Communication among hamsters by high-frequency acoustic signals: I. Physical characteristics of hamster calls.

In Exp I, 2 random-bred (Lak:LVG) female hamsters emitted high-frequency sounds at average intensities of 53 db (SPL). These calls tended to be 80–200 msec long and to emphasize frequencies of 34–42 kHz. However, female "ultrasounds" typically included rapid fluctuations in frequency and amplitude. In Exp II, male hamsters also emitted high-frequency vocalizations, with dominant frequencies of 32–38 kHz and average durations of 70–250 msec. Although male cells generally included fewer rapid changes in amplitude and frequency than did female calls, male call structures depended on contextual factors. Calls produced by males in the presence of estrous females tended to have lower minimum frequencies, higher maximum frequencies, longer durations, and fewer rapid frequency changes than calls by solitary males. These results show that both sex differences and situational factors influence the structures of hamster ultrasounds. The frequency and amplitude changes typical of calls by females and solitary males should facilitate the localization of a calling individual over moderate distances. Calls by males in the presence of females should be more difficult to localize and might operate over shorter distances to serve a different social function. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Odor preferences of female house mice (Mus domesticus) in seminatural enclosures.

Preferences for male odors by female house mice (Mus domesticus) were examined with respect to age, dominance status, and spatial relationships. Mice were free living in 6 field enclosures. Estrous or nonestrous females were placed in an aquarium with soiled bedding from live traps as the odor source. Females were tested for preferences between (1) adult and juvenile male odors, (2) dominant and subordinate male odors, and (3) "near" and "far" male odors. In dominance odor tests, estrous females preferred odors from dominant males; nonestrous females exhibited no significant preferences. In adult juvenile and spatial odor tests, there were no significant differences between odor preferences of estrous and nonestrous females. However, most females preferred odors from adult and "near" males. Male dominance status appears to be the strongest influence on female odor preference in these seminatural enclosures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Communication among hamsters by high-frequency acoustic signals: III. Response evoked by natural and synthetic ultrasounds.

Male and female golden hamsters showed clear behavioral responses to playback of recorded ultrasounds. In particular, it was found that (a) estrous females increased their rates of ultrasound production upon exposure to recorded ultrasounds (Exp I); (b) hamsters of both sexes, exposed to natural or artificial high-frequency calls in a Y-maze, were able to localize the ultrasound source and were attracted to it (Exp II); and (c) estrous females performing lordosis after brief male–female contact maintained that posture significantly longer in the presence of recorded ultrasounds than in silence (Exp III). On the basis of these findings and the results of other studies of hamster social behaviors, the functional significance of hamster ultrasounds is discussed in relation to other elements of a hormone-dependent communication chain regulating hamster reproduction. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responses of male hamsters to odors of females in different reproductive states.

Six experiments investigated the responses of male hamsters to the odors of estrous, diestrous, pregnant, and lactating hamsters. Scent-marking by males in the soiled cages of females was less frequent when the females were estrous (Day 1 of the cycle) than when females were on Days 2, 3, or 4. Sexually experienced males preferred the odors of bedding material from the cages of estrous Ss over odors of bedding of diestrous Ss. Both of these effects were eliminated by surgically removing the vagina and thereby eliminating vaginal secretions. The quantity of vaginal secretions deposited in the vicinity of the nest may be responsible for the observed effects. In contrast, neither males with sexual experience nor males with both sexual and nonsexual experience with females demonstrated preferences for the odors of the estrous or diestrous Ss themselves. Males were, however, more attracted to the odors emanating directly from estrous Ss than to the odors of pregnant or lactating Ss. For hamsters the important sexual message may be not "estrous" vs "diestrous" but rather may be "will soon be estrous" (i.e., cycling) vs "not soon estrous" (i.e., pregnant, lactating, or acyclic). (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of gonadal hormones and sexual behavior on ultrasonic vocalization in rats: I. Treatment of females.

