Development of a noninvasive photograph-based method for the evaluation of body condition in free-ranging brown bears

PeerJ

article

Yuri Shirane¹  Fumihiko Mori¹  Masami Yamanaka²  Masanao Nakanishi²  Tsuyoshi Ishinazaka²  Tsutomu Mano³  Mina Jimbo¹  Mariko Sashika¹  Toshio Tsubota¹  Michito Shimozuru¹ 

[1] Graduate School of Veterinary Medicine, Hokkaido University;Shiretoko Nature Foundation;Hokkaido Research Organization

关键词: Body condition;    Nutritional status;    Morphometrics;    Photographs;    Brown bears;    Ursus arctos;   

DOI  :  10.7717/peerj.9982

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Body condition is an important determinant of health, and its evaluation has practical applications for the conservation and management of mammals. We developed a noninvasive method that uses photographs to assess the body condition of free-ranging brown bears (Ursus arctos) in the Shiretoko Peninsula, Hokkaido, Japan. First, we weighed and measured 476 bears captured during 1998–2017 and calculated their body condition index (BCI) based on residuals from the regression of body mass against body length. BCI showed seasonal changes and was lower in spring and summer than in autumn. The torso height:body length ratio was strongly correlated with BCI, which suggests that it can be used as an indicator of body condition. Second, we examined the precision of photograph-based measurements using an identifiable bear in the Rusha area, a special wildlife protection area on the peninsula. A total of 220 lateral photographs of this bear were taken September 24–26, 2017, and classified according to bear posture. The torso height:body/torso length ratio was calculated with four measurement methods and compared among bear postures in the photographs. The results showed torso height:horizontal torso length (TH:HTL) to be the indicator that could be applied to photographs of the most diverse postures, and its coefficient of variation for measurements was <5%. In addition, when analyzing photographs of this bear taken from June to October during 2016–2018, TH:HTL was significantly higher in autumn than in spring/summer, which indicates that this ratio reflects seasonal changes in body condition in wild bears. Third, we calculated BCI from actual measurements of seven females captured in the Rusha area and TH:HTL from photographs of the same individuals. We found a significant positive relationship between TH:HTL and BCI, which suggests that the body condition of brown bears can be estimated with high accuracy based on photographs. Our simple and accurate method is useful for monitoring bear body condition repeatedly over the years and contributes to further investigation of the relationships among body condition, food habits, and reproductive success.

【 授权许可】

CC BY