| phylogeographic analyses of american black bears (ursus americanus) suggest four glacial refugia and complex patterns of postglacial admixture. | studies of species with continental distributions continue to identify intraspecific lineages despite continuous habitat. lineages may form due to isolation by distance, adaptation, divergence across barriers, or genetic drift following range expansion. we investigated lineage diversification and admixture within american black bears (ursus americanus) across their range using 22 k single nucleotide polymorphisms and mitochondrial dna sequences. we identified three subcontinental nuclear cluster ... | 2015 | 25989983 |
| bis(monoacylglycero)phosphate: a secondary storage lipid in the gangliosidoses. | bis(monoacylglycero)phosphate (bmp) is a negatively charged glycerophospholipid with an unusual sn-1;sn-1' structural configuration. bmp is primarily enriched in endosomal/lysosomal membranes. bmp is thought to play a role in glycosphingolipid degradation and cholesterol transport. elevated bmp levels have been found in many lysosomal storage diseases (lsds), suggesting an association with lysosomal storage material. the gangliosidoses are a group of neurodegenerative lsds involving the accumula ... | 2015 | 25795792 |
| introgressive hybridization: brown bears as vectors for polar bear alleles. | the dynamics and consequences of introgression can inform about numerous evolutionary processes. biologists have therefore long been interested in hybridization. one challenge, however, lies in the identification of nonadmixed genotypes that can serve as a baseline for accurate quantification of admixture. in this issue of molecular ecology, cahill et al. (2015) analyse a genomic data set of 28 polar bears, eight brown bears and one american black bear. polar bear alleles are found to be introgr ... | 2015 | 25775930 |
| bears benefit plants via a cascade with both antagonistic and mutualistic interactions. | predators can influence primary producers by generating cascades of effects in ecological webs. these effects are often non-intuitive, going undetected because they involve many links and different types of species interactions. particularly, little is understood about how antagonistic (negative) and mutualistic (positive) interactions combine to create cascades. here, we show that black bears can benefit plants by consuming ants. the ants are mutualists of herbivores and protect herbivores from ... | 2015 | 25534277 |
| big data in wildlife research: remote web-based monitoring of hibernating black bears. | numerous innovations for the management and collection of "big data" have arisen in the field of medicine, including implantable computers and sensors, wireless data transmission, and web-based repositories for collecting and organizing information. recently, human clinical devices have been deployed in captive and free-ranging wildlife to aid in the characterization of both normal physiology and the interaction of animals with their environment, including reactions to humans. although these dev ... | 2014 | 25496699 |
| trap array configuration influences estimates and precision of black bear density and abundance. | spatial capture-recapture (scr) models have advanced our ability to estimate population density for wide ranging animals by explicitly incorporating individual movement. though these models are more robust to various spatial sampling designs, few studies have empirically tested different large-scale trap configurations using scr models. we investigated how extent of trap coverage and trap spacing affects precision and accuracy of scr parameters, implementing models using the r package secr. we t ... | 2014 | 25350557 |
| using stable isotopes to assess dietary changes of american black bears from 1980 to 2001. | we measured stable carbon and nitrogen isotope ratios in 117 hair samples from american black bears (ursus americanus) in great smoky mountains national park, tennessee, during 1980-2001 from live-trapped bears. we also collected hair from bears with known diets to compare with the wild bears. we hypothesized that biological factors (age, mass, and sex), food availability (hard mast and wild hogs (sus scrofa)), and nuisance status would influence food selection by black bears and changes in thei ... | 2014 | 24998986 |
| comparative genomics of mammalian hibernators using gene networks. | in recent years, the study of the molecular processes involved in mammalian hibernation has shifted from investigating a few carefully selected candidate genes to large-scale analysis of differential gene expression. the availability of high-throughput data provides an unprecedented opportunity to ask whether phylogenetically distant species show similar mechanisms of genetic control, and how these relate to particular genes and pathways involved in the hibernation phenotype. in order to address ... | 2014 | 24881044 |
| influence of drift and admixture on population structure of american black bears (ursus americanus) in the central interior highlands, usa, 50 years after translocation. | bottlenecks, founder events, and genetic drift often result in decreased genetic diversity and increased population differentiation. these events may follow abundance declines due to natural or anthropogenic perturbations, where translocations may be an effective conservation strategy to increase population size. american black bears (ursus americanus) were nearly extirpated from the central interior highlands, usa by 1920. in an effort to restore bears, 254 individuals were translocated from mi ... | 2014 | 24712442 |
| application of large-scale parentage analysis for investigating natal dispersal in highly vagile vertebrates: a case study of american black bears (ursus americanus). | understanding the factors that affect dispersal is a fundamental question in ecology and conservation biology, particularly as populations are faced with increasing anthropogenic impacts. here we collected georeferenced genetic samples (n = 2,540) from three generations of black bears (ursus americanus) harvested in a large (47,739 km2), geographically isolated population and used parentage analysis to identify mother-offspring dyads (n = 337). we quantified the effects of sex, age, habitat type ... | 2014 | 24621593 |
| gm1-gangliosidosis in american black bears: clinical, pathological, biochemical and molecular genetic characterization. | g(m1)-gangliosidosis is a rare progressive neurodegenerative disorder due to an autosomal recessively inherited deficiency of lysosomal β-galactosidase. we have identified seven american black bears (ursus americanus) found in the northeast united states suffering from g(m1)-gangliosidosis. this report describes the clinical features, brain mri, and morphologic, biochemical and molecular genetic findings in the affected bears. brain lipids were compared with those in the brain of a g(m1)-mouse. ... | 2014 | 24581871 |
