Feeding methods and habits of brown bear in Sikhote-Alin are varied and specific for each type of feeding behavior depending on the composition and condition of food, its availability and abundance, season, animals sex, age, physical condition, personal preferences and experience, the presence of competitors and disturbance from other predators and humans. A feature of the feeding behavior of bears in Sikhote-Alin is consumption of the remains of meals of tigers.
Brown bear ; Ursus arctos ; Sikhote-Alin ; Feeding
Brown bears (Ursus arctos ) in Sikhote-Alin (Russian Far East) prefer pine–broad-leaf and broad-leaved forests. The diet of bears in the region is widely varied ( Bromlei, 1965 ; Seryodkin, 2012 ), which leads to behavioral diversity of the species associated with procuring and consumption of food. The study of traces of life activities of animals allows the researchers to determine the diet of the bear and the characteristics of its food-procuring behavior, which is important for the assessment of the predator population and development of scientific measures for its control.
This paper is based on the authors research conducted in Sikhote-Alin in 1998–2015, as well as on literature review.
Herbaceous vegetation is essential in the diet of Sikhote-Alin brown bears from May till August, and stays in the diet in September as well. The animals spend much time in floodplains of rivers and creeks where the most juicy and dense vegetation grows. Here they graze in mass feeding on aerial parts of grass, as well as underground parts of some species of plants.
The most common among the traces of grass eaten by bears is the remains of Tatewaki butterbur (Petasites tatewakianus ) — 80% of all traces. Bears often eat the leaves completely off the young plants of this species up to 15 cm high. For more mature plants only leafstalks are consumed, while leaf blades are not used for food. When grazing a bear grabs a juicy leafstalk at the bottom with its teeth and pulls it. The leaf with most of the stalk breaks off, and at the remaining part of the stalk revolute fragments of the tissue are formed (Fig. 1 ). In plants of Umbelliferae family (hogweed — Heracleum spp., angelica — Angelica spp.) bears prefer to eat the stems and leafstalks ( Bromlei, 1965 ). The animals usually feed on butterbur, angelica and hogweed up to the point of almost complete consumption of these plants in the places of their local habitat. Bears consume the entire vegetative part of many species of grass — leaves with the stem (Corydalis ochotensis , Urtica angustifolia , Impatiens noli-tangere , Filipendula palmate , etc.).
Remains of a plant Petasites tatewakianus eaten by brown bear.
At leisure grazing in floodplains bears trample down the grass leaving clearly discernible tracks. For a more rational use of the feeding territory bears walk in shuttle-manner, the center line of which is the course of the creek or animal tracks. Usually the animal moves parallel to the direction of the watercourse. In areas with high concentrations of preferred plants, such as butterbur, bears can remain until they crop all the plants. When grazing on herbaceous vegetation bears can be distracted from their main activity eating insects found in the grass and mollusks.
Brown bears eat up underground parts of grassland plants such as tubers of Arisaema amurense and Lilium distichum . The animals pry the bulbs with their claws pulling them to the surface, then bite them off the stem and eat. At the site of such dig an almost invisible hole remains next to the aerial part of the plant. When procuring the roots of Hedysarum branthii animals make more notable excavations.
Brown bears feed on berries by two basic ways: devour them from the plants or pick up fallen berries from the forest cover. The first way is more common. When feeding on berries of short-growing plants animals graze with their heads down to the ground picking berries in one or several pieces at once with their lips, depending on the density of berries on a plant. In this manner, the bears can for a long time eat red berry (Rhodococcum vitis-idaea ) and blueberry (Vaccinium uliginosum ) — the berries that are important for their diet. Tearing berries off medium sized shrubs (blue-berried honeysuckle — Lonicera spp., currant — Ribes spp., raspberry — Rubus spp., spiny eleutherococcus — Eleutherococcus senticosus ) bears raise their heads to the branches, or if necessary, stand up on their hind legs. In this manner, feeding on honeysuckle (Lonicera edulis ), the bear moves from one bush to another, tearing them one by one. At this the animal bows, crushes, and sometimes breaks the branches, going through them with its paws.
When feeding on the fruits of the vines (kolomikta actinidia — Actinidia kolomikta , tara vine — Actinidia arguta , Amur grape — Vitis amurensis , Chinese magnolia vine — Schisandra chinensis ) bears grab the vine and shake it trying to drag it down from the support tree. Some fruit falls down to the forest cover and the bears pick them up. Soft fruits growing on trees (apple — Malus spp., Dahurian buckthorn — Rhamnus davurica , pear — Pyrus ussuriensis , bird cherry — Padus spp., hawthorn — Crataegus spp.) are almost inaccessible for brown bears due to the fact that the majority of adult animals are unable to climb trees. The animals bend the branches and eat up the fruit that they can reach or settle with fallen berries. Brown bears feed on berries of common bird cherry (Padus avium ) more often than on fruit from other trees because bird cherry trunks often grow at a sharp angle to the surface which allows the animals to reach fruiting branches while standing.
