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Is supplemental feeding with carrion an effective way to reduce human-bear conflicts?
Abstract
Supplemental feeding is often believed to be a successful tool for reducing human–bear (Ursus
arctos) conflicts, especially in Europe. However, effectiveness of this measure is poorly
understood and there is growing concern for potential negative side-effects. This is particularly
true for supplemental feeding using livestock carrion. Carrion feeding is considered especially
effective in reducing livestock depredations by diverting bears from pastures and meeting their
protein needs.
In Slovenia, year-round supplementary feeding of bears with livestock carrion and maize was
intensive and in some areas practiced for over 100 years. However, in 2004 the use of livestock
carrion was banned in accordance with European Union regulations. This provided an
opportunity to study the effects of carrion feeding on livestock depredations by bears. We used
sheep for model species as they represented 97% of all depredation events by brown bears in
Slovenia. We analysed whether bears selectively used carrion feeding stations over maize
feeding stations (i.e., indicating that carrion might be more effective in diverting bears from
sheep pastures) during 1994–2011, and compared the annual frequency and seasonal
distribution of sheep depredations 5 years before and after the ban on livestock carrion feeding
during 1999–2009.
We found no support that bears selected carrion feeding sites over feeding sites with maize.
When controlled for changes in bear and sheep numbers, there was no indication that the ban
on carrion feeding increased sheep depredations. Moreover, complementary data indicated that
natural protein sources (e.g., invertebrates) were considerably more important than livestock
carrion and that use of carrion peaked in spring, when sheep are rarely outdoors and thus
unavailable for depredation.
Because of the observed lack of effectiveness, high costs, and potential negative side-effects, we
discourage supplemental feeding with livestock carrion to reduce livestock depredation.
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The total number of brown bears (Ursus arctos) in Europe is presently about 50,000 (about 14,000 outside Russia), within an area of more than 2.5 million km2 (800,000 km2 outside Russia). About 37,500 bears are found in the northeastern European population; 8,100 in the Carpathian Mountains; 2,800 in the Alps-Dinaric-Pindos; 1,000 in Scandinavia; 520 in the Rila-Rhodope Mountains; 200 in the Stara Planina Mountains; 50-65 in the western Cantabrian Mountains; 40-80 in Apennine Mountains; 20 in the eastern Cantabrian Mountains; 6 in the Western Pyrenees; 5 in the Central Pyrenees; and 4 in the southern Alps. The brown bear is either a protected or game species in all of the countries discussed in this paper. Most countries manage the brown bear at the national level, although several ministries are often involved. All European countries with bears within their national borders (except Bosnia and Herzegovina and the Yugoslav Federation) have signed the Bern Convention; almost half have prepared, or are preparing, a management plan for brown bears. In addition, most countries engage in monitoring, research, information dissemination, and conservation activities. In areas where bear range includes human settlements, damage to livestock, orchards, and beehives occurs but, in most countries, stakeholders are compensated for damage, either by the state, regional government, or hunter clubs. In 1995-96 about 1.15 million US$ was paid to compensate such damage throughout Europe.
Black bears (Ursus americanus) are opportunistic omnivores (Simpson 1945) that feed on grasses, grubs, insects, berries, human garbage, and they scavenge from animal carcasses (Cotton 2008, Thiemann et al. 2008). During the spring, they also girdle trees to feed on the newly forming phloem (Poelker and Hartwell 1973, Noble and Meslow 1998, Partridge et al. 2001). Extensive black bear damage to conifers coincided with the beginning of intensive forest management on industrial and smaller private lands in western Washington during the early 1940s; high-yield tree plantations (i.e., tree farms) required protection to reduce tree girdling by black bears. During the mid-1950s, bear damage occurrence and frequency was recorded on Douglas fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla), and western red cedar (Thuja plicata) after bear damage had spread across most of the Pacific Northwest (Lauckhart 1955).
