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Population Characteristics and Winter Ecology of Black Bears in Coahuila, Mexico
Abstract
Biology, status, and distribution of black bears (Ursus americanus) in Mexico are poorly under stood. We studied a population of black bears in the Serranias del Burro, Coahuila, Mexico, from 1991 to 1994 to address the hypothesis that the recolonization source for bears in Texas is the Sierra del Carmen range in northern Mexico. We also described aspects of winter ecology in this southerly population. We captured 42 bears (27 M, 15 F) and equipped 28 with radiotransmitters. All pregnant females (n = 13) and 2 of 5 females with yearlings denned, whereas all other bears, including 10 males, remained active during winter. Mean (+/- SE) den entry and exit dates for pregnant females (n = 5) were 25 December (+/- 5 days) and 22 April (+/- 2 days). Mean age at primiparity was 4.5 +/- 0.6 years (n = 4), interbirth interval was 2.0 +/- 0.0 years (n = 3), and litter size was 2.75 +/- 0.25 cubs/female (n = 12). Estimated adult female and cub annual survival rates were 0.94 +/- 0.05 and 0.81 +/- 0.10, respectivel
... The northern Coahuila, Mexico study area, at 28040'N, 102'15'W, is a rugged, mountainous landscape that varies from 1,400 to 2,100 m above MSL. Vegetation associations vary from chaparral grasslands to montane mesic forests (Doan-Crider and Hellgren, 1996). Mean annual temperatures are 23'C and 16'C for the Florida and Mexico study areas, respectively (Duever et al., 1986;Doan-Crider and Hellgren, 1996). ...
... Vegetation associations vary from chaparral grasslands to montane mesic forests (Doan-Crider and Hellgren, 1996). Mean annual temperatures are 23'C and 16'C for the Florida and Mexico study areas, respectively (Duever et al., 1986;Doan-Crider and Hellgren, 1996). Rainfall averages 67 cm in northern Mexico and 150 cm in southern Florida (Duever et al., 1986). ...
... Indeed, females in Florida consistently experienced their first estrus at 2.5 years-the earliest age reported for the species (Alt, 1989;Maehr, 1997). In Mexico, age at primiparity ranged from 3 to 6 years, indicating estrus at 2.5 to 5.5 years (Doan-Crider and Hellgren, 1996). ...
... Hibernation appears to be facultative in populations of black bears that occur '36?N, because overwinter food supplies are more abundant in southern North America (Hellgren and Vaughan, 1987). Winter-active black bears have been reported throughout southerly latitudes (Hamilton and Marchinton, 1980;Smith, 1985;Weaver and Pelton, 1995), with only pregnant females appearing to be obligate hibernators (Wooding and Hardisky, 1992;Doan-Crider and Hellgren, 1996). We examined serum chemistry and hematocrit in two populations of black bears at the southern terminus (<29?N) of the distribution of the species (Hall, 1981). ...
... We examined serum chemistry and hematocrit in two populations of black bears at the southern terminus (<29?N) of the distribution of the species (Hall, 1981). In these populations, which occurred in northern Mexico and southern Florida, only 13% (Doan-Crider and Hellgren, 1996) and 0% (Land, 1994) of nonpregnant bears, respectively, denned for at least 2 wk. We predicted that in populations with facultative hibernation, seasonal changes in blood variables that are characteristic of metabolic shifts should disappear or be of limited amplitude. ...
... Occasional snowfalls occurred from October to February. These events rarely accumulated >20 cm or persisted >2-3 days on the ground (Doan-Crider and Hellgren, 1996). ...
Serum metabolites change seasonally in black bears (Ursus americanus) in northern temperate regions. We studied variation in serum chemistry and hematology in populations of black bears from southern Florida (n = 55) and northern Coahuila, Mexico (n = 44). Our objective was to evaluate the magnitude of seasonal changes in metabolic indicators in these bears, which exhibited only facultative hibernation. We predicted that seasonal shifts would be smaller than in northern climates. Nine blood characteristics varied (P < 0.05) across seasons, with similar patterns observed across study areas for six of these variables. Serum chemistries tracked changes in diet. Red blood cell concentration (in Florida only) varied by a season-cohort interaction (P = 0.03) and hematocrit had a similar tendency (P < 0.10) on both areas, with increased red blood cell counts and hematocrits observed for adult females and subadult males, but not adult males, in autumn. Overall, reduced or absent hematological cycles in Mexico and Florida were consistent with our prediction of dampened cyclic amplitude in southern latitudes. Our data also supported the hypothesis that changes in hematopoiesis are adaptive to the hibernating state in the black bear.
... The collection of variables responds to their influence on the resource selection by black bears (Lara-Díaz et al. 2018), which represents the habitat suitability in the ensemble surfaces. Vegetation types and tree cover are interconnected to a range of habitat structures used by black bears, like areas covered by coniferous and broadleaf forests, and to the southern of their distribution, areas with open vegetation cover such as desert grasslands (Doan-Crider and Hellgren 1996;Rodríguez-Martínez et al. 2008;Lara-Díaz et al. 2018). ...
... The highest habitat suitability in the SMOr is concentrated in the mountain ranges in the states of Nuevo León and Coahuila, the latter considered to harbor the largest black bear population in Mexico (Doan-Crider and Hellgren 1996). Our BBC ensemble, shows the presence of isolated habitat fragments between the two Sierra Madres, however, they have a smaller geographic extent compared to those proposed by other authors and its geographic location varies (Scheick and McCown 2014;Monroy-Vilchis et al. 2016;González-Saucedo et al. 2021). ...
Context
Black bear connectivity studies are scarce in the southern distribution where the species is endangered. The identification of corridors is a strategy to promote conservation in human-modified landscapes.
Objectives
Assess and validate long-distance corridors in the southern black bear distribution using resistance models, occurrence records, and radio-telemetry of an individual that dispersed between the Sierras Madres of Mexico.
Methods
We acquired black bear occurrence records from several sources and telemetry records from one dispersal individual in northern Mexico. We generated ensemble habitat suitability models and resistance landscape surfaces to generate cumulative resistant kernel and least-cost paths to identify connectivity core areas and corridors of importance through Natural Protected Areas. Finally, we assessed long-distance corridors.
Results
We developed three habitat suitability models for black bears southern range; one matches the current distribution of the species. When including radio-tracking records, the landscape resistance is reduced to arid sites with low habitat suitability. We used least resistance connectivity surfaces to merge subpopulations within each Sierra Madre. The long-distance corridor models indicate narrow routes that require individuals with plastic behavioral dispersal capacity. Almost 20% of the connectivity core areas are within Natural Protected Areas. These are the first large-scale corridors using resistance layers in the southern black bear distribution.
Conclusions
Corridors can be functional for a range of temperate and dry habitat species. Landscape connectivity models should include the monitoring of dispersal individuals to identify the plasticity of organisms and the tangible barriers for them.
... American black bears hibernate for up to 7 months in the northern portions of their range (Bertram andVivion 2002, Chaulk et al. 2005), but for considerably shorter periods in more southerly areas Hardisky 1992, Waller et al. 2012). In some southern and low-elevation areas, where food is available year-round, some bears may remain active during winter (Hellgren and Vaughan 1987, Graber 1990, Doan-Crider and Hellgren 1996, Hightower et al. 2002. However, all parturient females den to give birth to cubs, typically in January-February. ...
... Mexico served as the original source of the recolonization of bears in southwest Texas after they had been eradicated during the 1940s (Onorato and Hellgren 2001). Movements by bears across the seemingly harsh, xeric environment of southwestern U.S. and Mexico once appeared to be anomalous (Doan-Crider and Hellgren 1996, Onorato et al. 2004), but it is now recognized as an integral part of the ecology of bears in this region. In 2011, northern Mexico experienced record drought and wildfires that not only caused high direct bear mortality, but also prompted immigration of bears of both sexes into unburned, previously unoccupied habitat in both Mexico and Texas. ...
... The American black bear is an omnivorous mammal that ranges across much of North America. They are found in large expanses of Canada and Alaska, many forested areas in the lower 48 states, and even northern Mexico (Doan-Crider and Hellgren 1996). ...
... Pregnant females in northern Mexico den for only four months, from late December to late April. Males and non-pregnant females in Mexico may den for only a few days or weeks, and some do not den at all (Doan-Crider and Hellgren 1996). ...
The American black bear (Ursus americanus) relies upon dens in order to successfully reproduce and protect their offspring. Black bears utilize a variety of den types, each providing a different degree of protection. Black bears also exhibit an extended maternal care period in which offspring stay with their mother for 18 months. Maine’s black bear population is one of the largest in the U.S. (>30,000 bears) and since 1975, the Maine Department of Inland Fisheries and Wildlife has conducted research and monitoring to manage the population. This unique dataset allowed for examination of several generations of multiple maternal lineages which was ideal for assessing both den type selection and primiparity (age of first reproduction).
My objectives for this study were to determine 1) whether subadult females chose the same den type as their mother (maternal effect) or if they selected a den near their yearling den, regardless of den type (philopatric effect); 2) whether differences among study areas explained observed differences in den site selection, 3) if there was regional variation in the age of primiparity of Maine black bears; 4) the relationship between the age of primiparity and the probability of recruitment from the primiparous litter; 5) the relationship between the age of primiparity and lifetime productivity; and 6) the relationship between the age of primiparity and body condition.
I analyzed den selection data of 168 subadult females and primiparity data of 85 females from 1981-2013 at four study sites in Maine using GIS, generalized linear modeling, model selection, and analysis of variance (ANOVA). The top den selection model, which included maternal effect and study area, accounted for 85% of the den type selection model likelihood. Maternal effect models were more strongly supported than philopatric effect models and regional variation in den type use was observed. These results suggest that not only is a behavioral maternal effect present in black bears and that this maternal effect combined with regional variation in den type availability influences den type selection, but also that the protection afforded by den type may be an important factor in selection decisions.
