利用穩定同位素分析台灣黑熊食性

外文標題: 
Use of Stable Isotopes to Infer Diets of Formosan Black Bears (Ursus thibetanus formosanus)
校院系所: 
屏東科技大學野生動物保育研究所
指導教授: 
黃美秀
張原謀
出版年份: 
2011年
主題類別: 
摘要: 

食物資源是影響個體生存和繁殖,以及限制族群成長的關鍵因素,食性遂為研究研究野生動物生態習性的重要一環,也是經營管理及保育的必要資訊。台灣黑熊(Ursus thibetanus formosanus )數量稀少且習性隱密,排遺食性分析法常受限取樣於時空上的偏差。毛髮具有記錄過去環境同位素訊號的特色,故本研究以毛髮的穩定碳、氮同位素訊號來瞭解台灣黑熊的食性。為了解穩定同位素吸收轉換率和毛髮的生長速度,以圈養黑熊為試驗對象,做為反映野外季節性毛髮片段的參考。圈養黑熊毛髮穩定同位素吸收轉換率為20.0±9.2天(n=3),圈養個體毛髮之每月平均生長長度在5-11月為1.45公分(n=3),在12至次年4為0.23公分。野外黑熊毛髮樣本收集自1998(n=6)、2000年(n=7)野外捕獲的個體,以及2008年玉山國家公園內架設的熊毛陷阱(n=14)。此三年的δ13C分別為-22.9±1.3、-22.9±0.6‰、-22.8±1.2‰,δ15N為4.4±0.7‰、3.9±0.3‰、4.6±1.2‰三年間的δ13C與δ15N分別皆無顯著差異(δ13C:F=0.198,df1=2,df2=25,p=0.306;δ15N:F=1.258,df1=2,df2=25,p=0.822)。2008年12月自玉山國家公園大分地區所採集的黑熊毛髮樣本中,在青剛櫟結果季的δ13C和δ15N分別為-22.9±1.0‰、5.4±1.3‰,而非結果季δ13C和δ15N則分別為-22.8±1.3‰、為4.3±1.2‰。同一個體毛髮樣本於結果季的δ15N明顯高於非結果季(Paired-t test;df=13,t=4.466,p=0.001),δ13C在結果季及非結果季則無顯著差異(Paired-t test;df=13,t=-0.535,p=0.602)。以蒙地卡羅模擬法估算各項食物類別在黑熊食性中的貢獻度,C3植物為黑熊貢獻度最高的食物種類,而食物的比例中,青剛櫟產量越豐富的年份,動物性食物的比例越高。

外文摘要: 

Food resource is an important factor for individual survival and reproduction. Diet has been a crucial aspect for understanding wildlife habits, which also provides the baseline information for conservation and management. Due to the rareness and illusiveness of Formosan black bears (Ursus thibetanus formosanus), diet analysis based on their scats are generally limited by spatial and temporal sampling error. Stable isotopes analysis has been used as a powerful tool in diet studies. I used carbon and nitrogen stable isotopes ratio in hairs to investigate the diets of Formosan black bears. A feeding trial study on captive bears was conducted to estimate the turnover rate and hair growth rate, which were used to refer dietary seasonal shift. The half-life time of the hair metabolic pool was 20±9.2(mean ±standard deviation, n=3) days. The growth rate of hairs was 1.45 cm and 0.23 cm per month during May-Nov. and Dec-April, respectively. Three years of wild bear hairs were collected in Yushan National Park: 1998 (n=6), 2000 (n=7), and 2008(n=14). The δ13C values of the hair samples from the 3 years were-22.9±1.3, -22.9±0.6‰ and -22.8±1.2‰; the δ15N values were 4.4±0.7‰, 3.9±0.3‰, and 4.6±1.2‰, respectively. There was no significant difference among years for both δ13Cand δ15N values. However, the δ15N values of hair from 2008 in acorn season were significantly heavier than non-acorn season (Paried-t test; df=13, t=4.466, p=0.001), but no significantly different in the δ13C values (Paried-t test; df=13, t=-0.535, p=6.02). In the 2008 acorn season, the δ13C和δ15N value were -22.9±1.0‰ and 5.4±1.3‰, respectively; on the other hand, the δ13C和δ15N value in the non-acorn season were-22.8±1.3‰ and 4.3±1.2‰ respectively. The δ15N value in the acorn season was higher than that in the non-acorn season (Paired-t test;df=13, t=4.466, p=0.001), but no seasonally significant difference was detected for the δ13C value (Paired-t test; df=13, t=-0.535, p=0.602). The Monte Carlo simulation indicated that vegetation and animal food contributed to 67-90% and 10-33% of bear diets, correspondingly. During the acorn masting season, bears tended to be more carnivorous, which may be related to seasonally increasing abundance of ungulates in the study area.