Dining from the coast to the summit: Salmon and pine nuts determine the summer body condition of female brown bears on the Shiretoko Peninsula

Body condition in mammals fluctuates depending on energy intake and expenditure. For brown bears (Ursus arctos), high‐protein foods facilitate efficient mass gain, while lipids and carbohydrates play important roles in adjusting dietary protein content to optimal levels to maximize energy intake. On the Shiretoko Peninsula, Hokkaido, Japan, brown bears have seasonal access to high‐lipid pine nuts and high‐protein salmon. To assess seasonal and annual fluctuation in the body condition of adult female brown bears in relation to diet and reproductive status, we conducted a longitudinal study in a special wildlife protection area on the Shiretoko Peninsula during 2012–2018. First, analyses of 2,079 bear scats revealed that pine nuts accounted for 39.8% of energy intake in August and salmon accounted for 46.1% in September and that their consumption by bears varied annually. Second, we calculated the ratio of torso height to torso length as an index of body condition from 1,226 photographs of 12 adult females. Results indicated that body condition continued to decline until late August and started to increase in September when salmon consumption increased. In addition, body condition began to recover earlier in years when consumption of both pine nuts and salmon was high. Furthermore, females with offspring had poorer body condition than solitary females, in particular in late August in years with low salmon consumption. Our findings suggest that coastal and subalpine foods, which are unique to the Shiretoko Peninsula, determine the summer body condition of female brown bears, as well as their survival and reproductive success.     

Testing the niche variation hypothesis with a measure of body condition

Individual variation and fitness are cornerstones of evolution by natural selection. The niche variation hypothesis (NVH) posits that when interspecific competition is relaxed, intraspecific competition should drive niche expansion by selection favoring use of novel resources and that among‐individual variation should confer a selective advantage. Population‐level niche expansion could be achieved by all individuals using all available resources, or by each individual using a unique combination of resources, thereby increasing among‐individual dietary niche variation. Although individual variation can lead to species‐level evolutionary and ecological change, observed variation does not ensure a beneficial outcome. We used carbon and nitrogen stable isotope analysis of claw keratin and a Bayesian stable isotope mixing model to estimate the summer (July–September) assimilated diet of individual female black Ursus americanus and brown U. arctos bears. We quantified variation in dietary niche in both populations, and assessed diet relative to percentage body fat. We hypothesized that if the NVH held, percentage body fat would be similar for individuals of the same species across much of the dietary range of observed proportional salmon contributions to individual bear diets. Although we found greater differences in dietary niches between than within species, we observed greater among‐individual dietary variation in the brown bear population. Moreover, we found that within each species individual female bears achieved similar ranges of percentage body fat at various levels of salmon in the diet. Our results provide support for the NVH. Linking individual dietary niches to measures of physiological condition related to fitness can offer new insights into eco‐evolutionary processes related to food resource use.     

Annual and seasonal changes in diets of martens: evidence from stable isotope analysis

Theory predicts that generalist predators will switch to alternative prey when preferred foods are not readily available. Studies on the feeding ecology of the American marten (Martes americana) throughout North America suggest that this mustelid is a generalist predator feeding largely on voles (Microtus sp.; Clethrionomys sp.). We investigated seasonal and annual changes in diets of martens in response to the changing abundance of small rodents (Peromyscus keeni, and Microtus longicaudus) on Chichagof Island, Southeast Alaska, using stable isotope analysis. We hypothesized that martens would feed primarily on small rodents during years with high abundance of these prey species, whereas during years of low abundance of prey, martens would switch to feed primarily on the seasonally available carcasses of salmon. We also hypothesized that home-range location on the landscape (i.e., access to salmon streams) would determine the type of food consumed by martens, and martens feeding on preferred prey would exhibit better body condition than those feeding on other foods. We live-captured 75 martens repeatedly, from mid-February to mid-December 1992–1994. We also obtained marten carcasses from trappers during late autumn 1991 and 1992, from which we randomly sub-sampled 165 individuals. Using stable isotope ratios and a multiple-source mixing model, we inferred that salmon carcasses composed a large portion of the diet of martens in autumn during years of low abundance of rodents (1991 and 1992). When small rodents were available in high numbers (1993 and 1994), they composed the bulk of the diet of martens in autumn, despite salmon carcasses being equally available in all years. Selection for small rodents occurred only in seasons in which abundance of small rodents was low. Logistic regression revealed that individuals with access to salmon streams were more likely to incorporate salmon carcasses in their diet during years of low abundance of small rodents. Using stable isotope analysis on repeated samples from the same individuals, we explored some of the factors underlying feeding habits of individuals under variable ecological conditions. We were unable to demonstrate that body weights of live-captured male and female martens differed significantly between individuals feeding on marine-derived or terrestrial diets. Therefore, martens, as true generalist predators, switched to alternative prey when their principal food was not readily available on a seasonal or annual basis. Although salmon carcasses were not a preferred food for martens, they provided a suitable alternative to maintain body condition during years when small rodents were not readily available. Received: 1 May 1996 / Accepted: 24 February 1997     

