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The diet of brown bears Ursus arctos in central Scandinavia: Effect of access to free-ranging domestic sheep Ovis aries
Abstract
The seasonal food habits of brown bears Ursus arctos were estimated based on the analysis of 266 scats in central Norway and Sweden. Free-ranging domestic sheep Ovis aries were common in the Norwegian part of the study area, but were not found in the Swedish part. Correction factors were used to correct for differences in digestibility and nutritional value of different foods. Because correction factors for ungulates are difficult to estimate, the results should be interpreted with some caution. In terms of digestible energy, ungulates, mostly carrion, were the most important food in both areas during spring. During summer, ants, forbs, and ungulates (reindeer Rangifer tarandus and moose Alces alces) were the most important food items in the Swedish area, and sheep were most important in the Norwegian area. The autumn diet was dominated by berries in the Swedish area and sheep and berries in the Norwegian area. Among berries, crowberry Empetrum nigrum was the most important species, followed by bilberry Vaccinium myrtillus in Sweden. The major difference between the Swedish and Norwegian areas was the large consumption of sheep in Norway, which provided protein and lipids, and was associated with a relatively reduced consumption of ants and forbs in summer and berries in the autumn. Based on different ingestion rates among the seasons, we estimated the relative contribution of major foods to total digestible energy. In the Swedish area, bears obtained 44-46 and 14-30% of their total annual energy from berries and ungulates, respectively. The remaining energy was obtained from insects (14-22%, mostly ants) and forbs and graminoids (12-18%, mostly blue sow thistle Cicerbita alpina). In Norway, bears obtained 65-87% of the energy from ungulates (mostly sheep), 6-17% from berries, 5-13% from insects, and 2-6% from forbs and graminoids. To gain weight prior to denning, brown bears in Norway selected lipid-rich and easily obtainable sheep in summer and autumn. In Sweden, they relied on carbohydrate-rich berries in autumn.
... The fact that brown bear utilizes different food sources depending on vegetation in the habitat indicates that the high ecological plasticity of this species and its ability to adjust dietary habits to food availability (Dahle et al. 1998, Edwards et al. 2010, Van Daele et al. 2012, Gunter et al. 2014, Hertel et al. 2016, Stenset et al. 2016, Klamarova 2019. In some regions, if fattening foods are deficient and farmed crops attract brown bears, human -bear conflicts may arise (Pazhetnova 1987, Obbard et al. 2014, Sakiyama et al. 2021). ...
... On the other hand, animal foods usually have a higher calorific value than plant foods (Gunther et al. 2014). No wonder that brown bears in Norway obtained most of the annual energy supply from consuming ungulates, and in Sweden -from berries and ungulates (Dahle et al. 1998). The most important berry species in Sweden in autumn were bilberry Vaccinium myrtillus L., crowberry Empetrum nigrum L. and cowberry Vaccinium vitis-idaea L. (Stenset et al. 2016), and their consumption was selective (Hertel et al. 2016). ...
... However, at high latitudes of European Russia, crowberry gains in importance. In central Sweden and north-eastern Norway (area adjoining the Pasvik NR in the Murmansk region), crowberry is a principal fattening food for brown bear (Dahle et al. 1998, Persson et al. 2001, Stenset et al. 2016, Klamárová 2019. It shows high prevalence in the carnivore scats in the south of the Kola Peninsula as well (Tirronen et al. 2016). ...
