The group and regional specificities of bear trees

Data on population communication systems of the brown bear that were obtained in the reserves of Upper Pechora (2002, 2004, and 2005) and the Western Sayan (2007–2009) were compared. Based on the marking regime, the bear trees were categorized into four groups. The share of bear trees from different groups, the intensity of marking, and the occurrences of 18 marking types were determined. Explanations for the originality of bear trees from different groups were suggested. Differences in the discussed parameters of communication systems between the bears of Upper Pechora and the Western Sayan were revealed. Possible application of these parameters for monitoring brown bear populations was discussed.     

Selection of rub trees by brown bears (Ursus arctos) in Hokkaido, Japan

Tree rubbing by brown bears (Ursus arctos) is a well-known behavior throughout the animal’s distribution. There is still insufficient information on the characteristics and function of the behavior. We investigated seasonal frequency of tree rubbing by brown bears, characteristics and reasons for selection of rub trees, and characteristics of bear signs on and around rub trees in a mixed coniferous–broad-leaved deciduous forest in Hokkaido, Japan. Between 1998 and 2009, we found 172 rub trees and confirmed 995 tree rubbings. We found that the rub trees were used repeatedly by bears within a year and for multiple years (more than 10 years). Tree rubbing by brown bears was observed from April to November, with a peak between May and June that corresponds to the mating season of brown bears. Abies sachalinensis was selected and broad-leaved trees were avoided for tree rubbing based on estimated availability in natural forest. The preference for Abies sachalinensis might be because the strong odor of resin attracts bears for rubbing their head and neck in resinous substances and for increasing the detectability of their markings by receptor bears. Selected trees for rubbing were located right beside the trail on relatively level ground among trees along roads or trails. Trees had a relatively large diameter at breast height. These characteristics would also serve to increase the access and detectability of their markings. Series of pad-shaped depressions was the most frequently observed (70 %) indication of bear rubbing, followed by debarking (51 %) and clawing (30 %). In terms of visual and olfactory signal amplification, physical damage by bears to the trees might have a function to enhance the smell as a result of increase in outflow of the resin. We conclude that tree rubbing behavior is associated with the mating season of brown bears and that the main purpose of this behavior is scent marking to communicate intraspecifically during the mating season.     

A hypothetico-deductive approach to assessing the social function of chemical signalling in a non-territorial solitary carnivore

The function of chemical signalling in non-territorial solitary carnivores is still relatively unclear. Studies on territorial solitary and social carnivores have highlighted odour capability and utility, however the social function of chemical signalling in wild carnivore populations operating dominance hierarchy social systems has received little attention. We monitored scent marking and investigatory behaviour of wild brown bears Ursus arctos, to test multiple hypotheses relating to the social function of chemical signalling. Camera traps were stationed facing bear 'marking trees' to document behaviour by different age sex classes in different seasons. We found evidence to support the hypothesis that adult males utilise chemical signalling to communicate dominance to other males throughout the non-denning period. Adult females did not appear to utilise marking trees to advertise oestrous state during the breeding season. The function of marking by subadult bears is somewhat unclear, but may be related to the behaviour of adult males. Subadults investigated trees more often than they scent marked during the breeding season, which could be a result of an increased risk from adult males. Females with young showed an increase in marking and investigation of trees outside of the breeding season. We propose the hypothesis that females engage their dependent young with marking trees from a young age, at a relatively 'safe' time of year. Memory, experience, and learning at a young age, may all contribute towards odour capabilities in adult bears.     