Stable isotope evidence indicates the incorporation into Japanese catchments of marine‐derived nutrients transported by spawning Pacific Salmon

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Microevolution of the mitochondrial DNA control region in the Japanese brown bear (Ursus arctos) population.

We investigated nucleotide sequences of the mitochondrial DNA control region to describe natural genetic variations and to assess the relationships between subpopulations of the brown bear Ursus arctos on Hokkaido Island, Japan. Using the polymerase chain reaction product-direct sequencing technique, partial sequences (about 930 bases) of the control region were determined for 56 brown bears sampled throughout Hokkaido Island. A sequence alignment revealed that the brown bear control region included a variable sequence on the 5' side and a repetitive region on the 3' side. Phylogenetic trees reconstructed from the 5' variable region (696-702 bases) exhibited 17 haplotypes, which were clustered into three groups (Clusters A, B, and C). The distribution of each group did not overlap with those of the others, and the three different areas were located in separate mountainous forests of Hokkaido Island. Furthermore, most of the phylogenetically close haplotypes within each group were distributed geographically close to each other. In addition, the 3' repetitive region (arrays of 10 bases) exhibited a much faster mutation rate than the 5' variable region, resulting in heteroplasmy. Such mitochondrial DNA divergence in each group could have occurred after the brown bears migrated from the continent to Hokkaido and became fixed in the different areas.     

Consumption choice by bears feeding on salmon

Consumption choice by brown (Ursus arctos) and black bears (U. americanus) feeding on salmon was recorded for over 20,000 bear-killed fish from 1994 to 1999 in Bristol Bay (sockeye salmon, Oncorhynchus nerka) and southeastern Alaska (pink, O. gorbuscha and chum salmon O. keta). These data revealed striking patterns of partial and selective consumption that varied with relative availability and attributes of the fish. As the availability of salmon decreased, bears consumed a larger proportion of each fish among both years and habitats. When availability was high (absolute number and density of salmon), bears consumed less biomass per captured fish, targeting energy-rich fish (those that had not spawned) or energy-rich body parts (eggs in females; brain in males). In contrast, individual fish were consumed to a much greater extent, regardless of sex or spawning status, in habitats or years of low salmon availability. The proportion of biomass consumed per fish was similar for males and females, when spawning status was statistically controlled, but bears targeted different body parts: the body flesh, brain and dorsal hump in males and the roe in females. Bears thus appeared to maximize energy intake by modifying the amount and body parts consumed, based on availability and attributes of spawning salmon.     

Role of brown bears (Ursus arctos) in the flow of marine nitrogen into a terrestrial ecosystem

We quantified the amount, spatial distribution, and importance of salmon (Oncorhynchus spp.)-derived nitrogen (N) by brown bears (Ursus arctos) on the Kenai Peninsula, Alaska. We tested and confirmed the hypothesis that the stable isotope signature (δ¹⁵N) of N in foliage of white spruce (Picea glauca) was inversely proportional to the distance from salmon-spawning streams (r=–0.99 and P<0.05 in two separate watersheds). Locations of radio-collared brown bears, relative to their distance from a stream, were highly correlated with δ¹⁵N depletion of foliage across the same gradient (r=–0.98 and –0.96 and P<0.05 in the same two separate watersheds). Mean rates of redistribution of salmon-derived N by adult female brown bears were 37.2±2.9 kg/year per bear (range 23.1–56.3), of which 96% (35.7±2.7 kg/year per bear) was excreted in urine, 3% (1.1±0.1 kg/year per bear) was excreted in feces, and <1% (0.3± 0.1 kg/year per bear) was retained in the body. On an area basis, salmon-N redistribution rates were as high as 5.1±0.7 mg/m² per year per bear within 500 m of the stream but dropped off greatly with increasing distance. We estimated that 15.5–17.8% of the total N in spruce foliage within 500 m of the stream was derived from salmon. Of that, bears had distributed 83–84%. Thus, brown bears can be an important vector of salmon-derived N into riparian ecosystems, but their effects are highly variable spatially and a function of bear density. Received: 11 February 1999 / Accepted: 7 July 1999     