... We previously reported that capture of hibernating brown bears resulted in den abandonment in 12 (92%) of 13 captures, compared with 22% overall den abandonment rate in the study area (Sahlén et al., 2015). Although we do not know of other reports of the effects of capture on denning brown bears, a study reporting the capture of 14 hibernating female American black bears with cubs found that none abandoned their dens (Doan-Crider and Hellgren, 1996); others have reported that capture or approach of black bears during denning resulted in den abandonment rates of 17% (Tietje and Ruff, 1980) and 29% (Goodrich and Berger, 1994). Based on these studies, the Scandinavian brown bear ...
... The two animals remaining at the den site had shorter disturbance periods, so future research could be targeted to investigating whether certain den types might result in less den abandonment. Also, it seems that, based on lower post-capture abandonment rates (0-17%), the American black bear may be less sensitive to winter captures and other types of winter disturbance (Tietje and Ruff, 1980;Goodrich and Berger, 1994;Doan-Crider and Hellgren, 1996). It is not possible say whether these differences are species related or result from historical differences in human pressures. ...
Human disturbance can affect animal life history and even population dynamics. However, the consequences of these disturbances are difficult to measure. This is especially true for hibernating animals, which are highly vulnerable to disturbance , because hibernation is a process of major physiological changes, involving conservation of energy during a resource-depleted time of year. During the winters of 2011–15, we captured 15 subadult brown bears (Ursus arctos) and recorded their body temperatures (n = 11) and heart rates (n = 10) before, during and after capture using biologgers. We estimated the time for body temperature and heart rate to normalize after the capture event. We then evaluated the effect of the captures on the pattern and depth of hibernation and the day of den emergence by comparing the body temperature of captured bears with that of undisturbed subadult bears (n = 11). Both body temperature and heart rate increased during capture and returned to hibernation levels after 15–20 days. We showed that bears required 2–3 weeks to return to hiber-nation levels after winter captures, suggesting high metabolic costs during this period. There were also indications that the winter captures resulted in delayed den emergence.
... The incidence of estrus climbed quickly through the month of June, peaked in early July, and then gradually tapered off through August (Figure 1.4). The timing of estrus we documented was consistent with results of previous studies indicating early summer peaks in estrus across the black bear's range including northern Mexico (Doan-Crider and Hellgren 1996), Tennessee (Eiler et al. 1989), Idaho (Reynolds and Beecham 1980), Washington (Lindzey and Melsow 1977), Minnesota (Rogers 1987), Ontario (Kolenosky 1990) and Alaska . Photoperiod is thought to regulate breeding season in most mammals (Sadleir 1973). ...
... My findings were generally similar to those from other black bear studies (Table 4.13). In unhunted populations in the southwest, annual survival was 0.98 in Arizona 0.94 in Mexico (Doan-Crider andHellgren 1996). In unhunted populations in Arkansas, annual adult female survival was 0.98 . ...
... Presence records were obtained in two ways: (1) review of scientific literature (Calderón 2009;Carvajal-Villareal, Maehr, Caso, & Marin, 2007;Delgadillo 2001;Doan-Crider and Hellgren, 1996;Gallo-Reynoso, Suárez-Gracia, Cabrera-Santiago, & Garza-Salazar, 2007; Juárez-Casillas, Peña-Mondragón, De la Peña-Cuellar, & Cervantes-Reza, 2007;Loaiza, 2005;Martínez-Muñoz, 2001;Moreno-Valdez 1998;Moreno, 2008;Nava 2011;Sierra, Sáyago, de C. Silva, & López, 2005;Varas-Nelson, González-López, Krausman, & Culver, 2007;Verdugo 2005;Zavala, López, & Niño, 2007); and, (2) digital data bases: CONABIO (www.conabio.gob.mx) and GBIF (www.gbif.org). We filtered the records, considering only those after 1990, due to the high rate of deforestation that occurred between 1964and 1990(FAO, 2001. ...
... In addition, the region of Serranías del Burro, Coahuila, México is identified as suitable. In this region, Doan-Crider and Hellgren (1996) reported the highest population density in Mexico, which has served as a reservoir for the reproduction of the black bear as well as for dispersion and recolonization into Texas (Onorato, Hellgren, & Doan-Crider, 2004;Rice et al., 2009). Likewise it has been reported the migration and dispersal of individuals towards areas of the State of Chihuahua (Hellgren, Onorato, & Skiles, 2005). ...
... Several studies have concentrated their efforts in understanding the denning ecology of particular sites (i.e. Fuller and Keith 1980, Miller 1990, Goodrich and Berger 1994, Doan-Crider and Hellgren 1996; however, the macroecological perspective has not been explored. Thus, based on the relationship between climate and physiological responses in small hibernating mammals (e.g. ...
... Also, during the months of hibernation, active bears were recorded. In Mexico, some males are active throughout the winter, while females with cubs may or may not hibernate (Doan-Crider and Hellgren 1996). The same is true on the Atlantic Coastal Plain, where some bears are active during the winter (Hamilton andMarchinton 1980, Hellgren andVaughan 1989). ...
The American black bear ( Ursus americanus ) has very plastic activity patterns that maximize its ability to adapt to changing environments. Hibernation length is positively correlated with latitude, where northern populations remain in hibernation for up to 5 months during the winter; however, the species may not hibernate at all in its southern range. Several studies have focused on the description of the species’ ecology from specific locations; however, the macroecological perspective of the seasonal activity in black bears has not been explored. Using ecological niche models and temporal climate transfers, we tested for a correlation between the 971 monthly activity records we obtained for this species within its whole distribution and monthly climatic conditions. We observed that there was a high degree of geographic overlap among the monthly potential transferred areas and the monthly presence locality records. Thus, we suggest that climate is one of the main factors affecting the cycles of activity of this species and explains its hibernation patterns.
... Presence records were obtained in two ways: (1) review of scientific literature (Calderón 2009;Carvajal-Villareal, Maehr, Caso, & Marin, 2007;Delgadillo 2001;Doan-Crider and Hellgren, 1996;Gallo-Reynoso, Suárez-Gracia, Cabrera-Santiago, & Garza-Salazar, 2007; Juárez-Casillas, Peña-Mondragón, De la Peña-Cuellar, & Cervantes-Reza, 2007;Loaiza, 2005;Martínez-Muñoz, 2001;Moreno-Valdez 1998;Moreno, 2008;Nava 2011;Sierra, Sáyago, de C. Silva, & López, 2005;Varas-Nelson, González-López, Krausman, & Culver, 2007;Verdugo 2005;Zavala, López, & Niño, 2007); and, (2) digital data bases: CONABIO (www.conabio.gob.mx) and GBIF (www.gbif.org). We filtered the records, considering only those after 1990, due to the high rate of deforestation that occurred between 1964and 1990(FAO, 2001. ...
... In addition, the region of Serranías del Burro, Coahuila, México is identified as suitable. In this region, Doan-Crider and Hellgren (1996) reported the highest population density in Mexico, which has served as a reservoir for the reproduction of the black bear as well as for dispersion and recolonization into Texas (Onorato, Hellgren, & Doan-Crider, 2004;Rice et al., 2009). Likewise it has been reported the migration and dispersal of individuals towards areas of the State of Chihuahua (Hellgren, Onorato, & Skiles, 2005). ...
In Mexico, black bear (Ursus americanus) is an endangered species. Human invasion of its habitat has provoked a change in its foraging behavior. Human–black bear interactions (HBIs) occur in a variety of locations and create conflict. Spatial information can predict the probabilities of interaction and identify environmental variables. We implemented ecological niche models to identified areas with high probability of HBI. Results indicated that the occurrence of interactions was related to submontane scrub, forest, and urban zones. Verification was carried out in the field, which confirmed the high performance and accuracy of the probability model.
... For GMU in the border sampling area, harvest limits were conservative and generally range from 1-3 females/GMU/yr. Black bears in Mexico were classified as ''endangered of extinction'' in 1986, and hunting seasons were closed indefinitely (Doan-Crider and Hellgren, 1996). Over the last several decades, the historical distribution of black bears in Mexico is believed to have been reduced by 20% due to habitat loss, poaching, and illegal trade (Doan-Crider and Hellgren, 1996;Sierra-Corona et al., 2005). ...
... Black bears in Mexico were classified as ''endangered of extinction'' in 1986, and hunting seasons were closed indefinitely (Doan-Crider and Hellgren, 1996). Over the last several decades, the historical distribution of black bears in Mexico is believed to have been reduced by 20% due to habitat loss, poaching, and illegal trade (Doan-Crider and Hellgren, 1996;Sierra-Corona et al., 2005). Relatively little is known about the status of black bears in Sonora. ...
Landscape features such as rivers, mountains, desert basins, roads, and impermeable man-made structures may influence dispersal and gene flow among populations, thereby creating spatial structure across the landscape. In the US–Mexico borderland, urbanization and construction of the border fence have the potential to increase genetic subdivision and vulnerability to isolation in large mammal populations by bisecting movement corridors that have enabled dispersal between adjacent Sky Island mountain ranges. We examined genetic variation in black bears (Ursus americanus) from three regions in central and southern Arizona, US, to assess genetic and landscape connectivity in the US–Mexico border Sky Islands. We found that the three regions grouped into two subpopulations: the east-central subpopulation comprised of individuals sampled in the central highland and high desert regions, and the border subpopulation comprised of individuals sampled in the southern Sky Islands. Occupancy for the border subpopulation of black bears was influenced by cover type and distance to water, and occupancy-based corridor models identified 14 potential corridors connecting border Sky Island habitat cores with the east-central subpopulation. Biological quality of corridors, defined as length:width ratio and proportions of suitable habitat within corridors, declined with Sky Island dispersion. Our results show that black bears in the border subpopulation are moderately isolated from the east-central subpopulation, the main population segment of black bears in Arizona, and that connectivity for border bears may be vulnerable to anthropogenic activities, such as those associated with urbanization and trans-border security.