| genetic connectivity for two bear species at wildlife crossing structures in banff national park. | roads can fragment and isolate wildlife populations, which will eventually decrease genetic diversity within populations. wildlife crossing structures may counteract these impacts, but most crossings are relatively new, and there is little evidence that they facilitate gene flow. we conducted a three-year research project in banff national park, alberta, to evaluate the effectiveness of wildlife crossings to provide genetic connectivity. our main objective was to determine how the trans-canada h ... | 2014 | 24552834 |
| trap configuration and spacing influences parameter estimates in spatial capture-recapture models. | an increasing number of studies employ spatial capture-recapture models to estimate population size, but there has been limited research on how different spatial sampling designs and trap configurations influence parameter estimators. spatial capture-recapture models provide an advantage over non-spatial models by explicitly accounting for heterogeneous detection probabilities among individuals that arise due to the spatial organization of individuals relative to sampling devices. we simulated b ... | 2014 | 24505361 |
| mediastinal teratoma in a free-ranging american black bear (ursus americanus). | a 2.75-yr-old female american black bear (ursus americanus) was found emaciated and unable to rise. it was euthanized due to the perceived poor prognosis. an approximately 18 x 8 x 10-cm, multiloculated, well-demarcated mass that extended from the bifurcation of the trachea, laterally displacing the lung lobes and caudally displacing the heart. the mass contained fibrous connective tissue, cartilage, bone, nervous tissue, smooth muscle, and a variety of epithelial structures. a mediastinal terat ... | 2013 | 24450083 |
| stochasticity in natural forage production affects use of urban areas by black bears: implications to management of human-bear conflicts. | the rapid expansion of global urban development is increasing opportunities for wildlife to forage and become dependent on anthropogenic resources. wildlife using urban areas are often perceived dichotomously as urban or not, with some individuals removed in the belief that dependency on anthropogenic resources is irreversible and can lead to increased human-wildlife conflict. for american black bears (ursus americanus), little is known about the degree of bear urbanization and its ecological me ... | 2014 | 24416350 |
| sequential ovulation and fertility of polyoestrus in american black bears (ursus americanus). | american black bears (ursus americanus) are seasonally polyoestrous and exhibit delayed implantation, which may allow equal and independent fertility of recurrent oestruses of a mating season. we postulated that the luteal inactivity during delayed implantation allows bears to have sequential ovulation during a polyoestrous mating season such that each oestrus of a polyoestrous female will have equivalent fertility, and pregnancy would not preclude subsequent ovulation and superfetation. control ... | 2014 | 27293672 |
| trichinella surveillance in black bears (ursus americanus) from oregon, usa. | we used serology and muscle digestion to test black bears (ursus americanus) from western oregon, usa, for trichinella. results indicate black bears in oregon are not part of a sylvatic cycle for trichinella, and risk of human exposure to trichinella larvae from eating black bear meat from oregon appears low. | 2014 | 24171562 |
| serum immune-related proteins are differentially expressed during hibernation in the american black bear. | hibernation is an adaptation to conserve energy in the face of extreme environmental conditions and low food availability that has risen in several animal phyla. this phenomenon is characterized by reduced metabolic rate (∼25% of the active basal metabolic rate in hibernating bears) and energy demand, while other physiological adjustments are far from clear. the profiling of the serum proteome of the american black bear (ursus americanus) may reveal specific proteins that are differentially modu ... | 2013 | 23825529 |
| the effects of hibernation and captivity on glucose metabolism and thyroid hormones in american black bear (ursus americanus). | american black bears (ursus americanus) have been shown to become transiently insulin resistant and hypothyroid during winter, but no studies have investigated these changes in long-term captive bears or in bears which remain awake year-round. wild, captive hibernating, and captive nonhibernating bears were evaluated at times corresponding to three of their major physiologic stages: fall (hyperphagic stage), winter (hibernation stage), and summer (normal activity stage). combined insulin and glu ... | 2013 | 23805551 |
| immobilization of wyoming bears using carfentanil and xylazine. | seven grizzly (ursus arctos; four male, three female) and three black (ursus americanus; two male, one female) bears caught in culvert traps or leg snares were immobilized in northwestern wyoming with carfentanil and xylazine at doses, respectively, of 0.011 ± 0.001 and 0.12 ± 0.01 mg/kg for grizzly bears and 0.014 ± 0.002 and 0.15 ± 0.04 mg/kg for black bears. these drugs were antagonized with 1 mg/kg naltrexone and 2 mg/kg tolazoline. induction and recovery times, respectively, were 4.3 ± 0.5 ... | 2013 | 23778620 |
| demographic connectivity for ursid populations at wildlife crossing structures in banff national park. | wildlife crossing structures are one solution to mitigating the fragmentation of wildlife populations caused by roads, but their effectiveness in providing connectivity has only been superficially evaluated. hundreds of grizzly (ursus arctos) and black bear (ursus americanus) passages through under and overpasses have been recorded in banff national park, alberta, canada. however, the ability of crossing structures to allow individual and population-level movements across road networks remains u ... | 2013 | 23758532 |
| evaluating the intersection of a regional wildlife connectivity network with highways. | reliable predictions of regional-scale population connectivity are needed to prioritize conservation actions. however, there have been few examples of regional connectivity models that are empirically derived and validated. the central goals of this paper were to (1) evaluate the effectiveness of factorial least cost path corridor mapping on an empirical resistance surface in reflecting the frequency of highway crossings by american black bear, (2) predict the location and predicted intensity of ... | 2013 | 25709825 |
| salmon fishing by bears and the dawn of cooperative predation. | although bears are an epitome of solitary predation, black (ursus americanus) and brown bears (u. arctos) occasionally act in pairs to capture salmon (onchorynchous spp.). i sought to identify conditions that promote pairing and how this relates to optimal foraging. this study on alaskan black bears assessed whether each mode of fishing (solo vs. paired) occurs mainly where it is most efficient at harvesting salmon--that is, whether modal group size (1 vs. 2) is also optimal size. not in this ca ... | 2012 | 23088647 |
