Millesi E, Huber S, Pieta K, Walzl M, Arnold W, Dittami J P
Institute of Zoology, University of Vienna, Austria.
Horm Behav. 2000 May;37(3):190-7. doi: 10.1006/hbeh.2000.1574.
The course of behavioral and vaginal estrus and patterns of circulating estrogens were followed in free-living European ground squirrels (Spermophilus citellus) after their emergence from hibernation. Normally mating females were compared to a second group in an area where males had been removed from the population before female emergence. Both groups showed vaginal estrus, but the patterns differed. Mating shortened vaginal estrus to a 3-day period compared to 8 days in unmated females. The extent (cell number) of cell cornification during estrus and the cellular components (percentage distribution) of metestrus did not differ between the two groups. Females in the area without males had significantly higher estrogen levels during estrus and metestrus compared to those in the control area. European ground squirrels were found to be monestrous, as none of the unmated females reentered estrus after metor diestrus was detected. The prolongation of vaginal estrus in unmated females can be viewed as either a physiological inevitability or an adaptation to low mate availability. The extension is still relatively short compared to other sciurid species and perhaps a product of constraints producing a strict time frame for reproduction.
对自由生活的欧洲地松鼠（Citellus citellus）从冬眠中苏醒后的行为和阴道发情过程以及循环雌激素模式进行了跟踪研究。将正常交配的雌性与另一组进行比较，后一组所在区域的雄性在雌性苏醒前已被移除。两组均出现阴道发情，但模式不同。与未交配的雌性相比，交配使阴道发情期缩短至3天，而未交配雌性的发情期为8天。发情期细胞角质化程度（细胞数量）和动情后期的细胞成分（百分比分布）在两组之间没有差异。与对照区域的雌性相比，无雄性区域的雌性在发情期和动情后期的雌激素水平显著更高。欧洲地松鼠被发现为单发情动物，因为在检测到动情间期或动情后期后，没有未交配的雌性再次进入发情期。未交配雌性阴道发情期的延长可被视为一种生理必然性或对低配偶可得性的一种适应。与其他松鼠科物种相比，这种延长仍然相对较短，可能是产生严格繁殖时间框架的限制因素的产物。
