陽明山國家公園流浪犬族群量之時空變化

Abstract

為了瞭解陽明山國家公園內流浪犬（Canis familiaris）的族群數量變動及空間分佈情形，自2002年4月起至2004年3月，每月在陽明山國家公園園區內繞行固定九個遊憩區及五大段公路巡察兩次（觀察時間每月約32小時），對流浪犬進行照相及環境因子紀錄，並不定期追蹤台北市環保局捕捉流浪犬狀況。兩年的調查共累積照相檔案並辨識了506隻流浪犬，估計平均每月最小族群量為131隻。兩年的族群量月變化分析發現，流浪犬數量於夏季達到高峰，冬季降至谷底，隔年春天數量會再度上升。流浪犬加入率呈現規律的季節變化，主要受幼犬加入量所影響，除了冬季未有新幼犬出現外，春夏秋三季加入量差異不大，然而新加入成犬與整體族群變化趨勢才有顯著相關，推測原因是幼犬存活率不高。持續照相紀錄發現，園區內的流浪犬壽命最長可達兩年多。流浪犬個體存留率曲線會因其加入的季節而異，冬季才加入的個體會維持較穩定的存留率，至於春夏秋三季中新加入的個體，其存留率會隨時間增長而下降，但下降速率會漸緩。本區流浪犬族群量減少的主因有二：冬季的低溫應是造成數量減少的主要因素，此外，短期的大量捕犬行動能夠立即壓制流浪犬族群量的成長，但是一旦中斷捕捉的干擾，族群會在兩個月之後回復到成長的趨勢。在空間分佈上，各路段間及各遊憩區間的數量有明顯差異，其中以龍鳳谷硫磺谷的流浪犬數量最高，密度也最大，佔遊憩區總量的40％，最靠近龍鳳谷的前山一帶公路數量也是公路段中最多的。流浪犬族群較大的地點多與遊客量出現頻繁、民眾餵食有關。

To understand the spatial and temporal variation of stray dogs in Yangminshan National Park, surveys have been conducted twice a month during April 2002 to March 2004. In 9 routes and 5 scenic spots, we recorded and assessed the population of stray dogs by photographic identification and mark-recapture method. Dog-catches data from Dep. of Environmental Protection of Taipei City have been traced and compared. 506 stray dogs were identified in two years, and the mean minimum number per month was 131. Population size reached the maximum in summer and the minimum in winter. Seasonal variation of recruitment was mainly affected by the puppy-recruits . Numbers of puppy-recruit was zero in winter, but about the same in other seasons. However, it was the adult recruitment that related to the whole population variation trend, because the survival rate of puppies was low. The longest age is more than 2 years. The survival curves were different from every season. The winter recruits have stable survival rate variation. As to other three seasons, survival rate declines more slowly as time goes by. The major cause of decrease in population was the low temperature in winter. Furthermore, population could be suppressed by short-term and large number of catches, but raise after two months. The abundance of stray dogs in routes and scenic spots are different apparently. Both numbers and density are the highest in Lungfengku, and accounted for the 40% of all scenic spots. Routes near Lungfengku were also discovered that contain the most stray dogs. Large populations appeared to live in places which attract many tourists and feeders.