| polar and brown bear genomes reveal ancient admixture and demographic footprints of past climate change. | polar bears (pbs) are superbly adapted to the extreme arctic environment and have become emblematic of the threat to biodiversity from global climate change. their divergence from the lower-latitude brown bear provides a textbook example of rapid evolution of distinct phenotypes. however, limited mitochondrial and nuclear dna evidence conflicts in the timing of pb origin as well as placement of the species within versus sister to the brown bear lineage. we gathered extensive genomic sequence dat ... | 2012 | 22826254 |
| bears "count" too: quantity estimation and comparison in black bears (ursus americanus). | studies of bear cognition are notably missing from the comparative record despite bears' large relative brain size and interesting status as generalist carnivores facing complex foraging challenges, but lacking complex social structures. we investigated the numerical abilities of three american black bears (ursus americanus) by presenting discrimination tasks on a touch-screen computer. one bear chose the larger of two arrays of dot stimuli, while two bears chose the smaller array of dots. on so ... | 2012 | 22822244 |
| magnetic resonance imaging diagnosis of intervertebral disc disease and myelomalacia in an american black bear (ursus americanus). | a 23-yr-old black bear (ursus americanus) was examined because of paralysis of unknown duration. the precise onset of clinical signs was unknown as a result of seasonal torpor. the bear was immobilized and transported to a university veterinary teaching hospital for further evaluation and treatment. radiography revealed increased mineral opacity and ventral bridging across vertebral segments t8-11. magnetic resonance imaging demonstrated dorsal and ventral compression of the spinal cord at t8-9. ... | 2012 | 22779249 |
| spatial memory in captive american black bears (ursus americanus). | the spatial memory and foraging strategies of four adult captive-born american black bears (ursus americanus) were explored in four experiments using a simulated foraging task. in the first three experiments, each session consisted of two phases separated by a delay: during the exploration phase, subjects foraged among a set of baited and unbaited sites. during the delay, the same locations were rebaited and subjects were released again and allowed to search the sites (search phase). in experime ... | 2012 | 22545764 |
| wound healing during hibernation by black bears (ursus americanus) in the wild: elicitation of reduced scar formation. | even mildly hypothermic body or limb temperatures can retard healing processes in mammals. despite this, we observed that hibernating american black bears (ursus americanus pallas, 1780) elicit profound abilities in mounting inflammatory responses to infection and/or foreign bodies. in addition, they resolve injuries during hibernation while maintaining mildly hypothermic states (30-35 °c) and without eating, drinking, urinating or defecating. we describe experimental studies on free-ranging bea ... | 2012 | 22405448 |
| preservation of bone mass and structure in hibernating black bears (ursus americanus) through elevated expression of anabolic genes. | physical inactivity reduces mechanical load on the skeleton, which leads to losses of bone mass and strength in non-hibernating mammalian species. although bears are largely inactive during hibernation, they show no loss in bone mass and strength. to obtain insight into molecular mechanisms preventing disuse bone loss, we conducted a large-scale screen of transcriptional changes in trabecular bone comparing winter hibernating and summer non-hibernating black bears using a custom 12,800 probe cdn ... | 2012 | 22351243 |
| investigating the mechanism for maintaining eucalcemia despite immobility and anuria in the hibernating american black bear (ursus americanus). | ursine hibernation uniquely combines prolonged skeletal unloading, anuria, pregnancy, lactation, protein recycling, and lipolysis. this study presents a radiographic and biochemical picture of bone metabolism in free-ranging, female american black bears (ursus americanus) that were active (spring bears and autumn bears) or hibernating (hibernating bears). hibernating bears included lactating and non-lactating individuals. we measured serum calcium, albumin, inorganic phosphate, creatinine, bone ... | 2011 | 21893223 |
| seasonal regulation of the growth hormone-insulin-like growth factor-i axis in the american black bear (ursus americanus). | the american black bear maintains lean body mass for months without food during winter denning. we asked whether changes in the growth hormone/insulin-like growth factor-i (gh-igf-i) axis may contribute to this remarkable adaptation to starvation. serum igf-i levels were measured by radioimmunoassay, and igf-binding proteins (igfbps) were analyzed by ligand blotting. initial studies in bears living in the wild showed that igf-i levels are highest in summer and lowest in early winter denning. det ... | 2011 | 21730258 |
| modulation of gene expression in heart and liver of hibernating black bears (ursus americanus). | hibernation is an adaptive strategy to survive in highly seasonal or unpredictable environments. the molecular and genetic basis of hibernation physiology in mammals has only recently been studied using large scale genomic approaches. we analyzed gene expression in the american black bear, ursus americanus, using a custom 12,800 cdna probe microarray to detect differences in expression that occur in heart and liver during winter hibernation in comparison to summer active animals. | 2011 | 21453527 |
| effects of intratesticular zinc gluconate treatment on testicular dimensions, echodensity, histology, sperm production, and testosterone secretion in american black bears (ursus americanus). | eight adult american black bears were used to evaluate the effects of chemical castration by intratesticular zinc gluconate treatment on testicular dimensions, echodensity, histology, sperm production, and testosterone secretion. treatment did not affect testicular dimensions and did not result in decreased resting or gnrh-stimulated testosterone secretion. multifocal hyperchoic areas in the testicular parenchyma were observed on ultrasound examination, and white foci were observed on gross path ... | 2011 | 21356548 |