One of the most important factors negatively influencing public attitudes toward brown bears (Ursus arctos) and other large carnivores is depredation on livestock. This is especially true in Norway, where a small population of 25-55 bears kills about 2,000 sheep annually. In other European countries the re-establishment of large carnivores is planned or underway, and similar problems may arise. As a basis for future large carnivore management in Europe, I compared depredation among 13 European countries having small, medium, or large bear, lynx (Lynx lynx), and wolf (Canis lupus) populations. I calculated annual per capita losses of livestock (ACLL) as the average annual loss of livestock divided by the estimated predator population in the area of concern. In Norway, the rates of livestock losses from bears, lynx and wolves were among the highest observed in Europe. Assuming predator population estimates are correct, each bear killed an average of 82 sheep annually, each wolf 41, and each lynx 9. Generally, in Europe, lynx were the least important predator on livestock. In all but one area (Cantabrian Mountains, Spain), sheep and goats were the livestock most often taken by all 3 of the large carnivores. Depredation levels were not related to the size of the bear population nor to the number of sheep available, but to differences in local husbandry traditions. Most attacks seemed to occur at night, and sheep were the most exposed on forested range. The high predation level in Norway can be explained by the large number of untended sheep that stay day and night on forested range. There is no example in Europe of extensive sheep farming with low losses and viable populations of bears and wolves on the same range.
Diversionary feeding of black bears (Ursus americanus) around campgrounds and residential areas has received little study because of concerns it might create nuisance bears and jeopardize public safety. To evaluate those concerns and assess its effectiveness in mitigating human-bear conflict, we studied diversionary feeding at a U. S. Forest Service campground/residential complex where 6 bears had been removed as nuisances in the previous 3 years (1981-1983). During 8 years of diversionary feeding tests (1984-1991), the only bear removed was a transient sub-adult male that had not yet found the diversionary feeding site. Nuisance problems were greatly reduced throughout the study despite the fact that garbage continued to be available and study bears were intentionally habituated and food-conditioned. The study included 1985—the year with the lowest bear food index recorded for Minnesota. In this study and other examples of diversionary feeding across North America, nuisance complaints, house break-ins, attacks, and bear removals were fewer, often drastically fewer, than elsewhere, and residents became more willing to coexist with bears. The study showed that hunger, not habituation or food- conditioning, is the primary factor creating bear-human conflict in urbanized areas. Habituated, food-conditioned bears did not become nuisances, did not jeopardize public safety, and did not behave in accordance with the stereotypes assigned to them. There is a need to reevaluate policies toward these bears in this light. Further study is needed to determine the situations in which long- term or short-term diversionary feeding can be most effective in mitigating human-bear conflict during periods of food shortage.
In many ecosystems, grizzly bears (Ursus arctos) and black bears (Ursus americanus) feed heavily on berries and fruits in the fall. While a few birds and mammals are exclusively frugivorous, bears and most other animals consume fruit as part of a mixed diet. The mixed-diet strategy avoids potential calcium, protein, amino acid, or other nutrient deficiencies that can occur on fruit diets. However, we hypothesized that the high carbohydrate - low protein content of fruit would increase energy metabolism and force bears to use dietary mixing to meet protein requirements and, thereby, reduce energy metabolism. We examined the effects of six plant-based diets containing from 2.3 to 35% crude protein on intake, maintenance costs, and efficiency of gain of captive grizzly and black bears. In addition, the food habits of six populations of wild grizzly and black bears were analyzed, to determine the crude protein and digestible dry matter content of their diets. Efficiency of gain (0.53 ± 0.02 (±SD) g gain/g digestible dry matter intake) did not differ across diets. However, maintenance costs differed, ranging from 24 g·(kg0.75·day)-1 (120 kcal (1 cal = 4.1868 J) digestible energy (DE)·(kg0.75·day)-1) on the 35% protein pelleted diet to 80 g·(kg0.75·day)-1 (340 kcal DE·(kg0.75·day)-1) on fruit diets containing 2.3-5.6% protein (P = 0.0001). Supplementation of the fruit diet with additional protein increased mass gain but did not completely reverse the growth-depressing effect of the fruit-only diet. Protein limitations or other characteristics of fruit diets that increase energy metabolism and intake may be strategies that also directly benefit plants, by increasing either seed dispersal or propagation.