The bears eat up berries and other soft fruit that fall from the trees, shrubs and vines by circling around fruiting trees. In this manner they pick up the fruits of Amur grape, actinidia, wild roses (Rosa spp.), honeysuckle, and spiny eleutherococcus.
Brown bears are more likely to visit berry beds with the most plentiful fruitage compared to neighboring berry beds (Mikhailovsky and Skryabina, 1972 ). If animals are not disturbed they repeatedly visit areas with the abundance of berries eating up a significant portion of the fruitage. Within two months (July, August) brown bears ate 43% of biological fruitage at a relatively large area in sedge blueberry bed. In a single feeding a bear ate up around 8 kg of blueberry, and in total the bears consumed approximately 7% of biological fruitage of the entire area of studied blueberry beds (Mikhailovsky and Skryabina, 1972 ).
In some seasons berries can be a background component of the diet of bears. Thus, cranberries constituted 97% of the diet of brown bears in the vicinity of the Sikhote-Alin Nature Reserve in the second half of August–September 1999. Animals come to berry beds long before the ripening of cranberries. As soon as the berry turns red the bears begin to eat it.
The nutritional value of berries is inferior to other fattening feed. In addition, thick-skinned berries, such as cranberries, are poorly crushed in the jaws of animals, and most of them remain intact passing through the digestive tract. Ripe berries are always better digested than underripe ones, especially bird cherry. The bears chew soft fruits of actinides, grapes, and wild rose, while blueberries are crushed at swallowing (Yudin, 1993 ).
Nuts and acorns are the most important caloric and fattening feed of brown bears in Sikhote-Alin (Bromlei, 1965 ; Yudin, 1993 ; Seryodkin et al ., 2012 ). Nuts of Korean pine (Pinus koraiensis ) are paramount for the diet of bears.
Unlike Asiatic black bears (Ursus thibetanus ) brown bears rarely procure pine cones by climbing into the crowns of trees. However, such cases are known. Females and juveniles are more adapted to climbing trees. E.N. Smirnov (Sikhote-Alin Nature Reserve, personal communication) observed an adult brown bear female in the crown of a pine tree breaking off branches with cones and throwing them down to the forest cover where her cubs awaited.
Fallen cones are very important for the bears. When there are not many cones the animals consume each cone where they find it, and then proceed to another one. With the abundance of fallen cones the animals may rake them in heaps (up to 50 pieces) and then pick the nuts out of the cones at their leisure. During the snow season (spring or late autumn) bears can dig up cones from under the snow leaving snow trenches or muzzle marks.
The ways brown bears procure nuts from the cones are different depending primarily on the ripeness of the cones. The animals bite open the least ripe, still strong and green cones, with sticky covering skin. They can tear off some parts of the skin from the green cones, and then pick the nuts. When dealing with more ripe cones bears tear off the skin only at the bottom and open the upper part with their paws or muzzles; they pick the nuts between the open cone skin. Instead of peeling ripe, dry cones, they crush them. Sometimes bears break cones in half along the axis or in several parts. Cones become soft after rain and can be peeled easily. The bears may try to peel some cones, but after finding bad nuts they move on to other cones.
The remains of cones eaten by brown bears are similar to those of Asiatic black bears and, to a lesser degree, of wild boar (Sus scrofa ). In spring bears prefer to dig up the cones out of the snow, rather than consuming newly fallen cones. This may be because it is easier to procure nuts out of wet cones that were under the snow, than from dry, newly fallen ones.
When feeding on the nuts of dwarf pine (Pinus pumila ) the bear bites and breaks branches and trunks of trees, and then eats the cones. The animal chews unripe cones completely. It browses ripe cones eating the nuts together with nutshells. The central axis with extending skin remains intact ( Fig. 2 ). The bear picks up nuts of Manchurian hazel (Corylus mandshurica ) and hazel (Corylus heterophylla ) from the forest cover or breaks the bushes with the fruit. Brown bears collect Manchurian walnuts (Juglans mandshurica ) only from the forest cover. While doing so they trample the grass under the trees racking the nuts in piles with their claws. After that they lie down on the ground, grab the nuts collected with one of the forepaws and eat them all in a row together with thick nutshell, cracking them with their teeth ( Bromlei, 1965 ).
Dwarf pine cones partially eaten by brown bear.