| why replication is important in landscape genetics: american black bear in the rocky mountains. | we investigated how landscape features influence gene flow of black bears by testing the relative support for 36 alternative landscape resistance hypotheses, including isolation by distance (ibd) in each of 12 study areas in the north central u.s. rocky mountains. the study areas all contained the same basic elements, but differed in extent of forest fragmentation, altitude, variation in elevation and road coverage. in all but one of the study areas, isolation by landscape resistance was more su ... | 2011 | 21261764 |
| right paw foraging bias in wild black bear (ursus americanus kermodei). | using field observations of ~15 wild adult black bear (ursus americanus kermodei) foraging on a salmon stream during two autumns on the central coast of british columbia, we tested for laterality of forelimb use during lunging and during handling of salmon. of 288 lunging events observed overall, 53% were non biased, 26% were right-limb biased, and 21% left-limb biased (p = .53 between left and right bias). among six bears in which we could ascertain individual identity (182 lunging events), the ... | 2011 | 21218352 |
| integrated population modeling of black bears in minnesota: implications for monitoring and management. | wildlife populations are difficult to monitor directly because of costs and logistical challenges associated with collecting informative abundance data from live animals. by contrast, data on harvested individuals (e.g., age and sex) are often readily available. increasingly, integrated population models are used for natural resource management because they synthesize various relevant data into a single analysis. | 2010 | 20711344 |
| sperm ultrastructure, morphometry, and abnormal morphology in american black bears (ursus americanus). | the objective of this study was to describe sperm ultrastructure, morphometry, and abnormal morphology in american black bears. electroejaculation was successful in 53.8% (7/13) of the attempts, but urine contamination was common. epididymal sperm samples were also obtained from five bears. sperm had a paddle-like head shape and the ultrastructure was similar to that of most other mammals. the most striking particularity of black bear sperm ultrastructure was a tightening of the nucleus in the e ... | 2010 | 20708230 |
| computed tomographic, magnetic resonance imaging, and cross-sectional anatomic features of the manus in a normal american black bear (ursus americanus). | 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 c ... | 2010 | 20500743 |
| using occupancy models to determine mammalian responses to landscape changes. | determining impacts of anthropogenic landscape changes on wildlife populations is difficult. besides the challenges of designing field studies to document conditions before and after landscape changes occur, assessment of population responses (e.g. changes in population density) often provide poor inference because of sampling limitations. estimation of occupancy, however, only requires data on detection or non-detection of a species and might provide better inference. to demonstrate the utility ... | 2009 | 21392293 |
| six months of disuse during hibernation does not increase intracortical porosity or decrease cortical bone geometry, strength, or mineralization in black bear (ursus americanus) femurs. | disuse typically uncouples bone formation from resorption, leading to bone loss which compromises bone mechanical properties and increases the risk of bone fracture. previous studies suggest that bears can prevent bone loss during long periods of disuse (hibernation), but small sample sizes have limited the conclusions that can be drawn regarding the effects of hibernation on bone structure and strength in bears. here we quantified the effects of hibernation on structural, mineral, and mechanica ... | 2009 | 19450804 |
| hierarchical models for estimating density from dna mark-recapture studies. | genetic sampling is increasingly used as a tool by wildlife biologists and managers to estimate abundance and density of species. typically, dna is used to identify individuals captured in an array of traps (e.g., baited hair snares) from which individual encounter histories are derived. standard methods for estimating the size of a closed population can be applied to such data. however, due to the movement of individuals on and off the trapping array during sampling, the area over which individ ... | 2009 | 19449704 |
| elevated expression of protein biosynthesis genes in liver and muscle of hibernating black bears (ursus americanus). | we conducted a large-scale gene expression screen using the 3,200 cdna probe microarray developed specifically for ursus americanus to detect expression differences in liver and skeletal muscle that occur during winter hibernation compared with animals sampled during summer. the expression of 12 genes, including rna binding protein motif 3 (rbm3), that are mostly involved in protein biosynthesis, was induced during hibernation in both liver and muscle. the gene ontology and gene set enrichment a ... | 2009 | 19240299 |
| tetranucleotide microsatellite loci from the black bear (ursus americanus). | we describe primers and polymerase chain reaction conditions to amplify 21 tetranucleotide microsatellite dna loci in black bears (ursus americanus). we tested primers using individuals from two populations, one each in georgia and florida. among individuals from georgia (n = 29), primer pairs yielded an average of 2.9 alleles (range, one to four) and an average observed heterozygosity (h(o) ) of 0.50 (range, 0.00 to 0.79). among individuals from florida (n = 19), primer pairs yielded an average ... | 2009 | 21564629 |
| sex-biased natal dispersal and inbreeding avoidance in american black bears as revealed by spatial genetic analyses. | 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 (>or= 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) d ... | 2008 | 18828781 |
| immobilization of black bears (ursus americanus) with a combination of butorphanol, azaperone, and medetomidine. | sixteen captive and five free-ranging black bears (ursus americanus) were immobilized with a combination of butorphanol, azaperone, and medetomidine (bam). the bam drug combination was premixed using 0.5 ml butorphanol (30 mg/ml), 0.25 ml azaperone (50 mg/ml), and 0.25 ml medetomidine (20 mg/ml) per milliliter to yield a final mix of (15 mg butorphanol+12.5 mg azaperone+5 mg medetomidine)/ml. this combination, dosed at 0.4 ml bam/approximately 23 kg estimated body weight, provided a mean inducti ... | 2008 | 18689666 |
| bayesian analysis of wildlife age-at-harvest data. | state and federal natural resource management agencies often collect age-structured harvest data. these data represent finite realizations of stochastic demographic and sampling processes and have long been used by biologists to infer population trends. however, different sources of data have been combined in ad hoc ways and these methods usually failed to incorporate sampling error. in this article, we propose a "hidden process" (or state-space) model for estimating abundance, survival, recover ... | 2008 | 18266894 |
