Ami Nakajima

Effect of Mast Production on Home Range use of Japanese Black Bears

ABSTRACT Although bears may expand their home ranges in times of low food availability, it is unclear what mechanisms directly affect home range extension in times of low mast production in Japanese forests. To clarify the relationship between home range utilization by Japanese black bears (Ursus thibetanus) and abundance and distribution of mast production, we collected data on habitat use from 13 bears (6 M and 7 F) fitted with Global Positioning System (GPS) collars equipped with activity sensors in the Ashio-Nikko Mountains on the eastern part of Honshu Island, Japan, during 2006–2008. We also collected data on mast production by 5 Fagaceae species. We categorized each fall as either poor (2006) or relatively-good (2007 and 2008) based on mast production. Bears used small patches in their large home ranges and the distances between core areas increased in the fall of 2006, when the mast of Japanese oak (Quercus crispula) were poorly distributed. Our findings suggest that localized patches of Japanese oak are the staple food for bears in our study area, even in poor mast years. However, in the fall of 2006, we also found that bears moved to lower elevations, relative to 2007 and 2008, in search of alternative foods (e.g., Konara oak [Q. serrata] and Japanese chestnut [Castanea crenata]), which were mostly at lower elevations and produced mast consistently over the study period. Our results suggest that dispersion and elevational distribution of mast-producing trees affect bear habitat use in fall, as well as amount of mast.

Effect of hard mast production on foraging and sex-specific behavior of the Asiatic black bear (Ursus thibetanus)

Abstract. We studied the relationships between movement and foraging habits of the Asiatic black bear (Ursus thibetanus) and hard mast production of five tree species in cool temperate forest during 2006–2008. The purpose of this study was to test the hypothesis that low mast production affects sexual differences in bear behavior. We summarized the movement pattern of 13 bears in terms of minimum movement distance and cumulative movement distance of the movement path followed during 24 hour. Masting of Quercus crispula acorns was low in 2006, high in 2007 and moderate in 2008. The dominant food items found in bear scats were hard mast, especially Quercus acorns. The percentage of Quercus acorns in the food items in scats was higher in 2007 than in 2006 and 2008. Movement distance of males and females increased in the low mast year. However, the increase of movement distance of females was larger than that of males. Thus, masting influenced the behavior of females more strongly than males. Our results indicated that low mast production changed the food habits and the size of the home range of bears, especially of females.

Fluctuation of daily activity time budgets of Japanese black bears: relationship to sex, reproductive status, and hard-mast availability

Abstract We documented the fluctuation of daily time budgets in Japanese black bears (Ursus thibetanus japonicus) throughout the year using continuous day-to-day data from activity sensors integrated into global positioning system collars, during 2003–2009. We evaluated the influence of availability of food resources on daily active time of bears in conjunction with differences in sex and reproductive status of females (with or without offspring). The daily active time of bears fluctuated nonlinearly throughout the year. There were 3 turning points at which the activity level clearly changed from increasing to decreasing, or vice versa. Level of activity gradually increased in spring and reached a peak in July, then decreased and reached a trough in late August, and increased and reached a peak again in October. Males and females exhibited similar patterns of seasonal fluctuation in daily active time, although there were differences of activity levels between sexes during some periods. Dates of the 3 turning points did not differ between sexes, or among years. Seasonal variation in food availability may explain the timings of the turning points, at least in part. In addition, yearly variation in food resources, especially hard mast, may have affected the increasing and decreasing pattern of daily active time during autumn. Our results suggest that evaluating activity level based on pooled data without examining differences within a season (or month), and differences in year, sex, and reproductive status may result in misinterpretation.

Baseline characterization of the diet and stable isotope signatures of bears that consume natural foods in central Japan