Solid understanding of species’ range and local population densities is important for successful wildlife management and research. Specific behavioural and ecological characteristics make brown bear Ursus arctos a difficult species to study. We present a map of range and local population densities of brown bears in Slovenia made with the use of new approach similar to voting classifications based on a combination of four datasets: GPS telemetry data, records of bear removals, systematic and opportunistic direct observations and signs of bear presence, and non-invasive genetic samples. Results indicate that the majority of bears in Slovenia live in Dinaric Mountains in the southern part of the country where local bear population densities exceed 40 bears / 100 km2. This is one of the highest population densities reported so far for this species worldwide. Population densities decrease towards the north (Alpine region) and are very low along the border with Italy and Austria where almost no females are present. This explains slow past and present expansion of this transboundary bear population into the Alps and should be considered in future bear re-colonization management strategies. Results also showed that data from observations and removals overestimate bear population densities at low values, while mortality and genetic data overestimate population densities in areas with more people. Nevertheless, all data types appeared useful for describing the general bear distribution patterns. Similar approach could be applied to studies of other charismatic or game species, for which several types of data are often available.
Livestock depredations are one of the main challenges in the management of the grey wolf (Canis lupus) and culling of the wolves is a measure often used in an attempt to reduce damages. In the present study we analyzed effects of the legal wolf culling on livestock depredations in Slovenia and made a review of similar studies from other regions. 51 wolves were legally culled and 2,221 attacks on livestock were recorded in Slovenia in 1995-2009. Our analysis did not show any effects of the culling on the number of depredations during the study period. No effects were detected even when the most extreme years were compared. Our results are in agreement with those from other studies that showed that sustainable hunting of wolves is not an effective measure to reduce livestock depredations. Wolf removal becomes efficient only when wolves are completely exterminated or when the majority of wolves are removed from a large area. Because depredation of small livestock in Slovenia presents a serious problem and since wolf culling does not seem to be efficient, we recommend that more attention and resources should be focused on more effective measures.
In the heavily managed boreal forest of Scandinavia, ants, especially large colonies of red forest ants (Formica spp.), are abundant and brown bears (Ursus arctos) intensively feed on them. In contrast, the beech (Fagus sylvatica) forests of Slovenia provide only suboptimal habitat for ants and large ant colonies are virtually absent. To quantify how much ant use by brown bears is a matter of availability or preference, we quantified ant availability, species composition, and ant use. The estimated biomass of ants available to brown bears was very low in Slovenia compared with those in Sweden, averaging 135 vs. 9600 g/ha, respectively. Nevertheless, the frequency of occurrence of ants in Slovenian brown bear scats was high, averaging 85% and accounting for 25% of the ingested dry mass during the summer, which was nearly as much as their frequency of occurrence in Swedish brown bear scats during the summer. Although brown bears in Slovenia had year-round access to artificial feeding sites and the availability of ants is only about 1% of the biomass found in Sweden, they consumed about 50% of the quantity of ants compared with the brown bears in Sweden. Our results show that ants are an important and sought-after food source for brown bears in Slovenia, and the occurrence of ants should be considered in habitat-suitability models.
Scavenging is an important but poorly understood ecological process. Dominant scavengers can impose a selection pressure that alters the predator’s fitness, morphology, behavior, and ecology. Interactions between ursids, likely the most important dominant scavengers in the Holarctic region, and solitary felids, which are characterized by long feeding times, provide a good opportunity for studying the effects of kleptoparasitism by dominant scavengers. We analyzed the effects of scavenging by brown bears Ursus arctos on Eurasian lynx Lynx lynx and predator’s response to kleptoparasitism in a European temperate forest ecosystem. Bears found 32 % of lynx prey remains and 15 % of all biomass of large prey killed by lynx was lost to bears. In response, lynx increased their kill rate by 23 % but were able to compensate for only 59 % of the losses. The frequency of bear scavenging was strongly dependent on bear activity patterns and was highest during the lynx pregnancy and lactation period, when up to half of lynx kills were usurped by bears. We suggest that ursid scavenging, by promoting the hunting of smaller prey, may have played an important role in the evolution of the Lynx genus as well as other predators in the Holarctic. Our study indicates that prey loss to dominant scavengers is a widespread phenomenon among felids worldwide, including forest habitats. We highlight several implications of scavenging that could considerably improve our understanding of the ecology of vertebrate communities and the evolution of predators as well as benefit the future management and conservation of endangered predators.