| polar bears (ursus maritimus), the most evolutionary advanced hibernators, avoid significant bone loss during hibernation. | some hibernating animals are known to reduce muscle and bone loss associated with mechanical unloading during prolonged immobilisation,compared to humans. however, here we show that wild pregnant polar bears (ursus maritimus) are the first known animals to avoid significant bone loss altogether, despite six months of continuous hibernation. using serum biochemical markers of bone turnover, we showed that concentrations for bone resorption are not significantly increased as a consequence of hiber ... | 2008 | 18249018 |
| laryngeal squamous cell carcinoma in a north american black bear (ursus americanus). | a 10-yr-old female black bear (ursus americanus) at the north carolina zoological park presented with a 2-wk history of intermittent coughing and stertor. the animal was anesthetized for examination, and at intubation, a large mass associated with the tonsils and larynx was observed obstructing the airway. cardiopulmonary collapse occurred during the procedure, and efforts at resuscitation were ineffective. at necropsy, an 8 cm times 6 cm times 5 cm mass was present in the larynx, infiltrating t ... | 2005 | 17312782 |
| hibernating black bears (ursus americanus) experience skeletal muscle protein balance during winter anorexia. | black bears spend four to seven months every winter confined to their den and anorexic. despite potential for skeletal muscle atrophy and protein loss, bears appear to retain muscle integrity throughout winter dormancy. other authors have suggested that bears are capable of net protein anabolism during this time. the present study was performed to test this hypothesis by directly measuring skeletal muscle protein metabolism during the summer, as well as early and late hibernation periods. muscle ... | 2007 | 17307375 |
| distribution and abundance of nutrient transporter mrna in the intestinal tract of the black bear, ursus americanus. | end products of digestion are absorbed by the body through the action of transporter proteins expressed on the apical membrane of intestinal epithelial cells. we investigated the mrna abundance and distribution of a peptide transporter (pept1), a glucose transporter (sglt1), two amino acid transporters (nbat and b(o,+)at), and a digestive enzyme, aminopeptidase n (apn), in the intestinal tract of black bears (ursus americanus). intestinal total rna was isolated from 10 bears and abundance of pep ... | 2007 | 17035058 |
| gene flow in complex landscapes: testing multiple hypotheses with causal modeling. | predicting population-level effects of landscape change depends on identifying factors that influence population connectivity in complex landscapes. however, most putative movement corridors and barriers have not been based on empirical data. in this study, we identify factors that influence connectivity by comparing patterns of genetic similarity among 146 black bears (ursus americanus), sampled across a 3,000-km(2) study area in northern idaho, with 110 landscape-resistance hypotheses. genetic ... | 2006 | 17004220 |
| parathyroid hormone may maintain bone formation in hibernating black bears (ursus americanus) to prevent disuse osteoporosis. | mechanical unloading of bone causes an imbalance in bone formation and resorption leading to bone loss and increased fracture risk. black bears (ursus americanus) are inactive for up to six months during hibernation, yet bone mineral content and strength do not decrease with disuse or aging. to test whether hibernating bears have biological mechanisms to prevent disuse osteoporosis, we measured the serum concentrations of hormones and growth factors involved in bone metabolism and correlated the ... | 2006 | 16621944 |
| plasma levels of ursodeoxycholic acid in black bears, ursus americanus: seasonal changes. | to date, no other studies have examined the seasonal changes in circulating levels of various bile acids in the plasma of wild north american black bears, ursus americanus. using gas chromatography, bile acid concentrations were measured in plasma samples obtained during either early or late hibernation, and during summer active periods. thus, specific compositional changes from individual animals were examined through a given year. total bile acid concentrations in the plasma of these normal an ... | 2006 | 16571381 |
| the tensile strength of black bear (ursus americanus) cortical bone is not compromised with aging despite annual periods of hibernation. | black bears (ursus americanus) may not develop disuse osteoporosis during long periods of disuse (i.e. hibernation) because they may be able to maintain bone formation. previously, we found that cortical bone bending strength was not compromised with age in black bears' tibias, despite annual periods of disuse. here we showed that cortical bone tensile strength (166-198mpa) also does not decrease with age (2-14 years) in black bear tibias. there were also no significant age-related changes in co ... | 2005 | 16115638 |
| hibernating bears as a model for preventing disuse osteoporosis. | the hibernating bear is an excellent model for disuse osteoporosis in humans because it is a naturally occurring large animal model. furthermore, bears and humans have similar lower limb skeletal morphology, and bears walk plantigrade like humans. black bears (ursus americanus) may not develop disuse osteoporosis during long periods of disuse (i.e. hibernation) because they maintain osteoblastic bone formation during hibernation. as a consequence, bone volume, mineral content, porosity, and stre ... | 2006 | 15975583 |
| bending properties, porosity, and ash fraction of black bear (ursus americanus) cortical bone are not compromised with aging despite annual periods of disuse. | in many species, including humans, disuse causes an imbalance in bone remodeling that leads to increased bone porosity as a result of increased bone resorption and decreased bone formation. however, black bears (ursus americanus) may not develop disuse osteopenia, to the extent that other animals do, during long periods of disuse (i.e. hibernation) because they maintain osteoblastic bone formation during hibernation, even though bone resorption is increased during hibernation. black bears may al ... | 2004 | 15336926 |
| evidence that bears are induced ovulators. | the objective of this study was to determine if black bears are induced ovulators. we conducted a single experiment with two replicates; each replicate was divided into two arms: females exposed to male bears and females without male exposure. we used laparoscopy to examine ovaries for corpora lutea and measured serum progesterone concentrations. six of the seven isolated females failed to ovulate, while seven of the eight females exposed to males produced one to four corpora lutea. furthermore, ... | 2004 | 15037003 |
