笼养雌性果子狸同性数量对发情状态的影响及繁殖季节尿液雌激素浓度的变化

EFFECTS OF NUMBER OF HOMOSEXUAL PARTNERS ON COPULATING DATE IN FEMALE CAPTIVE MASKED PALM CIVETS (PAGUMA LARVATA), AND FLUCTUATION OF URINE ESTROGEN DURING BREEDING SEASON

本研究试图揭示 (1)社会环境影响雌性果子狸 (Pagumalarvata)的交配日期 ,(2 )哺乳期母兽有雌二醇浓度升高的现象。通过检查是否排出交配栓并结合交配行为的发生与否确定开始交配的日期 ,使用放射免疫方法测定尿中雌二醇浓度。结果表明 (1)一雄两雌组中优势雌兽开始交配的日期显著早于劣势雌兽和单雌组雌兽 ,劣势雌兽和单雌组雌兽之间无差异 ;交配期优势雌兽尿液中雌二醇浓度明显高于劣势雌兽 ,而与单雌组中的雌兽无差异 ,但单雌组中雌兽尿液中雌二醇的浓度明显高于劣势雌兽雌二醇的浓度 ;(2 ) 5头母兽产后第二天雌二醇浓度开始上升 ,在第 5天时达到高峰 ,其中 4头母兽的雌二醇浓度共出现了两个峰值 ,其间隔为 16 75± 4 4 6 (4)天。上述结果说明 :(1)社会影响仅对优势雌性个体的繁殖有促进作用 ;(2 )哺乳期雌二醇水平的升高是季节性多次发情的基础。

Previous studies demonstrated that female social stimuli from the individuals of the opposite sex can cause females to elevate estradiol levels in female insectivores, rodents and primates. Further more, the presence of the homosexual partners can increase the ability to reproduce in the species where males and females reproduce seasonally, by advancing the onset of the rutting season. However, whether this is true of carnivores remains unclear. Previous studies also indicated that estradiol plays a role in the initiation of sexual behavior in primates. The masked palm civet, Parguma larvata , reproduces seasonally in variable social groups including multiple males and one female, multiple females and one male, or one male and one female. By studying captive masked palm civets, we aimed to determine if: (1) female civets will come into estrous earlier when presented with homosexual partners, and (2) estradiol level become elevated during lactation. The target animals included three groups with one male and one female, five groups with two females and one male, and three groups with two males and one female. To increase statistical power, we combined groups with one female, since the results indicated that there was not difference in copulating date between the group with one female and two males, and that with one female and one male. We identified the first day on which copulation occured by checking for the presence of the copulatory plug and mating behaviour, and determined the level of estradiol by using a radioimmunoassay kit. The results indicated that: (1) the five dominant females in the groups with one male and two females copulated 30 7 days earlier than the five subordinate females in the same groups, and 28 6 days earlier than the six females in the mono\|female groups. However, there was no statistical difference in the date of first copulation between the subdominant females and the females in mono\|female groups. The urine estradiol concentration of the dominant females was 1 909 7±336 7(4) pg/ml, significantly higher than that of the subordinate females (LSD test, P <0 05), which was 320 4±82 65 (5)pg/ml; (2) two days after the parturition, the estradiol concentration in five mother civets urine rose peaking on the 5th day, and a second peak appeared 16 75±4 46 days later in four of the five mother civets. The above results suggest that: (1) social influences only facilitate reproduction in dominant females, and (2) the elevation of estradiol in lactating females is the basis for female polyestry in this species.