Harvesting wild animals can affect demographic parameters and life history traits of surviving individuals. Most brown bear (Ursus arctos) populations currently experience low levels of hunting. We characterized mortality patterns in a heavily exploited transboundary brown bear population in Slovenia, Central Europe. Overall, 927 brown bears were reported removed from 1998 to 2008. Most (97%) removals were human caused including removals from hunting (59% of removals), management removals of problem individuals (18%), and vehicle collisions (16%). Median age of bears removed in Slovenia was 2.3 years, and 78% of bears removed were ,4 years old. Removal was male-biased overall (59%), mainly due to the high percent (49%) of young (,4 years old) males removed during hunting, a possible consequence of sex-related differences in bear behavior and harvest regulations. However, the effect of sex- biased removal was less than expected based on removal data, and it appears a different harvest regimen in neighboring Croatia and sex-biased dispersal of young bears buffered the demographic effects of selective harvest in Slovenia. We also observed that annual proportion of females in harvests increased with harvest intensity. More males were removed among younger classes, whereas females started to dominate above the age of 8 years. About 20% of the brown bear population was removed annually by legal harvest; this is one of the highest harvest rates reported for this species.
Illegal killings are a major threat to wildlife conservation worldwide. Combating illegal killings and understanding the motives behind them are among the top challenges for the conservation of controversial species such as large carnivores. In Europe, the Eastern Alps are a focal area for many active brown bear (Ursus arctos) conservation and restoration projects. The wider public generally has a positive attitude toward bears and bear restoration, but some hunters and farmers seem less supportive. The extent this opposition can reach was demonstrated by the well documented illegal killing of a bear in the three-country triangle of Slovenia, Italy, and Austria in June 2009. We provide detailed background information and discuss this case within the context of the lack of a northward expansion of the Dinaric–Pindos bear population and the failed bear re-introduction in central Austria.
For many years, the primary strategy for managing grizzly bears (Ursus arctos) that came into conflict with humans in the Greater Yellowstone Ecosystem (GYE) was to capture and translocate the offending bears away from conflict sites. Translocation usually only temporarily alleviated the problems and most often did not result in long-term solutions. Wildlife managers needed to be able to predict the causes, types, locations, and trends of conflicts to more efficiently allocate resources for pro-active rather than reactive management actions. To address this need, we recorded all grizzly bear–human conflicts reported in the GYE during 1992–2000. We analyzed trends in conflicts over time (increasing or decreasing), geographic location on macro- (inside or outside of the designated Yellowstone Grizzly Bear Recovery Zone [YGBRZ]) and micro- (geographic location) scales, land ownership (public or private), and relationship to the seasonal availability of bear foods. We recorded 995 grizzly bear–human conflicts in the GYE. Fifty-three percent of the conflicts occurred outside and 47% inside the YGBRZ boundary. Fifty-nine percent of the conflicts occurred on public and 41% on private land. Incidents of bears damaging property and obtaining anthropogenic foods were inversely correlated to the abundance of naturally occurring bear foods. Livestock depredations occurred independent of the availability of bear foods. To further aid in prioritizing management strategies to reduce conflicts, we also analyzed conflicts in relation to subsequent human-caused grizzly bear mortality. There were 74 human-caused grizzly bear mortalities during the study, primarily from killing bears in defense of life and property (43%) and management removal of bears involved in bear–human conflicts (28%). Other sources of human-caused mortality included illegal kills, electrocution by downed power-lines, mistaken identification by American black bear (Ursus americanus) hunters, and vehicle strikes. This analysis will help provide wildlife managers the information necessary to develop strategies designed to prevent conflicts from occurring rather than reacting to conflicts after they occur.