Ecotype and geographical variation in carbon and nitrogen stable isotope values in western North Pacific killer whales (Orcinus orca)

Killer whales are top predators in marine trophic chains, and therefore their feeding preferences can substantially affect the abundance of species on the lower trophic levels. Killer whales are known to feed on many different types of prey from small fish to large whales, but a given killer whale population usually focuses on a specific type of prey. Stable isotope analysis is widely used to study whale diets, because direct observations are often impossible. Killer whale feeding habits in the western North Pacific are poorly studied, and the large-scale stable isotope analysis provides a unique opportunity to gain insights into the trophic links of this top predator. In this study, we compare the δ¹³C and δ¹⁵N stable isotope values from killer whale skin samples obtained in different areas of the western North Pacific from fish-eating (R-type) and mammal-eating (T-type) killer whale ecotypes. The effect of ecotype was highly significant: both carbon and nitrogen stable isotope values were lower in R-type whales than in T-type whales. The geographical variation also affected killer whale stable isotope values due to both the differences in killer whale diet and the variation in baseline stable isotope values across the study areas.     

Feeding ecology of granivorous carabid larvae: a stable isotope analysis

Although most carabids are primarily carnivorous, some carabid species are omnivorous, with mainly granivorous feeding habits during the larval and/or adult stages (granivorous carabids). This feeding habit has been established based on laboratory and field experiments; however, our knowledge of the feeding ecology of these beetles in the field is limited owing to the lack of an appropriate methodology. In this study, we tested the utility of stable isotope analysis in investigations of the feeding ecology of granivorous carabids in the field, using two closely related syntopic species, Amara chalcites and Amara congrua. We addressed two issues concerning the feeding ecology of granivorous carabids: food niche differentiation between related syntopic species during the larval stage and the effect on adult body size of supplementing seeds with an animal diet during the larval stage. To investigate larval feeding habits, we analysed newly emerged adults, most somatic tissues of which are considered of larval origin. In the two populations examined, both δ¹⁵N and δ¹³C were significantly higher in A. chalcites than A. congrua, suggesting that the two species differentiate food niches, with A. chalcites larvae being more carnivorous than A. congrua larvae. The two isotope ratios of A. chalcites samples from one locality were positively correlated with body size, suggesting that more carnivorous larvae become larger adults. However, this relationship was not detected in other species/locality groups. Thus, our results were inconclusive on the issue of diet supplementation. Nevertheless, overall, these results are comparable with those of previous laboratory‐rearing experiments and demonstrate the potential utility of stable isotope analysis in field studies on the feeding ecology of granivorous carabids.     

Individual Distinctiveness in Brown Bears,Ursus arctos L

Individual brown bears, Ursus arctos, behave differently from each other. Consistent behavioural differences suggest that each bear has its own distinct personality. On Admiralty Island in south-eastern Alaska, we collected longitudinal data during three years of summer salmon runs on seven individual brown bears that could be recognized from year to year. Bears fed on vegetation and on salmon along a tidal creek. Ratings of individual bears by observers on different aspects of behaviour, comparisons of behavioural frequencies, and long-term observations of individual activities served to assess personality differences. Individual bears varied in five ways: 1. Some bears were lively, animated and playful in social situations and during solitary activities such as travelling or fishing. Other bears' movements and general demeanour seemed dull and humourless; 2. Some bears were irascible, others socially uninvolved and unreactive; 3. Some bears were expert at fishing but others fished ineptly; 4. Some bears were confident with other bears but others lacked confidence in social situations; 5. Some bears were often active and alert. Others rested more frequently and for prolonged periods.     