Ultrasonic vocalizations were measured when male Long-Evans rats were placed with ovariectomized females that had experienced various hormonal and behavioral treatment. In Exp I, 18 males were tested with females in each of the following conditions: nonestrous (OVX), estrogen treated (E), estrogen and progesterone treated (EP), and estrogen and progesterone treated and given 2 intromissions from a stud male prior to testing (EPI). Control conditions included clean cage (CL) and cage soiled by an estrous female (SOI). The treatments differed in effect on rate and maintenance of vocalization, in the order of greatest to least: EP, E, EPI, and OVX (equal), SOI, and CL. In tests in which males produced a high rate of vocalization, some males with short intromission latencies shifted from the normal 50-kHz pulse to a 22-kHz pulse. In Exp II, the effect of the female's vocalization and movement on the rate of and latency to vocalization was measured. 21 males were presented with each of the following stimulus conditions: estrous female with red light (EP), estrous female without red light (EP dark), estrous anesthetized female (EP anes), and nonestrous anesthetized female (OVX anes). Effects on vocalization of various treatments were in descending order: EP and EP-dark (equal), EP anes, and OVX anes. Data suggest that the 50-kHz vocalizations constitute a graded response influenced by the female's hormonal and sexual condition. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial amygdala involvement in discrimination of same-species and closely-related-species male stimuli in estrous female Mesocricetus hamsters.

Efficient discrimination between individuals of closely related species is important to maximize reproductive potential. Some studies using males as subjects have indicated that the medial amygdala (MeA) is involved in discrimination between odors of conspecific females and females from distantly related species. The authors investigated the involvement of the MeA in discrimination by females between odors of conspecific males and odors of males of a closely related species. The authors exposed estrous or diestrous female hamsters (Mesocricetus auratus) to saline, conspecific male odors, or heterospecific (M. brandti) male odors and quantified the expression of c-fos–related antigens in the anterior and posterior MeA. They found that estrous (but not diestrous) females investigated conspecific male odors longer than heterospecific male odors. Neural activity in both the anterior and the posterior MeA was higher in estrous than in diestrous females. In the anterior MeA, there were no significant differences in response to odors of conspecific and heterospecific males. In the posterior MeA, however, neural activity was higher when estrous females were exposed to conspecific odors than when they were exposed to heterospecific odors. No such difference was observed in diestrous females. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of vaginal secretion in hamster sexual behavior: Males' responses to normal and vaginectomized females and their odors.

Two experiments (with 60 adult male hamsters and 4 sexually naive male hamsters) examined the importance of vaginal secretion relative to other feminine odors for attraction of males and elicitation of copulatory behavior by comparing the behavior of males toward normal females with that toward vaginectomized Ss. Males were more attracted to intact females than to vaginectomized Ss when odors were the only cues available and also when auditory, visual, and odor cues were available but contact was prevented. There were no differences in the attractiveness of estrous and diestrous Ss whether intact or vaginectomized. When males and females were allowed to interact, there were no differences in any measures of male sexual behavior toward normal vs vaginectomized females, which indicates that the presence of vaginal secretion is not necessary for male sexual behavior. The significance for conceptions of pheromone action in mammals is discussed. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ultrasonic vocalizing by adult female mice (Mus musculus).

Conducted 5 experiments, using 1,029 female and 805 male mice, to examine adult female mouse ultrasound emission. Results indicate female ultrasonic vocalizing to be (a) typically displayed among female mouse dyads and (b) comparable to the ultrasonic vocalizing levels obtained among male–female pairs. Genotypically based variations in the production of ultrasounds by females were also noted. Like males, socially naive females readily ultrasonically vocalized to anesthetized female conspecifics and rarely vocalized to anesthetized males. Unlike males, socially experienced females emitted few ultrasounds to either female urine or female-soiled cage shavings. Although social experience increased the ultrasound emission of males to female sex cues, the production of ultrasounds by females to these cues was decreased by social experience. Implications with regard to the existence of a behavioral/functional sexual dimorphism in adult mouse ultrasonic vocalizing are discussed. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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

Five experiments were conducted with 196 collared and 243 brown male lemmings. When tested in a Y-maze olfactometer, sexually experienced and naive Ss of both species 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, findings suggest that 2 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. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ultrasonic vocalizations and male's urine on female rat readiness to mate.

Solitary estrous female Long-Evans rats were presented with ultrasonic vocalizations and/or urine of males to determine their effects on the females' subsequent copulatory behavior. Following exposure to ultrasounds, females exhibited a shorter latency to dart and a higher rate of darting when a male was presented. The vocalization effect was enhanced when male urine was present, but urine alone had no effect. The rate of copulation was also increased by the vocalization priming of the female. For a few individual females, ultrasounds elicited darting in the absence of a male. Results indicate that auditory cues, particularly in association with appropriate olfactory cues, prime estrous females for proceptive behavior. This increases both the likelihood and the rate of sexual performance and, therefore, the probability of successful mating. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intraspecific sexual preferences of female hamsters.