There is a long history of conflict in the western United States between humans and grizzly bears (Ursus arctos) involving agricultural attractants. However, little is known about the spatial dimensions of this conflict and the relative importance of different attractants. This study was undertaken to better understand the spatial and functional components of conflict between humans and grizzly bears on privately owned agricultural lands in Montana. Our investigations focused on spatial associations of rivers and creeks, livestock pastures, boneyards (livestock carcass dump sites), beehives, and grizzly bear habitat with reported human–grizzly bear conflicts during 1986–2001. We based our analysis on a survey of 61 of 64 livestock producers in our study in the Rocky Mountain East Front, Montana. With the assistance of livestock and honey producers, we mapped the locations of cattle and sheep pastures, boneyards, and beehives. We used density surface mapping to identify seasonal clusters of conflicts that we term conflict hotspots. Hotspots accounted for 75% of all conflicts and encompassed approximately 8% of the study area. We also differentiated chronic (4 or more years of conflicts) from non-chronic hotspots (fewer than 4 years of conflict). The 10 chronic hotpots accounted for 58% of all conflicts. Based on Monte Carlo simulations, we found that conflict locations were most strongly associated with rivers and creeks followed by sheep lambing areas and fall sheep pastures. Conflicts also were associated with cattle calving areas, spring cow–calf pastures, summer and fall cattle pastures, and boneyards. The Monte Carlo simulations indicated associations between conflict locations and unprotected beehives at specific analysis scales. Protected (fenced) beehives were less likely to experience conflicts than unprotected beehives. Conflicts occurred at a greater rate in riparian and wetland vegetation than would be expected. The majority of conflicts occurred in a small portion of the study area, where concentrations of attractants existed that overlapped with bear habitat. These hotspots should be the target of management and conservation efforts that focus on removing or protecting attractants using non-lethal techniques.
Because of its biological characteristics, its important place in the minds of humans, and the considerable international interest for its conservation, management of the brown bear (Ursus arctos) in Europe is challenging. The Brown Bear Management Plan for Croatia (BMPC) was approved in 2004 and addressed interests such as ecology, aesthetics, and economics, as well as concern for the safety of people and property. It attempts to ensure conditions for the long-term survival of the brown bear, a species listed as endangered by some international regulations but as a game species (subject to regulated hunting) in others, including Croatia. Careful evaluation of actions affecting population size represents the most critical part of this plan. Those actions should sustain long-term viability of the bear population while maintaining densities at a level that minimize human–bear conflict. To achieve this goal, a series of actions and measures have to be regulated that are related to (1) bear habitat, (2) human activities in the habitat (e.g., highway construction, feeding of bears by humans), (3) prevention of problematic bear occurrences, and (4) the scientific monitoring of population changes. Although the plan's development and implementation is the responsibility of bear management experts, various interests groups were considered. In large carnivore management, and especially in bear management, there are no final and universal solutions. Changes in the number of bears, areas of their presence, or behavior require new decisions. This plan offers guidelines for the decision-making process, and, because it includes a revision process, can be adapted to address new circumstances that arise. Citizens interested in conservation, not only in Croatia but also in neighboring countries, expect Croatia to work toward maintaining the long-term existence of as many bears as possible in appropriate habitats, with as few negative effects as possible. This plan is an important step in fulfilling those expectations.