Acorns of Mongolian oak (Quercus mongolica ) in the crowns of trees are almost inaccessible to brown bears. Before the acorns begin to fall down the bears may look for thin scrubby fruit-bearing oak trees. These trees grow on the ridges, in places exposed to frequent winds. The animals are able to break thin trees standing on hind legs. 9 Mongolian oaks damaged this way were found in the basin of Dzhigitovka River (Terney district) over 50 m of the route. The diameter of the trees was 5.4–7.6 cm. Three oaks had their trunks broken at a height of 100 cm, and six trees had broken branches (50–180 cm above the ground). The bear bit the branch and then pulled it down, some branches it broke without biting.
Since the beginning of acorn fall brown bears feed on acorns collecting them from the forest cover. For clarity, we will describe 4 stages of usage of this food resource by brown bears in the basin of Kunaleyka River (Sikhote-Alin Nature Reserve) in 1999. The time frame provided varies depending on the year and region, but generally reflects the sequence of phases of acorn consumption at uneven fruitage.
The behavior of bears grazing in oak forests has certain characteristics. The animals look for fallen acorns in the forest cover and eat them. They pick acorns from the cups with their lips, separating the kernel from the shell in their mouths. When chewing the acorns the shell is pushed to the corners of the mouth and falls down from both sides of the mouth. In addition, acorns can be chewed and swallowed together with the shell. Plowing through the leaf litter with its muzzle the animal often leaves behind tracks similar to those left behind by feeding boars. When moving, the bear circles around acorn-bearing oaks or moves in a straight line at an average speed of about 2 m/min. The animal keeps its muzzle to the ground, sometimes lifting it to listen and look around. With abundant fruitage of acorn some bears can feed for a long time in a small area of the forest without leaving it. By radiotelemetry it was revealed that a brown bear female with cubs was feeding for seven days in September at an area of 0.2 km2 (Seryodkin et al., 2012 ).
Bears are able to procure acorns from under the snow layer. After tracking for three months a bear that hasn't settled in its lair Kostoglod described the attempt to procure acorns from under snow cover 40 cm high. At a distance of 120 m in the oak stand this bear moving in shuttle-like manner with the search width of 30–40 m has made over 30 stops. At each stop it sank its nose repeatedly into the snow for 7–10 cm, leaving a semicircle of holes (up to 15–20 holes). In some places the snow was dug up to the forest floor where the animal probably could find and eat isolated acorns (Kostoglod, 1981 ).
The availability and the quantity of fattening feed affect the food relation of bears towards it. With a large number of pine nuts or acorns the animals manifest fastidiousness in feed and irrationality of its use. The bears bite open the nuts of Korean pine and dwarf pine and pick the seeds leaving the shell behind, so that some nuts are left in the cones. The animals choose the most ripe and large acorns picking them not very carefully from the forest cover, so that a large amount of acorns remain at the feeding site; the solid acorn shell is not consumed. In case of feed shortage caused by poor fruitage another peculiarity is observed in the beginning and the end of fattening: the bear tries to eat up all nuts and acorns, even bad ones, along with the shells. Wasteful attitude towards the feed during its abundance is true not only in respect to plant feed. For example, during mass spawning of salmon on Kamchatka brown bears do not eat up fish completely giving preference to its skin and hard roe (Revenko, 1993 ).
During the period of intensive fluctuation of birch sap from March to May brown bears tap the trees and lick the sap from bruises. The bear bites the trunks and rips the bark off in cross direction. The result is a horizontal bruise up to 35 cm wide and 15 cm high (Fig. 3 ). The animal taps birches at the height of 20 to 130 cm, usually at 40–60 cm from the ground. Sometimes an animal makes several tappings at different sides and different heights. Often one bear damages several adjacent birches in turns and drinks sap from them. Asiatic bears damage the trees in similar manner (Seryodkin, 2003 ).
Tapping of a birch by brown bear.
The trees bled by bears are more common in the upper reaches of streams where the lairs of brown bear are located. Three species of birch grow in such places in Sikhote-Alin: Asian white birch (Betula platyphylla ), Yellow birch (Betula costata ) and rockbirch (Betula lanata ). These species are subject to tapping by brown bears. Bears begin to feed on birch sap right after they exit their lairs. Bromlei suggested that animals use birch sap as a purgative ( Bromlei, 1965 ). Possibly, the sap also serves as the source of glucose, fructose, salts and microelements.
Presumably, actinidia vines are also used for the normalization of the digestive tract after the winter sleep. V.A. Solomatin (Sikhote-Alin Nature Reserve, personal communication) observed dedicated feeding of brown bear on A . kolomikta in Yasnaya River basin in March. The animal bit off and consumed the stems of vines moving along the thick of vegetation.