| breeding behavior of the american black bear ursus americanus. | by means of videotape, we observed and timed courtship, mating, and refractoriness in the american black bear while confined in a semicaptive environment. sixty-six courtships resulted in mating. during courtship, the male detected estrus and receptivity in the female. courtship lasted 22.5+/-2.3s (mean+/-s.e.m.). we videotaped and reviewed 61 matings that included mounts, pelvic thrusts, and flutters. mating lasted 51.6+/-4.2s. within these 61 matings, there were 24 pelvic thrusts and 14 flutte ... | 2003 | 12749942 |
| serum markers of bone metabolism show bone loss in hibernating bears. | disuse osteopenia was studied in hibernating black bears (ursus americanus) using serum markers of bone metabolism. blood samples were collected from male and female, wild black bears during winter denning and active summer periods. radioimmunoassays were done to determine serum concentrations of cortisol, the carboxy-terminal cross-linked telopeptide, and the carboxy-terminal propeptide of type i procollagen, which are markers of bone resorption and formation, respectively. the bone resorption ... | 2003 | 12616074 |
| genetic diversity and differentiation of kermode bear populations. | the kermode bear is a white phase of the north american black bear that occurs in low to moderate frequency on british columbia's mid-coast. to investigate the genetic uniqueness of populations containing the white phase, and to ascertain levels of gene flow among populations, we surveyed 10 highly polymorphic microsatellite loci, assayed from trapped bear hairs. a total of 216 unique bear genotypes, 18 of which were white, was sampled among 12 localities. island populations, where kermodes are ... | 2002 | 11972757 |
| inheritance and population structure of the white-phased "kermode" black bear. | we report that a single nucleotide replacement in the melanocortin 1 receptor gene [1] (mc1r) is responsible for the white coat color of the "kermode" bear [2], a color phase of the black bear (ursus americanus pallus) found in the rainforests along the north coast of british columbia. in a sample of 220 bears, of which 22 were white, there was complete association of a recessive tyr-to-cys replacement at codon 298 with the white phase. this variant has not been yet been reported in other mammal ... | 2001 | 11566108 |
| geochemical evolution of amino acids in dentine of pleistocene bears. | a linear correlation was established between aspartic acid racemization ratio from cave bear dentine collagen and absolute dating. the high correlation coefficient obtained allowed age calculation through amino acid racemization. aspartic acid and glutamic acid racemization kinetics have also been explored in dentine from a north american black bear (ursus americanus pallas). three sample sets were prepared for kinetic heating experiments in nitrogen atmosphere: one water soaked, one with a wate ... | 2001 | 11466777 |
| correlations of plasma lipid metabolites with hibernation and lactation in wild black bears ursus americanus. | during the denning period, black bears (ursus americanus) are capable of enduring several months without food. at the same time, female bears that are pregnant or lactating have an added metabolic stress. based on laboratory studies, much of the energy required to support metabolism and lactation during denning in black bears comes from lipid reserves. these lipid reserves are mobilized and the most metabolically active lipid fraction in the blood are nonesterified fatty acids (nefa). therefore, ... | 2001 | 11409630 |
| testicular recrudescence in the male black bear (ursus americanus): changes in testicular luteinizing hormone-, follicle-stimulating hormone-, and prolactin-receptor ribonucleic acid abundance and dependency on prolactin. | testicular recrudescence in male black bears (ursus americanus) is initiated in january and completed in may. the goals of this study in the black bear were to determine 1) if testicular abundance of lh-receptor (lhr), fsh-receptor (fshr), and prolactin-receptor (prlr) mrna changes during recrudescence; 2) if these changes in mrna abundance are associated with changes in serum lh, prl, and testosterone (t) concentrations; and 3) if the spring increase in serum prl concentrations is required for ... | 2000 | 10906048 |
| coastal refugia and postglacial recolonization routes: a reply to demboski, stone, and cook. | | 1999 | 28565436 |
| sex steroid and prolactin profiles in male american black bears (ursus americanus) during denning. | serum sex steroid and prolactin profiles were examined in the male american black bear, ursus americanus during denning. sera collected in december and the following march from 8 denning male black bears in minnesota, u.s.a. were assayed for testosterone, estradiol-17 beta and prolactin. eight bears were confirmed to be the denning mode based on a serum urea to creatinine ratio less than 10. serum testosterone concentrations tended to increase from december to the subsequent march whereas serum ... | 1999 | 10027172 |
| serum progesterone, oestradiol, luteinizing hormone and prolactin profiles in the female black bear (ursus americanus). | identifying steroid and pituitary hormone profiles in the female black bear (ursus americanus) throughout pregnancy may provide a greater understanding of the reproductive cycle and indicate which hormones are required for implantation. our objective was to assess endocrine activity in black bears oestrus onset, at oestrus, during pregnancy and after parturition. serum samples were obtained from 12 captive, 16 uncollared and five radiocollared free-ranging female black bears from march through t ... | 1998 | 9835370 |
| muscular sarcocystis infection in a bear (ursus americanus). | sarcocysts of an unidentified sarcocystis species were found in sections of skeletal muscles of a black bear (ursus americanus) from north carolina. two sarcocysts in a section measured 45 x 37.5 microm and 67.5 x 50 microm and had a thin (<2 microm) sarcocyst wall. the villar protrusions on the cyst wall were up to 2 microm long and up to 0.7 microm wide. the bradyzoites were approximately 6 x 2.5 microm in size. this is the first report of muscular sarcocystis in a bear. | 1998 | 9576526 |
| geographical distribution of demodex ursi in black bears from florida. | from may 1990 to february 1996, 55 black bears (ursus americanus floridanus) (38 males, 17 females) from 21 counties in florida (usa), were examined for demodex ursi (acari: demodecidae). the sample included cubs < 1-yr-old (n = 12), juveniles (1 to < 3 yr, n = 20), and adults (3 to 12 yr, n = 23). demodex ursi was collected from four bears by deep scrapings of 15 sites on the head and forelimb of each bear. all four bears with demodicosis had crusty, scaly skin lesions, and moderate alopecia. n ... | 1998 | 9476240 |