The Chronicles of Nature (Letopis Prirody) kept in the nature reserves of the Russian Federaton aggregate a wide spectrum of systematic field records. Information of particular interest therein is the timing of ripening of berries and their yields across years, since berries are an important food for many wildlife species, including brown bear (Ursus arctos), a core species in boreal European Russia. Such trophic links are most explicit and interesting in the autumn during fattening or hyperphagia period in bears, when the animals depend on berry availability for storing up fat. We aimed to identify the ecological relationships of brown bear applying integrated analysis of field data on the carnivore diet and of records from the Chronicles of Nature of the Kivach Nature Reserves (the middle taiga) and the Pinega Nature Reserve (the northern taiga). We have determined the prevalence (%) of the certain foods in brown bear scats sampled from transects along forest roads and paths. The number and productivity of fruit-bearing rowan trees (Sorbus aucuparia) were determined along permanent transects. Bilberry (Vaccinium myrtillus) and cowberry (Vaccinium vitis-idaea) berries dominate in brown bear diet. Berry ripening dates (19-43 days) and the average yield (scores 1.3 to 5.0) vary greatly over years. Trends in ripening onset dates follow a vector towards earlier dates. In the Pinega NR, the rate of this process is faster in bilberry. The coefficient of rank correlation between the number of fruit-bearing rowans along dirt roads and rowan prevalence in scats was r=1. The same significant correlation was found between the number of fruit-bearing rowan trees and rowan berry yield. The prevalence of different foods in brown bear scats during the hyperphagia period shows the high dietary plasticity of species. A reliable strong correlation was detected in the Pinega NR between the last sighting of brown bear tracks in autumn and the onset of berry ripening in bog bilberry and rowan. The relatively stable food supply for brown bear in the middle and northern taiga of European Russia is one of the factors defining the high numbers and wide distribution of the species. Keywords: Chronicles of Nature, nature reserves, middle and northern taiga subzones, fattening foods, berry fruiting, trophic links, dietary plasticity, Ursus arctos.
... Brown bears are omnivorous and their diet varies among populations and seasons. In Scandinavia, the diet is mainly composed of graminoids, forbs, berries, ants, and ungulates (Dahle et al. 1998, Persson et al. 2001. During spring and early summer, adult brown bears accumulate lean mass reserves (Hilderbrand et al. 1999) from foods rich in protein (Swenson et al. 2007). ...
... During spring and early summer, adult brown bears accumulate lean mass reserves (Hilderbrand et al. 1999) from foods rich in protein (Swenson et al. 2007). The period of fat accumulation (hyperphagia) starts in August, when the bears in Sweden consume mainly berries rich in carbohydrates to gain adipose fat tissue before entering the winter den (Dahle et al. 1998). ...
Abstract
This is a report about the second year of collaboration between Biosphere Expeditions and Björn & Vildmark with the overall purpose of researching the behaviour of free ranging brown bears (Ursus arctos) in central Sweden for the Scandinavian Brown Bear Research Project (SBBRP). This collaboration investigates, amongst other topics, how climate change as well as human activities affect the brown bear behaviour and population, and provides managers in Sweden with solid, science-based knowledge to manage brown bears.
From 28 May to 4 June 2022, six citizen scientists collected data on bear denning behaviour and feeding ecology by investigating the 2021/2022 hibernation season den sites of GPS-marked brown bears and by collecting fresh scats from day bed sites. All field work was performed in the northern boreal forest zone in Dalarna and Gävleborg counties, south-central Sweden, which is the southern study area of the SBBRP. After two days of field work training, citizen scientists were divided into three to four sub-teams each day. All study positions were provided by the expedition scientist and only data and samples from radio-marked bears with a VHF or GPS transmitter were collected.
Citizen scientists defined den types (anthill den, soil den, rock den, basket den or uprooted tree den), recorded bed material thickness, size and content, as well as all tracks and signs around the den sites to elucidate whether a female had given birth to cubs during hibernation. All first scats after hibernation and hair samples from the bed were collected, and the habitat type around the den and the visibility of the den site were described.
Twenty-six winter positions of 21 different bears were investigated. Two bears shifted their dens at least once during the hibernation season. In total, the expedition found 23 dens; two soil dens, eight anthill dens, one anthill/soil den, one stone/rock den, four dens under uprooted trees and seven basket dens. Unusually, one pregnant female that gave birth to three cubs during winter, and four females that hibernated together with dependent offspring spent the winter in basket dens. Normally basket dens are mainly used by large males.
Excavated bear dens had an average outer length of 2.0 m, an outer width of 2.2 m, and an outer height of 0.8 m. The entrance on average comprised 28% of the open area. The inner length of the den was on average 1.3 m and the inner width was 1.1 m. The inner height of the dens was on average 0.6 m. Bears that hibernated in covered dens used mainly mosses (47%), field layer shrubs (36%) and branches (14%) as nest material, which reflected the composition of the field layer and ground layer that was present at the den site. However, bears that hibernated in open dens such as basket dens, preferred branches (43%) followed by grass (26%); mosses (19%) and field shrubs (12%) as nest material. The expedition found two first post-hibernation bear scats at the den sites.
Ten bears selected their den sites in older forests, and eleven bears in younger forests, only two bears hibernated in very young forest. The habitat around the dens was dominated by spruce (Picea abies) 37%, scots pine (Pinus sylvestris) 35% and birch (Betula pendula, Betula pubescens) 27%.