During spring and summer brown bears in Sikhote-Alin rip the bark off pine trees (Khingan fir — Abies nephrolepis , Korean pine and larch — Larix cajanderi ) and eat bare cambium. Feeding on cambium is less specific for brown bears than for Asiatic black bears ( Seryodkin and Pimenova, 2002 ).
Brown bears dig out burrows of chipmunks (Tamias sibiricus ), mouse-like rodents (Clethrionomys spp., Apodemus spp.), badgers (Meles meles ), raccoon dogs (Nyctereutes procyonoides ), and nests of wasps (Vespinae ). They seek them out using their sense of smell and hearing.
Chipmunk burrows (Fig. 4 ) are unearthed for the purpose of consuming the hoards of nuts or acorns. Apparently, sometimes a bear manages to catch and eat a chipmunk itself or its brood. The animals are actively searching for and consuming hoards in autumn, rarely in spring and winter before settling in lairs (Bromlei, 1965 ; Telegin, 1980 ; Kostoglod, 1981 ; Sobansky, 1981 ; Pikunov, 1987 ; Smirnov and Shurygin, 1991 ). We know of a case when the animals were actively digging out chipmunks' hoards containing pine nuts in August. This was due to the fact that only by that time pine nuts from last years abundant fruitage have come to an end, and chipmunks had time until August to fill their hoards. Bears unearth burrows of chipmunks both in starving time, and in periods with abundance of fattening feed. However, the number of such dig sites significantly increases with the shortage of nuts and acorns. For example, in autumn of 2005 Korean pine nuts from the hoards of chipmunks were essential in fattening of brown bear in Terney region of Primorsky Krai. It was due to the fact that pine nuts were generally consumed by squirrels (Sciurus vulgaris ) which could pick cones from the trees and chipmunks which were high in number. Brown bears could not climb trees, so they had to consume hoards made by chipmunks.
Digging out a chipmunks hoard by brown bear.
A bear finds chipmunk burrows guided by its sense of smell. V.A. Solomatin observed a bear in the Sikhote-Alin Nature Reserve stops short, sniffs the ground in the radius of 2–3 m, and then digs the hoard of a rodent. The animal digs with its front paws turning towards the hole. It bites through the roots of trees and shrubs that get in its way. The animal rakes the soil under itself making a heap of earth and rocks. A bear can turn over rocks weighing over 50 kg. If a bear is digging on the slope, it stands with its muzzle turned uphill, raking the sole downwards. Measurements of 40 dig sites revealed the following results: the width of the pit — 40–155 cm (101 cm on average), the length of the pit — 30–217 cm (84 cm on average), and the depth of the pit — 24–100 cm (55 cm on average). Sometimes theres a deepening about 30 cm wide and up to 50 cm deep at the bottom of the pit. This deepening corresponds to the size of the bears paw, and it is formed when the bear removes the contents of the hoard with one paw. A heap at a dig site is up to 3 m long, it contains from 0.04 to 3.6 m3 of soil (0.7 m3 on average) and can be located not only on one side of the pit, but around the entire pit as well. A bear can stop digging a pit if it stumbles upon an obstacle and resume digging nearby where the soil is softer. Most often animals dig chipmunks burrows on the slopes of varying steepness and exposures, more rarely – on the terraces, even more rarely – in flood plains and on ridges. The largest number of dig sites (90%) that we encountered was located in pine–broad-leaf forests.
Up to 10 active sites of chipmunk burrows dug out by bears were counted by Kostoglod in pine forests along Serebryanka and Dzhigitovka rivers per 1 km of route (Kostoglod, 1981 ). During one days course a brown bear usually unearths 1–2, rarely three hoards in conditions of average population of chipmunks and bountiful fruitage. With average and a poor pine fruitage the stock of nuts in chipmunks' hoards is smaller in number, so a bear may need to unearth up to 5–6 hoards a day (Pikunov, 1987 ). Up to 20 kg of stored feed may be found in a chipmunks hoard (Oshmarin and Pikunov, 1990 ).
The animals dig out nests of wasps in the summer and spring. Bears eat up the eggs and larvae of insects. Dig sites of nests are inferior in size to dig sites of chipmunks' hoards. Normally their size does not exceed 70 cm in diameter and 35 cm in depth. Bears can spend a lot of time searching for wasp nests in the summer. In areas with a relatively high number of bears over ten freshly dug out nests per 0.5 ha can be found. When digging out burrows of mouse-like rodents a bear digs trenches or turns over pieces of turf.