Measures of δ13C and δ15N in tissues of Asiatic black bears (Ursus thibetanus) can be useful in helping researchers identify nuisance bears and in determining whether a specific bear might be consuming anthropogenic food such as garbage and corn. However, the δ13C and δ15N values of native foods vary across the bear’s range. The purposes of this study were to characterize the stable isotope ratios of bear tissues and potential non-anthropogenic food items and compare that characterization to other studies and an independent analysis of bear food habits. We collected hair from bears in the Ashio–Nikko Mountains (ANM) that, based on capture location and radiotelemetry data, were consuming non-anthropogenic food. We found that the δ13C ratios of bear hair from the ANM were significantly higher than those of bears sampled in another area in central Japan where bears were also eating native food. Bears in the ANM consumed large amounts of ants in summer. Ants in this part of the ANM have relatively higher δ13C value than ants from other areas. Miscanthus sinensis, a C4 plant with a high δ13C value close to that of corn , is abundant in parts of the ANM. We also found that the δ13C of herbivorous insects that may not be consumed by bears also had high δ13C content. From these analyses, the δ13C in bear hair in the ANM was high because bears consume ants in summer and because ants in turn may consume herbivorous insects that feed on C4 plants. Past studies indicate that high δ13C values in bear hair may be used to identify nuisance individuals that damage corn on farms. However, our results showed that bears consuming natural foods may also have high δ13C levels in some regions. Thus, identification of nuisance bears based on isotope data should account for variation in the isotopic signatures of non-anthropogenic food items and should identify and use locally appropriate isotopic end members.

Influence of Food Availability on Matrilineal Site Fidelity of Female Asian Black Bears

Abstract. To describe the maintenance process of matrilineal site fidelity in large, solitary mammals, we investigated both the site fidelity over time and the effect of kinship on the space use at a fine (home range) scale under different levels of food availability. We collected location data for female Asian black bears, Ursus thibetanus, using GPS collars and identified microsatellite DNA markers from bears in the Ashio-Nikko Mountains, Japan. We investigated autumn food resources by assessing hard mast productivity. We found high site fidelity over the years from the denning to summer season, and there was spatial proximity among related females (i.e., mother—daughter, grandmother—granddaughter, and sister—sister pairs) from spring to summer and through mid-autumn in moderate/good hard mast years. In autumns of poor hard mast years, although females used sites far from their primary home ranges, they returned to sites near their primary range before den entry. In habitats, where good denning habitat is spatially close to the spring and summer range, maternal communities may range throughout the area during the denning, spring, and summer seasons. When matrilineal site fidelity was suspended during poor mast years, it was reformed by the end of autumn.

Feeding Habits of Asian Black Bears (Ursus thibetanus) in Relation to the Abundance and Timing of Fruiting in 13 Tree Species

Abstract. We examined the relationship between the feeding habits of Asian black bears (Ursus thibetanus) and fruit availability during summer and autumn from 2008 to 2011 in the Ashio-Nikko Mountains, Japan. Our main questions were as follows: 1) How does the availability of multiple fruit species influence the feeding habits during summer and autumn? and 2) When do bears begin to forage on hard mast in relation to the availability of various fruit species during summer and autumn? The relationship between feeding habits and fruit availability differed between seasons: in summer, bears ate any fruit species that was available, whereas in autumn, Quercus crispula was the first fruit used, even in poor masting years when other fruit species were more available. In addition, the time when bears started to consume Q. crispula differed between years; more than half a month earlier in years when Padus grayana, the main food item prior to Q. crispula in this area, was not available. Thus, the timing of presence of prior foods may influence the timing of food transition. This demonstrates that both the abundance and timing of fruiting influence the feeding habits of bears.

Using a novel method of potential available energy to determine masting condition influence on sex-specific habitat selection by Asiatic black bears

Abstract Habitat selection is assumed to accrue fitness benefits. Where resource availability is variable, individuals should respond by changing habitat selection to increase resource availability. However, direct links between observed changes in habitat selection and energetic benefits of this behavior are rarely detected. We used a novel method whereby we converted interannual production levels of three hard-mast-producing Fagaceae species into a comparative energetic productivity score to investigate potential energetic benefits of Asiatic black bear habitat selection. We captured and fitted GPS collars on 19 bears between 2006 and 2010 in the Ashio-Nikko Mountains, Japan. We also collected data on hard-mast production and integrated these data with fine-scale vegetation maps. Then we mapped the potential available mast energetic production for each vegetation type to evaluate their potential energetic benefit for bears. Habitat use differed between poor and good mast years. Bears mostly used Japanese oak in good mast years, and there were sexual differences in September of poor mast years; females used mostly Japanese oak, whereas males used Konara oak. In those years, bears may have benefitted energetically by changing habitat use; however, the mean potential available energy to bears never exceeded that in good mast years, even if they used different habitats.