As part of its intensive data collection activities, the expedition investigated about half of all winter den positions that the SBBRP recorded in 2021/2022 and collected 64 scats at cluster positions, which represents all scat samples that the SBBRP normally collects during a time period of 14 days. A detailed food item analysis will be performed in 2025 and the data will be published.
It appears that climate change is altering bear denning behaviour and may reduce food resources that bears need for fat production. Overharvesting (hunting) of bears and habitat destruction are the major reasons why brown bear populations have declined or have become fragmented in much of their range. In Scandinavia, human activity around den sites has been suggested as the main reason why bears abandon their dens. This can reduce the reproductive success of pregnant female brown bears and increases the chance of human/bear conflict. Understanding denning behaviour is critical for effective bear conservation. Further research is needed to determine whether good denning strategies help bears avoid being disturbed. Additionally, enclosed dens offer protection and insulation from inclement weather. A continued fragmentation of present bear ranges, inhibiting dispersal, together with an increasing bear population, might lead to bears denning closer to human activities than at present, thereby increasing human/bear conflict. The dens that were investigated by the expedition were visible from 22 m on average. Cover opportunities and terrain types not preferred by humans are thereby presumably important for bears that are denning relatively close to human activities, but further research needs to be done to validate this theory.
Through all of the above, the expedition made a very significant contribution to the SBBRP’s field work in a showcase of how citizen science can supplement existing research projects run by professional scientists.
Sammandrag
Detta är en rapport om det andra året av samarbete mellan Biosphere Expeditions och Björn & Vildmark med det övergripande syftet att forska om beteendet hos vild levande brunbjörnar (Ursus arctos) i mellansverige för det skandinaviska björnforskningsprojektet (SBBRP). Samarbetet undersöker bland annat hur klimatförändringar och mänsklig aktivitet påverkar brunbjörnens beteende och population, och ger myndigheter i Sverige gedigen, vetenskapligt baserad kunskap för att förvalta brunbjörnstammen.
Från den 28 maj till den 4 juni 2022 samlade sju expeditionsdeltagare in data om björnens idesval och födoval. De undersökte idesplatserna där björnar har legat i vintersömnen under säsongen 2021-2022 och de samlade samla färsk spillning från daglegor från GPS-märkta brunbjörnar.
Allt fältarbete utfördes i norra boreala skogszonen i Dalarna och Gävleborgs län, södra mellersta Sverige, som är SBBRP:s södra studieområde.
Efter två dagars utbildning inom fältarbete delades expeditionsdeltagaren in i tre till fyra grupper. Alla studiepositioner tillhandahölls av expeditionsforskaren och endast data och prover från radiomärkta björnar med en VHF- eller GPS-sändare samlades in.
Expeditionsdeltagaren definierade idestyper (myrstackide, jordiden, steniden, korgiden eller iden under en rotvälta), och undersökte bäddmaterialet i idet, samt alla spår och tecken runt iden för att ta reda på om en hona hade född ungar under vintern. Alla första spillningar samlades in samt och hårprover från bäddmaterialed. Dessutom beskrevs habitatet och hur dold idet var placerad i terrängen.
26 vinterpositioner för 21 olika björnar undersöktes. Två björnar flyttade från sina iden minst en gång under vintersömnen. Totalt hittade expeditionsdeltagaren 23 iden; två jordiden, åtta myrstackiden, ett myrstackide / jordide, ett steniden, fyra iden under en rotvälta och sju korgiden. Ovanligt nog övervintrade en dräktig björnhona ett korgide där hon födde sina ungar under vintern. Dessutom övervintrade fyra honor med ungar i olika korgiden. Vanligtvis är det framförallt hanbjörnar som använder korgiden.
Utgrävda björniden hade en genomsnittlig yttre längd på 2,0 och yttre bredd på 2,2 m och en yttre höjd av 0,8 m. Ingången utgjorde i genomsnitt 28% av det öppna yta. Den inre längden på idet var i genomsnitt 1,3 m och den inre bredden 1,1 m. Den inre höjden på idena var i genomsnitt 0,6 m. Björnar använde främst grenar (43%), gräs (26%) bärris (12%) och mossor (19%) som bäddmaterial, vilket återspeglade sammansättningen av fältskiktet och jordskiktet som fanns vid idesplatsen. Expeditionsdeltagare hittade två första björnspillningar efter vintersömnen.
