圈飼台灣黑熊之繁殖性狀

Reproduction Behavior and Characters of the Formosan Black Bear in Captivity

本試驗利用二雄二雌圈飼之台灣黑熊（Ursus thibetanus formosanus Swinhoe）觀察其發情、交配、攝食、體重、生產前後的狀況及行為，並檢測類固醇性荷爾蒙的變化以探討其繁殖性狀。雌熊1號與雄熊1號在2000年交配後並未懷孕，但交配後雌熊之攝食量及體重均增加，另以酵素免疫分析法（enzyme immunoassay，EIA）檢測其糞孕酮（fecal progesterone）發現於交配後約5個月明顯上昇；雌熊2號與雄熊2號在2001年交配後懷孕生產，交配後雌熊之攝食量與體重亦均增加，其糞孕酮亦於交配後約6個月明顯上昇；雌熊1號與雄熊2號在2001年亦曾合欄飼養但未有交配行為，雌熊之攝食、體重、糞孕酮則無明顯變化。由有交配行為才會引起攝食、體重及糞孕酮的變化，認為台灣黑熊屬誘發排卵（induced ovulation），且交配後會有假懷孕（pseudopregnancy）現象。交配懷孕者在5-6個月之後糞孕酮才上昇，在此5-6個月期間，推測是胚胎停滯發育而延遲著床（delayed implantation），著床同時糞孕酮昇高，並於著床後約2個月後生產，總懷孕期7個月半。假懷孕與真懷孕的糞孕酮濃度均會明顯變化，故認為糞孕酮無法單獨作為診斷懷孕與否的依據。懷孕雌熊的外表特徵在產前一個月攝食量劇減、行動較緩慢、反應較遲鈍、多蜷縮於窩巢、舔自身乳房及產前一週完全拒食。產後約20多天不吃、不喝、不排糞、不排尿，與冬眠熊隻的生理性狀相似，以自身儲存的能量轉換為乳汁育幼。 Two male and two female Formosan black bears (Ursus thibetanus formosanus Swinhoe) incaptivity were paired to study their reproductive behavior and characters from April 2000 to March 2002.After being paired, three reproductive conditions of the females were obtained. They were a pregnant female, a pseudopregnant female, and an unmated female. For both pregnant and pseudopregnantfemales, the food intake and body weight increased after mating, and its fecal progesterone contentsrapidly elevated five to six months later. Also, the blood progesterone contents of the pregnant femalechanged with the fecal progesterone contents. For the unmated female there was no change in foodintake, body weight and fecal progesterone content. The increases in food intake and body weight forboth pregnant and pseudopregnant females suggested that ovulation of the female Taiwan black bear wasinduced by act of copulation, the so-called induced ovulation. The occurrence of rapid elevation of theprogesterone contents 5-6 months later after mating suggested that there was a delayed embryoimplantation. The gestation period was seven and half months. The parturition occurred two months afterthe elevation of progesterone. The pregnant female decreased food intake a month prior to theparturition, and was in fasting condition without intake of food, urination and defecation for about a weekprior to and three weeks after the parturition. Because the elevation of fecal progesterone occurred inboth pregnant and pseudopregnant females, a measurement of fecal progesterone content is useless fordiagnosis of the pregnancy. About a month long fasting of the female Formosan black bear, which doesnot hibernate in the subtropical region in this study is fairly similar to the case reported for black bearswhich hibernate in the cold climatic region.