Continuous variation in the pattern of marine v. freshwater foraging in brown trout Salmo trutta L. from Loch Lomond, Scotland

Carbon stable-isotope analysis showed that individual brown trout Salmo trutta in Loch Lomond adopted strategies intermediate to that of freshwater residency or anadromy, suggesting either repeated movement between freshwater and marine environments, or estuarine residency. Carbon stable-isotope (δ¹³C) values from Loch Lomond brown trout muscle tissue ranged from those indicative of assimilation of purely freshwater-derived carbon to those reflecting significant utilization of marine-derived carbon. A single isotope, two-source mixing model indicated that, on average, marine C made a 33% contribution to the muscle tissue C of Loch Lomond brown trout. Nitrogen stable isotope, δ¹⁵N, but not δ¹³C was correlated with fork length suggesting that larger fish were feeding at a higher trophic level but that marine feeding was not indicated by larger body size. These results are discussed with reference to migration patterns in other species.     

Trophic ecology of Pacific salmon (<Emphasis Type="Italic">Oncorhynchus</Emphasis> spp.) in the ocean: a synthesis of stable isotope research

Increasing interest in the marine trophic dynamics of Pacific salmon has been motivated by the recognition of their sensitivity to changing climate and to the competitive effects of hatchery fish on wild stocks. It has become more common to use stable isotopes to supplement traditional diet studies of salmon in the ocean; however, there have been no integrated syntheses of these data to determine whether stable isotope analyses support the existing conventional wisdom of feeding strategies of the Pacific salmon. We performed a meta-analysis of stable isotope data to examine the extent of trophic partitioning among five species of Pacific salmon during their marine lives. Pink, sockeye, and chum salmon showed very high overlap in resource use and there was no consistent evidence for chum relying on alternative food webs dominated by gelatinous zooplankton. δ¹⁵N showed that Chinook and coho salmon fed at trophic levels higher than the other three species. In addition, these two species were distinctly enriched in ¹³C, suggesting more extensive use of coastal food webs compared to the more depleted (pelagic) signatures of pink, sockeye, and chum salmon. This paper presents the first synthesis of stable isotope work on Pacific salmon and provides δ¹⁵N and δ¹³C values applicable to research on the fate of the marine derived nutrients these organisms transport to freshwater and riparian ecosystems.     

Increased brown bear predation on sika deer fawns following a deer population irruption in eastern Hokkaido, Japan

By the 1970s, brown bears (Ursus arctos) in Hokkaido, northern Japan, were opportunistic omnivores that mainly depended on plant materials. Because the sika deer (Cervus nippon) population irrupted in eastern Hokkaido in the 1990s, we expected that brown bears might prey on sika deer fawns. First, we developed a simple and cost-effective method of monitoring possible bear predation on deer fawns by analyzing the widths of deer hairs remained in bear scats. Based on hair thickness standards, we distinguished the brown bear consumption of deer fawns from adults by analyzing bear scats (n?=?108) collected during the deer birthing season (late May?Clate July) in 1999?C2008. To evaluate the importance of fawns to bears, we compared the occurrence of fawn and adult deer hairs in bear scats among three periods (I, 1999?C2000; II, 2003?C2005; III, 2006?C2008) in eastern Hokkaido. The occurrence of fawn hairs in bear scats increased from 12.5 to 27.3?% in volume and from 6.3 to 33.6?% in frequency from period I to period III, whereas adult hairs in scats decreased from 42.8 to 26.1?% in volume and from 34.4 to 22.7?% in frequency during the same time. These data suggest that bears increasingly preyed on deer fawns after the deer population irruption and decreasingly used adult carcasses because of the enforcement of deer carcass treatment by the Hokkaido government.     

Influence of morphology and amphibious life-style on the feeding ecology of the mudskipper Periophthalmus argentilineatus

The potential feeding advantages that are offered to the barred mudskipper Periophthalmus argentilineatus by its amphibious life-style were investigated. To this end the feeding ecology of these fish, the position they occupy in the mangrove food web and the importance of different morphological factors for their diet were studied. Analysis of gut contents showed that the major component of the barred mudskipper diet changes during growth from small crustaceans ( e.g. copepods and amphipods) to polychaetes to mangrove crabs. This dietary shift was found to be facilitated through enlargement of the mouth, as well as elongation of the gut. The use of stable isotope analysis revealed that barred mudskippers had a similar trophic position as other zoobenthivore fish species, but that their diet did not appear to be affected by competition for food with other zoobenthivores. The amphibious habits of the barred mudskipper provide specific advantages to its feeding ecology, such as access to an abundant food source of mangrove crabs, which are mostly inaccessible for other fish species.     