... Our Kaplan-Meier estimate of cub survival was higher (81%) than survival estimates obtained in other studies (Strathearn et al. 1984, Hellgren 1988, Doan-Crider and Hellgren 1996. The Heisey-Fuller estimate (76%), viewed by some as the more reliable method for smaller sample sizes (S. ...
... Estimated black bear cub annual survival rates in MA , Ontario (Strathearn et al. 1984), and AZ (LeCount 1987) were 59%, 46%, and 52%, respectively, all lower than that of the present study. Doan-Crider and Hellgren (1996) in Mexico and Schwartz and Franzmann (1991) in Alaska reported 81% and 74-91% black bear cub first year survival rates, respectively. Because of the different methods of estimation, and the small sample sizes, comparison of these survival estimates may not be valid, but they provide valuable insight into the range of values observed for this critical demographic variable. ...
... We determined survival of cubs-of-the year (''cubs'') and yearlings by following their mothers. This method has been used in American black bears (Ursus americanus) and brown bears (Doan-Crider and Hellgren, 1996;McLellan et al., 1999;Schwartz et al., 2003bSchwartz et al., , 2006Swenson et al., 2001). Survival was estimated by dividing the number of young surviving to the next year by the total number of young in an age class. ...
Deosai Plateau in Northern Pakistan was designated a national park to protect the largest remnant population of brown bears in Pakistan. The natural resources of this high elevation (3500–5000 m) park make a significant contribution to the livelihood of local and nomad communities. The present legislation excludes people from a park, which increases conflicts between management and local people. However, a pragmatic approach was adopted to involve people in conservation in Deosai. Community participation, achieved by recognizing rights and introducing incentives, reduced resistance against the conservation efforts, reduced grazing pressure in bear habitat and helped reduce poaching. The size of the brown bear population was set as an indicator of park success, and was monitored annually from 1993 through 2006. We observed a 5% annual growth of the brown bear population, suggesting that the conservation program has been successful due to a successful cooperation between an NGO, people, and the park management.
... In American black bears (Ursus americanus),winter dens serve not only as hibernacula but also as parturition chambers and nurseries (Nelson et al. 1983, Hellgren 1998. Whereas researchers have thoroughly documented some aspects of black bear denning ecology such as site selection (Hellgren and Vaughan 1989, Schooley et al. 1994, Doan-Crider and Hellgren 1996, Kasbohm et al. 1996 and reproduction (Clark and Smith 1994, Garshelis 1994, Noyce and Garshelis 1994, relatively little is known about behavior of bears while denning and no formal techniques for examining and quantifying behavioral characteristics have been described. ...
Researchers examining American black bear (Ursus americanus) denning behavior have relied primarily on den-site visitation and radiotelemetry to gather data. Repeated den-site visits are time-intensive and may disturb denning bears, possibly causing den abandonment, whereas radiotelemetry is sufficient only to provide gross data on den emergence. We used remote cameras to examine black bear denning behavior in the Allegheny Mountains of western Virginia during March-May 2003. We deployed cameras at 10 den sites and used 137 pictures of black bears. Adult female black bears exhibited greater extra-den activity than we expected prior to final den emergence, which occurred between April 12 and May 6, 2003. Our technique provided more accurate den-emergence estimation than previously published methodologies. Additionally, we observed seldom-documented behaviors associated with den exits and estimated cub age at den emergence. Remote cameras can provide unique insights into denning ecology, and we describe their potential application to reproductive, survival, and behavioral research.
... ). Small populations survived in the remote mountains of northern México(DoanCrider and Hellgren 1996). Some populations were able to increase due to changes in Mexican law and in public attitude towards large predators in the 1960s and 1970s. ...
... Similarly, Laurie and Seidensticker (1977) saw 7 times as many adults as subadults (classified visually) in roughly the same study area in the early 1970s. This is very different from most other bear studies, where subadults tend to be particularly vulnerable to capture (Noyce et al. 2000) and thus compose a large proportion of capture samples (Beecham 1983;LeFranc et al. 1987;Hellgren and Vaughan 1989;Kane and Litvaitis 1992;Doan-Crider and Hellgren 1996;Mace and Waller 1998); hence, the situation in our study area is a bit enigmatic. The reproductive output of our radio-collared adult females (one to two cubs every 2-3 years) was low, but not unusually low among ursids, and survival of young bears (Fig. 3) was not especially low. ...
Ursids have adapted to environments ranging from the tropics to the arctic, and although the family is noted for its omnivory, some species have specialized food habits. The sloth bear (Melursus ursinus) has specialized on insect prey, particularly termites and ants, and exhibits some characteristics and behaviors that are common among myrmecophagous mammals. We examined whether myrmecophagy has affected its sociobiology. During 1990-1994 we studied a high-density population of sloth bears in Royal Chitwan National Park, Nepal. We found extensive seasonal overlap among home ranges of adults of the same sex (>50%) and between subadults and adults of both sexes (>70%). Moreover, overlap zones between adjacent ranges were used in proportion to their area. This, and observations of unrelated bears feeding or traveling in proximity to one another (not at concentrated food sources), suggested a high degree of mutual tolerance in this population. However, subadults and females with young may have temporally avoided other bears by limiting their activity to daylight hours. Predators (which were chiefly nocturnal) may also have affected the activity patterns of these (the most vulnerable) bears, and were probably responsible for the females' habit of giving birth in an underground den, fasting for several weeks so as not to leave cubs unattended in the den, and carrying the cubs on their back for 6-7 months after leaving the den. The young left their mother at 1.5 or 2.5 years old (this varied by family) and remained together and (or) later rejoined a sibling or another subadult, possibly to form a coalition against either predators or older bears. We documented few mortalities and no permanent juvenile dispersal in this study, but we also found few subadults in our study area, which indicates undetected mortality or dispersal. We cannot discount the possibility that some aspects of the sociobiology of sloth bears (e.g., cub-carrying, mutual tolerance) are related to myrmecophagy, but the social system and life-history traits of this species seem to fit well within the range observed among other ursids.
... Similarly, Laurie and Seidensticker (1977) saw 7 times as many adults as subadults (classified visually) in roughly the same study area in the early 1970s. This is very different from most other bear studies, where subadults tend to be particularly vulnerable to capture (Noyce et al. 2000) and thus compose a large proportion of capture samples (Beecham 1983;LeFranc et al. 1987;Hellgren and Vaughan 1989;Kane and Litvaitis 1992;Doan-Crider and Hellgren 1996;Mace and Waller 1998); hence, the situation in our study area is a bit enigmatic. The reproductive output of our radio-collared adult females (one to two cubs every 2-3 years) was low, but not unusually low among ursids, and survival of young bears (Fig. 3) was not especially low. ...
Ursids have adapted to environments ranging from the tropics to the arctic, and although the family is noted for its omnivory, some species have specialized food habits. The sloth bear (Melursus ursinus) has specialized on insect prey, particularly termites and ants, and exhibits some characteristics and behaviors that are common among myrmecophagous mammals. We examined whether myrmecophagy has affected its sociobiology. During 1990-1994 we studied a high-density population of sloth bears in Royal Chitwan National Park, Nepal. We found extensive seasonal overlap among home ranges of adults of the same sex (>50%) and between subadults and adults of both sexes (>70%). Moreover, overlap zones between adjacent ranges were used in proportion to their area. This, and observations of unrelated bears feeding or traveling in proximity to one another (not at concentrated food sources), suggested a high degree of mutual tolerance in this population. However, subadults and females with young may have temporally avoided other bears by limiting their activity to daylight hours. Predators (which were chiefly nocturnal) may also have affected the activity patterns of these (the most vulnerable) bears, and were probably responsible for the females' habit of giving birth in an underground den, fasting for several weeks so as not to leave cubs unattended in the den, and carrying the cubs on their back for 6-7 months after leaving the den. The young left their mother at 1.5 or 2.5 years old (this varied by family) and remained together and (or) later rejoined a sibling or another subadult, possibly to form a coalition against either predators or older bears. We documented few mortalities and no permanent juvenile dispersal in this study, but we also found few subadults in our study area, which indicates undetected mortality or dispersal. We cannot discount the possibility that some aspects of the sociobiology of sloth bears (e.g., cub-carrying, mutual tolerance) are related to myrmecophagy, but the social system and life-history traits of this species seem to fit well within the range observed among other ursids.
... 12 Al finalizar la hiperfagia, el oso negro se vuelve apático a la comida y comienza a hacer recorridos para ubicar, construir o excavar su madriguera, que puede ser una cavidad en un tronco o entre rocas; en este sitio permanecerá hasta 118 días. 20 Las hembras preñadas son las primeras en entrar a las madrigueras, seguidas de los juveniles y al final las hembras con crías. 10 El tiempo de entrada a la madriguera varía según las regiones geográficas; en sitios donde la temperatura no disminuye drásticamente, como ocurre en el norte de México, algunos osos no entran en hibernación e incluso algunos continúan en menor frecuencia con sus hábitos alimenticios. ...
... High elevation feeding sites should be covered in snow sooner than low elevation sites, making high elevation food sources unavailable earlier than low elevation food sources. Although instances of winter-active females have been documented, to our knowledge all gestating females hibernate (Hellgren et al. 1987;Van Daele et al. 1990;Doan-Crider and Hellgren 1996), and in accordance with observations on other hibernators (e.g. Otsu and Kimura 1993;Humphries et al. 2003a), food availability plays a significant role in triggering hibernation for grizzly bears (Van Daele et al. 1990;Graber 1990). ...
