Effect of the interintromission interval on lordotic response and attack latency in golden hamsters (Mesocricetus auratus)

After 12-15 ejaculatory series, each consisting of several short intromissions (2- to 3-s vaginal penetration) and an ejaculation, male golden hamsters adopt an altered copulatory pattern consisting of long intromissions (5- to 25-s penetration with intravaginal thrusting). Receptivity declines and the tendency for the female to attack the male increases at about the time of this shift in copulatory pattern. Because the mean interintromission interval (III) between short intromissions is about 8 s compared to 100 s between long intromissions, it is possible that females detect this difference and adjust their mating accordingly. When the III between short intromissions from a rested male was experimentally increased to 100 s by use of a halter and lead device, the duration of lordosis was significantly less than that displayed by females paired with control males (8-s III) and virtually the same as that displayed by females paired with males that produced only long intromissions. This suggests that the female uses the temporal patterning of intravaginal stimulation as one criterion for terminating mating with a particular male.     

Research Report: Correlates of learning styles and counsellor trainees' age and gender

Counselling relationships are important indices of therapeutic efficacy. In the Fall 2001, 71 counsellor trainees in a Counsellor Education programme at a Mid-western university participated in the current investigation. The purpose of the study was to examine relationships of learning styles in terms of counsellor trainees' age and gender (using a recently developed Preferred Learning Style Inventory, namely KPLSI). Results of the present study suggest that counsellor trainees' learning styles are varied, except that there are statistically strong groupings in analytic, global and particularistic learning styles domains among this particular body of students. Additionally, the age of trainees tend to relate to superficial and sensational learning styles, whereas gender is, participatory.     

Differential effects of environmental enrichment on the open-field behavior of wild and domestic Norway rats.

Early postweaning experience in an enriched environment had a greater influence on the open-field behavior and body weight of wild Norway rats than of their domestic counterparts. Genetic changes accompanying the domestication process may have reduced the relative impact of postweaning experience on the development of the domestic rat's response to changes in its environment.     

Mating-induced inhibition of receptivity in the female golden hamster. I. Short-term and long-term effects

Female golden hamsters (Mesocricetus auratus) which have actively terminated mating with one male will respond in succession to two or more novel males. However, mating with the first male results in a reduction in receptivity shown toward a second male, with the size of the decrease being proportional to the amount of copulatory stimuli provided by the first male. Furthermore, the decreased receptivity shown toward the second male results in his achieving fewer ejaculations. These effects are more pronounced when the second mating occurs 5 min or 8 h after the first mating than when it occurs 1 or 4 h later, suggesting both short-term and long-term inhibitory effects. Copulation with a single male also effects a 40% shortening of behavioral receptivity. In a promiscuous species such as the hamster, prolonged copulation by the male may enhance the short-term inhibition of female receptivity, thereby reducing the risk of subsequent sperm displacement. The long-term effect occurs too late to affect sperm competition and may, instead, function to reduce the risk of predation as a result of unnecessary further mating.     

Social olfaction in male brown lemmings (Lemmus sibiricus = trimucronatus) and collared lemmings (Dicrostonyx groenlandicus): I. Discrimination of species, sex, and estrous condition

When tested in a Y-maze olfactometer, sexually experienced and sexually naive brown and collared lemmings (Lemmus sibiricus = trimucronatus and Dicrostonyx groenlandicus) preferred the odor of conspecific females to the odor of females of another species. Both experienced and naive males also preferred the odor of conspecific females to that of conspecific males. Only sexually experienced males showed a significant preference for estrous over nonestrous conspecific females. Sexually experienced males also discriminated between estrous and nonestrous heterospecific females of a familiar (lemming) and unfamiliar (meadow vole, Microtus pennsylvanicus) species. In conjunction with the results of earlier studies of the development of species-specific olfactory preferences, these findings suggest that two olfactory cues mediate a male's attraction to receptive females: a species-specific odor that is learned during early development and a sexual attractant whose saliency is established as a result of adult experience with a receptive female.     

Social olfaction in male brown lemmings (Lemmus sibiricus = trimucronatus) and collared lemmings (Dicrostonyx groenlandicus): II. Discrimination of mated and unmated females

When tested in a Y-maze olfactometer, male brown and collared lemmings (Lemmus sibiricus = trimucronatus and Dicrostonyx groenlandicus) preferred the odor of unmated receptive females to the odor of females with which they had just copulated. Similarly, sexually satiated males preferred the odor of an unmated receptive female to that of a strange female that had recently copulated with another male. Sexually experienced males without recent copulatory experience also demonstrated this preference, but sexually naive males did not. Sexually satiated collared lemmings preferred the odor of bedding from a novel estrous female to bedding from the female with which they had just copulated even when the bedding was collected before mating occurred. These results suggest that discrimination between prior mates and unmated females may be based on individual recognition as well as recognition of subclasses of females (i.e., mated vs. unmated, familiar vs. unfamiliar).     

Offspring sex ratio in hamsters is correlated with vaginal pH at certain times of mating

Golden hamsters (Mesocricetus auratus) are sexually receptive for 19-21 h around the time of ovulation. Vaginal pH was measured immediately before mating in four groups of animals each mated at a different time during the female's receptive period. Litter size and sex ratio (percentage male offspring) were recorded at parturition. Mean litter size decreased while offspring sex ratio increased in matings occurring later in estrus. Significant negative correlations were found between vaginal pH and sex ratio of subsequent litters when matings occurred during midestrus. Fluctuations in vaginal pH may differentially affect longevity, motility, or fertilizing capacity of X and Y sperm and/or may reflect other physiological changes in the female which occur over the receptive period. Such a prefertilization mechanism for sex ratio regulation could be highly adaptive since little or no parental reproductive potential is lost.     

Programmatic prevention of adolescent problem behaviors: The role of autonomy,relatedness, and volunteer service in the teen outreach program

Explored the mechanisms by which a well-validated intervention to prevent school failure, suspension, and teenage pregnancy produces its effects, using site-level data from 66 sites involving over 1,000 students participating in national replication of the Teen Outreach Program. Multiple informants provided data on operating characteristics of each site. These were then used to explain differences across sites in levels of success in reducing youth problem behaviors using a pre-post design and a well-matched comparison group. In accord with predictions from developmental theory, middle school sites that promoted student autonomy and relatedness with peers and with site facilitators achieved significantly greater levels of success in reducing problem behaviors. Offering volunteer experiences perceived as teaching middle school students new skills and leaving them real choices about the type of work they did was also linked to program success. Although the program was equally sucessful with students from a wide range of sociodemographic backgrounds, links of program factors to site-level outcomes were found only for middle school but not high school sites. Implications of these findings for the development of programmatic interventions targeted at adolescents are discussed. The Teen Outreach program and its evaluation have been supported by grants from the Charles Stewart Mott Foundation, the Lila Wallace Reader's Digest Fund and other sources. We also thank the Association of Junior Leagues International, local Junior Leagues around the country, and the students and facilitators who made this program possible. The Spencer and W. T. Grant Foundations also provided support to the first author for the write-up of this study.