從伴侶偏好看台灣高山田鼠的婚配制度—兼論固醇類賀爾蒙之影響

Abstract

台灣高山田鼠 (Microtus kikuchii) 的婚配制度極可能是哺乳類中罕見的一夫一妻制。一夫一妻制動物會表現伴侶偏好行為，即行為上偏好同居或配對過的異性個體顯著多於陌生個體，但伴侶偏好可能會受到固醇類賀爾蒙(性賀爾蒙及壓力賀爾蒙) 濃度左右。我們以伴侶偏好行為實驗 (partner preference test) 測試台灣高山田鼠是否表現 [同居過的雌雄個體接觸時間應顯著多於與陌生個體的接觸時間]。實驗個體在實驗前皆無配對經驗，同居時間長度為24小時，配對結束後即進行3小時的伴侶偏好行為實驗，過程以錄影記錄並進行分析。另一方面，在行為實驗的前及後4~5天收集高山田鼠每日的糞便，以酵素免疫分析法 (enzyme-immunoassay method) 獲得實驗雄性田鼠的睾固酮 (testosterone) 、雌性田鼠的孕酮 (progesterone) 和雌二醇 (estradiol) 及每隻田鼠的壓力賀爾蒙 (corticosterone)。伴侶偏好行為實驗結果顯示雌性高山田鼠沒有任何伴侶偏好；但雌性田鼠的伴侶偏好(p = 0.04) 以及與某一個體接觸的時間長度 (p = 0.04) 皆會受到對方是否為熟悉個體的影響。在實驗前後的固醇類賀爾蒙濃度則未顯示對高山田鼠的伴侶偏好有任何顯著性的影響。另一方面，高山田鼠具有較小的體重雌雄二型性，與一夫一妻制的草原田鼠 (M. ochrogaster) 相似。綜合結果顯示只有雌性高山田鼠表現出伴侶偏好行為，且伴侶偏好並未明顯受到固醇類賀爾蒙的影響，本實驗結果並未完全支持台灣高山田鼠為嚴謹的一夫一妻制。

The mating system of the Taiwan field voles (Microtus kikuchii) has been suspected to be monogamous. In monogamous animals, individuals should exhibit a strong social preference for a familiar partner versus a strange one. In this study, we examined the effect of cohabitation (pair-bonding) on the partner preference in Taiwan field voles. In the reciprocal experiments, all individuals were sexually naive and cohabited with a heterosexual vole for 24 hr prior to the 3-hr partner preference trials. We collected the feces of Taiwan field voles before and after the partner preference trials, and used the enzyme-immunoassay (EIA) method to analyze the concentration of steroid hormones, including testosterone of males, progesterone and estradiol of females, and corticosterone of all voles. The results showed that the voles did not spend more time in the partner chamber (male: p = 0.33; female: p = 0.098), but the female voles’ preference (p = 0.04) and time that the female voles spent in each chamber (p = 0.04) were both significantly related to if the preferred vole was the partner. In addition, the EIA results indicated that there was no significant relationship between steroid hormones and partner preference. Also, the sexual dimorphism of the Taiwan field vole in body weight was reduced, and similar to the monogamous prairie vole (M. ochrogaster). The results indicated that only female voles had partner preference, and the steroid hormones did not affect the preferences. This study did not support that mating system of the Taiwan field voles is strictly monogamy.