The study of behavioural plasticity aims at understanding the physiological and behavioural responses of individuals to limiting factors. Climate change has the potential to influence the life history of individuals by altering environmental conditions. Thus, studying the mechanistic links between animal behaviour and environmental conditions is necessary to understand the potential impacts of climate change on individuals. The first part of my thesis focuses on the links between environmental conditions, hibernation behaviour, and habitat selection of grizzly bears, a threatened species in Alberta, Canada. The phenology of den entry and exit was driven by sex and reproductive status, food availability in autumn, winter precipitation, and spring temperature. There was no difference in the dimensions and characteristics of dens excavated by male and female grizzly bears, and males and females selected similar landscape attributes to dig their dens. At the broadest scale investigated, grizzly bears avoided wetlands and selected high-elevation dry conifer stands with abundant high-quality spring foods. At the home-range scale and within the den vicinity, grizzly bears selected dense conifer stands associated with little high-quality autumn food and abundant Hedysarum spp. in areas with low road densities. The second part of my thesis focuses on the links between habitat selection and thermoregulation during the active season, and highlights the thermal constraints associated with increasing ambient temperatures on habitat selection patterns. Grizzly bear habitat selection followed a daily and seasonal pattern that was influenced by ambient temperature, with adult males showing a stronger response than females to warm temperatures. With increasing ambient temperatures, male and female grizzly bears increased their selection for open stands with abundant food resources during the coolest periods of the day, and concurrently decreased their selection for these open stands during the warmest periods of the day. My thesis increases our understanding of the role of intrinsic and extrinsic factors on hibernation behaviour, habitat selection, and thermoregulation constraints of grizzly bears. Ultimately, my results enhance our understanding of the factors regulating the distribution of individuals in time and space; improving our ability to predict the potential impacts of climate change on large mammals.
... We captured black bears with Aldrich spring-activated snares modified for bear safety (Johnson and Pelton 1980) and with barrel traps in May- August andOctober-November, 2001-2002. We anesthetized most bears (trap: n = 66; den: n = 28) with Telazol (A.H. Robins Company, Richmond, Va., at a dosage rate of 4.8 mg/kg (Doan-Crider and Hellgren 1996). We tranquilized 7 bears with a 2:1 mixture of ketamine-xylazine ) at a rate of 6.6 mg/kg. ...
Understanding how populations expand to recolonize former habitats is important to restoration efforts in wildlife management and conservation. Translocation of black bears (Ursus americanus) to Arkansas in the 1950s and 1960s has led to recolonization of former bear range in Oklahoma, with substantial increases in distribution and abundance of the species in Oklahoma over the last 15 years. We studied demographics of black bears in southeastern Oklahoma from May 2001 to November 2002 to provide insight into characteristics of recolonizing populations of large carnivores. We trapped 51 black bears (22 M, 29 F) 77 times and radiocollared 25 female bears. Sex ratios of adults and cubs were skewed toward females, and the age structure was younger than observed in other unharvested populations. Survival of adult females was estimated at 0.9±0.1, and fertility was estimated at 0.77 female young/female/year. Density on the study area was estimated at 0.21 bears/km2 and the current finite growth rate (λ) of the study population was estimated to be 1.11/year. Demographic characteristics of the Oklahoma population of black bears were similar to those of other recolonizing populations of large carnivores.
... The current status of the black bear population in the southeastern highlands of Coahuila and Nuevo León, Mexico, is poorly understood due to the scarcity of records in scientific collections and the lack of reliable data from observations of individual animals. On the other hand, the black bear populations in western Coahuila appear to be healthy and stable as a result of conservation management in the protected areas and well-preserved suitable habitats (Doan-Crider & Hellgren 1996). ...
The black bear Ursus americanus is one of the largest terrestrial carnivores that has a wide distribution in northeastern Mexico, the only country in which black bears are listed as endangered. We used 10 nuclear microsatellite loci to evaluate black bear genetic variability in 6 disjointed populations from northeastern Mexico. Non-invasive genetic techniques were applied to fecal and hair samples. Using a panel of 10 polymorphic microsatellites we identified 64 individuals. Black bears showed low to moderate levels of genetic diversity in all sampled populations (mean ± SD expected heterozygosity, He = 0.63 ± 0.628). Pairwise comparisons between all 6 populations (ΦST = 0.315, p < 0.05) detected significant genetic differentiation between the western Coahuila and the northeastern Nuevo León regions, suggesting that black bears have low levels of gene flow between these 2 regions. Microsatellites revealed significant structure within the complex of disjoint areas in the region. The inbreeding coefficient was also significant (ΦIS = 0.143). The largest proportion of genetic variation (82.7%) was found between individuals within populations. Distance and anthropogenic activities may serve to limit gene exchange among populations which form at least 3 distinct genetic clusters; these may respond differently to environmental changes and should be considered distinct management units.
... The American black bear is the most widely distributed bear species in North America (Lariviere 2001). Breeding occurs in summer, and litters (typically 1-4 young) are born in January or February (Alt 1983;Doan-Crider and Hellgren 1996;Eiler et al. 1989). The NLP in Michigan is a natural unit to study because it is closed to immigration and emigration to the north, east, and west by Lakes Huron and Michigan, and to the south by agricultural lands and urbanization ( Figure 1). ...
The idealized concept of a population is integral to ecology, evolutionary biology, and natural resource management. To make analyses tractable, most models adopt simplifying assumptions, which almost inevitably are violated by real species in nature. Here we focus on both demographic and genetic estimates of effective population size per generation (Ne), the effective number of breeders per year (Nb), and Wright's neighborhood size (NS) for black bears (Ursus americanus) that are continuously distributed in the northern lower peninsula of Michigan, USA. We illustrate practical application of recently-developed methods to account for violations of two common, simplifying assumptions about populations: 1) reproduction occurs in discrete generations, and 2) mating occurs randomly among all individuals. We use a 9-year harvest dataset of >3300 individuals, together with genetic determination of 221 parent-offspring pairs, to estimate male and female vital rates, including age-specific survival, age-specific fecundity, and age-specific variance in fecundity (for which empirical data are rare). We find strong evidence for overdispersed variance in reproductive success of same-age individuals in both sexes, and we show that constraints on litter size have a strong influence on results. We also estimate that another life-history trait that is often ignored (skip breeding by females) has a relatively modest influence, reducing Nb by 9% and increasing Ne by 3%. We conclude that isolation by distance depresses genetic estimates of Nb, which implicitly assume a randomly-mating population. Estimated demographic NS (100, based on parent-offspring dispersal) was similar to genetic NS (85, based on regression of genetic distance and geographic distance), indicating that the >36,000 km2 study area includes about 4-5 black-bear neighborhoods. Results from this expansive data set provide important insight into effects of violating assumptions when estimating evolutionary parameters for long-lived, free-ranging species. In conjunction with recently-developed analytical methodology, the ready availability of non-lethal DNA sampling methods and the ability to rapidly and cheaply survey many thousands of molecular markers should facilitate eco-evolutionary studies like this for many more species in nature.
... The black bear is the largest carnivore and the only Ursid species present in Mexico (Hall 1981;Doan-Crider and Hellgren 1996). Historically, its distribution included the States of Sonora, Chihuahua, Coahuila, Tamaulipas, Durango, Zacatecas, Sinaloa, San Luis Potosí, Jalisco, Nayarit, and Aguascalientes (Leopold 1959;Baker and Greer 1962;Hall 1981; Delfín-Alfonso and others 2011). ...
The Sky Island region is a mountainous region surrounded by grasslands, deserts and intermountain valleys, located between Mexico and the United States. However, different land management and human impact can have an effect on its wildlife populations. Currently, the border wall poses an immediate threat to the survival of black bears (Ursus americanus), considered an endangered species in Mexico. Our aim was to determine the conservation status of black bears in the Sierra San Luis as affected by the border fence. We determined population size through camera traps and radio-telemetry, and modeled population occupancy using PRESENCE. We documented a bear population with more than 500 individuals. Surveys along the border failed to detect bears crossing it, but we identified linkages between the two countries, which shall be important for future landscape planning. Increased vehicular traffic, migration, and drug traffic have a negative effect on bear populations, exacerbated by an increase in anthropogenic activities resulting from the construction and maintenance of the border wall. We recommend modifications to the structure of the border wall, and to increase wildlife monitoring by the United States authorities in order to reduce the potential impacts that this structure has on black bears and other wildlife populations.
... Consequently, marked adult females are observed with dependent young to estimate survival. Such an approach has been used successfully to estimate cub and yearling survival in both black Franzmann 1991, Doan-Crider andHellgren 1996) and grizzly bears (McLellan et al. 1999, Schwartz et al. 2003b where sightability is reasonably good. ...
... Black bears make use of a wide range of plant associations, outstanding among them conifer and broadleaf forests (Servheen 1990). In northern Mexico and southwestern United States, black bears use conifer, oak and juniper forests, open forests, semidesert areas, scrub, and grasslands (Hoffmeister 1986, LeCount and Yarchin 1990, Hellgren 1993, Doan-Crider and Hellgren 1996, Rodr ıguez-Mart ınez et al. 2008. Black bears are found at middle-range elevations (e.g., 1015-2809 m in Sierra Madre Occidental; Delf ın-Alfonso et al. 2011), restricted to areas with no large human settlements; black bears avoid areas near roads or high-speed highways (Aune 1994, Pelton and Van Manen 1994, Fecske et al. 2002, Matthews et al. 2006. ...
Management and conservation strategies for endangered species require information on their temporal and spatial behavioral and habitat use relationships. We evaluated activity patterns and resource selection of black bears in northwestern Mexico. We surveyed 29 localities with 1450 camera traps stations from 2009 to 2013 in the states of Sonora and Chihuahua, Mexico. In each locality, we calculated the proportion of diurnal, nocturnal, and crepuscular activity through a kernel density estimator based on the time of independent photographic events, and we built a beta regression between diurnal density and annual temperature, seasonal rainfall (SR), human density, road density, daylight hours, season, and management type. To evaluate resource selection, we built a binomial logistic regression model incorporating Normalized Difference Vegetation Index (NDVI), mean and coefficient of variation of annual temperature, human population density (PD), terrain roughness, and season. Black bear activity was primarily diurnal with a bimodal tendency around sunrise and sunset. Diurnal activity (between sunrise and sunset) was positively influenced by daylight hours, SR, and private reserves and negatively influenced by anthropogenic factors. Resource selection was positively influenced by the coefficient of variation in temperature and NDVI and negatively associated with average annual temperature, PD, and terrain roughness. Activity patterns and resource use were similar to other regions in North America. However, temperature was one of the main factors influencing black bear activity and resource selection in our study areas and should be considered when developing management plans given projected increases in temperature expected under climate change scenarios. We present the first work of its kind for northwestern Mexico and considered it as an important component in future survey and management protocols for the species in the southern portion of its distribution.
