Changes in body condition and behavior of Hokkaido brown bears in relation to seasonal and annual variations in diet

• Main Author: 白根, ゆり
• Other Authors: 石塚, 真由美, 坪田, 敏男, 野中, 成晃, 下鶴, 倫人, 山﨑, 晃司
• Format: Doctoral or Postdoctoral Thesis
• Language: English; Japanese
• Published: Hokkaido University
• Subjects: 649; Pink salmon
• Online Access: http://hdl.handle.net/2115/91657; https://doi.org/10.14943/doctoral.k14544

Nutrient balance is an important determinant of animal fitness and demography. Brown bears are omnivores that can change their diet opportunistically in response to temporal variation in resources. On the Shiretoko Peninsula, Hokkaido, brown bears have seasonal access to high-lipid foods, Japanese stone pine nuts, and high-protein foods, pink salmon. This study aimed to clarify seasonal and annual variation in the consumption of high-nutrition foods among Shiretoko brown bears, and how those variations affect bear body condition and behavior. Chapter 1: A noninvasive method that uses photographs was developed to assess the body condition of free-ranging brown bears. The precision of photograph-based measurements was examined using photographs of an identifiable bear in the Rusha area, a special wildlife protection area. As a result, the torso height:horizontal torso length (TH:HTL) was adopted as the best method that could apply to bears with various postures and reflected seasonal changes of body condition. Then, body condition index (BCI) was calculated from actual measurements of captured 7 females and TH:HTL from photographs of the same individuals. The significant positive correlation between TH:HTL and BCI (r = 0.78) suggested that the body condition of bears can be estimated with high accuracy. Chapter 2: To assess seasonal and annual fluctuation in adult female body condition in relation to diet and reproductive status, a longitudinal study was conducted in the Rusha area during 2012–2018. Analyses of 2,079 bear scats revealed that pine nuts in August and salmon in September accounted for 39.8% and 46.1% of energy intake, respectively, with large annual fluctuation. Using the method developed in chapter 1, body condition was evaluated from 1,226 photographs of 12 adult females and found that body condition continued to decline until late August and started to increase in September. In addition, body condition began to recover earlier in years with high pine nuts and salmon consumption. Furthermore, ...