Ursus 2024 Volume 35 Articles 24-25

Ursus 2024 Volume 35 Articles 24-25

We are pleased to share these recent URSUS articles with you. Both articles are open access and can also be accessed through your IBA membership account link to BioOne. 


Akino Inagaki, Yuji Sugimoto, Maximilian L. Allen, Shinsuke Koike

Ursus 2024 (35e24), 1-8, (31 December 2024) https://doi.org/10.2192/URSUS-D-24-00013R1

KEYWORDS: Asiatic black bears, Japan, population control, predation, predator–prey, trap, Ursus thibetanus, wildlife management

Open Access Article

Asiatic black bears (Ursus thibetanus) rarely prey on living adult deer. We report video documentation, obtained May 2024, of a bear subduing and killing a sika deer (Cervus nippon) that was captured in a leg-hold snare trap, then staying in the area for repeated feeding visits. Leg-hold snare traps for deer capture are widely used in Japan for population control of high deer densities. The predation by bears on deer with restricted movements in this study shows that deer trapping by humans may be providing bears with a new form of deer as a food resource. If bears perceive such a deer as a regular food resource, it may have some effect on bears’ ecology (e.g., feeding habits, behavior). In addition, through foraging on captive deer, bears could endanger trappers and the general population. Our record highlights the necessity of evaluating trap management practices to mitigate risks to humans and wildlife.

要旨:ツキノワグマ (Ursus thibetanus) がニホンジ カ (Cervus nippon) 成獣を捕食することは稀であ る。本研究では、くくり罠で捕獲されたシカにク マが襲い掛かり、その後死亡した個体に繰り返し 訪問し、シカを採食する様子を捉えた一連の動画 を報告する。シカの高密度化に伴うシカの捕獲強 化に際して、くくり罠は広く使用されている。本 事例において身動きが制限されたものの、生きた 成獣のシカをクマが捕食したことは、人によるシ カの捕獲行為がクマに新たな形態の食物資源とし てのシカを提供していることを示唆する。さら に、クマがこのような状態のシカを通常の食物資 源として認識している場合、クマの生態(たとえ ば、食性や行動など)に何かしらの影響を及ぼし ている可能性がある。また、捕獲されたシカのク マによる採食行動は、罠周辺でのクマの長時間の 滞在や錯誤捕獲の危険性を高めることで、捕獲従 事者および周辺住民との人身事故の可能性を高め る可能性がある。本事例は人と野生動物へのリス クを軽減するためにも、適切なくくり罠の運用を 検討する必要性を示唆している。


Tsutomu ManoHiroyuki MatsudaShosuke NatsumeHifumi Tsuruga

Ursus 2024 (35e25), 1-20, (7 January 2025) https://doi.org/10.2192/URSUS-D-23-00016.1

KEYWORDS: brown bear, estimator, field sign survey, harvest, Hokkaido, hunting, monitoring, population estimate, population trend, uncertainty, Ursus arctos

Open Access Article

We constructed a population dynamic model using demographic parameters with uncertainties by using long-term harvest data and estimated population dynamics of brown bears (Ursus arctos) on the Oshima Peninsula, Hokkaido, Japan, from 1968 to 2021 with population trend indicators obtained by forest sign survey and an upper population limit calculated by extrapolating an estimated density in a high-density area in some years. We assumed mean litter size of 1.8, age of first parturition of 6 years, birth interval of 2.3–3.0 years, and natural mortality of 0.35 for cubs and 0.02 to 0.08 for subadults and adults, with 10% uncertainty for every parameter. The initial female population size was randomized from 1 to 1,809, which was set by extrapolating the 95% value of the female population density (0.327 bears/km2) estimated in 2012 to the entire forested area of brown bear distribution (5,531 km2). This value was used as the upper population limit for 2012. The assumptions for the simulation were that males and females aged ≥6 years were present in 2020, the population size in 1990 when the Spring Bear Removal was abolished did not exceed that in 1968, and the population size in 2012 did not exceed 1,809. Population dynamics differed significantly depending on the demographic parameters; however, the difference in estimation became small and converged after 2012. Continuous harvest and population trends over 40 years maintained the findings within a specific range, even when accounting for parameter uncertainties. Continuous harvest and population trends over 40 years maintained the findings within a certain range, even when accounting for parameter uncertainties. The median population estimates obtained under the conditions of subadult and adult survival of 94%, cub survival of 65%, and birth interval of 2.6 years were 1,107 in 1968; 916 in 1990; 1,715 in 2012; 2,030 in 2021. However, the method outlined in this article has limitations in its application for estimating recent population size and trend. It is crucial to conduct iterated population censuses to ensure accurate and up-to-date data.