Copulation in Golden Hamsters: Behavior of Intact Versus Ovariectomized Females Given Hormonal Replacement

Abstract

Abstract Behavior of Syrian golden hamsters (Mesocricetus auratus) during sexual satiety tests was examined across estrous cycle days in intact females and as a function of hormonal replacement in ovariectomized (OVEX) females. The purpose of this investigation was to evaluate differences between artificially induced and naturally occurring estrous behavior and to determine whether such differences affected the behavior of the male partner. The results of this study indicated that: 1. The hormonal replacement regime given to OVEX females primarily affected the induction of, but not the amount of time spent in, receptive behavior. a. When given only estradiol benzoate (EB) very few females exhibited frozen lordosis, and when such behavior did occur, the latency was quite long and little time was spent in this posture. b. Following administration of EB and progesterone (P), the number of females that became receptive increased with increasing dosages of EB. For females that showed frozen lordosis, the latency was short and a considerable portion of the test was spent in this posture. 2. Achievement of ejaculations by the male partner did not imply that the female was receptive. Males ejaculated on several tests with females that were not considered receptive because lordosis was either absent or occurred intermittently; lordosis typically was no maintained during the male's intercopulatory intervals, and female attempts to reject or abort mounts by the male were frequent. 3. The hormonal replacement regime given to OVEX females did not mimic naturally occurring events. The behavior of OVEX females differed significantly from that of intact females: a. Receptive behavior of natural estrous females differed from that of induced estrous females in that the former showed facilitated initiation and maintenance of frozen lordosis. b. Toward the end of the tests, natural estrous females were more likely than induced estrous females to approach and attack the male. Such behavior has been proposed to promote reinitiation of copulation by males (BUNNELL et al. , 1977), but it remains to be demonstrated empirically that such approaches or attacks facilitate the continuation of copulation. c. Although fights occasionally occurred with induced estrous females, natural estrous females never engaged in fighting. d. Nonestrous intact females showed a higher frequency of defensive-rolls, vaginal scent marking, and attacks than nonreceptive OVEX females. 4. The type of female with which the male was tested affected his performance. Males initiated copulation more quickly and achieved more ejaculations with natural estrous than induced estrous females. 5. A particular response pattern, defensive-rolls, was identified that may represent rejection behavior: a. This pattern was characteristic of nonreceptive females, and was rarely observed in receptive females. b. The frequency of this response was elevated during tests in which males achieved ejaculations with nonreceptive females.