Language：English   Publishing type：Research paper (scientific journal)   Publisher：INT ASSOC BEAR RESEARCH & MANAGEMENT-IBA  

The reproductive tracts of 130 adult female brown bears (Ursus arctos) in Hokkaido, Japan, euthanized during 2010-2013 for conflict management, were examined for the presence and number of corpora lutea (CL) in the ovary and placental scars (PS) in the uterine horns. We scored PS on a 0-5 scale based on morphological features including their rim and color. They were characterized as representing either current-year parturition, as determined by accompanying cubs, or previous year parturition, as determined by accompanying yearlings. In total, 128 females were divided into 3 reproductive categories: 44 females with current-year parturition, 39 with previous-year parturition, and 45 solitary females that had not given birth for >2 years. The estimated ovulation rate was 2.21 +/- 0.55 (mean +/- SD), the implantation rate was 1.91 +/- 0.74, and the litter size was 1.54 +/- 0.51. Implantation rates were lower than ovulation rates and changed annually during 2010-2013. Systematic observation of PS and CL allowed us to evaluate the reproductive history and parameters in Hokkaido brown bears and ascertain their annual variation.

DOI： 10.2192/URSU-D-16-00005.1

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Understanding natal dispersal patterns is fundamental in the ecology and conservation biology of large wild carnivores. In this study, we used two approaches to determine genetic variation and dispersal patterns of brown bears in the Shiretoko Peninsula, eastern Hokkaido, Japan. The first approach was a large-scale genetic analysis. We analyzed haplotypes from the mitochondrial DNA (mtDNA) control region of 760 individual samples collected throughout the peninsula during 1998-2016. We detected seven haplotypes, including two that were confirmed for the first time. In females, the distribution of haplotypes was geographically structured, whereas haplotypes in males were distributed widely throughout the peninsula. Only some males in the lower peninsula had haplotypes that were not detected within the peninsula. The second approach was a local-scale genetic analysis, including intensive focal sampling in the Rusha area, a special wildlife protection area on the peninsula. Proportions of mtDNA haplotypes in adult bears were investigated and compared between the sexes. Although more than half of the females had the same haplotype, males had more diverse haplotypes, suggesting that they came to the Rusha area from other regions. Thus, our study revealed that mtDNA haplotype distribution has been maintained by female philopatry, and that bears exhibit male-biased dispersal. Furthermore, the lower peninsula appears to act as a contact zone between the peninsula and mainland Hokkaido, which is important for maintaining genetic diversity.

DOI： 10.1007/s10344-018-1222-x

Web of Science

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：HOKKAIDO UNIV  

Chest girth and body mass of 3,576 brown bears (Ursus arctos yesoensis) harvested for conflict management in Hokkaido, Japan during 1991-2012 were used to establish methods to assess body condition and to compare the body condition of bears by sex, month, year, and reproductive status. The body mass was estimated based on the chest girth in cases with no measurements of the bear body mass. Using the measured and estimated body mass, a growth curve by age was demonstrated to ascertain the mean asymptotical body mass (245 kg for males, 114 kg for females) and ages at 95% asymptotic body mass (14.2 years for males, 7.1 years for females). The body condition value of bears was evaluated as body mass difference (kg) between the individual body mass and the standard body mass as estimated from the growth curve. Body condition value changed seasonally with a low in summer and the highest in the autumnal hyperphagic period. Female body condition value was higher than the males during September. Fluctuation in annual body condition value was found for females; however, there was no difference between solitary adult females and females with offspring (cubs, yearlings, or offspring of unknown age). No significant fluctuation was found for males. Our body condition evaluation method using chest girth and body mass of brown bears is useful to elucidate different trends across sex, year, and season.

DOI： 10.14943/jjvr.66.2.71

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

servation and management of wildlife. In this study, we investigated the demographic parameters, including age of primiparity, litter size, inter-birth interval, reproductive rate, and cub survival rate, of Hokkaido brown bears (Ursus arctos yesoensis) in the Rusha area on the Shiretoko Peninsula, Hokkaido, Japan, based on a long-term, individual-based monitoring survey. A total of 15 philopatric females were observed nearly every year from 2006 to 2016, and these observations were used to estimate reproductive parameters. The mean age of primiparity was 5.3 +/- 0.2 (SE) years (n = 7, 95% CI = 5.0-5.6). We observed 81 cubs in 46 litters from 15 bears. Litter size ranged from one to three cubs, and averaged 1.76 +/- 0.08 (SE) cubs/litter (95% CI = 1.61-1.91). Inter-birth intervals ranged from 1 to 4 years, and the mean value was estimated as 2.43 (95% CI = 2.16-2.76) and 2.53 (95% CI = 2.26-2.85) years in all litters and in litters that survived at least their first year, respectively. The reproductive rate was estimated from 0.70 to 0.76 young born/year/reproductive adult female, depending on the method of calculation. The cub survival rate between 0.5 and 1.5 years ranged from 60 to 73%. Most cub disappearances occurred in July and August, suggesting that cub mortality is mainly due to poor nutrition in the summer. All reproductive parameters observed in the Rusha area on the Shiretoko Peninsula fell within the range reported in Europe and North America, and were among the lowest or shortest age of primiparity, litter size, and inter-birth intervals, and ranked at a high level for reproductive rate.

