BROWN BEAR ( URSUS ARCTOS ) ( CARNIVORA , MAMMALIA ) DENS OF THE KRONOTSKY NATURE RESERVE

1 Pacific Geographical Institute of the Far Eastern Branch, Russian Academy of Sciences 7 Radio Str., Vladivostok 690041, Russia 2 Kamchatka Branch of Pacific Geographical Institute of the Far Eastern Branch, Russian Academy of Sciences 6 Partizanskaya Str., Petropavlovsk-Kamchatsky 683000, Russia 3 Alberta Environment and Parks 800 Railway Avenue, Canmore, Suite 201, T1W 1P, Canada E-mail: seryodkinivan@inbox.ru

Dens areas are critical habitat for brown bears, and the animals select locations for their dens based on both, human activities and presence of suitable natural habitat (Schoen et al., 1987;McLellan, Hovey, 2001).
The studies were carried out in the framework of the research program of the brown bears Ursus arctos Linnaeus, 1758 in Kamchatka region at the territory of the Kronotsky Nature Reserve in the Shumnaya River basin in 2005 -2006.Bear dens were found by searching in the habitat potentially suitable for dens, in places where bears were observed in post-denning period and by visiting the locations of animals with GPS-collars (Paczkowski et al., 2005).

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Dens were described and measured, including signs of bear activity inside and outside of the dens.The characteristics of the location of dens were evaluated, such as: elevation, slope aspect, and position at the slope (upper third, middle third or bottom third).The vegetation was described; including vegetative cover, the number of trees and shrubs within 10 meters of the den, crown density above the den and the visibility in four directions from the entrance of the den.
Seventeen brown bear dens were found in the research area.One den located in the volcanic caldera Uzon Caldera, six -in the basin of Geysernaya River (vicinity of the Valley of Geysers), and 10 -on the left bank of the middle reach of Shumnaya River.The last 10 dens were located on a small area of the upper third of the southwestern slope of the Shumnaya River at an area of only 12 km 2 .Brown bears have specific requirements for their dens and often select similar areas for many generations.Dens concentrations are typical for different parts of the species' range (Sobansky, 1974;Van Daele et al., 1990;Vaisfeld, Chestin, 1993).
All dens were located on slopes.Most of them (80%) were at the top third of the slope (of which 13.3% were on the ridge), and 20% -at the middle third of the slope.Dens were located on the slopes between 26° and 46° (36.9° on average).The average elevation was 512.8 meters (SD = 145.2m) with a maximum of 863 m and a minimum of 333 m.
Eleven dens were located on south-west aspects; two -on south and west aspects, and the rest were located on different aspects.The preference of southern and western aspects is typical for the north of the Far East, Yakutia, the Volga-Kama region and the Carpathians (Tavrovsky et al., 1971;Slobodyan, 1979;Vaisfeld, Chestin, 1993).The reasons for the preference of these aspects has not been determined yet.
Eleven dens were in the birch forest dominated by Erman's birch Betula ermanii Chamisso, 1831, and the remaining were found in patches of shrubs.Alder Alnus fruticosa Rupr., 1845 was found near all 17 dens, and dwarf Siberian pine Pinus pumila Pallas (Regel), 1859 -next to seven dens.In addition, mountain ash Sorbus sp. was found growing near five dens.
Trees and shrubs grew within a 10 m radius of 64.7% of dens.Five to 10 trees were recorded seven times in this area, up to 5 trees -three times, and in one case 20 trees were recorded.The density of shrubs was average in most cases (52.9%) or high (41.2%)and only once were there isolated shrubs.Visibility from the dens varied from 0 to 1000 m in one direction.In 43% of cases the visibility from a den was up to 15 meters on average.With rare exceptions, the visibility in any direction did not exceed 50 m.No bear dens were found in the open or visible from afar.
All but two dens were excavated in the ground (ground type dens).One den was located in a cave.Another den was a natural niche undercut by water, surrounded from the top and the sides with boulders (the animal has only dug out the entrance to it).Ground type dens are typical for regions with long cold winters and are predominant in the Russian Far East (Batalov, 1982;Chernyavsky et al., 1993;Seryodkin et al., 2003).
The structure was typical for the ground type dens.They consisted of the following components: entrance (covered from all sides entrance into the den), entrance hall (partially covered area outside the entrance or a deepening dug by bear at the entrance), corridor (underground area between the entrance and the chamber, more narrow than the chamber), and the chamber (the extended underground portion of the den).There were piles of excavated earth next to the dug out dens, and inside each chamber there was a deepening where the animals lay.
The entrance of the majority of dens was perpendicular to the slope on which they were located.Only twice the directions differed by 90°, and in the case of the cave -by 180°.Five times the entrance was concealed in tree roots.The chamber had the largest volume in relation to other parts of the den (Table ).The entrance hall was not always present in dens.The bed was usually located in the center of the chamber.In three dens the bears did not use any bedding.The bed was filled with dry grass and leaves in two cases.Ground dens were dug in the ground consisting of clay or clay mixed with sand.When choosing a place for a den the type of soil is very important for bears (Schoen et al., 1987).
In six cases dens were located under trees.Tree roots functioned as a structural framework binding the soil and strengthened the roof of the dens.Nine dens were used by the animals only once, four -repeatedly, and in four cases we failed to determine the number of hibernations.Two ground dens, a cave and a niche in rocks were used repeatedly.The cases of repeated denning in ground type dens are known for other brown bear habitats, for example, Yakutia, Volga-Kama region (Vaisfeld, Chestin, 1993), andYellowstone National Park (Judd et al., 1986).
Brown bears living in the Kronotsky Nature Reserve prefers to arrange ground type dens on the slopes close to the south-west aspect in the area of birch forests and dwarf trees.The preferences in selecting the sites for dens are not yet sufficiently researched, and further work in this area is important for the conservation study of brown bears.

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Brown bears in the region typically select for den sites with similar features and these habitats are critical to grizzly bear conservation.Denning habitat should be granted effective protection measures to reduce anthropogenic impacts.The vicinity of the Valley of Geysers is one of the most attractive habitats for brown bears in Kamchatka during the winter and spring, and this factor should be taken into account in exploitation of the area.Other research of brown bear den site selection indicate that bears select den not only by habitat features but also proximity to spring food sources (Pigeon et al., 2014), like those provided in the Valley of the Geysers.The combination of suitable denning habitat and proximity to geothermally enhanced vegetation should merit further study.We suggest to further research of brown bears denning ecology be conducted to compare denning ecology in the Valley of the Geysers to other denning habitats used by throughout the range of brown bears in Kamchatka.

Table .
The sizes of brown bear dens in the Kronotsky Nature Reserve