Sexually selected infanticide (SSI) has been documented in some species with a mating system in which males have almost exclusive breeding rights with 1 or more females. When the dominant male is removed, the new male kills the offspring sired by the previous male to enable the mother to be bred earlier. It has been suggested that this immigrant male hypothesis of SSI operates in grizzly bears (Ursus arctos) and that removing dominant males by hunting results in high cub mortality due to killing by immigrant males, or in low reproductive rates because of a female counterstrategy of using suboptimal habitat to avoid potentially infanticidal immigrant males. I tested 2 predictions of the immigrant male hypothesis in a hunted area adjacent to protected areas with high densities of grizzly bears that could supply immigrant males. These predictions were not supported. Over 25 years, 134 grizzly bears were captured: most of the 77 male and 57 female grizzly bears were ≤3 years of age when first captured (54.5% and 52.6%, respectively), and 22.1% of the males and 19.3% of the females were 4–6 years of age when first captured. Similarities of these sex ratios suggest that there was not a substantially greater influx of subadult males than females into the hunted area. Cub survival to the end of the breeding season was high (0.93 or 0.95; n = 87), as was annual cub survival (0.85, n = 81); 15% of the 39 litters monitored for an entire year were completely lost. Yearling survival was 0.95 to the end of the breeding season, when SSI should cease. These results do not support the immigrant male hypothesis of SSI but suggest that grizzly bears either do not exhibit SSI, or that SSI exists in a different form. I propose a second hypothesis of how SSI may operate in bears. This mate recognition hypothesis of SSI is that males of any age may, if they are able, kill cubs that they believe they did not sire the previous year and try to mate with the mother. I use a simulation model to evaluate factors that may influence the existence and likely form of SSI in bears. Results of this study suggest that killing some adult males under a sustainable management regime does not decrease cub survival.

Wildlife managers often rely on data from hunter-harvested animals for monitoring structural and numerical changes of hunted animal populations, including American black bears (Ursus americanus). Some analyses of hunter-harvested animals assume that sex and age data from harvested animals accurately reflect the demographic structure of the population. We compared sex and age structure from black bears harvested by hunters to estimates of survival rates and causes of mortality for 136 radiomarked male and female black bears at 3 locations in Washington state. These areas reflect the vegetative and geographic variation within Washington and differ in amount of precipitation, vegetation conditions, behavioral ecology of bears, and hunter harvest. We estimated survival rates from marked bears for hunting and non-hunting seasons to determine whether these data may be represented in the hunter-harvest sample, and compared median age and survival rates for marked bears with life-table survival estimates for bears killed by hunters in each of the 3 regions during 1994–99. We compared survival rates from marked bears and from hunter-harvest data before and after a 1996 voter initiative that banned hunting bears with hounds and bait to determine whether changes in harvest regulations influenced survival of bears and was detectable in hunter-harvest data. Humans accounted for 98% of mortalities for study-marked bears, and legal hunter harvest and hunter-wounding loss accounted for 64% of documented mortalities. Survival rates calculated from marked males (0.73) and females (0.93) were similar to those from hunter-harvested males (0.76) and females (0.83). Median ages for bears from hunter-harvest data were greater than for study-marked bears. We lacked power to detect possible differences in survival rates between pre- and post-initiative periods among marked bears or hunter-harvest samples. We conclude that data from hunter-harvest reports may be adequate for management objectives; however, they do not represent all mortalities, with non-reported hunter harvest, wounding loss, and depredation control hunts likely accounting for additional mortalities.

Spawning Yellowstone cutthroat trout (Oncorhynchus clarki) provide a source of highly digestible energy for grizzly bears (Ursus arctos) that visit tributary streams to Yellowstone Lake during the spring and early summer. During 1985–87, research documented grizzly bears fishing on 61% of the 124 tributary streams to the lake. Using track measurements, it was estimated that a minimum of 44 grizzly bears fished those streams annually. During 1994, non-native lake trout (Salvelinus namaycush) were discovered in Yellowstone Lake. Lake trout are efficient predators and have the potential to reduce the native cutthroat population and negatively impact terrestrial predators that use cutthroat trout as a food resource. In 1997, we began sampling a subset of streams (n = 25) from areas of Yellowstone Lake surveyed during the previous study to determine if changes in spawner numbers or bear use had occurred. Comparisons of peak numbers and duration suggested a considerable decline between study periods in streams in the West Thumb area of the lake. The apparent decline may be due to predation by lake trout. Indices of bear use also declined on West Thumb area streams. We used DNA from hair collected near spawning streams to estimate the minimum number of bears visiting the vicinity of spawning streams. Seventy-four individual bears were identified from 429 hair samples. The annual number of individuals detected ranged from 15 in 1997 to 33 in 2000. Seventy percent of genotypes identified were represented by more than 1 sample, but only 31% of bears were documented more than 1 year of the study. Sixty-two (84%) bears were only documented in 1 segment of the lake, whereas 12 (16%) were found in 2–3 lake segments. Twenty-seven bears were identified from hair collected at multiple streams. One bear was identified on 6 streams in 2 segments of the lake and during 3 years of the study. We used encounter histories derived from DNA and the Jolly-Seber procedure in Program MARK to produce annual estimates of grizzly bears visiting streams. Approximately 68 grizzly bears visited the vicinity of cutthroat trout spawning streams annually. Thus, approximately 14–21% of grizzly bears in the Greater Yellowstone Ecosystem (GYE) may have used this threatened food resource annually. Yellowstone National Park (YNP) is attempting to control the lake trout population in Yellowstone Lake; our results underscore the importance of that effort to grizzly bears.

