The Relative Abundance and the Distribution Prediction Models of Formosan Black Bears (Ursus thibetanus formosanus)

• Main Authors: Shin-Chien Tsai, 蔡幸蒨
• Other Authors: Mei-Hsiu Hwang
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/58318542330286366357

碩士 === 國立屏東科技大學 === 野生動物保育研究所 === 99 === Geographic distribution and habitat use of animals are essential information for wildlife conservation and management. Due to the recently rapid development of computer, GIS (Geography Information Systems) and remote sensing techniques, the power and efficiency of studies in species distribution and habitat evaluation has been greatly improved. The study objective was to investigate the distribution status and habitat characteristics of the locally endangered Formosan black bear (Ursus thibetanus formosanus) through sign surveys. Maxent and logistic regression models were also applied by using presence/absence data to establish the distribution prediction models of different time periods. Country-wide sign surveys were conducted in 20 survey areas from Mar 2007 to May 2009. Bear claw marks were most frequently founded (71.2%, n=236), and then scats (16 %). The sign densities varied by areas and ranged from 0 to 3.8/ha, with an overall average of 0.7/ha or an encounter rate of 0.42/km. Compared to the data of related studies in other bear countries, this study seemed to have a relatively low bear density. Among 1,017 presence locations, mainly based on the literatures (Hwang et al., 2010), the sign survey accounted for 12%. After excluding 2 locations with unknown dates, the data were divided into two period: the first period (1990-1999, n=300) and the second period (2000-2010, n=715). The Maxent prediction model showed that the distribution range covered 5,853 km2 and 8,588 km2 (i.e., 15.9% and 23.3% of the island area) for the first and second period, respectively. Both ranges were mainly located in Central mountain range, but with extremely small and fragmented patch in the Coastal mountain range. The habitat selection of bears revealed a similar pattern between both periods. Moreover, compared to the bear range in the first period, the distribution range seemed to expand in the second period, expect for the Danda Major Wildlife Habitat area. Through three data sources, including local interviews, paper reviews and sign survey, 470 absence grids were selected. The best-fitted logistic regression model included 5 factors of elevation, road density, distance to the nearest road, distance to the nearest national park and aspect. Although the prediction map showed that bears concentrated in three mountainous national parks, the Hosmer-Lemeshow index indicated a low prediction power of the model. It may be related to the precision of absence data and other variables which was not applied for simulations. The result indicated that elevation, road density, distance to the nearest road and distance to the nearest national park were important variables for bear distribution. According to field sign surveys and prediction models, the study suggested that the Sheipa and Taroko National Parks, and Yushan National Park and Guanshan Wildlife Habitat were potential hot spots of bear habitats in the northern and southern Taiwan, respectively. The study further suggested that different types of benchmark should be applied in different areas while local population status and threats were considered in order to enhance effective monitoring and management.