Abstract We analyzed harvest data to describe hunting patterns and harvest demography of brown bears (Ursus arctos) killed in 3 geographic regions in Sweden during 1981–2004. In addition, we investigated the effects of a ban on baiting, instituted in 2001, and 2 major changes in the quota system: a switch to sex-specific quotas in 1992 and a return to total quotas in 1999. Brown bears (n=887) were harvested specifically by bear hunters and incidentally by moose (Alces alces) hunters. Both hunter categories harvested bears 1) using dogs (37%), 2) by still hunting (30%), 3) with the use of bait (18%), and 4) by stalking (16%). The proportion of bears killed with different harvest methods varied among regions and between bear- and moose-oriented hunters. We found differences between male (52%) and female bears (48%) with respect to the variables that explained age. Moose-oriented hunters using still hunting harvested the youngest male bears. Bears harvested during the first management period (1981–1991) were older and had greater odds of being male than during the subsequent period. It appears that hunters harvesting bears in Sweden are less selective than their North American counterparts, possibly due to differences in the hunting system. When comparing the 4 years immediately prior to the ban on baiting with the 4 years following the ban, we found no differences in average age of harvested bears, sex ratio, or proportion of bears killed with stalking, still hunting, and hunting with dogs, suggesting that the ban on baiting in Sweden had no immediate effect on patterns of brown bear harvest demography and remaining hunting methods. As the demographic and evolutionary side effects of selective harvesting receive growing attention, wildlife managers should be aware that differences in harvest systems between jurisdictions may cause qualitative and quantitative differences in harvest biases. (JOURNAL OF WILDLIFE MANAGEMENT 72(1):79–88; 2008)
We tested six hypotheses to explain expected geographical differences in body masses of 1,771 brown bears (Ursus arctos) from northern and southern Europe (Sweden and Norway compared with Slovenia and Croatia): Bergmann’s rule, the fasting endurance
hypothesis, and the dietary meat hypothesis, which predicted larger bears in the north; and hypotheses stressing the role
of high primary productivity, high population density, low seasonality, and length of the growing season, which predicted
larger bears in the south. Although brown bear populations in North America vary greatly in body mass, we found no significant
difference in body mass between the two European populations using a new analytical approach incorporating modeled age-standardized
body masses in linear models, when correcting for sex and season. The greater variation in North America may be due primarily
to the presence of large bears that feed on salmon (Oncorhynchus spp.), which does not occur in Europe. Asymptotic body masses were 115±9 (SE) kg in spring and 141±9kg in autumn for
southern females, 248±25 and 243±24kg for southern males, 96±2 and 158±4kg for northern females, and 201±4 and
273±6kg for northern males, respectively. Northern bears gained more body mass before hibernation and lost more during
hibernation than southern bears, probably because hibernation was twice as long in the north. Northern bears gained and southern
bears lost mass during the spring, perhaps due to the greater availability and use of protein-rich food in spring in the north.
As reproductive success in bears is correlated with adult female body mass in interpopulation comparisons, brown bears may
have relatively similar reproductive rates throughout Europe, although minimum age at primiparity and litter interval are
lower in the south.
In recent years, events within Canada and the United States have drawn attention to potential negative consequences of feeding and baiting wild animals, especially enhanced transmission of infectious diseases such as bovine tuberculosis and chronic wasting disease. This report was prepared to gather available science-based information on the ecological and human social effects of artificial feeding and baiting of wildlife into one readily accessible document. The contracting agencies, Parks Canada and Saskatchewan Environment, recognize that an objective review of existing literature may help to answer questions and concerns within and outside the agencies, and help to guide subsequent decision-making concerning management and research pertaining to feeding and baiting.
The practice of feeding brown bears Ursus arctos for recreational purposes is common in the easternmost areas of Finland, but this may, however, result in human-habituated bears. From 1995 to 2008, 3% of all bears killed by humans (N = 1, 108 bears) in Finland represented incidents where bears were either killed for reasons of human safety under a license issued by the police or as a result of actual emergency situations where bears were shot in self defence. We constructed binary logistic regression models for comparing bears shot under police license and in self defence with bears killed in regular sport hunting by using the sex of the bear, human density, bear observation density and the distance from the nearest feeding site as independent variables. High human density was the most important factor differentiating bears shot under a license issued by police from bears killed in sport hunting. The difference in human density was largest for places located far from feeding sites. Increasing distance from feeding sites differentiated bears shot under police license and in self defence from sport hunted bears. The sex of the bears and the density of bear observation were more weakly associated with the category of shooting. Our study did not provide evidence that bear feeding for recreational purposes is associated with the nuisance-bear problem in Finland. Nevertheless, some risks for human safety might be associated with artificial bear feeding for tourism purposes. If the practice of feeding bears continues to be accepted by Finnish legislation, game management should include an action plan for occasions when bears visiting feeding sites will lose their wariness of humans.