The largest pits are dug by bears when they dig out the burrows of badgers hoping to catch these animals. In some cases they succeed. Bears dig deep pits pulling out thick trees and turning over large rocks. I.G. Nikolaev (private message) during tracking of a male brown bear in Pogranichniy Region of Primorsky Krai in November found a network of badger burrows dug out by it. The width of the trench corresponded to the width of the bear, and the height reached 160 cm. The bear was engaged in excavation for two days, but in that case it couldn't procure the badger. In another case, a bear procured and ate a badger after digging its temporary shelter in the basin of Chaschevity creek (Sikhote-Alin Nature Reserve) in late October. The dimensions of the pit: 180 × 150 × 75 cm; when digging the animal pulled from the ground and threw away a rock with dimensions of 60 × 50 × 40 cm.
Bear excavations are clearly visible in the forest and they stay untouched for many years. In places of the permanent habitat of brown bears excavations of different time ranges may be found on some hills every tens of meters. In such cases, one can state the impact of brown bears on the micro-relief and vegetation of forest slopes.
The manner of digging out burrows and nests by brown bear is different from that of the Asiatic black bear. Brown bear digs wider pits, pulling over the roots of trees and shrubs, removing fallen trees and rocks. Asiatic black bear digs a smaller funnel-type pit (Pikunov, 1987 ). In addition, the nests of wasps are unearthed by badgers. Their excavations look even smaller than those of Asiatic black bears.
Biting through the wood brown bears procure wood insects, social hymenopterans, small mammals, and Asiatic black bears.
Most often one can encounter marks on the trunks of live or dry, but not yet fallen trees formed as a result of procuring nests of bees (Apis cerana ) and bumble bees (Bombus spp.) by bears. Having reached the nest the animals eat honey stored by insects, their eggs and larvae. Similar marks are formed when the animal tries to procure chipmunks or flying squirrels (Pteromys volans ) hidden in hollows of tree trunks, and nests of birds living in tree hollows. The damages done to trees by two species of bears are hardly different from each other. Usually nests and hollows are found in trees with hollow core, and the bear needs to bite through the wood layer to reach the hollow. If a tree is bent, the animal usually bites it from the obtuse angle formed with the ground and less often from the acute angle, generally if the timber is less thick at that side.
Out of the 34 marks described 22 were located on living trees and 12 — on dried-up ones. In 91% of cases the bears bite through the wood of coniferous trees: larch — L. cajanderi (n = 1), Ajan spruce — Picea ajanensis (n = 7), Korean pine (n = 9), and most often, the softest coniferous species — Khingan fir (n = 10). Most of the trees were located in pine–broadleaved and dark coniferous forests. Yellow birch, aspen (Populus tremula ), and Japanese elm (Ulmus japonica ) each had one mark as well. The average diameter (at chest level) of damaged trees was 32 cm (from 16 to 83 cm). The part of the tree damaged by bear has a bit-through hole and damaged surface around it with the bark and the upper layer of wood ripped off. The lower level of damage is located at a height of 0 to 150 cm (42 cm on average), and the upper level reaches 285 cm (148 cm on average) above the ground. The bit-through hole is usually of vertically elongated shape with a width of 5–25 cm (11 cm on average) and a height of 13–120 cm (44 cm on average). To achieve the desired result a bear, according to our observations, bites through up to 24 cm thick wood.
Ripping off the bark and biting through the wood of living, dried-up or windfallen trees, bears procure the larvae of bark beetles (Scolytidae ), longhorn beetles (Cerambycidae ) and other xylophage insects. The animals ravage ant-hills at the bottoms of dead trees or in rotten deadwood eating adult insects, larvae and eggs. Bears break rotten deadwood and stump into splinters in search of ants. Most often, dry trees with marks and deadwood broken by bears are found at old burned areas, where there are many dead trees with insects living inside.
There are cases when brown bears were trying to reach Asiatic black bears that chose hollows at the bottom of trees as their lairs. Brown bear bites and scratches the basis of a tree trying to widen existing holes. For example, in 2000 a brown bear widened the hole in the basis of a poplar in the Sikhote-Alin Nature Reserve until it was able to push its way into the lair of an Asiatic black bear.
In the summer, before the start of fattening, brown bears spend much time searching for invertebrates. In the period of feeding on herbaceous vegetation invertebrates introduce diversity into the vegetarian diet.