... However, not all American black bears in southern latitudes hibernate. In Mexico, pregnant females typically hibernate, whereas males remain active all winter; females with yearlings mayor may not hibernate (Doan-Crider and Hellgren 1996). In the central Atlantic coastal plain, several individuals remained active throughout winter (Hamilton and Marchinton 1980;Hellgren and Vaughan 1989b). ...
... However there is not much information on current black bear populations in Mexico. The published information is mainly from populations in the northern Sonora and Coahuila (Doan-Crider and Hellgren 1996;Sierra-Corona et al. 2005;Onorato et al. 2004), and bear occurrence is not well documented in other parts of Mexico. Although little scientific information is available for Mexico, it is known that black bears have lost at least 30% of their historical range in Mexico (Pelton et al. 1997). ...
... It is plausible that black bears may have recently recolonized the Chinati Mountains through a gradual series of immigration events, as is the situation with the nearby Chisos Mountains (Onorato and Hellgren, 2001;Onorato et al., 2003;Schmidly and Bradley, 2016). Recolonization of the Chisos Mountains by black bears is thought to be the result of individuals dispersing from larger mountain ranges in northern Mexico (Doan-Crider and Hellgren, 1996;Onorato and Hellgren, 2001;Onorato et al., 2004). The naturally fragmented, xeric conditions of the Chihuahuan Desert impede dispersal and subsequent colonization, but they do not completely inhibit it. ...
As part of an ongoing, large-scale project to monitor mammalian diversity, we set camera traps at four localities in Chinati Mountains State Natural Area, Presidio County, Texas. On 7 June and 3 and 7 July 2017, one of the cameras captured images of a subadult American black bear (Ursus americanus). The photo-verified individual represents the first account of the American black bear in the Chinati Mountains of western Texas. This record documents the species in an area spatially separated from other black bear populations in the region and supports the mainland–island metapopulation recolonization concept previously proposed for the American black bear in northern Mexico and Trans-Pecos Texas.
... An impermeable fence could stop bear migration from the United States to Mexico, which could be the only source of migrants to the endangered black bear population in Sonora, Mexico. The connectivity of habitats in the United States and Mexico have allowed dispersal from source populations in Coahuila, Mexico to subpopulations in Texas (Don-Crider and Hellgren 1996, Onorato and Hellgren 2001, Onorato at al. 2004, therefore, making possible the long-term viability of the metapopulation in Big Bend National Park. Actions by the current administration could eliminate this two-way movement, which is vital to the survival of the black bear. ...
... Although we do not have den chronology data for brown bears in the southernmost parts of the extant or extirpated ranges, it is likely that male and unmated female bears remain or remained active during winter in response to sufficient food availability. This is similar to observations of male and unmated female American black bears remaining active through winter in subtropical, lowelevation portions of their range in response to sufficient food availability (Doan-Crider & Hellgren 1996, Waller et al. 2012, with similar effects reported for Asiatic black bears (Nowak 1999). ...
• Through realisation of ecological opportunities, populations and species can experience relaxed selection pressures, facilitating ecological release and leading to rapid speciation and morphological diversification. Behavioural plasticity in response to environmental change contributes to diversification by exposing individuals to novel conditions through their interactions with resources or dispersal to new areas. Despite strong theoretical support, demonstrations of this evolutionary process are rare.
• The family Ursidae is the product of one or more adaptive radiations following the Miocene–Pliocene transition. Denning behaviour associated with over-winter seclusion, fasting, and parturition coinciding with seasonally decreased food availability appears to be paraphyletic in Ursidae phylogenies. However, female bears of all species undergo varying degrees of seclusion and fasting during parturition and early post-natal care, which is not consistent with periods of seasonally decreased food availability. As denning behaviour is tightly linked to fitness through energetics and reproduction, these behaviours are suspected to be under strong selection. Mechanisms responsible for the observed variability among species, populations, and individuals have not been explored.
• In this review, we detail the evolutionary history of extinct and extant Ursidae regarding expression of denning behaviour and as a function of realised ecological opportunities. We compare behaviours across Ursidae and contextualise our results within extant species ecology.
• We demonstrate the role of relaxed extrinsic and intrinsic factors in the expression of metabolic suppression among Ursidae species, and across populations and reproductive groups, through the realisation of ecological opportunities. In doing so, we propose a more refined consideration of and perspective on this behaviour and provide a mechanism for the adaptive radiation in Ursidae.
... 12 Al finalizar la hiperfagia, el oso negro se vuelve apático a la comida y comienza a hacer recorridos para ubicar, construir o excavar su madriguera, que puede ser una cavidad en un tronco o entre rocas; en este sitio permanecerá hasta 118 días. 20 Las hembras preñadas son las primeras en entrar a las madrigueras, seguidas de los juveniles y al final las hembras con crías. 10 El tiempo de entrada a la madriguera varía según las regiones geográficas; en sitios donde la temperatura no disminuye drásticamente, como ocurre en el norte de México, algunos osos no entran en hibernación e incluso algunos continúan en menor frecuencia con sus hábitos alimenticios. ...
Un recorrido con el oso negro muestra parte de la biología y ecología del úrsido en México. Se mencionan algunos de los aspectos que lo hacen merecedor de nuestra atención, y también se hace ver el impacto que las actividades antropogénicas y las actitudes humanas pueden tener en sus poblaciones.
bears averaged 14.5 and 21.0 km 2 as estimated by minimum convex polygon and adap- tive kernel methods, respectively. Based on compositional analysis, pine-hardwood and oak-hardwood poletimber stands were the highest-ranked habitat types at the study-area scale annually and during summer, whereas sawtimber of shortleaf pine (Pinus echinata), regeneration areas, and oak-hardwood sawtimber were the highest-ranked habitats at the home-range scale. Selection varied on a seasonal basis and by scale, but bears consistently avoided pine-hardwood sawtimber stands. The unusual preference for pine stands by black bears in our area may be tied to local forest management practices, which include thinning and burning. © 2007 Oklahoma Academy of Science
American black bears (Ursus americanus) are common predators of ungulates in interior Alaska, yet little research has described bear demographics. This study examines movement, denning, and reproductive characteristics of a black bear population in the Yukon Flats in eastern interior Alaska. To our knowledge, this location at 66&N latitude is the northernmost study of black bears. A total of 29 ind ividual black bears were captured 53 times between 1995 and 1997. Capture rates were high with a mean annual rate of 2.3 black bears/I 0 trap days. A total of 900 telemetry locations was obtained from 23 radiocollared black bears. Mean annual home ranges for adult female and male black bears were 15.5 and 182.5 km2, respectively. The mean date of den entry was 26 September (range: 19 Sep-8 Oct, n = 42) and the mean date of den emergence was 2 May (range: 26 Apr-6 May, n = 31). Mean length of denning exceeded all previous reports at 220 days (range: 213-229 days, SD = 4, n = 31). Females excavated all dens in well drained terrain in forested areas. Mean litter size for 7 adult females was 2.1 (n = 10). The recruitment and reproductive intervals were 2.0 years (n = 2) and 1.6 years (n = 5), respectively. The survival rate for cubs weaned to 1 year was low (0.45). The mean annual survival rate for adult males was 0.86. We report 2 likely instances where, during spring, grizzly bears (Ursus arctos) preyed on adult female black bears with young.
Little is known about the effects of wildfire on black bears (Ursus americanus). Following a wildfire in Arizona, we hypothesized that the local black bear population would decline due to direct mortality or reductions in food and cover. We also hypothesized that remaining bears would have larger home ranges than bears in unburned areas because of decreased food resources and cover. To test our hypotheses, we studied short‐term effects of a wildfire on black bear demographics in the Mazatzal Mountains, central Arizona, from 1997–2000 and compared these parameters to those in an unburned area. We also compared density estimates, survival, cub production and survival, and home‐range sizes in the same area prefire (1973–1978) to postfire (1997–2000). We captured 31 adult bears within the burn perimeter on Four Peaks and 15 on unburned Mt. Ord during 1997–2000. Adult sex ratio within the burn perimeter on Four Peaks was more skewed toward males (4 M:1 F) than in the unburned area on Mt. Ord (1.7 M:1 F), or the same area prefire (1.4 M: 1 F). Subadults comprised 20% of captured bears in both study areas. The largest apparent impact of the wildfire was lack of recruitment of cubs to the yearling age class. Five adult females produced 16 cubs within the burn perimeter on Four Peaks during 1997–1999, but none survived to 1 year of age. Four females in the unburned area produced 13 cubs, and 36% survived to 1 year of age; in a prefire study, 48% of cubs survived to 1 year on Four Peaks. Hunting was the greatest cause of adult mortality in both areas. Estimated black bear superpopulation size within the burn ranged from 27–36; a simultaneous density estimate of the 120‐km² area was 13.3/100 km². Because the majority of activity occurred in the 26.2 km² of unburned area within the burn perimeter, the density could have been as high as 73.8 bears/100 km². Superpopulation size in the 120‐km² unburned study area ranged from 21–30; density was estimated at 12.5 bears/100 km². Female home‐range sizes were similar between pre and postburn and unburned Mt. Ord. Managers should be aware of possible negative short‐term consequences of wildfire on black bear populations and manage to increase cub survival.