Black bear (Ursus americanus) damage to managed conifer stands during the spring in the U.S. Pacific Northwest is a continuing management concern. Because bear damage to managed conifers may reflect the limited availability of nutritious foods, supplemental feeding has been used to decrease damage. Highly palatable, pelleted feed is provided ad libitum from April until late June when berries ripen and such damage stops. We examined black bear use of supplemental feed during the spring and summer of 1998 and 1999 in western Washington. Bears were captured in areas where supplemental feed was provided and in control areas where no effort to reduce conifer damage occurred. Mass gains for bears captured twice were 153 ± 119 g/day (x̄ ± SD) in the fed areas and 12 ± 104 g/day in non-fed areas. Fat gain for bears in the fed areas was 42 ± 50 g/day and 4 ± 59 g/day in the non-fed areas. However, because age-specific body masses and fat content did not differ between the 2 areas, short-term pellet feeding probably has no long-lasting effect on bear condition or productivity. The diet of bears in the fed areas was 55 ± 22% pelleted feed, 7 ± 7% animal matter, and 38 ± 18% vegetation. The diet of bears in the non-fed areas was 13 ± 17% animal matter and 87 ± 17% vegetation. Grass and sedge composed the majority of vegetation consumed in both areas. The energy content of Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) sapwood was more digestible (60-67%) than grasses and forbs (18-47%). Smaller bears (adult females and subadult males and females) may do most of the damage because sapwood harvesting rates minimize nutritional gain to larger adult males.
Foods and habitat use of black bears (Ursus americanus) in the Coastal Plain of southeastern North Carolina were determined from 732 fecal droppings and contents of 28 stomachs, and from radiomonitoring 10 bears. Major habitat components were (1) a variety of habitats producing seasonal foods; (2) extensive, inaccessible areas (Carolina bays, hardwood swamps) for denning; and (3) escape cover for bears hunted with dogs (large swamps). Carolina bays contributed most natural foods (berries and succulent plants), except in spring when bears fed in swamps on arrow-arum (Peltandra virginica) leaves and in fall when they fed in swamps on black gum (Nyssa sylvatica) or on sand ridges on oak (Quercus spp.) mast. Hunters had maintained sites baited with corn for many years, and corn from bait piles or agricultural fields was used by bears throughout the year. Major pre-denning foods were high in nitrogen-free extract and fats, while post-denning foods were high in protein. Summer fruits were high in sugars and other carbohydrates. Bears in this region apparently need large areas with a variety of habitat types to meet annual food and cover requirements.
In many ecosystems, grizzly bears (Ursus arctos) and black bears (Ursus americanus) feed heavily on berries and fruits in the fall. While a few birds and mammals are exclusively frugivorous, bears and most other animals consume fruit as part of a mixed diet. The mixed-diet strategy avoids potential calcium, protein, amino acid, or other nutrient deficiencies that can occur on fruit diets. However, we hypothesized that the high carbohydrate - low protein content of fruit would increase energy metabolism and force bears to use dietary mixing to meet protein requirements and, thereby, reduce energy metabolism. We examined the effects of six plant-based diets containing from 2.3 to 35% crude protein on intake, maintenance costs, and efficiency of gain of captive grizzly and black bears. In addition, the food habits of six populations of wild grizzly and black bears were analyzed, to determine the crude protein and digestible dry matter content of their diets. Efficiency of gain (0.53 +/- 0.02 (+/- SD) g gain/g digestible dry matter intake) did not differ across diets. However, maintenance costs differed, ranging from 24 g.(kg(0.75).day)(-1) (120 kcal (1 cal = 4.1868 J) digestible energy (DE).(kg(0.75).day)(-1)) on the 35% protein pelleted diet to 80 g.(kg(0.75).day)(-1) (340 kcal DE.(kg(0.75).day)(-1)) on fruit diets containing 2.3-5.6% protein (P = 0.0001). Supplementation of the fruit diet with additional protein increased mass gain but did not completely reverse the growth-depressing effect of the fruit-only diet. Protein limitations or other characteristics of fruit diets that increase energy metabolism and intake may be strategies that also directly benefit plants, by increasing either seed dispersal or propagation.