Studied the sexual preference behavior of 32 estrous females of 3 species of hamsters of the genus Mesocricetus by introducing individual females into an arena with a pair of males from 2 different species. When 1 male of the pair was a conspecific, females of all 3 species spent significantly more time investigating the conspecific male. When neither male was a conspecific, female Turkish hamsters (M. brandti) strongly preferred male Romanian hamsters (M. neutoni) to male Syrian hamsters (M. auratus), and female Romanian hamsters preferred male Turkish hamsters to male Syrian hamsters. Female Turkish hamsters displayed significantly more presentation behavior than did Romanian females, and Syrian females rarely presented. Female Turkish hamsters also displayed a stronger degree of preference behavior to a conspecific male than did females of either of the other species. The relatively stronger sexual preferences and greater amount of presentation displayed by Turkish hamsters may relate to the greater opportunity for sympatry with closely related forms and the polymorphic state of this species in the wild. The similarity of Turkish and Romanian hamsters on several characteristics may explain the preference of these species for each other when the alternative was a Syrian hamster. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alterations of male sexual behavior by learned aversions to hamster vaginal secretion.

32 male hamsters poisoned after their 1st adult exposure to the vaginal secretion of female hamsters became hesitant to approach and ingest the secretion. The same aversion-training procedure also altered the responses of males to estrous females, changing the latency, frequency, and duration of a variety of behaviors that are commonly taken as indexes of sexual attraction or arousal and of copulatory performance. Results suggest that the aversions to vaginal secretion alter the perceived meaning of the secretion for male hamsters, and analysis of the correlations between various measures of sexual arousal and performance support the hypothesis that separate mechanisms underlie the effects of the secretion on appetitive and consummatory sexual behavior. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Histochemical localization of adenylate cyclase in cultured sympathetic neurons

The influence of female odors on agonistic behavior among grouped male prairie voles (Microtus ochrogaster) was studied. After the introduction of female odors, investigative behavioral interactions between the males increased in frequency. The source of the odor, the sexual experience of the males, and the ongoing behavior of the group influenced the intensity of the behavioral response. Sexually experienced males showed the greatest number of agonistic instances and attempted sexual interactions after the introduction of urine from estrous females. Agonistic interactions did not decrease upon the introduction of female odors, as has been reported for Mus musculus. It is concluded that these behavioral changes are not due to a response to a releaser pheromone, but are the result of confusion in communication between males.     

Odor preference and urine-marking scales in male and female rats: Effects of gonadectomy and sexual experience on responses to conspecific odors.

Investigation and urine-marking responses of 112 male and female Long-Evans rats toward conspecific urine odors were recorded in pair-wise comparison tests. Each of 16 S groups was given 15 preference tests, 1 for each of the possible pairs of 5 urine odors and a no-odor control (N). The urine sources were own group (G), intact male (M), castrated male (Mc), ovariectomized female (Fo), and estrous females (F). Results were scaled by using a technique based on L. L. Thurstone's (1927) law of comparative judgment. Intact males with sexual experience ordered their odor preferences N?     

Lesions centered on the medial amygdala impair scent-marking and sex-odor recognition but spare discrimination of individual odors in female golden hamsters.

The medial amygdala (Me) has been implicated in various social behaviors that depend on chemosensory cues, but its precise role in discriminating and learning social odors is not known. Female golden hamsters (Mesocricetus auratus) received electrolytic lesions of the Me or sham surgery and were tested for their ability to (a) discriminate between odors of individual males in a habituation–discrimination task, (b) show preferences for male over female odors in a Y maze, and (c) scent-mark in response to male and female odors. All females discriminated between scents of individual males. In contrast, Me lesions eliminated female preferences for male odors in a Y maze. Females with Me lesions also showed a substantial reduction in vaginal marking and virtually no flank marking in response to odors. Thus, the Me in female hamsters is critical for differential investigation of opposite-sex odors and for scent-marking behavior but is not involved in discrimination between odors of individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Male-produced ultrasonic vocalizations and mating patterns in female rats.

Investigated the influence of male-produced 50-kHz vocalizations on mating behavior and choice of partner in estrous female rats. In Exp I, 17 estrous female Long-Evans rats were given a mating-choice test; 2 tethered males, one of which was devocalized, were used as incentives. Darting was directed toward the vocalizing male more frequently than toward the muted test partner, but ultrasonic vocalizations had no influence on visit rate or the amount of time that the females spent with each male. When 2 intact or 2 muted males were used as stimulus objects, the females' solicitation behavior was more evenly distributed between the 2 males. In Exp II, 16 estrous females were given a mating-choice test between 2 muted males; tape-recorded 50-kHz vocalizations or tape hiss was transmitted from a speaker located behind one of the males. Females spent equal amounts of time with the tethered males in both the vocalization and tape-hiss conditions; however, females directed more darting toward the males that were tethered in front of the speaker transmitting the ultrasonic vocalizations than toward the other muted tethered males. Findings demonstrate that the principal function of the male-produced ultrasounds is to facilitate and orient the solicitation behavior of the estrous female during mating. The vocalizations have little demonstrable effect in attracting the female to the immediate physical proximity of the male. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The paternally expressed gene Peg3 regulates sexual experience-dependent preferences for estrous odors.