Between 1993 and 2003, 40 adult female brown bears (Ursus arctos) were radiocollared and monitored in the southwest Kuskokwim Mountains of Alaska. The 95% kernel home range size for individuals with ≥50 relocations (n = 20) ranged from 93–623 km² (x̄ = 356 km²). Bears occupied lower elevations during July and August (x̄ = 454 m) when salmon (Oncorhynchus spp.) were available and higher elevations in September (x̄ = 520 m), presumably to feed on berries, ground squirrels (Spermophilus parryii), and caribou (Rangifer tarandus). During the denning period, bears moved to higher average elevations (x̄ = 632 m), generally remaining through June (x̄ = 570 m). Radiomarked females entered the den in mid October and exited in mid May. There was fidelity to denning areas, with an average distance between consecutive dens of 4.5 km (SD = 3.1). Females with cubs were found at higher average elevations than females without young or with yearlings. Radiomarked females were found closer to anadromous streams from 16 July–15 August, coinciding with chinook (O. tschawytscha), chum (O. keta), and sockeye salmon (O. nerka) availability. Beginning in 1998, chinook and chum salmon escapement was low in the Kuskokwim drainage. There was an inverse relationship between measures of salmon availability and bear distances to anadromous streams. This indicates that although the study area was at the fringe of salmon range, salmon abundance influenced bear seasonal movements and distribution. With reduced salmon availability, this area may support a lower bear density, and brown bear population management should be considered in salmon escapement goals.

Grizzly bears (Ursus arctos horribilis) in Montana and Wyoming killed between 1978–95 reached puberty between the ages of 3.5–5.5 years, consistent with similar studies on brown bears in Hokkaido (Japan), Alaska, and Yukon. Our study considers age-related variation in testicular and epididymal characteristics for 14 pre-pubertal and 11 post-pubertal grizzly bears. Testis mass increased 200% in bears between 1.5 and 7.5 years old and reached an asymptote at 10.5 years. Similarly, seminiferous tubule mass increased rapidly in bears between 1.5 and 5.5 years of age and reached an asymptote in 10.5 years. Testis mass and volume, seminiferous tubule and interstitial volume, and seminiferous tubule diameter were smaller in pre-pubertal bears than in post-pubertal bears. Seminiferous tubule volume increased rapidly between 1.5 and 7.5 years of age. Seminiferous tubule volume reached an asymptote at approximately 10.5 years of age. Interstitial tissue volume increased rapidly between 1.5 and 3.5 years of age and reached an asymptote at approximately 6.5 years of age. Epididymal mass was smaller in pre-pubertal than in post-pubertal bears. Epididymal tubule diameters, percent areas occupied by the tubule, the lumen of the tubule, and the muscularis and epithelium of the tubule did not differ between pre- and post-pubertal bears. The epididymis:testis mass ratio did not differ between pre- and post-pubertal bears. Epididymal mass was linearly related to testis mass. Epididymal tubule diameter increased from the caput, through the corpus, to the cauda. Percent tubular area of the caput was smaller than either the corpus or cauda. Percent tubular areas occupied by the lumen and the muscularis and epithelium did not differ among the caput, corpus, and cauda. This was the first detailed study of the effects of age on testicular and epididymal characteristics of grizzly bears in the continental US.