Black Bears Select Large Woody Structures for Dens in Southeast Alaska

Timber interests target coastal temperate rainforests, and within them stands composed of large trees potentially selected by American black bears (Ursus americanus) for denning. We identified the location of 75 black bear dens (used ≥14 days) in an intensively logged area on Prince of Wales Island, Alaska, USA. We ground-visited a subset (n = 43) of these sites to measure the diameter of living trees and woody structures used by black bears for denning. We contrasted dens with random trees available in the study area in a series of models to characterize black bear den selection. All but 1 of 43 ground-visited dens were located within woody structures, and all but 2 of these structures were >1 m diameter at breast height (dbh). We built resource selection functions (RSFs) to investigate black bear den selection across a range of spatial scales, though estimated selection was generally scale invariant. Black bears strongly selected large-diameter woody structures (dead or alive) as dens at the home-range scale, with the estimated relative strength of selection (RSS) for a 2-m-diameter tree approximately 166 times that of a 1-m-diameter tree. The estimated RSS of logged forest was unexpectedly greater (2.75 times) than that of the remaining commercially valuable old-growth forest. Selection for den structures within stumps in previously logged stands suggests features of the woody structure may be of greater importance to black bears selecting dens than attributes of the surrounding forest. There was no observed correlation between bear den selection and second-growth age, indicating that stumps may persist as suitable dens well after logging. Because denning is an important part of their life history and the denning structures used by black bears on Prince of Wales Island will eventually decay, retaining habitat value for bears in areas intensively managed for timber harvest requires strategies to recruit very large, old trees throughout the landscape. © 2021 The Wildlife Society.     

Longevity and reuse of black bear dens in managed forests of coastal British Columbia

We evaluated longevity and reuse of denning structures by American black bears (Ursus americanus) in coastal temperate rainforests of British Columbia from 1992 to 2010 to assess potential impacts of forest management on these critical habitat features over time. We identified 67 dens during a 4-yr intensive radio-telemetry study (1992–1995): 40 dens of 21 radio-collared black bears and 27 dens found incidentally. Dens occurred in or beneath large diameter trees or wooden structures derived from trees (i.e., logs, root boles, and stumps; = 143 cm diameter, SD = 49 cm). Longevity of dens varied by type, tree species that formed the den, and forest management that occurred at or near the den. Twenty-four of 28 dens of radio-collared bears that were monitored were still usable in 2010, whereas only 5 of 14 dens found incidentally were still usable in 2010. We assessed reuse of bear dens 3 times following initial identification: during the radio-telemetry study, again in 2000, and finally in 2010. Radio-collared bears reused dens from previous years on 7 of 25 potential occasions during the course of the radio-telemetry study. Upon assessment in 2000 and 2010, 17 of 24 (71%) available dens first used by radio-collared bears were reused at least once between 1993 and 2010. The high rate of reuse may indicate low availability of den structures in our study area. Because black bears in coastal British Columbia only used trees or structures derived from trees for winter dens and forest harvesting reduces the supply of these necessary structures, conservation and recruitment of suitable den trees is necessary if maintaining black bear populations is a management goal in these areas. © 2011 The Wildlife Society.     

Selectivity of tree species as activity target of brown bear in taiga

Data on trees with signs of activity of brown bears (Ursus arctos L.) were collected in Yar raion of Udmurtia, in the Pechora-Ilych State Reserve (Komi Republic), and the Sayan-Shusha State Reserve (Western Sayan, Krasnoyarsk krai). The forest stands in all studied areas consist of deciduous and coniferous species. The percentage of deciduous trees varies from 10 to 76%, averaging 35%; conifers are represented by four or five species. The author has analyzed papers that describe more than fifty bear trees. The original data on the species composition of bear trees and the fraction of bear trees in the local forest stands was analyzed with Student’s t-test. It has been deduced that bears definitely prefer coniferous species, especially fir and spruce. Bears can also mark deciduous trees, but if conifers are present, they choose coniferous rather than deciduous species.     