Tio björnar valde bygga sina iden i äldre skogar, elva i yngre skogar och två björnar övervintrade i väldigt ung skog. Habitatet runt idesplatsen dominerades av tall (Pinus sylvestris) 35%, gran (Picea abies) 37%, och björk (Betula pendula, Betula pubescens) 27%.
Expeditionen undersökte ungefär hälften av alla vinterpositioner som SBBRP registrerade under 2021/2022 och samlade in 63 spillningar på klusterpositioner, vilket motsvarar alla av de spillnings-prover som björnprojektet normalt samlar in under en tidsperiod på 14 dagar. En detaljerad spillnings analys kommer att genomföras under 2025 och uppgifterna kommer att publiceras efteråt.
Genom allt ovanstående gav expeditionen ett mycket viktigt bidrag till SBBRP: s fältarbete som visade hur expeditionsdeltagare kan komplettera befintliga forskningsprojekt som drivs av professionella forskare. Klimatförändringar förändrar björnens beteende och kan minska födotillgången. Intensiv björnjakt och förstörelse av habitat är de främsta orsakerna till att populationer av brunbjörnar har minskat eller blivit fragmenterade i stora delar av världen. I Skandinavien är mänsklig aktivitet kring idesplatser troligtvis det främsta skälet varför björnar byta iden. Detta kan minska reproduktionen bland dräktiga björnhonor och ökar risken för konflikt mellan människor och björnar. Förståelse av vinterbeteende är avgörande för effektiv bevarande av björnen. Ytterligare forskning behövs för att avgöra om goda vinterstrategier hjälper björnar att undvika störningar. Dessutom erbjuder väl isolerade ide skydd från dåligt väder. En fortsatt fragmentering av nuvarande björnstammen, som hämmar spridning, tillsammans med en ökande björnpopulation, kan leda till att björnar kommer närmare mänsklig bebyggelse, vilket ökar konflikterna mellan människa och björnar. De iden som undersöktes av expeditionen var synliga från 22 m i genomsnitt. Täta terrängtyper som inte föredras av människor är därmed förmodligen viktiga för björnar som bygger sina iden relativt nära mänsklig bebyggelse, men ytterligare forskning måste göras för att validera denna teori.
... Every scat was weighed, and scat volume was determined by water displacement. Dietary ingredients were determined following the methods of Hamer and Herrero (1987), Dahle et al. (1998) and Stenset et al. (2016). Each scat was homogenized and then thoroughly washed over a 0.6 mm sieve. ...
The dietary nutrient profile has metabolic significance and possibly contributes to species' foraging behavior. The brown bear (Ursus arctos) was used as a model species for which dietary ingredient and nutrient concentrations as well as nutrient ratios were determined annually, seasonally and per reproductive class. Brown bears had a vertebrate- and ant-dominated diet in spring and early summer and a berry-dominated diet in fall, which translated into protein-rich and carbohydrate-rich diets, respectively. Fiber concentrations appeared constant over time and averaged at 25% of dry matter intake. Dietary ingredient proportions differed between reproductive classes; however, these differences did not translate into a difference in dietary nutrient concentrations, suggesting that bears manage to maintain similar nutrient profiles with selection of different ingredients. In terms of nutrient ratios, the dietary protein to non-protein ratio, considered optimal at around 0.2 (on metabolizable energy basis), averaged around 0.2 in this study in fall and around 0.8 in spring and summer. We introduced the minimal non-fat to fat ratio necessary for efficient maintenance metabolism. This ratio varied across seasons but never fell beneath the theoretically estimated minimum to ensure metabolic efficiency. This population thus managed to ingest diets that never exerted a lack of glucogenic substrate, suggesting that metabolic efficiency may either be a driver of active diet selection or that natural resources available to bears did not constitute a constraint in this respect. Given the considerable proportion of fiber in the diet of brown bears, the relevance of this nutrient and its role in foraging behavior might be underestimated.
... Brown bears are mostly found in central and northern Sweden. They are omnivorous, but frequently prey on moose and reindeer 3 calves in spring after hibernation (Dahle et al. 1998). Lynx, which are smaller than the two foregoing, are present all over the country, in particular in central Sweden where roe deer are abundant. ...