DOI： 10.1371/journal.pone.0176251

Web of Science

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1078/0723202041748154

Total pages：4   Responsible for pages：201-204   Language：Japanese

Language：Japanese  

CiNii Books

J-GLOBAL

J-GLOBAL

Language：Japanese   Publisher：日本霊長類学会  

 2012年知床半島では，夏期に極度に痩せたヒグマがメディアで報道され話題となるなど，夏期の食物不足の深刻さが窺える状況であった．斜里町・羅臼町におけるヒグマの目撃数・駆除数は例年の約2倍近くとなり，特に 8月に目撃数・駆除数がピークとなったことは例年にない特徴であった．また，親とはぐれたであろう当歳子や，餓死とみられる死体が夏期に複数確認されたことは，例年以上に夏期の死亡率が高かったことを推測させた．これらの原因として，カラフトマスの遡上が 8月末まで遅れたことや，ハイマツ等の実りが悪かったことが考えられるが，因果関係の有無については今後検証する必要がある．知床半島先端付近に位置するルシャ地区において実施しているヒグマ個体追跡調査においても同様の状況が見てとれた．同地区に定住している成獣メスの体型を追跡すると，7月初旬までは多くの個体が軽度に肥満していたが，8月に入ると急激に削痩し，そのうちの一頭は 8月末に死体で発見された．カラフトマスの遡上が始まった 9月以降は体型が回復し，10月には全個体が充分に肥満した状態となった．成獣メスの連れ子数を追跡した結果，当歳もしくは一歳齢の子を連れた個体（全 8頭）のすべてが 7月から 9月にかけて子の数を減らしたことが明らかとなった．2011年ではこのような事例は全 9頭中 1例のみしか認められなかったことから，2012年の連れ子の離別率は顕著に高かったといえる．さらに同地区ではこれまで多くの個体が 2年周期の繁殖サイクルを示す傾向にあったが，2012年は一歳齢を連れた成獣メスが例年に比べて多く，3年周期の繁殖サイクルを示す傾向にあった．このようなことから，知床半島先端部ではカラフトマスをはじめとした夏期の食物の豊凶が，ヒグマの生存率や繁殖率に大きく影響を与えていることが示唆された．尚，本研究はダイキン工業寄付事業の一環として行われたものである．

DOI： 10.14907/primate.29.0_92_2

J-GLOBAL

Language：Japanese   Publisher：日本霊長類学会  

 動物が高密度に生息する地域において，集団の血縁関係を明らかにすることは，その地域を利用する個体毎の繁殖，行動および分布様式を解明する上で重要である．そこで知床半島ルシャ地区におけるヒグマの繁殖，行動および移動分散様式を解明することを目的として，個体識別調査および集団遺伝学的解析により，個体間の血縁関係を解析した．材料は，同地区でヘアートラップ，ダートバイオプシー等により収集された遺伝子材料 51頭（雄 21頭，雌 30頭）分と，周辺地区（斜里，羅臼および標津地区）で学術捕獲あるいは捕殺個体 164頭分の遺伝子材料および各種メディアの情報を利用した．遺伝子解析には 22座位のマイクロサテライト領域を利用した．その結果，ルシャ地区には 15頭の成獣メスと，その子供からなる集団が生息しており，血縁は大きく２つの母系集団に分かれていた．また，最大で 3世代が共存していた．ルシャ地区で繁殖に関与する父親は，現在までに 5頭認められ，近親交配やマルチプルパタニティーが存在することが明らかになった．ルシャ地区を利用する個体の中で，5頭の亜成獣オスが斜里および羅臼地区側へ移動分散して捕殺されていることも明らかになった．このように，高密度に生息する知床半島ルシャ地区でのヒグマ集団の血縁関係を明らかにすることは，従来の野外調査では明らかには出来ないヒグマの繁殖システムの解明に寄与するだけではなく，繁殖個体の周辺地域への移動分散を明らかにすることができる．尚，本研究はダイキン工業寄附事業 「知床半島先端部地区におけるヒグマ個体群の保護管理，及び，羅臼町住民生活圏へ与える影響に関する研究」の一環として行われたものである．

DOI： 10.14907/primate.29.0_242_2

J-GLOBAL

Language：Japanese   Publisher：[日本クマネットワーク事務局]  

Event date： 2023.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鹿児島県鹿児島市  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2018.9

Language：English   Presentation type：Poster presentation  

Event date： 2017

Event date： 2013.9

Language：English   Presentation type：Poster presentation  

Audience： Company

Type：Seminar, workshop