Characteristics of Asian black bears stripping bark from coniferous trees

Stripping of conifer tree bark by Asian black bears (Ursus thibetanus) has been observed in parts of Japan. To identify and characterize the bears exhibiting this behavior, we performed a genetic analysis using DNA extracted from the hairs left on damaged trees. We analyzed 219 samples of bear hair collected from damaged trees at 33 sites and 64 tissue samples from captured bears as controls by using ten microsatellite DNA loci, ca. 706 bp of the mitochondrial DNA d-loop region, and the amelogenin locus. Sixteen bears were identified; some of them had damaged trees at more than one site. bark-stripping and the captured bears. Spatial autocorrelation analysis for increasing distance class revealed a significantly positive genetic correlation coefficient within 40 km among the bark-stripping bears (P < 0.05). Relatedness among the bark-stripping bears was higher than among the captured bears when the distance between bears was within 25 km. We concluded that bark-stripping behavior is associated with relatedness.     

Restoration of Old Forest Features in Coast Redwood Forests Using Early‐stage Variable‐density Thinning

To accelerate development of old forest features in coast redwood, two thinning treatments and an unthinned control were compared in three treatment areas in north coastal California. One thinning treatment was designed to restore old forest densities of 125 trees/ha and the other 250 trees/ha representing a one‐step and partial treatments to the desired stand density. Four years after treatment, numbers of trees had increased in the thinning treatments due to recruitment of new trees, but had decreased in the control due to self‐thinning. Residual trees increased in stem volume following thinning by 128% in low‐density thinning compared to 70% in the controls indicating thinning accelerated stand development. The thinning treatments also moved the species composition of these stands to a greater proportion of redwood. Considerable slash was produced by the thinning treatments but was decomposing rapidly. Black bears damaged approximately 15% of all trees and more than 38% of residual trees in the thinned treatments compared to less than 2% of all trees in the control. This damage included killing some trees and damaging other trees that survived. Decisions over restoration densities in these stands are complicated by prolonged stand development, and balancing risks and costs. In this case, the bears represent a stochastic factor that dramatically increases risk. Thinning appears to be an effective means of enhancing old forest development by accelerating tree growth, modifying species composition, and increasing stand‐level variability. Continued monitoring will be necessary to evaluate long‐term trends in density relative to effects of bear damage.     

Rapid radiation events in the family Ursidae indicated by likelihood phylogenetic estimation from multiple fragments of mtDNA.

The bear family (Ursidae) presents a number of phylogenetic ambiguities as the evolutionary relationships of the six youngest members (ursine bears) are largely unresolved. Recent mitochondrial DNA analyses have produced conflicting results with respect to the phylogeny of ursine bears. In an attempt to resolve these issues, we obtained 1916 nucleotides of mitochondrial DNA sequence data from six gene segments for all eight bear species and conducted maximum likelihood and maximum parsimony analyses on all fragments separately and combined. All six single-region gene trees gave different phylogenetic estimates; however, only for control region data was this significantly incongruent with the results from the combined data. The optimal phylogeny for the combined data set suggests that the giant panda is most basal followed by the spectacled bear. The sloth bear is the basal ursine bear, and there is weak support for a sister taxon relationship of the American and Asiatic black bears. The sun bear is sister taxon to the youngest clade containing brown bears and polar bears. Statistical analyses of alternate hypotheses revealed a lack of strong support for many of the relationships. We suggest that the difficulties surrounding the resolution of the evolutionary relationships of the Ursidae are linked to the existence of sequential rapid radiation events in bear evolution. Thus, unresolved branching orders during these time periods may represent an accurate representation of the evolutionary history of bear species.     

Influence of canopy tree size on stand basal area may reflect uncoupling of crown expansion and trunk diameter growth

Abstract A recent article by Midgley and colleagues suggests that large trees give rise to inordinately high stand basal areas because they pack canopy space more efficiently than smaller trees. We argue that this phenomenon bears more relation to the fact that diameter increment is not necessarily accompanied by significant crown expansion during all stages of a tree's life. Using data from a canopy tree population in an old‐growth temperate forest, we found that crown area scaled as roughly the 3/5 power of trunk basal area. Rather than reflecting fixed scaling laws, we suggest that this pattern arises because of limited opportunities for crown expansion in dense stands. Old canopy trees in dense stands can thus accumulate large basal areas without occupying a commensurately large canopy area.     