We estimated survival, fertility, and realized and asymptotic population growth rates from 1981 to 2002 for a protected population of black bears (Ursus americanus) in the southern Appalachian Mountains. We used Akaike©s information criterion to assess the time interval for averaging observations that was best for estimating vital rates for our study, given our yearly sample sizes. The temporal symmetry approach allowed us to directly assess population growth and to address all losses and gains to the population by using only capture data, offering an alternative to the logistically intensive collection of reproductive data. Models that averaged survival and fertility across 5- and 7-year time intervals were best supported by our data. Studies of black bear populations with annual sample sizes similar to ours should be of at least 5 years in duration to estimate vital rates reliably, and at least 10 years in duration to evaluate changes in population growth rate λ. We also hypothesized that survival would not track changes in λ because λ is influenced by both survival and fertility. The 5-year model supported our hypothesis, but the 7-year model did not. Where long-term dynamics of large, relatively stable bear populations are of interest, monitoring survival is likely to be sufficient for evaluating trends in λ. For rapidly changing, small populations, however, failure to incorporate fertility into assessments of λ could be misleading.
American black bears (Ursus americanuś) have recolonized Big Bend National Park (BIBE), Texas, in the past 15 years from adjacent habitat in northern Mexico. Range expansion by the Big Bend bear population across the Chihuahuan Desert landscape has considerable consequences for the recolonization of areas north of BIBE in western Texas (Glass, Del Norte, and Davis Mountains). We studied black bear ecology from 1998 to 2001 in BIBE. Thirty bears were marked (15 with radiocollars) during the study, including newborn cubs. Home ranges of bears (males x = 97.7, SE = 35.8 km2, females x = 32.1, SE = 4.3 km2) were larger than in southwestern populations in Arizona and northern Mexico, but smaller than those in the nearby Black Gap Wildlife Management Area (BGMWA). Bears were mainly restricted to the Chisos Mountains and their foothills, with 65% of radiolocations in the pinyon (Pimts cembroides)-odk (Qitercus spp.)-juniper (Jitniperus spp.)-talus-meadow-grass vegetation association. Habitat selection analyses indicated that bears used oak-dominated vegetation types more than expected based upon availability. Bears were more likely than random to be <100 m from anthropogenic features (e.g., roads, trails), but that effect was much stronger in summer when visitor use was low. These data provide predictive capability to managers regarding recolonization of other montane islands north of BIBE and provide information that will help managers ensure the persistence of the small island population of black bears in BIBE.
The accuracy of population estimates derived from mark–recapture sampling will be compromised when marked animals are more or less likely to be recaptured than unmarked animals. We used a "test" population of radiocollared black bears (Ursus americanus) to identify the sources and extent of sampling biases in trapping, camera-trapping, and hunter harvest. We investigated whether and how sex, age, family status, and percent of time on the study area affected the likelihood of bears (in this test population) being sampled by each of these methods and calculated biases in resulting population estimates. Vulnerability to trapping and camera sampling varied by sex and age; trapping was biased toward adult females without cubs and subadult males (3–5 years old) and against juvenile females (1–2 years old) and adult males. Bears present in the study area >50% of the time were trapped and camera-trapped more often than those that spent less time there. All sampling methods showed bias toward particular individuals, irrespective of sex, age, or time spent in the study area. Bears that were initially radiocollared in dens, without being trapped, were less likely to be trapped in future years than those that were initially radiocollared via trapping. Radiocollared bears trapped or photographed 1 summer were more likely than others to be trapped or photographed again the next summer or to be shot by hunters in the fall. This linkage between the marked and recaptured samples caused population estimates to be biased low. When we treated previously radiocollared bears that were trapped or camera-trapped 1 summer as a "marked" sample, and bears so sampled the following summer or shot by hunters the following fall as a "recapture" sample, in 12 of 13 cases we underestimated the known size of the population of radiocollared bears by 12–47%. We discuss ways to reduce bias, but warn that bias is likely inescapable. Ursus 12:211–226
Reliable estimates of first-year survival of black bears (Ursus americanus) are largely unavailable because a technique to attach a telemetry device that can accommodate the rapid growth of black bear cubs has not been perfected. We designed and tested an expandable radiocollar on 47 cubs in 23 litters (20M:27F). Cubs wore radiocollars for an average of 132 days (1-268 days). Twenty of 47 (43%) cubs wore functioning radiocollars from their first denning period to the next or until their death. The remaining collars slipped prematurely (n=25) or the collar battery failed prematurely (n=2). No mortalities appeared to be related to the collar or its design, although we observed some minor injuries.
Little is known about the denning ecology of American black bears (Ursus americanus) in the Cascade Mountains of western Oregon. Extensive logging during the late 20 th century altered the landscape significantly and may have affected the availability and quality of denning habitat. We visited 104 dens of 54 radiocollared bears during 1993-98 to document den-site characteristics and bear behavior in the Cascade Mountains of western Oregon. We also monitored bears in the spring and fall to estimate denning chronology. In addition, we randomly selected 5-ha quadrats to search for fungal activity and potential den sites. Eighty percent of dens we located were in trees that had cavities created by fungal activity. The remaining dens were located in rocky outcroppings and caves, under logs, or on the ground. We found no selection of dens based on micro-or macro aspect, elevation, or slope. Bears denned more than expected in mature timber with trees that averaged >50.8 cm diameter at breast height (dbh). Mean den entry date for bears in our study was November 20, and mean den emergence date was April 15. Pregnant females entered dens earlier and emerged later than barren females, females with yearlings, and all male age classes. Bears were more likely to abandon dens at lower elevations with little snow accumulation and less secure den structures. Fungal activity was randomly distributed throughout the study area. Fifty-one potential tree and log den structures were found in 27 of 64 quadrats we sampled. This information can help federal and state foresters schedule and design management activities within stands of timber containing denning habitat, aid wildlife managers in setting bear hunting seasons, and help timber cruisers and biologists detect and avoid disturbance of active dens.
Chapter 1 - Introduction, Chapter 2 - Life history and management in New Mexico, Chapter 3 - Study areas, Chapter 4 - Capture outcomes and physical characteristics, Chapter 5 - Variation in mast production, Chapter 6 - Reproduction and cub survival, Chapter 7 - Survival rates and causes of mortality, Chapter 8 - Denning chronology and den site selection, Chapter 9 - Home range, movements, and habitat use, Chapter 10 - Population density and sex-age composition, Chapter 11 - A model of statewide Habitat suitability and population size, Chapter 12 - Reliability of harvest data, Chapter 13 - Patterns in harvest data, Chapter 14 - The black bear population model, Chapter 15 - Management tools and applications
The lesser long nosed bat Leptonycteris yerbabuenae (Phyllostomidae: Glossophaginae), is a migratory species highly specialized for nectar and pollen consumption. Although they can consume fruits of columnar cactus (Family Cactaceae, tribes Pachicereeae and Cereeae), this habit has not been studied sufficiently to know the importance of this frugivory. Available information shows that this bat can consume actively fruit of columnar cactus, and indeed seven of these fruits have been cited as part of their diet in North America. Nevertheless, it is unknown whether other cactus fruits are edible for them. In Tehuacán Valley, located in south central México L. yerababuenae co-occur with 21 species of cactus that produce sweet, juicy and soft fruits, with small seeds appropriate to be eaten by the long-nosed bat. We conducted one study to determine the identity of cacti fruits eaten by L. yerababuenae, through the identification of seeds deposited as guano and obtained in the Obispo cave (municipality of Santiago Chazumba, Oaxaca). Seeds of all species of cactus that inhabit Tehuacan Valley were identificated in guano. We recollected 31,895 seeds inside the cave, but more than the 84% corresponded to four species of cacti seeds: Isolatocereus dumortieri, Stenocereus pruinosus, Stenocereus stellatus and Neobuxbaumia macrocephala. The species Escontria chiotilla, Pachicereus hollianus, Hilocereus undatus, Pachicereus fulviceps and Stenocereus treleasei, were rare and they had less than 20 seeds in the sample. So results obtained suggest that L. yerababuenae, may eat fruits as an important part of its diet, and probably serves as an important disperser of columnar cactus in dry environments of South Central Mexico.
The diet of the andean bear Tremarctos ornatus was assessed in dry equatorial, tropical rainy, premontane, montane, and upper montane forests, and puna, whithin nine natural protected areas in Peru (Laquipampa, Chaparrí, Cutervo, Yanachaga, Yanesha, Megantoni, Amarakaeri, Manu and Machu Picchu) between 2001 and 2008. Six hundred forty six records were obtained related to the bear's diet: 522 (80.8%) food waste, 62 (9.6%) feces, 55 (8.5%) climbed trees with sign supplies, and 7 (1.1%) scrabbled roots and trunks. Two animal (1.7%) and 114 plant species (98.3%) included in 36 families, were identified. Fruits (35.2%), leaf bases (31.9%), stems (12.3%), and piths (10.2%) were the eaten plant parts. Bromeliaceae (58.5%), Arecaceae (10.3%), Cyclanthaceae (5.9%) and Poaceae (4.1%) were the botanical families most frequently used. The piths of palms (Arecaceae) were the main diet components in the tropical rainy and premontane forests, the fruits were during the rainy season in the dry equatorial one, while the resource availability produced diverse diets in the montane forest.
Black bears are widely distributed in North America; historically their range included most of northern Mexico. By the middle of the twentieth-century their distribution was reduced to about 20% and by 1994, black bears were classified as endangered. In recent years, however, there has been an increase in the number of black bears sightings in some of their historic distribution, suggesting that black bears in Mexico may be dispersing and recovering historical habitats. In spite of the fact that the black bear is one of the important mammals that inhabits Mexican territory, there is little knowledge concerning its life history. We present information about black bear presence in the Sierra Madre Occidental and Sierra Madre Oriental. Also, we present a review of available research results on habitat, diet and population density. We include a review of peer-reviewed publications, theses, and grey literature, some of which are available only in Spanish. Our goal is to present a country-wide overview to show where studies of black bears have been conducted, where there is need for further research, and to make the information available for researchers in and outside of Mexico.
