than neighbouring males. The potential for inbreeding was low. Most opposite-sex pairs that lived sufficiently close to facilitate mating were unrelated, and few were close relatives. We found no evidence that bears actively avoided inbreeding in their selection of mates from this nearby pool, as mean r and relationship frequencies did not differ between potential and actual mating pairs (determined by parentage analysis). These basic patterns were apparent in both study areas despite a nearly two-fold difference in density. However, the sex bias in dispersal was less pronounced in the lower-density area, based on proportions of bears with male and female relatives residing nearby. This result suggests that male bears may respond to reduced competition by decreasing their rate or distance of dispersal. Evidence supports the hypothesis that inbreeding avoidance is achieved by means of male-biased dispersal but also indicates that competition (for mates or resources) modifies dispersal patterns. [source] | ||||||||||