The benefits and costs of wildlife are contingent on the spatial overlap of animal populations with economic and recreational human activities. By using a production function approach with dynamic spatial panel data models, we analyze the effects of human hunting and carnivore predation pressure on the value of ungulate game harvests. The results show evidence of dynamic spatial dependence in the harvests of roe deer and wild boar, but not in those of moose, which is likely explained by the presence of harvesting quotas for the latter. Results suggest the impact of lynx on roe deer harvesting values is reduced by 75% when spatial effects are taken into account. The spatial analysis confirms that policymakers’ aim to reduce wild boar populations through increased hunting has been successful, an effect that was only visible when considering spatial effects.
... Bears commonly scavenge on slaughter remains discarded by hunters (Elfström et al., 2014;Friebe et al., 2001;Lafferty et al., 2016), and dietary analyses in Scandinavian brown bears showed that~14% of scats collected during the fall contained vertebrate materials (Stenset et al., 2016). Scandinavian brown bears rely mostly on berries (e.g., Vaccinium spp., Empetrum spp.) during hyperphagia in the fall (Stenset et al., 2016), but consume meat when available (Dahle et al., 1998;Elfström et al., 2014;Persson et al., 2001). Therefore, we can expect brown bears to scavenge on slaughter remains discarded by moose hunters during the fall. ...
Hunters can affect the behavior of wildlife by inducing a landscape of fear, selecting individuals with specific traits, or by altering resource availability across the landscape. Most research investigating the influence of hunting on wildlife resource selection has focused on target species and less attention has been devoted to non-target species, such as scavengers that can be both attracted or repelled by hunting activities. We used resource selection functions to identify areas where hunters were most likely to kill moose (Alces alces) in south-central Sweden during the fall. Then, we used step-selection functions to determine whether female brown bears (Ursus arctos) selected or avoided these areas and specific resources during the moose hunting season. We found that, during both day and nighttime, female brown bears avoided areas where hunters were more likely to kill moose. We found evidence that resource selection by brown bears varied substantially during the fall and that some behavioral changes were consistent with disturbance associated with moose hunters. Brown bears were more likely to select concealed locations in young (i.e., regenerating) and coniferous forests and areas further away from roads during the moose hunting season. Our results suggest that brown bears react to both spatial and temporal variations in apparent risk during the fall: moose hunters create a landscape of fear and trigger an antipredator response in a large carnivore even if bears are not specifically targeted during the moose hunting season. Such antipredator responses might lead to indirect habitat loss and lower foraging efficiency and the resulting consequences should be considered when planning hunting seasons.
... Også i Skandinavia er brunbjørnen en generalist, og nyttiggjør seg flere typer naering (Stenset et al., 2016). Tilgjengeligheten av mat, i tillegg til bjørnenes krav til ernaering gjennom året styrer mye av dens diett (Dahle et al., 1998). I Skandinavia er plantekost, maur og klauvvilt de viktigste innslagene i dietten til bjørnen, med plantekost som den vanligste naeringskilden. ...
... In addition, stable isotope analyses of hair samples are thought to integrate the assimilation of protein, carbohydrate, and lipids (Mowat & Heard, 2006). Acorns (a source of lipids, Naves et al., 2006), fruits (a source of carbohydrates, Hertel et al., 2018), and pine nuts (a source of lipids, L opez-Alfaro et al., 2015) contribute more to the assimilated diet because these food items are more digestible and absorbable for brown bears than herbaceous plants (e.g., Bojarska & Selva, 2013;Dahle et al., 1998;L opez-Alfaro et al., 2015;Persson et al., 2001). Perhaps, this was the reason why the contribution of plant categories was higher in the Utoro and Shari areas and that of alpine plants was higher in the Rausu area. ...
Exploring the process of diet selection will contribute to improvement in our understanding of animal foraging strategies. The overwhelming majority of ecological research on animal learning and foraging concentrates on how social learning influences the feeding styles of animals living in groups. In solitary animals that live long after independence from their mothers, foraging experience after independence is expected to have a significant influence on diet selection, but few studies have addressed this point. We used brown bears (Ursus arctos), which spend 1–2 years with their mothers before foraging alone, as a model species and investigated how their diet changed later in life. We estimated the diets of bears at the individual level by using stable isotope analysis of guard hairs and examined the factors that drove dietary variation. We also quantified the extent to which the diets of bears shifted by comparing the diets of bears at the time of capture with the average diet in their natal habitat. Our results indicated that females retained the average diet of their natal habitat, whereas the diets of males significantly changed more than 6 years after becoming independent from their mothers, when they reached physical maturity. Males were dependent on energy‐rich marine animals at older ages regardless of their natal habitats, which we attribute to several factors, including habitat exploration, acquisition of foraging experience, and social dominance. Our results provide the first evidence, suggesting that foraging experience after independence influences diet selection later in life in solitary large mammals.