Often bears seek out and ravage ant-hills. This is characteristic of brown bears in different regions (Yurgenson, 1937 ; Kucherenko, 1983 ; Chernyavsky and Petrichenko, 1984 ; Vyrypaev, 1984 ; Pazhetnov, 1990 ; Loskutov and Radchenko, 1991 ; Mordosov et al ., 1993 ; Swenson et al ., 1999 ; Mattson, 2001 ). A bear finds ant-hills using its sense of smell, sometimes at a distance of a few tens of meters (Rukovsky and Kupriyanov, 1970 ). After finding an ant-hill the bear removes its upper layer (the outer mound) with its paw, revealing the nest chamber, eats away its contents, and sometimes brutally destroys the entire ant-hill (Pazhetnov, 1990 ). In Lapland Reserve bears destroy up to 40% of ant nests in their feeding area (Nasimovich and Semyonov-Tyan-Shansky, 1951 ). The animals may completely eat away this feeding component (ants) on a certain territory (Pazhetnov, 1990 ). Some ant-hills ruined by bears are reconstructed by the insects, while others cannot be restored.
In search of insects and earthworms bears often turn over rocks and fallen trees (Bromlei, 1965 ; Yudin, 1993 ). In Sikhote-Alin similar traces of life activities are often found in mountain ranges along bear trails. E.P. Krasnikova in August of 1973 observed a bear turn over stones in the channel of Serebryanka River to collect caddis worm — Trichoptera (records of the Sikhote-Alin Nature Reserve).
About 10 places were found in scattered stones in Cheryomukhovaya river-valley (Dalnegorsk region) where brown bear, apparently, was trying to catch lizards (Amur grass lizards), that were warming themselves in the sun. The animal threw away the stones under which the reptiles were hiding, leaving pits among the stones.
Predation on the ungulates is a trait of ecology of brown bears typical for different areas of the species range (Bromlei, 1965 ; Semyonov-Tyan-Shansky, 1979 ; Zavatsky, 1979 ; Lavov, 1987 ; Pazhetnov, 1990 ; Bobyr, 1991 ). The extent and nature of predation vary with the seasons. In most cases, this method of feeding behavior is of the greatest importance for bears in the spring (Pazhetnov, 1990 ). This statement is typical for brown bears in Sikhote-Alin (Bromlei, 1965 ; Yudakov and Nikolaev, 1987 ; Yudin, 1993 ; Kostoglod, 2006 ). In summer there is a decline of predation related to the abundance of feed (Bromlei, 1965 ). In autumn with the abundance of fattening feed of vegetable origin predation is not expressed, but during hungry years it is on the contrary typically occurring among bears (Bromlei, 1965 ; Rakov, 1966 ; Abramov, 1972 ). Wild boar and red deer (Cervus elaphus ) are the most common ungulate prey of brown bears in Sikhote-Alin.
Brown bears are commonly consuming dead animals found by them (Zavatsky, 1979 ; Zyryanov, 1979 ; Kaletskaya, 1981 ; Zhiryakov, 1987 ; Pazhetnov, 1990 ), including in Sikhote-Alin (Bromlei, 1965 ; Matyushkin, 1974 ; Darman, 1982 ; Yudin, 1993 ; Zaitsev and Seryodkin, 2011 ). The results of the capture of bears conducted by us in the Sikhote-Alin Nature Reserve have shown that they are attracted to carrion (Seryodkin et al., 2005b ). In 1992–2001 six brown bears were caught with the use of bait: three animals using meat bait and three — using fish bait. The rate of successful capture was much higher using these baits (560 days/individual), rather than using trails and marked trees (1196 days/individual). Meat baits are consumed by the animals in any season.
Besides dead and wounded animals bears eat the prey of other predators and the remnants of their meals in Sikhote-Alin. Most often, the bears consume prey of tigers and lynxes (Matyushkin, 1974 ; Kostoglod, 1976 ; Seryodkin et al ., 2005a ). A case of using the prey of yellow-throated marten is known (Zaitsev, 1991 ). Large bears cannot only eat up remains after tigers, but also chase them off their prey or join the fight (Sysoev, 1966 ; Kucherenko, 1971 ; Kostoglod, 1976 ; Seryodkin et al ., 2005a ). In the snow period some bears purposely track tigers and lynxes to find the remains or take away their prey (Kostoglod, 1976 ; Seryodkin et al ., 2012 ). According to observations of Kostoglod, the trail of a bear not settled in its lair tracking other predators in order to capture their prey was 22% of the total length of the bear trail (44 km out of 200 km) (Kostoglod, 1976 ). In the spring before snow melting bears look for animals which died during winter and prey of tigers buried in snow (Seryodkin et al., 2005a ). For this purpose bears go along the floodplain of a river or a creek, often leaving the path to examine interesting places, winding, sometimes stopping to sniff. A bear is able to smell the odor of the remains of an animal at a distance of 250 m at a temperature below 0 °C. Bears also go in the footsteps of their relatives, picking uneaten remains of carrion. Snowtracking of three brown bears in the basin of a creek in the Sikhote-Alin Nature Reserve in April revealed that along the 17 km trail the bears have four times found the remains of red deer crushed by tigers during the winter, and once — a whole red deer that died of a broken limb. In three cases other bears have been on these tiger prey before them.