| black bear (ursus americanus) bile composition: seasonal changes. | gallbladder contents from 8 active and 14 dormant black bears were analyzed for individual bile acids by high-performance liquid chromatography and for cholesterol, phospholipids, sodium, potassium, calcium, magnesium, zinc, iron, and copper. only three bile acids occurring as taurine conjugates were detected: tauroursodeoxycholate, taurochenodeoxycholate, and taurocholate. the proportion of tauroursodeoxycholate to the sum of the three bile acids decreased. calcium, cholesterol, phospholipids, ... | 1997 | 9467890 |
| phylogeography and pleistocene evolution in the north american black bear. | to determine the extent of phylogeographic structuring in north american black bear (ursus americanus) populations, we examined mitochondrial dna sequences (n = 118) and restriction fragment length polymorphism profiles (n = 258) in individuals from 16 localities. among the bears examined, 19 lineages falling into two highly divergent clades were identified. the clades differ at 5.0% of nucleotide positions, a distance consistent with an origin 1.8 mya, and have different but overlapping geograp ... | 1997 | 9364767 |
| north american black bear mtdna phylogeography: implications for morphology and the haida gwaii glacial refugium controversy. | the controversial role of haida gwaii (queen charlotte islands) as a biological refugium on the northwestern coast of north america has been widely discussed for more than fifty years. the presence of morphologically divergent subspecies on haida gwaii is one of the major lines of evidence suggesting this archipelago's role as a refugium during the wisconsin. however, since morphological distinction can be derived postglacially as well as in extended isolation, such evidence is ambiguous. to exa ... | 1997 | 28568643 |
| physiological effects of medetomidine-zolazepam-tiletamine immobilization in black bears. | a combination of medetomidine-zolazepam-tiletamine (mzt) was used to immobilize four black bears (ursus americanus). the drugs were used at a dose of approximately 52 micrograms/kg of medetomidine, 0.86 mg/kg of zolazepam, and 0.86 mg/kg of tiletamine. induction occurred in 6.3 +/- 3.3 min (mean +/- sd). the combination produced minimal adverse cardiopulmonary effects. hypertension occurred in all four bears. oxygenation and ventilation was good in three of the four bears. one bear demonstrated ... | 1997 | 9249709 |
| cryptorchidism and delayed testicular descent in florida black bears. | retained testes were found in 11 (16%) of 71 black bears (ursus americanus) examined over a 3-year period in florida (usa). four of the 11 bears were older than one year and weighed more than 32 kg; therefore, they were considered to be cryptorchid. the remaining seven bears may have had delayed testicular descent due to their apparent normal immature development. this is the first known published report of the prevalence of cryptorchidism and apparently normal delayed testicular descent in a bl ... | 1996 | 9359066 |
| senile plaques and other senile changes in the brain of an aged american black bear. | a female american black bear (euarctos ursus americanus) over 20 years old had shown epileptiform neurologic signs starting in march 1992 and was found dead unexpectedly 8 months later. at necropsy, pulmonary and intrabronchial hemorrhage was noted. in the brain, the leptomeninges exhibited slight thickening, and petechiae were evident in the hippocampus. histopathologic examination of the brain revealed several senile changes: numerous senile plaques, amyloid deposition in cerebromeningeal arte ... | 1995 | 7483216 |
| measurement and seasonal variations of black bear adipose lipoprotein lipase activity. | the black bear (ursus americanus) provides a unique model for the study of adipose physiology because it exhibits seasonal periods of rapid weight gain and weight loss without marked changes in its metabolic rate. to better understand fat cycling in this model, we obtained plasma and gluteal adipose tissue from five captive adult bears at approximately 20-day intervals from october 1 1992 through march 31 1993. the study included a predenning and denning period for each animal. sampling during t ... | 1995 | 7716203 |
| nutrition and growth of suckling black bears (ursus americanus) during their mothers' winter fast. | in black bears the last 6-8 weeks of gestation and the first 10-12 weeks of lactation occur in winter while the mother is in a dormant state, and reportedly does not eat, drink, urinate or defaecate. measurements were made of the body composition and organ weights of cubs, of the composition of milk, and of milk intake (by dilution of 2h2o), in the first 3 months after birth. additional milk samples were collected until 10 months postpartum. bear cubs were small at birth, only 3.7 g/kg maternal ... | 1993 | 8399119 |
| fatal hepatic sarcocystosis in an american black bear. | | 1993 | 8373869 |
| fatty acid composition of black bear (ursus americanus) milk during and after the period of winter dormancy. | black bears give birth and lactate during the 2-3-mon fast of winter dormancy. thereafter the female emerges from the den with her cubs and begins to feed. we investigated fatty acid patterns of milk from native pennsylvania black bears during the period of winter dormancy, as well as after den emergence. throughout winter dormancy, milk fatty acid composition remained relatively constant. the principal fatty acids at all times were 14:0, 16:0, 16:1, 18:0, 18:1, 18:2n-6, 18:3n-3 and 20:4n-6. aft ... | 1992 | 1491615 |
| seasonal variation in stereotypic pacing in an american black bear ursus americanus. | the behaviour of a male american black bear ursus americanus was observed for over 2400 h across all seasons of the year. stereotypic pacing was most frequent, oriented away from the exhibit, and performed mainly after feeding during the period may-july; from august-november pacing was oriented towards the exhibit and performed mainly around feeding time. placing bear odors in the enclosure slightly reduced pacing and increased exploring/foraging in the late spring. hiding small food items in th ... | 1991 | 24923974 |
| weights and hematology of wild black bears during hibernation. | we compared weights and hematological profiles of adult (greater than 3-yr-old) female black bears (ursus americanus) during hibernation (after 8 january). we handled 28 bears one to four times (total of 47) over 4 yr of varying mast and berry production. mean weight of lactating bears was greater (p less than 0.0001) than that of non-lactating females. white blood cells (p less than 0.05) and mean corpuscular volume (p = 0.005) also differed between lactating and non-lactating bears. hemoglobin ... | 1991 | 1758029 |
| biochemical changes in skeletal muscles of denning bears (ursus americanus). | 1. biopsies of the extensor hallucis longus (ehl) and gastrocnemius (g) muscles of four captive black bears (ursus americanus) were obtained prior to denning (pre), during denning (den) and following the spring arousal (post). 2. glycogen, triglyceride and protein concentrations did not differ significantly between the three groups. likewise, the activity of citrate synthase, a mitochondrial oxidative enzyme, was not significantly different between the three groups. 3. dna concentrations in den ... | 1991 | 1724746 |