Effects of population density on forest structure and species richness and diversity of trees in Kampong Thom Province, Cambodia

This study examined differences in stand structure, tree species richness, and tree species diversity in relation to population density in Kampong Thom Province, Cambodia. Tree data were obtained from a 1997 forest inventory involving 60 clusters (540 plots) systematically distributed over 30% of the provincial forest area. Spatially referenced population data were obtained from the 1998 national population census. The average number of trees per cluster was 356/ha, the average basal area, 23 m²/ha, the average stand volume, 217 m³/ha, and the average aboveground biomass, 273 Mg/ha for all trees of DBH 10 cm and larger. The average species richness per cluster was 37 species, while average species diversity was measured as 0.916 using Simpson’s index and 2.98 by Shannon’s index. Significant negative correlations were generally found between population density surrounding clusters and tree density, basal area, stand volume, aboveground biomass, and species richness and diversity for three examined diameter classes (DBH of 10–30, ≥30, and ≥10 cm). As the distance from clusters for calculating population density increased, the correlation levels increased up to 5 or 7 km, depending on the variables and diameter class, and then stayed relatively constant for stand structure variables and decreased for species richness and diversity. The results indicate that evidence of disturbance was more pronounced at higher population density up to around 5 to 7 km. We suggest that introduction of greater controls on human disturbance should be a high priority for resource management and conservation in Kampong Thom Province and, presumably, Cambodia as a whole.     

Development processes and growth pattern of Pinus densiflora stands in central eastern Korea

Stand growth and developmental processes were investigated in Pinus densiflora Siebold et Zucc. stands of different ages in the central eastern region of Korea. Stands were inventoried and five trees per stand were sampled for stem analysis, age estimation, and growth analysis. More than 80% of sampled trees in a stand were established within 3–5 years, and most stands had a single cohort structure. The initial growth of pine seedlings was slow, but the height growth accelerated beyond 2–3 m height, 5–10 years after establishment. Linear growth was maintained until 10–12 m height, at which suppressed trees fell behind and might die out. The young stand was composed of pure pines, while few pine seedlings and saplings were found in the understory of older stands. The peak of diameter growth rate occurred around 5–15 years after tree establishment, implying that competition begins during that period. The pine stand development follows four stages: (1) the young stage when the growth rate increases and peaks; (2) the height competition stage when trees focus on height growth for light while maintaining a narrow DBH and height distribution; (3) the differentiation stage when suppressed trees die out, and the DBH distribution becomes wider; and (4) the mature stage when stands have a multi-canopy structure with a wide DBH and height distribution, while the understory is dominated by other tree species. The changes in growth rates and stand structure through forest development would be implemented to predict alterations of above-ground carbon sequestration rates.     

Spatial and temporal patterns of problem polar bears in Churchill,Manitoba

Human–bear interactions near the town of Churchill, Manitoba occur annually because the Western Hudson Bay polar bear population spends 4–5 months on-land each year when the sea ice melts completely. Significant changes have occurred in the Hudson Bay ecosystem and in the bear population as a result of climate warming; however, how these changes may have influenced human–bear interactions near Churchill is unclear. This study examined the temporal and spatial patterns of 1,487 problem bears captured in the Churchill area from 1970 to 2004. We also examined the relationship between problem bears and environmental variables as well as the Nunavut harvest. The number of individual problem bears caught near Churchill varied from 10 to 90 individuals per year and increased over time. Subadult males comprised 39%, subadult females 23%, adult males 18%, females with young 14%, and solitary females 6% of captures. Bears that became problem individuals were in closer proximity to the Churchill area. Nutritional stress and a northward shift in the distribution of the bears that spend the summer on-land in northeastern Manitoba may account for the increase in problem bear numbers. The date of sea ice freeze-up, which is getting progressively later, was the best predictor explaining the annual variation in the occurrence of problem bears. These results provide an understanding of how a warming climate may directly impact polar bear behaviour. This information may allow wildlife managers to predict relative levels of human–bear interactions and thereby implement effective management strategies to improve human safety and the conservation of polar bears.     