The objectives of this study were to determine whether there are seasonal changes in spermatogenesis for pre-pubertal and post-pubertal grizzly bears (Ursus arctos horribilis), and investigate the seasonal association between testis mass and serum testosterone (T) concentrations for post-pubertal grizzly bears from the continental US from May through October. Testes from 25 grizzly bears were collected from bears killed by federal and state wildlife personnel in Montana and Wyoming from 1978 to 1995. Fifty blood samples were obtained from wild, post-pubertal (≥5.5 years) male grizzly bears from May through October in Montana and Wyoming from 1993 through 1995. In pre-pubertal bears, the seminiferous tubules were small and surrounded by abundant interstitial tissue in May. Tubules were enlarged and closely packed July through September. Tubules began to degenerate in November. Although spermatogonia and spermatocytes were present from May through September, spermatids never occurred within seminiferous tubules. The epididymal tubules in pre-pubertal bears were well organized from May through September, although they never contained spermatozoa. In post-pubertal bears, spermatogenesis changed seasonally: the entire spermatogenic population from spermatogonia through spermatids was present May through August, and spermatogonia and spermatocytes were present in October and November. The seminiferous epithelium began to deteriorate in July. The epididymal tubules contained spermatozoa May through August only. Both testis mass and T concentrations peaked in June. Mean T concentrations during May and June were greater (P = 0.02) than those during July through October. These results suggest that in grizzly bears in the continental US, seasonal changes in spermatogenesis are accompanied by changes in testis mass and T concentrations and both are associated with photoperiod.

Because of the suppressive effect of stress on reproduction and health, it is important to evaluate potential stressors that may compromise captive breeding programs for endangered species. However, behavioral and physiological measures of stress are sometimes difficult to interpret, and their relationship to stress can be obscured by factors unrelated to stress, such as seasonal and diurnal patterns. Here we present findings for daily and seasonal variation in glucocorticoid (GC) secretion and behavior from a 6-year study of 2 giant pandas (Ailuropoda melanoleuca). In the American black bear (Ursus americanus), seasonal patterns of corticoid secretion are putatively linked to metabolic demands of hibernation. Although pandas do not hibernate, we have found a similar pattern of GC dynamics. Using radioimmunoassay of urinary GC metabolites, we found seasonal variation in GC levels in an adult female and an adult male panda. As in black bears, winter and spring GC levels were significantly higher than summer levels. Additionally, in the female, GC levels during the period of parental care and lactation were higher, regardless of calendar season, than during other periods. Diurnal patterns were also detected in both the female and male panda, with elevated GCs in the morning sample. However, these diurnal patterns were not evident during the fall and summer months. Daily levels of several behaviors potentially indicative of stress also varied significantly with season in both male and female. Additionally seasonal dynamics of feeding behavior were documented. In the female, periods of elevated and diminished appetite were associated with embryonic diapause and post-implantation, respectively. The male had elevated feeding during the fall. Although these patterns are instructive for comparison with other species, we urge caution because our limited sample size does not allow us to extrapolate beyond the individuals studied.

We sought to identify priority areas for the conservation of Andean bear (Tremarctos ornatus) habitat in the northern portion of the eastern Andean cordillera in Ecuador. The study area included páramo and montane forest habitats within the Antisana and Cayambe-Coca ecological reserves, and unprotected areas north of these reserves with elevations ranging from 1,800 to 4,300 m. We collected data on bear occurrence along 53 transects during 2000–01 in the Oyacachi River basin, an area of indigenous communities within the Cayambe-Coca Ecological Reserve. We used those data and a set of 7 environmental variables to predict suitability of Andean bear habitat using Mahalanobis distance, a multivariate measure of dissimilarity. The Mahalanobis distance values were classified into 5 classes of habitat suitability and generalized to a resolution of 1,650-m × 1,650-m grid cells. Clusters of grid cells with high suitability values were delineated from the generalized model and defined as important habitat areas (IHAs) for conservation. The IHAs were ranked using a weighted index that included factors of elevation range, influence from disturbed areas, and current conservation status. We identified 12 IHAs, which were mainly associated with páramo and cloud forest habitats; 2 of these areas have high conservation priorities because they are outside existing reserves and close to areas of human pressure. The distribution of the IHAs highlighted the role of human land use as the main source of fragmentation of Andean bear habitat in this region, emphasizing the importance of preserving habitat connectivity to allow the seasonal movements among habitat types that we documented for this species. Furthermore, the existence of areas with high habitat suitability close to areas of intense human use indicates the importance of bear–human conflict management as a critical Andean bear conservation strategy. We suggest that a promising conservation opportunity for this species is linked to its occurrence in highland habitats, which play a key role in the maintenance of long-term water supplies.