Natural recolonization by large carnivores has rarely been documented. American black bears (Ursus americanus) recently (1988-present) recolonized portions of their former range in western Texas. We used mtDNA sequence data (n = 144 bears) from 7 populations of southwestern black bears in New Mexico, Texas, and northern Mexico to test predictions regarding metapopulation structure of the species in this region and the source of recolonization in western Texas. Six variable nucleotides were detected, resulting in 5 mtDNA haplotypes. Although within-site diversity of haplotypes (h) and nucleotides (π) was low, a high degree of genetic partitioning among sites was detected (ϕST = 0.6301). Analyses pinpointed northern Mexico as the source of black bears for western Texas. Female-mediated gene flow is proceeding slowly in this system (Nfm = 0.4961 individuals/generation), but its occurrence was inferred via field observations. Nested clade analyses indicated that populations of bears in the Mexico–Texas region (area that encompasses mountain ranges within Nuevo Leon and Coahuila, Mexico, northward to smaller ranges located in the Trans-Pecos region of western Texas) were connected via restricted gene flow due to isolation by distance. Long-distance colonization is the likely cause of extant geographical associations between New Mexican and Mexico–Texas populations. The naturally fragmented, xeric environment of the Chihuahuan Desert impedes colonization, but is not a complete barrier to this process. Conservation initiatives concerning recolonization by black bears within the Mexico–Texas mainland–island metapopulation should focus on preventing human–bear interactions and maintaining corridors for dispersal between the mainland populations in Mexico and the island populations in western Texas.
The black bear is an endangered species in Mexico, like the majority of the large carnivores they are distributed in small and isolated populations and thus their conservation depends on understanding their population status. During 2009, we estimated the abundance and density of the black bear in Sierra de Ajos and Sierra de San Luis in the Northeast Sonora, using camera traps. We defined patches (Sierras) as a combination of elevation and vegetation types in this part of the range. We extrapolated the densities to patch area to estimate population size, obtaining a density of 14.0 ind/100 km² in San Luis and 2.0 ind/100 km² in Ajos and a population size of 218 and 24 individuals respectively. Sierra de San Luis is a larger patch than Sierra de Ajos, which influences directly the population size directly. Furthermore, Sierra de Ajos is isolated from other Sky Islands, resembling a sinkhole population with no evidence for reproduction. It is necessary to continue monitoring black bear populations of the Sky Islands, to determine population trends and related factors that cause the variation of population size among the Sky Islands.
Prior to the twentieth century, black bears (Ursus americanus) roamed the North American landscape in abundance. Their range reached as far south as northern Mexico and as far north as Alaska (Pelton 2000). But as human population soared to unprecedented numbers during the Industrial Revolution, black bear populations began to dwindle. Humans expanded across the landscape and intensified resource extraction, contributing directly and indirectly to black bear attenuation (McKee 2005; Orians and Soule 2001; Pelton 2000). Humans intensively hunted black bears for fur and reduced viable habitats in which black bears forage, hibernate, and mate (Pelton 2000). Many populations shrank or disappeared. When faced with ecological change, black bears are impressively plastic. As omnivores they can subsist on a variety of plant and animal tissues. Diet, body size, and hibernation (i.e., duration and location) vary between populations living in different habitats and climates. While this flexibility has enabled black bears to persist in certain regions, they have not been so successful in the state of Missouri. Both paleozoological (zooarchaeological and paleontological) and his torical data indicate black bears were widespread in Missouri prior to the twentieth century (Graham and Lundelius 1994; McKinley 1962). By the end of the nineteenth century, more than 98% of Missouri's hardwood forests had been cut (Korte and Frederickson 1977), thereby depleting prime black bear habitat. By about 1930 black bears were thought to be extirpated in Missouri (Schwartz and Schwartz 1981), though some suggested a small relict population might remain in the Missouri Ozarks. Whether or not that relict population did indeed exist may be difficult to determine because there is now a population in southeastern Missouri that could be descendants of the relict population of black bears, that immigrated from a population transplanted to Arkansas between 1958 and 1968, or of a combination of the two (Smith and Clark 1994). Analysis of ancient DNA from some of the Lawson Cave bears discussed in this chapter has failed to clarify this matter (Hudson 2009). Whatever the case, management of twenty-first- century Missouri black bears is a subject of some interest (Etling 2000; Hudson 2009; Rosania 2010; Wolverton 2008). In particular, what can be done to ensure their survival? The easy answer is to determine appropriate habitats for black bears and then to manage the landscape so as to create (if necessary) and to maintain those habitats. Unfortunately, the extirpation of black bears from the modern landscape prior to study of their local ecology means that we know very little about native Missouri black bears. To learn more about their behavior and ecological requirements, in relation to habitat range, mate accessibility, and diet, modern studies have focused on extant populations, including the recently transplanted populations in Arkansas (Smith and Clark 1994) and the small population in southeastern Missouri (Schwartz and Schwartz 1981). Despite the knowledge gleaned from these studies, we still know very little about black bear behavior in the Midwestern United States (Garshelis et al. 2008). This means that any wildlife management or conservation actions will at best be based on information from other populations in distant regions. Fortunately, information gleaned from paleozoological remains can expand our knowledge of local black bear ecology by elucidating the behavior and ecological requirements of pre-and periextirpation black bears in Missouri (e.g., Wolverton 2008). Paleozoology can indicate where black bears existed on the landscape and also suggest size of populations. Additionally, paleozoology can indicate what was available on the landscape for black bear consumption and, particularly, what materials were included in their diet. Dietary data will be important for identifying suitable habitats for management of resident black bear populations. We know that black bears are flexible consumers, but research to facilitate future conservation programs should concern questions about what native black bears should eat (or what they did eat prior to historic-period and modern anthropogenic effects), and not what they often do eat (i.e., human refuse in human modified landscapes) (Beck mann and Berger 2003). Due to extirpation of Missouri black bears, we have no modern reference data or benchmarks with which to assess native Missouri black bear diet. Thus any sort of conservation, management, or restoration activity must assume that native Missouri black bears had the same ecology as extant extralocal (non-M issouri) black bears. Fortunately, analysis of paleozoological remains can answer some questions about native Missouri black bear diet and habitat use. How might such data be gleaned from paleozoological remains? For over 30 years, geologists, anthropologists, paleozoologists, and zoologists have used stable isotope signatures recorded in organism tissues to study prehistoric and modern human and animal populations. Stable isotopes reflect diet, climate, migration, and weaning age. In this study I examine stable carbon and nitrogen isotopes in a paleontological assemblage of 200-to 600-year- old black bear remains from central Missouri in order to determine native Missouri black bear diet. Specifically, I sought answers to three questions. First, are there observable differences in diet among paleontological omnivores, herbivores, and carnivores from central Missouri? Second, did native black bear diet change through time in Missouri? And third, do native late Holocene paleontological bears differ from modern Missouri black bears in terms of diet?.
American black bear (Ursus americanus) populations were significantly reduced throughout their range, particularly in southeastern North America. Currently, populations in this region are very fragmented, resulting in concern over possible barrier effects of rivers to normal bear movements and dispersal. This is particularly true for Mississippi, where black bear dispersal into the state is critical if populations are to be recovered. Thus, we studied the relative effects of rivercourses on bear movements and dispersal patterns in southeastern Arkansas, 1992–1996. We captured, radiocollared, and uniquely tagged 40 bears and used radiotelemetry to determine their movements. The Mississippi River (width ≈1600 m) deflected bear movements, whereas the White River (width ≈200 m) was not a barrier to bear movements or dispersal patterns. Frequency of river crossing differed by gender (P=0.007) and season (P<0.001). Male bears crossed rivers more frequently than females. Rivers were crossed less from December to March compared to other seasons. Rivers acted as a semipermeable barrier to bear movements and dispersal patterns, which may have major implications for conservation of large mammal metapopulations. Males appear to be influenced less by rivers, so female translocations across rivers may be necessary to recover fragmented bear populations. We provide an example describing direct implications of this study to the recovery of the threatened Louisiana black bear (U. a. luteolus).
Methods are presented for estimating survival and cause-specific mortality rates from radiomarked animals. Time is partitioned into intervals during which the daily rates are assumed to be constant. The rates are estimated from the number of transmitter-days, the number of mortalities due to particular causes, and the number of days in the time intervals. Potential biases arising from combining data from several individuals marked at different times within an interval or from combining rates from different intervals are identified. Variances and confidence intervals for the estimators are presented. Hypothesis testing and sample-size considerations are also illustrated. Simulation showed that the influence of errors in date of death was small, but misdiagnosis of fate had serious consequences. A microcomputer program is available for performing the analyses.
Population management for black bears (Ursus americanus), brown-grizzly bears (U. arctos) and polar bears (U. maritimus) in North America is reviewed. In different areas bear populations are managed to achieve goals of population control, conservation, or sustained yield. Most North American bears are managed for sustained yields and this topic is emphasized. The consequence of error in population management is high as bears reproduce slowly and reduced populations will require many years to recover. Simulation results where reproductive rates were generous, natural mortality rates were low, and harvests were 75% of maximum sustainable rates indicated that populations reduced by half will require >40 years to recover for brown (grizzly) bears and >17 years for black bears. Under optimal conditions for reproduction, natural mortality, and with males twice as vulnerable as females, maximal sustainable hunting mortality was estimated as 5.7% of total population for grizzly bears and 14.2% for black bears. In recent decades, all 3 species have obtained the status of game animals in most jurisdictions and management for control objectives is increasingly uncommon. Management for conservation requires primary emphasis on habitat protection and on minimizing mortalities from any source. Managers of hunted bear populations use information from hunters, from sex and age composition of killed bears, from research programs, and from computer simulation studies. Non-critical uses of data from any of these sources may lead to management error. Data on age-at-harvest is especially prone to misinterpretation. Techniques used to limit harvests by managers of hunted bear populations are reviewed. The primary constraints facing bear population management derive from inadequate habitat protection, political pressures, technological limitations of available population management techniques, and inadequate financial support for management.