Some bear hunters in Virginia, primarily houndsmen, feed American black bears (Ursus americanus) to attract them to hunting sites, but also because some hunters believe that supplemental food improves bear reproduction and survival. However, a regulation prohibiting unauthorized feeding of bears, deer (Odocoileus virginianus), and turkey (Meleagris gallopavo) on national forest and state-owned lands in Virginia became effective 1 July 1999. We sent a survey to all members of the Virginia Bear Hunters Association (VBHA) (n = 459) to determine the amount of food provided to bears by hunters between 1 July 1998 and 30 June 1999. Survey response rate was 52%. One hundred thirteen of 238 (48%) survey respondents spent $18,378 on supplemental food during that time. One hundred twenty-eight respondents provided 2,942,394 kilograms of food to bears between 1 July 1998 and 30 June 1999. Whole-shelled corn, pastries, and rendered animal fat (grease) accounted for 58% of the total mass; however, whole-shelled corn, pastries, and bread were the 3 most common foods offered. July, August, and September were the months during which most respondents fed bears. Food supply can affect reproduction, survival, harvest rates, nuisance occurrences, population size, and distribution of bears. If supplemental feeding has an effect on bear population dynamics, changes in regulations regarding feeding may negatively impact black bear populations, as well as public relations and future cooperation between wildlife agencies and hunters.
Information theory and log-likelihood models - a basis for model selection and inference practical use of the information theoretic approach model selection uncertainty with examples Monte Carlo insights and extended examples statistical theory.
In this paper, we address three aspects of the brown bear population in Slovenia: its size (and its evolution over time), its spatial expansion out of the core area, and its potential habitat based on natural habitat suitability. Data collected through measurement/observation of the bear population and from the literature are used. A model is developed for each aspect. The results are estimates of population size, a picture of the spatial expansion of the population and maps of its optimal and maximal potential habitat (based on natural suitability). Overall, the brown bear population has been increasing since the establishment of a core protective area and has been expanding outside this area. The habitat suitability maps show that there is room for further expansion. Based on habitat suitability and bear population density, as well as human activity and current damage reports, we recommend that the Alps should be temporarily kept free of the bears, until the necessary mitigation measures regarding human–bear conflicts are carried out. On the other hand it is of crucial importance to adapt human activities and improve bear management in the optimal habitat, with which the goals of successful conservation of the species might be achieved.
Recently, researchers in several areas of ecology and evolution have begun to change the way in which they analyze data and make biological inferences. Rather than the traditional null hypothesis testing approach, they have adopted an approach called model selection, in which several competing hypotheses are simultaneously confronted with data. Model selection can be used to identify a single best model, thus lending support to one particular hypothesis, or it can be used to make inferences based on weighted support from a complete set of competing models. Model selection is widely accepted and well developed in certain fields, most notably in molecular systematics and mark-recapture analysis. However, it is now gaining support in several other areas, from molecular evolution to landscape ecology. Here, we outline the steps of model selection and highlight several ways that it is now being implemented. By adopting this approach, researchers in ecology and evolution will find a valuable alternative to traditional null hypothesis testing, especially when more than one hypothesis is plausible.
Percent monthly sheep depredations by brown bears before pre-ban) and after
Fig. 2. Percent monthly sheep depredations by brown bears before (1999–2003; pre-ban) and after (2005–
2009; post-ban) the ban on feeding livestock carrion in Slovenia.
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