... The majority of scavenging vertebrates that utilize cadavers as a food source are facultative scavengers (DeVault et al., 2003), that is, they are not solely dependent on carrion material and can include plant material as part of their diet. For example, during peak fruiting season, berries can constitute up to 30% of the diet in red fox (Needham et al., 2014) and as much as 82% in brown bears (Dahle et al., 1998). Such facultative scavengers often have large home ranges and thus considerable capacity as vectors for long-distance endozoochorous seed dispersal (González-Varo et al., 2013;Schaumann & Heinken, 2002). ...
The regeneration niche of many plant species involves spatially and temporally unpredictable disturbances, called recruitment windows of opportunity. However, even species with clear dispersal adaptations such as fleshy berries may not successfully reach such elusive regeneration microsites. Ericaceous, berry-producing species in the northern hemisphere demonstrate this dispersal limitation. They are said to display a reproductive paradox owing to their lack of regeneration in apparently suitable microsites despite considerable investment in producing large quantities of berries.
Cadavers generate vegetation-denuded and nutrient-rich disturbances termed cadaver decomposition islands (CDIs). Cadavers attract facultative scavengers with considerable capacity for endozoochorous seed dispersal. We hypothesize that CDIs facilitate recruitment in berry-producing ericaceous species due to endozoochorous dispersal directed toward favorable microsites with low competition.
We examined seedling establishment within a permanent, semi-regular 10 × 10 m grid across an ungulate mass die-off on the Hardangervidda plateau in southeastern Norway. Competing models regarding the relative importance of factors governing recruitment were evaluated, specifically cadaver location (elevated seed rain) and microsite conditions (competition).
We found that CDIs did facilitate seedling establishment, as cadaver density was the best predictor of seedling distribution. Other important factors governing seedling establishment such as percentage cover of soil and vascular plants alone were inadequate to explain seedling establishment.
Synthesis: This study provides a novel understanding of sexual reproduction in species with cryptic generative reproduction. The directed nature of endozoochorous dispersal combined with long-distance dispersal abilities of medium to large vertebrate scavengers toward cadavers allows plants to exploit the advantageous but ephemeral resource provided by CDIs.
Structure of dead wood supplies in Świętokrzyski National Park and its importance for the conservation of some species of saproxylobiontic beetles. A complex inventory of dead wood supplies in Świętokrzyski National Park was conducted in a few last years. The results of line interscet method and circular plots method are presented. This data is analyzed according to the categories of protection (strict and active protection), development phases of forests, forest habitat types, plant communities and species structure of dead trees. Presence of dead trees of an appropriate quality and quantity is crucial for preserving many species inhabiting such microhabitats. Two species of saproxylobiontic beetles (wrinkled bark beetle Rhysodes sulcatus and cinnabar flat bark beetle Cucujus cinnaberinus), which are an object of protection in Natura 2000 site Łysogóry PLH260025, are analyzed. The study presented conditions relevant to the occurrence of these species in relation to dead wood supplies in forest ecosystems.
The Asiatic black bear (Ursus thibetanus) is known to use the fruits of various fleshy-fruited plant species as food resources. However, there is no published evidence regarding whether they feed on the berries of 4 ericaceous dwarf shrub species that are widely distributed in alpine regions in Japan (Empetrum nigrum, Vaccinium uliginosum, Gaultheria pyroloides, and Vaccinium vitis-idaea). We assessed the use of, and preference for, these berries by black bears and identified the production and morphological and nutritional characteristics of these berries in the alpine zone of Mt. Asama, central Japan. Using camera-trap survey and scat analyses between July and November in 2017, 2018, and 2019, we obtained the first evidence that these bears consume large quantities of E. nigrum berries in the alpine zones during the summer. The density of berries per square meter was highest for E. nigrum. By contrast, the costbenefit ratio of morphological fruit attractiveness (i.e., fresh pulp weight and dry pulp weight divided by total fresh seed weight per fruit), crude protein, crude fat, and nitrogen-free extract levels were lowest in E. nigrum berries. Therefore, fruit use by black bears appeared to be influenced by fruit production rather than the morphological or nutritional value of the fruits. Bears may compensate for this nutritional deficit by consuming large quantities of these berries. Consequently, E. nigrum berries are key food items for black bears in Japan and may compensate for summer food shortages.