Sexual experience has marked and long-lasting effects on male behavior in mammals, regulating traits such as the anticipation and display of sexual behavior, aggression, and olfaction. The authors conducted urine preference, habituation-dishabituation, and partner choice tests with sexually experienced and naive male mice and found that wild-type males acquire adaptively significant preferences for the odors of receptive, estrous females with sexual experience, and that these preferences are matched by changes in main olfactory system responses involving the piriform cortex, as indicated by c-Fos expression. The authors also report that these experiential effects are disrupted in male mice carrying a knockout of the imprinted gene Peg3. This paternally expressed gene regulates maternal care and offspring development, but the authors here report that Peg3 mutant males suffer a complex olfactory deficit that affects estrous odor preferences and the responses of the main olfactory system to such odors. Peg3 appears to have evolved to regulate the experience-dependent preference for receptive females, an adaptive trait that would enhance male reproductive success and so potentially increase paternal transmission of this paternally expressed gene. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determinants of mating success in the golden hamster (Mesocricetus auratus): III. Female acceptance of multiple mating partners.

Four studies with golden hamsters investigated females' acceptance of multiple mating partners. Findings show that females that mated only with a single, recently mated male ran a high risk of pseudopregnancy or reduced litter size. Females paired with males that had mated to satiety 30 min, 8 hrs, or 24 hrs earlier showed a reduced willingness to engage in lordosis than did females paired with a sexually rested (2 wks) male. Females paired with recently mated males were also more likely to mate with additional (fresh) males than were females exposed to rested males. Females presented with 2 anesthetized stimulus males readily discriminated between sexually rested and recently mated individuals. Neither prior sexual experience nor recent copulatory activity was required for this discrimination. It is suggested that multiple-male mating (promiscuity) in female hamsters may be an adaptation against an infertile mating as a consequence of mating with a single, recently mated, sperm-depleted male. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of vomeronasal organ removal from male mice on their preference for and neural Fos responses to female urinary odors.

Four experiments were conducted to determine whether vomeronasal organ (VNO) inputs in male mice mediate the rewarding properties of estrous female urinary odors. Sexually naive male mice with either an intact (VNOi) or lesioned (VNOx) VNO preferred to investigate female urine over water in Y-maze tests. Subsequently, VNOi males ran significantly more quickly and remained in nasal contact longer with estrous female urine than with male urine, whereas VNOx males investigated these odors equally. In home-cage habituation-dishabituation tests, VNOi males also investigated female urine significantly longer than did VNOx males, although both groups investigated female urine longer than other non-body odors. Finally, female urinary odors induced Fos in the nucleus accumbens core of VNOi males but not of VNOx males. Our results suggest that female urinary odors retain some incentive value in VNOx males. However, once direct nasal contact is made with female urine, VNO inputs further activate forebrain mechanisms that amplify the reward salience of this stimulus for the male mouse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aggressive behavior in female hamsters: The hormonal basis for fluctuations in female aggressiveness correlated with estrous state.

The frequency and sequencing of aggressive behaviors by naive female hamsters has been found to change during series of brief encounters, probably because of the lack of stable dominance relations. Such initial encounters seem most representative of interactions likely in free-ranging hamsters and have been emphasized in studies of the hormonal mediation of female aggression. The present 4 experiments, conducted with a total of 72 random-bred female hamsters, found that nonestrous females exhibited intense aggression toward conspecifics of either sex. Estrous females were not aggressive and spent much time in lordosis, indicative of sexual receptivity. While oil-injected adrenalectomized-ovariectomized females fought at high levels, comparable with intact nonestrous females, the combination of 17-β-estradiol benzoate and progesterone suppressed fighting completely. In contrast, replacement of estradiol, progesterone, or testosterone propionate individually had no consistent effect. Hypophysectomized females also fought at high levels, indicating that pituitary hormones are not required for vigorous aggression. Further, individual anterior pituitary hormones did not produce marked changes in fighting. Results emphasize the roles of estrogen and progesterone in synchronizing aggression with current reproductive state. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)