Consumption of salmon by Alaskan brown bears: a trade-off between nutritional requirements and the risk of infanticide?

The risk of infanticide may alter foraging decisions made by females, which otherwise would have been based on nutritional requirements and forage quality and availability. In systems where meat resources are spatially aggregated in late summer and fall, female brown bears ( Ursus arctos) would be faced with a trade-off situation. The need of reproductive females to accumulate adequate fat stores would likely result in a decision to frequent salmon streams and consume the protein- and lipid-rich spawning salmon. In contrast, aggregations of bears along salmon streams would create conditions of high risk of infanticide. We investigated consumption of salmon by brown bears on Admiralty and Chichagof Islands in Southeast Alaska from 1982 to 2000 using stable isotope analysis and radiotelemetry. While nearly all males (22 of 23) consumed relatively large amounts of salmon (i.e., >10% relative contribution to seasonal diet), not all females ( n =56) did so. Five of 26 females for which we had reproductive data, occupied home ranges that had no access to salmon and thus did not consume salmon when they were mated or accompanied by young. Of females that had access to salmon streams ( n =21), all mated individuals ( n =16) had ¹⁵N values indicative of salmon consumption. In contrast, 4 out of 16 females with cubs avoided consuming salmon altogether, and of the other 12, 3 consumed less salmon than they did when they were mated. For 11 of 21 females with access to salmon streams we had data encompassing both reproductive states. Five of those altered foraging strategies and exhibited significantly lower values of ¹⁵N when accompanied by young than when mated, while 6 did not. Radiotelemetry data indicated that females with spring cubs were found, on average, further away from streams during the spawning season compared with females with no young, but both did not differ from males and females with yearlings and 2-year-olds. Females with young that avoided salmon streams were significantly lighter indicating that female choice to avoid consumption of salmon carries a cost that may translate to lower female or cub survivorship. The role of the social hierarchy of males and females, mating history, and paternity in affecting the risk of infanticide and foraging decisions of female brown bears merit further investigation.     

Ontogenetic shift to dependence on salmon-derived nutrients in Dolly Varden char from the Iliamna River,Alaska

The upstream migration, spawning, and death of anadromous, semelparous Pacific salmon brings nutrients to terrestrial and aquatic communities around the Pacific Rim. Many fishes use these resources but the relationship between fish body size and the reliance on salmon-derived nutrients might follow one of several patterns related to the onset of egg consumption with body size as fish grow, and possible shifts to alternative prey such as fishes as they grow larger still. In this study, these size-dependent hypotheses of marine subsidy use by resident Dolly Varden, Salvelinus malma, were tested using diet and stable isotope analyses. S. malma did not shift abruptly to a reliance on salmon eggs after they became large enough to eat eggs (i.e., no gape limitation). Rather, fish large enough to eat eggs but < 150 mm showed diets that blended salmon nutrients with aquatic insects, likely because they were spatially segregated from the highest concentration of spawning sockeye salmon, Oncorhynchus nerka. From intermediate through the largest sizes observed (150 to > 600 mm long) S. malma received ca. 80 % of their nutrients from salmon (eggs, flesh, and maggots that had scavenged dead salmon) based on diet analysis and stable isotope ratios despite being large enough to consume fish, as many similarly-sized salmonids do in other ecosystems. The few fish sampled in June, prior to the availability of salmon subsidies, had stable isotope signatures that also reflected heavy (ca. 90 %) reliance on marine sources, likely because they had eaten little since the end of the salmon run the previous fall. This apparent avoidance of piscivory in favor a rich yet pulsed marine subsidy highlights the importance of healthy salmon runs for the sake of not only the salmon but resident fishes that consume them.     

Biomechanical consequences of rapid evolution in the polar bear lineage

The polar bear is the only living ursid with a fully carnivorous diet. Despite a number of well-documented craniodental adaptations for a diet of seal flesh and blubber, molecular and paleontological data indicate that this morphologically distinct species evolved less than a million years ago from the omnivorous brown bear. To better understand the evolution of this dietary specialization, we used phylogenetic tests to estimate the rate of morphological specialization in polar bears. We then used finite element analysis (FEA) to compare the limits of feeding performance in the polar bear skull to that of the phylogenetically and geographically close brown bear. Results indicate that extremely rapid evolution of semi-aquatic adaptations and dietary specialization in the polar bear lineage produced a cranial morphology that is weaker than that of brown bears and less suited to processing tough omnivorous or herbivorous diets. Our results suggest that continuation of current climate trends could affect polar bears by not only eliminating their primary food source, but also through competition with northward advancing, generalized brown populations for resources that they are ill-equipped to utilize.     