The term "negative foraging period" has been used to describe the time between the emergence of black bears (Ursus americanus) from their dens and the ripening of fleshy fruits in summer; the implication is that spring foods lack adequate energy for bears to gain or even maintain weight. Few biologists, however, have examined data on weight changes to determine if the concept applied to the bears they studied. We investigated age and sex-specific weight changes of black bears in northcentral Minnesota between denning and early July. Weights were obtained from bears trapped (n = 350) or handled at dens (n = 270) during 1981-89. Weights of 1- to 2-year-old males and females rose from late winter (Feb-Mar) to late spring (May-early Jun) and again from late spring to early summer (early Jun-mid-Jul), with gains averaging 8-14 kg over the period. Bones (head length) of young bears also grew during spring, although chest girth decreased, indicating loss of fat. Mean weights of 4- and 5-year-old males increased 21 and 10 kg, respectively, from winter to late spring, but decreased 20 and 25 kg between late spring and early summer. Only males ≥ 6 years old lost weight during both periods (x = 16 kg). Behavioral and physiological changes associated with breeding, including increased testosterone, increased activity, and decreased feeding, probably explained most weight loss in breeding-age males. In females, most weight loss was associated with lactation. Lactating females either lost weight from winter to early summer (sequential weights of individuals) or showed no significant change (mean weights of pooled sample), whereas non-lactating adult females gained weight. Despite a spring diet that is generally low in carbohydrates and fats, bears apparently make efficient use of plant protein. Past studies, with small samples and data pooled among sex-age groups, did not recognize the importance of spring as a period of growth for young bears.
We fed 27 different food items to captive grizzly bears (Ursus arctos) to investigate the need for correction factors (CF's) when estimating grizzly bear food habits from fecal residue. The amount of food necessary to produce 1 ml of fecal residue ranged from 0.16 to 40.8 g dry matter, suggesting that uncorrected fecal analysis are rarely equivalent to food habits. We propose CF's that relate the volume of residue in the feces to the mass of dry matter ingested. The ranges of these CF's were 0.16-0.35 for vegetation, 0.51-1.84 for berries, 0.35-1.40 for roots, 0.91-1.25 for insects, 1.54 for pine nuts, 1.54-12.5 for mammals, and 40.8 for fish. The CF for large mammals depends upon how much skin, hair, bones, or other poorly digested components are consumed.
Records of bountied brown bears Ursus arctos in Norway and Sweden were analysed to estimate population size in the mid-1800's, and changes in population size and distribution in relation to the bear management policies of both countries. In the mid-1800's about 65% of the bears in Scandinavia were in Norway (perhaps 3,100 in Norway and 1,650 in Sweden). Both countries tried to eliminate the bear in the 1800's; Sweden was more effective. By the turn of the century, the numbers of bears were low in both countries. The lowest population level in the population remnants that have subsequently survived occurred around 1930 and was estimated at 130 bears. Sweden's policy was changed at the turn of the century to save the bear from extinction. This policy was successful, and the population is now large and expanding. Norway did not change its policy and bears were virtually eliminated by 1920-30. Since 1975, bear observations increased in Norway. This coincided temporally with an abrupt increase in the Swedish bear population, and bears reappeared sooner in areas closer to the remnant Swedish populations. Both conditions support our conclusion that the bear was virtually exterminated in Norway and suggest that bears observed now are primarily immigrants from Sweden, except for far northern Norway, which was recolonised from Russia and Finland. Today, we estimate that the Scandinavian bear population numbers about 700, with about 2% in Norway (on average about 14 in Norway, 650-700 in Sweden). This is a drastic reduction in the estimate of bears in Norway, compared with earlier studies. The trends in bear numbers responded to the policies in effect. The most effective measures used in Scandinavia to conserve bears were those that reduced or eliminated the economic incentive for people to kill them. Our analysis also suggests that population estimates based on reports from observations made by the general public can be greatly inflated.