Covering the prey with soil, forest cover, branches and other forest products is typical, but not necessary for brown bears in Sikhote-Alin (Matyushkin, 1974 ). The burial of the prey may be complete when the whole animal is hidden, or partial. Apparently, the act of covering primarily provides saving the prey from spongers, as the bears prey attracts corvid birds, and the predator guards it from them (Pazhetnov, 1990 ). On the Kola Peninsula, burying of the remnants allows to distinguish the bears prey from accidental carrion (Semyonov-Tyan-Shansky, 1972 ). For the Sikhote-Alin this assumption is not true. Out of 28 known cases of brown bears feeding on dead bodies of animals in 8 cases (28.6%) the burial occurred. Four times out of five bears were burying their prey, twice — the prey of tigers (out of 20), in both cases the tigers were chased off by the bears, and twice the bears buried dead wounded animals found by them. It is clear from these data that the bears are more likely to bury whole carcasses of animals rather than their remains left after other predators.
A brown bear may cover its prey after he had already started to eat it (Matyushkin, 1974 ), or after burying the carcass, may wait for some time without eating it. In the latter case, covering the prey with the forest cover by maintaining the temperature contributes to faster fermentation processes that make fresh meat “ripe” that is more attractive for animals (Korytin, 1998 ). We know of two cases when brown bears buried dead animals, but did not eat them at once. In the first case, a bear buried a dead wounded boar and returned to the place of burial on the third day. In another case, a brown bear that killed another brown bear covered it with forest cover and left the place without touching the food. For covering a red dear one of predators had to dig up and bring to the center the soil and forest cover from an area of 60 m2 . The author also observed Kamchatka brown bears waiting for “ripening” of dead prey. A large male bear began to eat a buried female bear three days after procuring it at Kronotskaya River (Kronotsky Reserve) in September 2003.
Burial instinct can be observed at one-time feeding on small prey immediately after it is procured or discovered. For example, a bear was spotted in Kamchatka which was feeding on kalan (Enhydra lutris ) for 40 min and during that time it would periodically tear down shrubbery and cover the prey with it using its fore paws.
When a brown bear finds carrion or prey of another predator it often drags it away, typically within 50 m. Sometimes the predator moves separate pieces of prey over long distances where it eats them. A bear can also drag its prey to another location with better protective properties. Moving prey is seen as a manifestation of concern for protection of prey (Pazhetnov, 1990 ).
On the first day of eating meat bears usually suffer from indigestion and their excrements are of liquid consistency. Already on the second day gastrointestinal tract is usually back to normal (Kostoglod, 1981 ). In the spring of 2001 a male brown bear found a whole carcass of red deer in the Sikhote-Alin Nature Reserve and ate about 50 kg of meat on the first day; the predator didn't get indigestion, probably because before that he had eaten the remnants of another red deer. A bear lives near the carcass of a large ungulate from 3 to 10 days. A bear eats a red deer weighing 150 kg completely in 5–6 days (Kostoglod, 1981 ).
In the first place a bear eats meat from croup and proximal parts of hindlegs of an animal, as well as internal organs. The bear does not touch the contents of the stomach and intestines of the ungulate. Then the bear eats meat from other parts of the body; after finishing with the meat it eats the skin, distal parts of limbs, head and small bones. It eats soft antlers of ungulates completely and bites off tips of hard antlers. In the valley of Serebryanka River in April 1983 V.A. Palkin found a female red deer killed and covered by a bear; the predator has only eaten the embryo from the red deer (from the archive of the Sikhote-Alin Nature Reserve).
Usually a bear leaves behind partially consumed limb bones of large animals, upper and lower jaws, and parts of the spinal bone; sometimes pelvic bones, shoulder bones and ribs. With a shortage of feed (in winter and early spring) bear consumes carcasses to a greater extent. A bear that has not fallen into winter sleep fully utilizes animals, including all the bones (Kostoglod, 1976 ). The smaller the animal eaten by the bear, the better it is utilized. For example, a brown bear ate a musk deer in summer, leaving behind only the lower jaw, two cuspid teeth of the upper jaw and a few small fragments of shattered limb bones.