We studied American black bears (Ursus americanus), on the northwest periphery of Okefenokee Swamp in southeast Georgia, to assess landowner attitudes toward bears, estimate the extent of damage to commercial honey bee operations by bears, and evaluate methods to reduce bear depredations to apiaries. We collected 8,351 black bear radiolocations and identified 51 bee yards on our study area. Twenty-seven of 43 home ranges contained ≥1 bee yard, averaging 11.3 and 5.1 bee yards/home range of males (n = 7) and females (n = 20), respectively. From 1996 to 1998, we documented 7 instances of bears raiding bee yards within our study area and 6 instances in adjacent areas. All but 1 of the 13 raided yards were enclosed by electric fencing. In the 12 cases of damage to electrically fenced yards, however, the fences were not active because of depleted batteries. Based on compositional analysis, bear use of areas 800–1,400 m from bee yards was disproportionately greater than use 0–800 m from bee yards. Bears disproportionately used bay (red bay: Persea borbonia, loblolly bay: Gordonia lasianthus, and southern magnolia: Magnolia virginia), gum (water tupelo: Nyssa aquatic and black gum: N. sylvatica), and cypress (Taxodium spp.) and loblolly bay habitats, however, compared with slash pine (Pinus elliottii) or pine–oak (Quercus spp.), where bee yards usually were placed. The distribution of bear radiolocations likely reflected the use of those swamp and riparian areas, rather than avoidance of bee yards. Distances to streams from damaged bee yards (x̄ = 1,750 m) were less than from undamaged yards (x̄ = 4,442 m), and damaged bee yards were closer to unimproved roads (x̄ = 134 m) than were undamaged bee yards (x̄ = 802 m). Our analysis suggests that bee yard placement away from bear travel routes (such as streams and unimproved roads) can reduce bear depredation problems. Our results strongly indicate that working electric fences are effective deterrents to bear damage to bee yards, even in areas frequented by bears. A survey of beekeepers indicated that apiarists often relied on more expensive, less effective, and sometimes illegal methods to protect their bee yards from bears. Beekeepers within bear range should be urged to consider electric fencing, which can almost eliminate bear damage to their yards.

American black bears (Ursus americanus) have been extirpated from all but a few areas in southwestern Alabama, and the remaining habitat is being rapidly lost to development. Remnant bear populations exist near extensive (>125,000 ha) bottomland hardwood forests in the Mobile–Tensaw Delta (MTD), but those bottomland areas are rarely used by bears. Reintroduction of black bears to the MTD may improve viability of the remaining bear populations in southwestern Alabama. To evaluate the suitability of this area for bears, we compared habitat conditions at the MTD with similar alluvial habitats at White River National Wildlife Refuge (White River NWR), where bears are numerous. We measured overstory, midstory, and understory vegetation in the MTD and on the North and South management units at White River NWR. We used principal components analysis and principal variable selection to identify 9 variables associated with 5 principal components (hard mast, soft mast, cavity tree availability, large tree availability, and total basal area) that best explained variation among study areas. Differences among the study areas were associated with hard mast, soft mast, and cavity tree availability (P ≤ 0.001). Hard and soft mast production in the MTD was lower than at White River NWR, but we believe it was adequate. However, suitable den trees, which may be a critical habitat component given the duration and severity of winter flooding, appeared to be lacking in the MTD.

Both the American black bear (Ursus americanus) population in the San Gabriel Mountains of Los Angeles County, California, USA, and the human population at the base of these mountains have grown, and human–bear interactions are common. Little is known about the habits of urban bears in southern California. From July 1998 to December 1999, I studied the activity patterns of urban black bears in the foothills of the San Gabriel Mountains and described their use of adjacent cities. I trapped and radiocollared 2 female and 4 male bears and monitored their movements in forest and city habitats using ground-based and aerial radiotracking. The female bears used city habitat all seasons (spring, summer, fall, winter) of this study, with the exception of the second fall season by one female. Male bears used city habitat during summer, with little exception. Female bears used city habitat equally during 4 6-hr periods daily in summer 1998 and used the city heaviest from 1600–0359 hr in spring 1999 and from 2200–0959 hr in summer 1999. Male bears used city habitat most during the 2200–0359 hr period. Bears were most active in cities during late night when human activity was minimal. Public education efforts to inform residents about activities and behaviors to reduce bear attractants appeared to be successful, are supported by the Department's current black bear policy, and indicate that a focus on human education and enforcement of attractant containment and removal are necessary for minimizing bear–human conflict.

Sloth bears (Melursus ursinus) are endemic to the Indian subcontinent and frequently come into conflict with humans. In the North Bilaspur Forest Division, a total of 137 attacks (resulting in 11 deaths) occurred between April 1998 and December 2000. Most (54%) incidents took place during the monsoon season. Attacks occurred (45%) early in the morning (0400–0800 hrs) more frequently than at other times; human activities at the time of attack were most frequently defecation (27%); locations of attacks were in kitchen gardens, crop fields, and in adjoining forests. A single bear was involved in a majority (56%) of incidents, but groups of 2 (20%) and 3 (21%) bears were also involved. Attacks were predominantly by a single bear (93%) and rarely by 2 (4%) or 3 bears. In most cases, the attacking bear ran away (55%) or was chased by other people (39%) or livestock. Most victims suffered multiple injuries (52%); single injuries on legs (25%), hand (12%), and head (8%) regions were also recorded.