The number of scats dropped by captive European brown bears (Ursus arctos) was recorded in all months of the year, 1971-73. An overall total of 3,634 scats was recorded in 1,094 bear-days. Clear seasonal differences were found, with low values of about 2 scats per bear-day from November through June and higher values in the remaining months, and with a distinct peak in August of 7.19 scats per bear-day for adults. Extremes observed ranged from 0 to 11 scats per bear-day. Preliminary data indicate at least a 28 percent higher defecation rate for cubs. Significant (P < 0.01) differences were found among individual bears kept under identical conditions. Possible application of these findings to estimation of bear densities or bear use in the wild is discussed.
The density of adult (≥3 years) female brown bears Ursus arctos was estimated in two areas of Sweden from ratios of radio-marked and unmarked females consorting with radio-marked adult males during the breeding season. The resulting densities were 1·2 ± 0·81 (95% confidence interval) adult females/1000 km2 in a northern study area and 1·06 ± 3·44 adult females/1000 km2 in a southern area. These estimates were extrapolated to obtain a population estimate for Sweden using relative densities throughout the range of the species in Sweden, based on hunter-kill statistics, and observed rates of reproduction and juvenile and subadult survival. The total population in spring 1991 was estimated to be about 620 bears, with almost all females confined to four geographically separated areas, termed female core areas. A supplementary estimate, based on estimated kill rates of adult females in the study areas, was about 660 bears. Estimates based on hunter kill rates of marked bears gave minimum and maximum estimates of about 300 and 900 bears, respectively. Although these are not confidence intervals of the total population estimate, we believe that the true population size is included within these limits. Densities within the female core areas varied from 50 to 100% of those in similar habitats in European Russia. The bear population in Sweden appeared to have increased at a stable rate of about 1·5% annually during the past 50 years. Mean annual rate of legal harvest during 1943–1991 was estimated to be 5·5% (±2·1% SD), suggesting a maximum sustainable rate of 7·0% for this population. The harvest increased at a rate of 9·6% annually during 1981–1991, and apparently was at the maximum sustainable level during 1987–1991.
Grizzly bear (Ursus arctos horribilis) scats were collected from 4 western Montana study areas from 1976 to 1979 to determine differences in food item selection. Fruit was important to grizzly bears in all areas although the species consumed and the apparent degree of use varied. Globe huckleberry (Vaccinium globulare) was important to grizzly bears in the North and South forks of the Flathead River but was rarely eaten in other areas. Domestic apples (Malus spp.) and plums (Prunus spp.) were eaten extensively by Mission Mountain grizzly bears. Grasses and sedges were a staple food to bears in all areas; variable use of Umbelliferae was found. The nuts of whitebark pine (Pinus albicaulis) were eaten extensively by East Front grizzly bears only, and biscuit-root (Lomatium spp.) roots were dug to varying degrees in all areas. Yellow hedysarum (Hedysarum sulphurescens) roots were an important spring and autumn food to North Fork grizzly bears only. Horsetails (Equisetum spp.), clover (Trifolium spp.), and dandelions (Taraxacum spp.) were important in all areas throughout the grizzly bears' active period. These data suggest that substantial local variation occurs in grizzly bear food habits in Montana. These differences should be considered in land management plans that call for maintenance or enhancement of grizzly bear habitat. Int. Conf. Bear Res. and Manage. 6:105-110 The omnivorous nature of the grizzly bear was recognized decades ago (Wright 1909, Storer and Trevis 1955); their opportunistic selection of food items has permitted bears to occupy a great variety of vegetation types in North America (Herrero 1972). Although much information is available on the food habits of this species throughout North America, few investigations have compared the diet of a single pop- ulation occupying several diverse areas. This inves- tigation examined and compared grizzly bear food habits among 4 areas in western Montana: the North and South forks of the Flathead River, the Mission Mountains, and the Rocky Mountain East Front. We wish to thank all employees of the Border Grizzly Project who aided in the collection of scats. Specific thanks go to Allen Schallenberger, Peter Husby, Nanka McMurray, Gayle Joslin, and Chris- topher Servheen. We also wish to thank L. Jack Lyon (U.S. Dep. Agric., For. Serv.) for use of laboratory facilities. This research was funded in part by the U.S. Dep. Int., Bur. Land Manage., Mont. Dep. of Fish, Wildl. and Parks, and the U.S. Dep. Int., Fish and Wildl. Serv.