| rectal temperatures of immobilized, snare-trapped black bears in great dismal swamp. | rectal temperature was determined for 84 black bears (ursus americanus) during 99 handlings in great dismal swamp, virginia and north carolina (usa). all bears had been trapped with cable snares and immobilized with a 2:1 ketamine hydrochloridexylazine hydrochloride mixture. temperatures were significantly greater in males and varied significantly by season. immobilized bears began panting at rectal temperatures greater than 42.0 c. one death occurred at 43.0 c. we recommended cooling measures o ... | 1989 | 2761021 |
| metabolism of the black bear under simulated denning conditions. | oxygen consumption of three black bears (ursus americanus) under simulated denning conditions are reported. the results indicate that metabolic rate in large mammals can be significantly reduced during natural starvation. the paper summarizes data on the lowest and average metabolic rate of black bears during simulated denning. | 1988 | 3239417 |
| blood chemistry of black bears from pennsylvania during winter dormancy. | twenty-four serum chemistries were measured in blood samples collected from 20 adult female black bears (ursus americanus) and their offspring, including 14 yearlings and 37 cubs, in northeastern pennsylvania during winter 1984. four other captive adult females were bled before, during, and after they were subjected to unseasonably warm temperatures during february. levels of serum urea nitrogen (sun) and creatinine were lower (p less than 0.05), and iron was higher (p less than 0.05) in male cu ... | 1988 | 3411708 |
| annual changes in serum sex steroids in male and female black (ursus americanus) and polar (ursus maritimus) bears. | the adaptation of black and polar bears to their environments is proportional to the severity of climate and food restriction. both black and polar bears mate during the spring, despite differences in their recent metabolic state. reproductive activity in black bears follows 4 mo of torpor, whereas reproduction in polar bears occurs prior to torpor. the goals of this study were to measure the annual changes in serum sex steroids in male and female black and polar bears, and to determine if chang ... | 1988 | 3408772 |
| microvasculature of the bear heart demonstrated by scanning electron microscopy. | morphological features of the coronary microvasculature were examined in ten black bears (ursus americanus). tissue samples were collected for scanning electron microscopy from five animals, and vascular casts of the coronary vessels were prepared from five. each portion of the microvasculature examined had specific morphological characteristics which may contribute to the control of blood flow. all indications from the present study suggest that the structure of the coronary microvasculature in ... | 1988 | 3376736 |
| error in hematocrit of edta-preserved whole blood from black bears caused by delayed analysis. | hematocrit values for k3edta-preserved whole blood from black bears (ursus americanus) were found to increase during refrigerated storage causing error in delayed laboratory analysis. this error was quantified using a regression type model based on repeated hematocrit testing of 66 blood samples over time. the model proved to fit quite well and provided corrected-to-day-zero hematocrit values for 42 samples from which day-zero values were not available. | 1987 | 3108525 |
| epizootic of adenovirus infection in american black bears. | | 1984 | 6096334 |
| plasma progesterone concentrations in pregnant and non-pregnant black bears (ursus americanus). | plasma levels of progesterone were determined from serial samples taken from 2 black bears over 3 consecutive fall periods. each animal was pregnant during the 1st and 3rd years. variations in progesterone levels were seen between animals and within each animal between pregnancies. average baseline levels during the mid-to-late preimplantation period were 5.0-12.5 ng/ml and increased 2-3 fold at the approximate time of implantation. values during non-pregnancy were detectable but much lower (0.6 ... | 1983 | 6842455 |
| fibroma in an american black bear. | | 1982 | 7174480 |
| clinical mange of the black bear, ursus americanus, associated with ursicoptes americanus (acari: audycoptidae). | numerous specimens of a mite, ursicoptes americanus fain and johnston, 1970 (acari: audycoptidae), were found in skin scrapings from an aged female black bear, ursus americanus, afflicted with a severe generalized mange. the mite had not been found previously in association with clinical dermatitis. the male, nymph and larva of ursicoptes americanus, heretofore unknown, are described and the generic diagnosis is amplified. discovery of the male aids in resolving the questionable taxonomic status ... | 1980 | 7411740 |
| use of ketamine hydrochloride and xylazine hydrochloride to immobilize black bears (ursus americanus). | ketamine hydrochloride (kh) and xylazine hydrochloride (xh) used in combination (kh-xh) were effective immobilants for captive and wild black bears (ursus americanus). single intramuscular injections of 1.5-17.1 mg of kh per kg body weight combined in an approximate ratio of 2:1 with 0.9-10.0 mg of xh per kg body weight immobilized bears for 1.5-197 min. dosages most frequently used were 4.5-9 mg kh/kg with 2-4.5 mg xh kg. supplemental administrations maintained tractability for up to 31 h. immo ... | 1979 | 480516 |
| helminth and arthropod parasites of black bear, ursus americanus, in central ontario. | | 1978 | 737598 |
| protein metabolism in the black bear before and during hibernation. | during 3 to 5 months of hibernation, the american black bear does not defecate, urinate, or require food or water. although the bear loses 15 to 25% of its body weight during this period, there is no significant change in its lean body mass. no net accumulation of the usual nitrogenous products of protein catabolism can be demonstrated in the dormant bear, and there is a decrease in urea production during hibernation. because of these findings, it has been hypothesized that the black bear can al ... | 1976 | 825685 |
| annual testosterone rhythm in the black bear (ursus americanus). | | 1976 | 963146 |
| morphogenesis of the fetal membranes and placenta of the black bear, ursus americanus (pallas). | | 1974 | 4844439 |
| seasonal variation in blood viscosity of the black bear (ursus americanus). | | 1972 | 4404320 |
| hypersensitivity angiitis in a dormant black bear (ursus americanus). | | 1970 | 5465570 |
| [a new acarina of the family audycoptidae in the black bear ursus americanus (sarcoptiformes)]. | | 1970 | 5527696 |