Genetic monitoring of a founder population of brown bears (Ursus arctos) in central Austria

The small population of brown bears in central Austria originated from a single migrant bear that had settled in the area in 1972 and three bears that were released in the years 1989–1993. Subsequently, the population has been monitored by radio-tracking and collecting data on bear signs and observations. In 2000 we started a genetic monitoring program of the population with the aim to obtain data on population size, sex ratio, relationships as well as movements of individuals. We present results from six years of genetic monitoring, which were combined with field observations. During this time 1,005 hair and faecal samples were gathered in an area of >3,000 km2, most of them in the core area of <1,000 km². Furthermore we analysed blood samples from captured individuals. Eight microsatellite and two sex determination loci were employed for DNA profiling. The number of detected individuals is surprisingly low, ranging from 5–8 per year. Concerning relationships the analysis reveals that all genotyped individuals are descendants of the founder individuals indicating that no immigration took place. Only one male and three females (mother and 2 daughters) took part in reproduction. Considering the fact that 28 bears were born in this region since 1991 the question arises where the bears disappear to. Our results suggest that subadult bears migrate from the core area. However, indices of bear occurrence outside the core area are rare and migration could be proved only for two young males. Other explanations, such as increased natural mortality and illegal hunting are discussed.     

MOLECULAR GENETIC-DISTANCE ESTIMATES AMONG THE URSIDAE AS INDICATED BY ONE- AND TWO-DIMENSIONAL PROTEIN ELECTROPHORESIS

Evolutionary relationships among eight species of Ursidae (including the giant panda) relative to two Procyonidae species (raccoon and red panda) were estimated based on the extent of electrophoretic variation of 289 radiolabelled fibroblast proteins resolved by two-dimensional gel electrophoresis and among 44 isozyme loci resolved by one-dimensional electrophoresis. Allelic differences among these species were converted to genetic distances, and phenetic trees were constructed. In addition, the electrophoretic data were coded as unit characters, and minimum-length trees were derived based on the Wagner method using maximum parsimony. Regardless of the tree-building method employed, the data sets agreed on the following branching sequence: between 22.4 and 32.3 million years (MY) ago, the ancestors of the procyonids and the ursids split into two lineages. Within 10 MY, the red panda split from the line that led to the raccoon. An ancestor of the giant panda split from the ursid line 18–22 MY ago, and the South American spectacled bear split from the line leading to ursine bears 10.5–15.0 MY B.P. A group of six closely related ursine bears (brown bear, polar bear, Asiatic black bear, Malayan sun bear, American black bear, and sloth bear) diverged from a common ancestor during the past 4–8 MY. Much of this ursine radiation was not resolved by our results, with the exception of a recent (2–3 MY B.P.) divergence of brown bear and polar bear. The topological concordance of the data sets from one- and two-dimensional electrophoresis supports the usefulness of these procedures for evolutionary inference and provides additional precision to the reconstruction of divergence nodes of this carnivore group.     

The trade in bear parts from Myanmar: an illustration of the ineffectiveness of enforcement of international wildlife trade regulations

We assessed the effectiveness of national and international wildlife trade regulations in Asia by surveying four wildlife markets in Myanmar for bears and bear parts. Bears are protected in Myanmar and neighbouring countries, and are included in CITES Appendix I, precluding international trade. Three of the four wildlife markets were situated at the border with neighbouring countries (China and Thailand) whereas the fourth, situated in Myanmar’s interior, also catered to international markets. During seven checks (1999–2006) we recorded 1,200 bear parts, representing a minimum of 215 individual bears. Most items were from Asiatic black bears Ursus thibetanus but also sun bear Helarctos malayanus parts were offered for sale. There were significant temporal and spatial differences in what items were offered for sale. Prices were low (USD 4–40 per item) and the total monetary value of the items for sale was USD 6,500–9,500 (not including gall bladders). Carcasses, skulls, canines, paws, claws, whole skins, pieces of skin, gall bladders and derivates, were openly displayed, with vendors being frank about prices, origin, and potential buyers. Only in the interior were prices quoted in the local currency; at the other three markets currencies of the neighbouring countries were used. Legal (international) trade in bears or bear parts from Myanmar is virtually non-existent, and the observed trade in bear parts strongly indicates a serious lack of enforcement effort. International trade in bear parts from Myanmar is significant, and open, and we conclude that the enforcement of wildlife trade regulations, at least when they concerns bear species, have by and large failed.     