Usually the bones that a bear eats are not digested and remain intact. In two places in the Sikhote-Alin Nature Reserve we found excrement of a brown bear containing homogeneous white mass with minor inclusions of wool of ungulates. They were dated to the end of March. Chemical analysis of the samples showed that these were digested bone remains, with domination of calcium oxide (31.2%) and phosphorus (21.6%). These substances could be formed in the intestines of the animal in an alkaline medium by restoring the phosphate salts formed in turn by dissociation of bone substance in the acidic environment of the stomach. Dissolution of the bones of mammals in the stomach is possible only when a bear is feeding on bones exclusively, without other food components (e.g., meat) diluting the stomach acid. This is possible when a bear finds bone remains after it leaves its lair, when the lack of feed forces it to be omnivorous. This assumption is confirmed by the fact that one of the above samples was found close to an almost bare wild boar skeleton that was eaten by a bear. It is also possible that the bones were eaten by bears not in spring, but before hibernation in lair, and the conversion of bone substance was occurring during the winter.
While eating the prey a bear usually lives in close proximity to it, but sometimes it stays near it for a short time and, having utilized a small part of the carcass, leaves the place. The bear sets up its beds (one or more) close to the prey, sometimes directly near it. Parts of skeletons are often found near the beds, because a bear often feeds when lying in bed. The area of the active movement of a bear around the prey while feeding on it does not usually exceed 500 m2 , here one can find remnants of the prey, beds and excrement of the predator. Often bears break and bite the trees, shrubs and branches close to the prey. From the prey the animals go to watering creating a footworn path. In winter, bears can be satisfied with the snow (Kostoglod, 1976 ).
Brown bears can be aggressive towards the predators (other bears, tigers) and people approaching their prey or carrion.
Consumption of man-made feed is an exception rather than a rule for brown bears in Sikhote-Alin. This is due to the fact that the scale of agricultural activities (growing of crops, cattle breeding) is low in the habitats of the species. On the other hand, various high-calorie natural feeds are readily available, except in rare hungry years with low fruitage of all fattening fruit. However, the animals consume man-made food resources.
Most often bears visit agricultural crops sites: oats, corn and soybeans. In the western regions of Russia (in the southern taiga subzone) oats is a major fattening feed for bears which feed on its crops damaging the agriculture (Pazhetnova and Pazhetnov, 1987 ). In the Far East brown bears also feed on oats crops, but to a small extent.
In 1994, a radiolabeled male brown bear 3–4 years old was living in the delta of Dzhigitovka River in an area subject to significant human impact. From July 28 to August 7 the bear lived in a 1.5 km2 littered alder forest surrounded by crops of oats and forage grasses (Seryodkin, 2006 ). During the day, the animal hardly moved, and at nightfall went to the fields to feed. It made a continuous path along the forest at the edge of the field, which branched in the direction of individual trees in the field. There we no other bears at the site at the time, judging by the trail. 500 m long parallel transects set out on in the field at the distances of 10, 35 and 65 m from the forest edge allowed to assess the intensity of the use of the feeding territory by the bear depending on the distance from its main shelter. 55 bear passes were recorded at the transect located at 10 m from the forest, 22 passes – at a distance of 30 m, and only 5 – at a distance of 65 m. The observed bear was actively using a 40–50 m wide strip of field along the forest, rarely going further into the field.
This example shows the dependence of the behavior of the animal during feeding on oats on the living conditions of the animal, covered in detail for the bears of the European part of Russia (Pazhetnova and Pazhetnov, 1987 ; Pazhetnov, 1990 ).
As in other regions (Zhiryakov, 1975 ; Loskutov et al ., 1993 ; Slobodyan, 1993 ; Sobansky and Zavatsky, 1993 ) brown bears in the Sikhote-Alin visit bee-gardens where they steal and break hives in hope to feed on honey. In August–September 1960 (a hungry year for bears) 16 bears were killed in bee-gardens in Yakovlevsky region of Primorsky Krai (Abramov, 1972 ).
Some brown bears attack domestic animals, mostly cattle. Such cases are recorded about once every 2–3 years in various parts of the south of the Russian Far East (Bromlei, 1965 ). Some individuals may specialize in procurement of cattle (Pazhetnov, 1990 ). Bears visit dumpsites and steal bait. At the dumpsites of meat plants located in forest zone (Spassky region of Primorsky Krai) the animals do not react to arriving cars, come here at 4 p.m. and feed dragging the waste to the nearest shelter (Yudin, 1993 ). Bears kidnap bait from the traps of hunters (Bromlei, 1965 ) and ruin winter huts in search of food. Destroying tree-stands the animals take the products and bags of hunters. There was a case when a bear ate muskrats from traps and at night approached the camp of muskrat trappers in search of food (Abramov, 1972 ). There were cases when the animals were trying to dig up the graves in the cemetery of Komsomolsk town, and 4 predators were shot at this (Dunishenko, 1991 ). From time to time, brown bears kill and eat people. The latter often happens to the wounded and sick predators.