We examined relationships befween reproductive performance of female Minnesota black bears (Ursus americanas) and various potential indicators of nutritional condition during late hibernation. Litter size (n = l0l litters) was influenced more by litter order (first or subsequent) than by matemal condition, except perhaps in very large females. An increased proportion of male cub births corresponded with increased maternal weight and serum alkaline phosphatase (ALKP) and decreased serum creatinine (CR). Weight and growth of cubs and yearlings were closely related to mother's size; they also conelated positively with maternal ALKP, and negatively with serum total protein (TP), and mean corpuscular volume (MCV). Cub survival was affected only when mother's weight 2 months postpartum was below about 65 kg. No juvenile females (2-8 years old) weighing <41 kg in March produced their first cubs the following spring, but 57% of those above this threshold weight produced cubs. Litter frequency and yearling recruitment were unrelated to maternal condition. Life history parameters of black bears appear to respond to declining nutrition in the following sequence: (l) litter size declines, then stabilizes across a broad range of maternal weights; (2) age of first reproduction increases; (3) juvenile survival decreases; (4) first-year cub survival decreases; and (5) litter frequency decreases. Better definition of these relationships, particularly at nutritional extremes, will likely require collaborative efforts of researchers studying diverse populations.
We examined the influence of body mass in early winter on litter size, growth and sex ratio of young, as well as the influence of gestation and lactation on overwinter loss of mass among female black bears (Ursus americanus) in La Mauricie National Park, Quebec, Canada. All adult females weighing greater than or equal to 77 kg gave birth and no female reproduced when weighing <56 kg. Litter size (two to four young) was influenced by maternal condition in early winter, and overwinter loss of mass greater for females producing litters of three and four young. For a particular litter size, heavier females tended to produce more male young than expected from an equal sex ratio. Maternal condition, however, could not explain the strongly male-biased sex ratio (2.5 males:1.0 female) at birth observed in this population. Significance of sex ratio at birth in relation to the regulation of the population of bears at La Mauricie National Park is discussed.
Canine and matching premolar teeth were extracted from 117 unknown-age hunter-killed black bears (Ursus americanus) to determine if the first premolar was a reliable substitute for the canine in aging. Exact age agreement was realized in 109 cases; ages of the remaining eight bears were generally in close agreement. The first premolar was ascertained to be equally as reliable as the canine tooth as an age indicator of black bears. Advantages of the first premolar over the canine include ease of collection, near elimination of tooth replacement costs, and increased sample size.
Estimated annual population of Ursus americanus in the Pinaleno Mts, SE Arizona, was 102-150 bears (1 bear/3.0-4.2 km2). Half the population was male; only 50-65% of females were breeding-age adults, and annual recruitment rate was low - 0.43 cubs/adult females or 11-22 animals recruited each year. Taking hunting and natural mortality into account the population appears to be slowly increasing in numbers, but there is a real risk of overharvest.-P.J.Jarvis
Denning characteristics of black bears (Ursus americanus) were observed in northcentral Florida from 1983 to 1988 for 17 individuals (nine males, eight females). Fourteen den sites were found—all were ground beds located in hardwood swamps or dense shrub thickets. Pregnant bears denned for periods similar to those reported for other areas of the southeastern United States. However, males and barren females denned for shorter periods than reported in other studies. We suspect that the availability of winter food in Florida has allowed bears to shorten the length of denning relative to that which occurs further north where winter food is unavailable. Pregnant bears, however, may be obligated by intrinsic factors to den for a minimum of 3-4 months.
A simple approximation to the Lotka equations permits using various combinations of population dynamics parameters to determine adult female survival rates needed to sustain a constant population level under various conditions suggested by observed data on grizzly (Ursus arctos) and polar bears (U. maritimus). The approximation should be useful in evaluating more complex models. Some data on polar bears were used to illustrate a method for estimating the ratio of early survival rates to that for adults. Such a ratio may be useful in establishing appropriate combinations of subadult and total adult survivorship for sustained population levels.
Home range and survival were determined for cottontail rabbits (Sylvilagus floridanus) living in woodlots in southwestern Wisconsin. Home ranges were determined for 25 radio-tagged cottontail rabbits in a 14-acre (5.7-ha) woodlot where fall densities were 3.6 rabbits per acre (0.4 ha). Home range size varied by season, sex, and individual. Adult male home ranges increased from a mean of 6.8 acres (2.8 ha) in spring to a mean of 9.9 acres (4.0 ha) in early summer, then decreased significantly to a mean of 3.8 acres (1.5 ha) in late summer. This decrease coincided with testes regression. Adult female home ranges were largest (mean = 4.3 acres [1.7 ha]) in spring, then decreased significantly to a mean of 2.1 acres (0.8 ha) in early summer and remained about this size until mid-January. Female home ranges did not overlap in late summer. Between mid-September and mid-November the home ranges of four juveniles did not differ in size from 10 adults which showed no difference according to sex. Retreats (holes, woodpiles, junkpiles) were used as daytime resting locations mostly during periods of snow cover. Less than 8 percent of daytime resting locations occurred in agricultural land. Bimonthly survival rates determined radiotelemetrically for 51 cottontails were 0.77, 0.79, 0.94, 0.80, 0.68, and 0.63 for 2-month periods beginning in March, May, July, September, November, and January, respectively. Annual survival calculated from the bimonthly rates was 0.20; mean annual survival determined demographically was 0.15. Cottontail survival appeared to be related to exposure in insecure cover.
The estimation of survival distributions for animals which are radio-tagged is an important current problem for animal ecologists. Allowance must be made for censoring due to radio failure, radio loss, emigration from the study area and animals surviving p88l. :~the end of the study period. First we show that the Kaplan-Meier .procedure wid~ly used in medical and engineering studies can be applied to this problem. An example using some quail data is given for illustration. As radios maItunction -or are lost, new radio-tagged animals have to be added to the study. We show how this modification can easily be incorpor~.ted inf.<? the basic Kaplan-Meier procedure. Another example using quail data is used to illustrate the extension. We also show how the log rank test commonly used to compare two survival distributions can be generalized to allow for additions. Simple computer programs which can be run on a PC are available from the authors.
Between July 1979 and May 1982 movements of 23 radio-tagged black bears (Ursus americanus) were studied in a remnant bottomland hardwood forest in eastern Arkansas. Estimates of annual and seasonal home range varied substantially within age-sex groups. Mean annual home ranges of males were significantly larger than those of females in adult and subadult age classes. Within sex classes, mean annual home ranges of adult and subadults were similar. The size of annual home range was inversely related to habitat diversity and, in adult males, to weight. Typically, bears used significantly larger ranges in summer, when their diets were complex and breeding occurred, than in spring or fall-winter, when their diets were simple. Home ranges of 4 neighboring males overlapped considerably. Among 2 groups of females, home range overlap varied and may have been related to reproductive condition or kinship. Radio-tagged bears did not disperse from the study area nor far from their natal ranges, indicating that this remnant population is closed.
Typescript. Thesis (Ph. D.)--West Virginia University, 1989. Vita. Includes bibliographical references (leaves 74-86).
Black bears of west-central Colorado
- T D I Beck
BECK, T. D. I. 1991. Black bears of west-central
Colorado. Colo. Div. Wildl. Tech. Pub. 39. 86pp.
Denning ecology of the black bear in west-central Idaho
- J J Beecham
- D G Reynolds
- M G Hornocker
BEECHAM, J. J., D. G. REYNOLDS, AND M. G.
HORNOCKER. 1983. Denning ecology of the
black bear in west-central Idaho. Int. Conf. Bear
Res. and Manage. 5:79-86.
Denning and related activities of black bears in the coastal plain of North Carolina
- R J And
- R L Marchinton
HAMILTON, R. J., AND R. L. MARCHINTON. 1980.
Denning and related activities of black bears in
the coastal plain of North Carolina. Int. Conf.
Bear Res. and Manage. 4:121-126.
Use of breakaway cotton spacers on radiocollars
VAUGHAN. 1988. Use of breakaway cotton
spacers on radiocollars. Wildl. Soc. Bull. 16:216-218.
Population characteristics of Arizona black bears
- A L Lecount
LECOUNT, A. L. 1982. Population characteristics
of Arizona black bears. J. Wildl. Manage. 46:861-868.
.1983. Denning ecology of black bears in
Central Arizona. Int. Conf. Bear Res. and Manage. 5:71-78.
Vegetation and climate in Coahuila
- C H Muller
MULLER, C. H. 1947. Vegetation and climate in
Coahuila, M6xico. Madrofio 9:33-57.
Chihuahuan Desert climate. Pages 40-63 in
- R H Schmidt
SCHMIDT, R. H. 1986. Chihuahuan Desert climate.
Pages 40-63 in J. C. Barlow, A. M. Powell, and
B. N. Timmermann, eds. Second Symp. on Resources of the Chihuahuan Desert. Chihuahuan
Desert Res. Inst., Alpine, Tex. 172pp.
Lower cretaceous stratigraphy, northern Coahuila, M6xico
- C I Smith
SMITH, C. I. 1970. Lower cretaceous stratigraphy,
northern Coahuila, M6xico. Univ. Texas Bur.
Econ. Geol., Austin. Rep. Inv. No. 65. 101pp.
Texas Parks and Wildl. Dep. Fed. Aid Proj. No. W-125-R-3, Job. 68. 5pp. 1994. Black bear status. Texas Parks and Wildl
TAYLOR, R. B. 1992. Black bear status. Texas Parks
and Wildl. Dep. Fed. Aid Proj. No. W-125-R-3,
Job. 68. 5pp.
1994. Black bear status. Texas Parks and
Wildl. Dep. Fed. Aid Proj. No. W-125-R-5, Job.
68. 9pp.
Population characteristics and home range dynamics of a black bear population in northern Coahuila
- D L Doan-Crider
DOAN-CRIDER, D. L. 1995. Population characteristics and home range dynamics of a black bear
population in northern Coahuila, Mexico. M.S.
Thesis, Texas A&M Univ.-Kingsville, Kingsville.
117pp.
Characteristics of a northern Arizona black bear population. Arizona Game and Fish Dept
1987a. Characteristics of a northern Arizona black bear population. Arizona Game and
Fish Dept. Fed. Aid Proj. W-78-R, Work Plan 2,
Job 22. 26pp.
1987b. Causes of black bear cub mortality.