Effects of diet on female fecundity and larval development in the carrion beetle Necrophila japonica

The carrion beetle subfamily Silphinae (Coleoptera: Silphidae) contains dominant macroinvertebrates of soil ecosystems in temperate zones. However, their feeding habits, which determine the role of each species in the ecosystem, have not been sufficiently studied. Moreover, although a diet shift from necrophagy on vertebrate carcasses to predatory feeding on invertebrates is known to occur in this subfamily, the processes and mechanisms of this shift have also been inadequately addressed. We examined female fecundity and larval development on various diets in a Silphinae species, Necrophila (Eusilpha) japonica (Motschulsky). The experimental diets included a meat diet and various invertebrate diets, which reflect the ‘ancestral’ feeding habit in Silphinae, necrophagy, and the ‘derivative’ feeding habit, predatory feeding. Female fecundity was significantly higher on the meat diet (minced beef) than on an insect larvae diet (mealworms and dipteran larvae) but did not significantly differ from that on an earthworm diet. Larval developmental performance was significantly higher on the earthworm diet than on the meat and insect larvae diets. Our results for larval development were consistent with those of previous stable isotope analyses of the same species, in which isotopic values of larval samples agree with those of hypothetical consumers that utilize earthworms. The consistency of results among different methods indicates that N. japonica larvae are most likely earthworm feeders. In contrast, our results for the female fecundity experiment differed from those of previous stable isotope analyses, in which vertebrate carcasses unlikely serve as the staple diet of adults in the field; thus, the feeding habits of N. japonica adults remain unresolved. Our observations that females and larvae performed best on the meat and earthworm diets, respectively, may indicate that, in Silphinae, the diet shift from necrophagy to predatory habits occurs earlier in larvae than in adults.     

Cranial distinctiveness in the Apennine brown bear: genetic drift effect or ecophenotypic adaptation?

Molecular studies highlighted a strong genetic affinity between the remnant and isolated population of the Apennine brown bear and other southern European populations. Despite this genetic closeness a recent morphometric study revealed a marked phenotypic distinctiveness of the Apennine population, supporting the reinstatement of a distinct taxon (Ursus arctos marsicanus). By building upon previous morphological analyses, we adopted geometric morphometrics to better investigate the skull morphology of the Apennine brown bear with reference to the other, closely related southern European populations. Both skull shape and size differences confirmed the strong divergence of U. arctos marsicanus. In particular, the Apennine bears are characterized by an enlargement of the supraorbital apophysis and a larger distance across the zygomatic arches. Furthermore, our analyses highlighted significant shape differences of the first upper molar in the Apennine bears. Our results suggest that the Apennine bears underwent a rapid morphological change, possibly driven by genetic drift and local selective pressures. Because the greatest morphological differentiation is likely to be related to the muscles involved in mastication, we hypothesize that local selective pressures might be related to a shift in food habits, with highly reduced depredation and feeding on large carcasses in favour of vegetation and hard mast (beech nuts and acorns). These results suggest an adaptive distinctiveness of the Apennine bears, which should be carefully considered in any management and conservation action addressed to this highly endangered population. Although more in‐depth molecular studies are required to better assess the taxonomic and genetic status of the Apennine brown bear population, our study emphasizes the importance of morphological analyses as a complementary tool for a more thorough characterization of variation and divergence in endangered taxa. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Food habits of sika deer and nutritional value of sika deer diets in eastern Hokkaido, Japan

Rumen content analysis and field observations were used to investigate the food habits and diet quality of sika deer (Cervus nippon yesoensis Heude) from 1991 to 1993 in eastern Hokkaido, Japan. Diets varied seasonally, with deer consuming graminoids and browse in winter, forbs and agricultural crops in spring and summer and all of these plant foods in autumn. Eighty-four plant species with sika deer bite marks were identified and their use also varied seasonally. The diversity of food resources available provided both critical protein and digestible energy, allowing for physiological maintenance and seasonal growth. With these high-quality diets, deer maintained good body condition in eastern Hokkaido, where the population density was relatively low.