Influence of fruit on habitat selection of Asian bears in a tropical forest

Wild bear populations in Southeast Asia are threatened with extinction, but the ecology and distribution of the 2 species occurring in the region's protected areas is poorly known, so there is little scientific basis underlying conservation strategies. We used bear signs, primarily claw marks on climbed trees, to study habitat selection and distribution of Asiatic black bear (Ursus thibetanus) and sun bear (Helarctos malayanus) across Khao Yai National Park, Thailand from March to December 2008. We found black bear claw marks in 24 of 30 random sample blocks (80%), indicating that this species was widely distributed across Khao Yai. Sun bear signs were much scarcer: their claw marks occurred in 11 blocks (37%); data were too sparse for sun bear so we limited our focus to Asiatic black bear. Using logistic regression, we found that fruit abundance best explained variation in presence of black bear, whereas human disturbance, distance to park edge, elevation, and ground cover had little influence. Fruits appear to be a key resource for Asiatic black bears, and factors affecting fruit abundance or shifts in seasonality (e.g., climate change) will impact bear populations. Knowledge of this relationship will allow managers to be more proactive in managing bears. We recommend using sign surveys for monitoring changes in black bear occupancy as they are inexpensive, efficient, and can be conducted by trained park rangers. © 2011 The Wildlife Society.     

Phylogenetic Relationships of Bears (the Ursidae) Inferred from Mitochondrial DNA Sequences

The phylogenetic relationships among some bear species are still open questions. We present here mitochondrial DNA sequences of D-loop region, cytochrome b, 12S rRNA, tRNA^Pro, and tRNA^Thr genes from all bear species and the giant panda. A series of evolutionary trees with concordant topology has been derived based on the combined data set of all of the mitochondrial DNA sequences, which may have resolved the evolutionary relationships of all bear species: the ancestor of the spectacled bear diverged first, followed by the sloth bear; the brown bear and polar bear are sister taxa relative to the Asiatic black bear; the closest relative of the American black bear is the sun bear. Primers for forensic identification of the giant panda and bears are proposed. Analysis of these data, in combination with data from primates and antelopes, suggests that relative substitutional rates between different mitochondrial DNA regions may vary greatly among different taxa of the vertebrates.     

Grizzly Bear Density in Glacier National Park,Montana

Abstract: We present the first rigorous estimate of grizzly bear (Ursus arctos) population density and distribution in and around Glacier National Park (GNP), Montana, USA. We used genetic analysis to identify individual bears from hair samples collected via 2 concurrent sampling methods: 1) systematically distributed, baited, barbed-wire hair traps and 2) unbaited bear rub trees found along trails. We used Huggins closed mixture models in Program MARK to estimate total population size and developed a method to account for heterogeneity caused by unequal access to rub trees. We corrected our estimate for lack of geographic closure using a new method that utilizes information from radiocollared bears and the distribution of bears captured with DNA sampling. Adjusted for closure, the average number of grizzly bears in our study area was 240.7 (95% CI = 202–303) in 1998 and 240.6 (95% CI = 205–304) in 2000. Average grizzly bear density was 30 bears/1,000 km², with 2.4 times more bears detected per hair trap inside than outside GNP. We provide baseline information important for managing one of the few remaining populations of grizzlies in the contiguous United States.