Abstract: Predation has long been implicated as a major selective force in the evolution of several morphological and behavioral characteristics of animals. This study aims to determine experimentally how indirect cues of mustelids affect the social behavior , foraging , reproduction and sexual hormones of root voles ( Microtus oeconomus). We predict that delayed breeding and changed mating behavior presented with Silver fox , Mustila eversmanni predation risk occur in root voles. Further , we discuss the possible ultimate and proximate cause behind delayed breeding.
We carried out the study at Northwest Plateau Institute of Biology , the Chinese Academy of Science , during April-December 1997. We caught voles and Silver fox for experiment in the site of Haibei Alphine Meadow Ecosystem Research Station of Chinese Academy of Science which located northwest Qinghai-Tibet Plateau with (37°29′- 37°45′N , 101°12′- 101°23′E) .
The animals were housed in clear plastic cages (29 cm ×19 cm ×13 cm) and maintained in a 12:12 h light/dark photoperiod and in 20 ±1 ℃temperature.
We carry out 18 days experiments in two main arenas (first three days) and in breeding cages (15 days thereafter) situated indoors. The 40 cm×40 cm ×40 cm arenas were made of Plexiglas.
The study consisted of 34 (17 experimental and 17 control) experiments with female - male pairs of voles. We examined the mating and foraging behavior (the frequency and amount of food eaten in grams) during the first three days of the study. Then we transferred the voles pairs to breeding cages where the breeding experiments continued. We offered water , Purina rabbit chow , and carrot to the voles ad libitum throughout the experiment1 On the 18th day , the voles were killed and weighted , and the reproductive stage of females , the weight of female ovaries , the litter size , the sperm count , and the weight of the male testes and epididymis were measured.
We sprayed the sawdust in the experimental arenas with predator odor daily during the study1 The odor was a filtered dilution of urine and feces of Silver fox1 We sprayed the control arenas daily with distilled water.
We observed the pairs in behavior arenas to study the effects of Silver fox odor on the behavior of voles. Each behavior observation lasted for 40 min. We recorded the following activates (as in Esa and Yl onen , 1995) : general activate , amicable interactions , aggressive behavior , self-grooming , investigating behavior , and copulatory behavior.We counted the frequencies and total time of all variables.
After the behavioral observation period , we removed each pair from the arenas to breeding cages for foraging trails of voles. We recorded the amount of Purina rabbit chew in grams. Then the voles were removed to the breeding cages for 15-day breeding trial.
We found that 82 % paired root voles delayed breeding and significantly lowered the frequency of the general activity , investigating , self2grooming , and copulatory behavior after being exposed to Silver fox odor. Comparing with the control , the total time of general activity in both sexes and amicable behavior of females increased under Silver fox odor. The total time of attacking behavior and amicable interactions of females , self2grooming of males decreased significantly. The ovary index and litter weight decreased in females , whereas in males the sperm count in epididymis decreased significantly1 The progesterone in the blood serum of females were increased significantly under fitch odor1

Key words: Silver fox ( Vulpes vulpes), Root voles ( Microtus oeconomus), Reproduction, Foraging, Predation risk

摘要： 在实验室条件下, 主要测定银狐的气味对根田鼠社会行为、觅食、繁殖特征及性激素水平的影响, 并探讨银狐气味使根田鼠产生繁殖迟滞的机制。结果表明, 银狐气味对82 %的配对根田鼠产生显著的繁殖迟滞, 对根田鼠一般动作、探究、自我修饰及婚配行为的频次具有显著的抑制作用( P < 0105) 。对各种行为累积时间的作用则产生明显的性别差异, 银狐气味可提高雄体及雌体一般动作及雌体亲密行为的累积时间; 对雄体自我修饰行为, 以及雌体攻击、探究及自我修饰行为的累积时间有显著的降低作用( P < 0105) 。雄体附睾精子计数、雌体卵巢指数及胚胎重量极显著地减低( P < 0101) , 相应地, 雌体血清孕酮显著地提高( P< 0101) 。

关键词: 银狐, 根田鼠, 繁殖, 觅食, 捕食风险