Sensory cues that elicit ultrasonic vocalizations in female rats (Rattus norvegicus)

Female rats emit ultrasonic vocalizations during copulation. Female vocalizations are associated with darting and other proceptive behavior. In addition, females frequently call while approaching the male. A series of experiments was undertaken to determine whether female rats emit ultrasonic vocalizations in response to other rats or to their odors. Females were exposed either to bedding soiled by males or females or to devocalized conspecifics separated from the subject by a barrier. Females vocalized more to male cues than to female cues, regardless of whether the odor cues were from soiled bedding or from a devocalized conspecific. In addition, subjects vocalized more when presented with a devocalized female rather than a neutral stimulus. Furthermore, devocalized adult males, separated by a barrier, were more effective than either devocalized castrated or juvenile males in eliciting vocalizations; in turn, castrates and juveniles were more effective than neutral stimuli. Female calling was likely induced by odors from the male. In one experiment, the female subject was positioned in such a way that she could neither see or touch the stimulus male. Presentation of tape-recorded male vocalizations did not affect calling by the female. Vocalizations emitted by females in response to male odors may attract males or may facilitate subsequent copulatory behavior by the male.     

Ultrasonic vocalizing by adult female mice (Mus musculus)

Though an extensive body of literature exists concerning the emission of 70-kHz ultrasonic vocalizations by adult male mice (Mus musculus), almost nothing is known about the ultrasonic vocalizing of adult females. A series of five experiments was conducted to examine adult female mouse ultrasound emission. Results indicated female ultrasonic vocalizing to be typically displayed among female mouse dyads and 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 male mice, 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 served to increase the ultrasound emission of male mice 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.     

Effects of male pre-ejaculatory vocalizations on female receptive behavior in the rat (Rattus norvegicus)

Both male and female rats (Rattus norvegicus) emit ultrasounds during copulation. Bursts of ultrasounds from males that occur as ejaculation approaches are lower in frequency, longer in duration, and louder than those that appear earlier in the ejaculatory series. We attempted to determine if these pre-ejaculatory calls affect female sexual behavior. The behavior of females paired with devocalized males was compared with that of females paired with intact males, and in a second experiment tape-recorded vocalizations were played to females paired with devocalized males. Females were less receptive when paired with devocalized males; they were less likely to remain stationary when males attempted to mount. Playback of both types of calls restored female immobility toward control levels, although pre-ejaculatory calls were more effective than mating ones. Pre-ejaculatory calls restored running and training levels somewhat toward control level but to a lesser extent than female immobility.     

Analysis of ultrasonic vocalizations emitted by intruders during aggressive encounters among rats (Rattus norvegicus)

This investigation was concerned with the identification of the ultrasonic vocalizations produced by intruders during aggressive interactions and the role of these signals in agonistic behavior of rats. In the first experiment, experienced resident males were paired with both devocalized and intact vocalizing naive intruder males. Devocalization of the intruder males resulted in a drastic decrease in 50-kHz vocalizations and the elimination of all 22-kHz vocalizations. This almost total absence of ultrasonic vocalizations was not accompanied by any change in resident aggressive behavior or intruder defensive and submissive behavior. In a second experiment, naive intruders were tested with either deafened or intact resident males. Similarly, preventing residents from hearing intruder ultrasounds had no detectable effect on any aggressive behavior. These experiments are not consistent with the correlative evidence that intruder-produced 22-kHz vocalizations inhibit the aggressive behavior of the resident. The results also show that most of the ultrasonic vocalizations emitted during aggressive encounters are probably produced by the intruder.     

70-kHz vocalizations by male mice do not inhibit aggression in lactating mice

Two experiments investigated the relationship between adult male 70-kHz vocalizations and aggression by lactating female mice (Mus domesticus). Intact, vocalizing males, surgically devocalized males, and naturally nonvocalizing males were used to assess the effects of high frequency vocalizations on maternal aggression. The emission of high frequency vocalizations promoted aggressive behavior by the females. In both experiments, lactating females attacked the vocalizing males more rapidly and showed a higher incidence of aggressive behaviors toward these males than they did to the nonvocalizing male. We suggest that these vocalizations are only one of many situational cues that the female uses to determine her final behavioral response.     

Sexual dimorphism in ultrasonic vocalizations of mice (Mus musculus): gonadal hormone regulation

Male mice (Mus musculus), during courtship and sexual behavior, vocalize substantially more 70-kHz ultrasounds than do females. Four experiments demonstrated that testosterone propionate (TP) substantially increased ultrasonic emissions and mounting by ovariectomized females and the long-term gonadectomized males and females increased their amount of ultrasound production in response to TP to approximately the same levels. From these results it is suggested that the sexual dimorphism normally seen in ultrasonic vocalizations can be accounted for by the activational effects of androgen in adulthood.     

Mate recognition by urine odors in the Mongolian gerbil (Meriones unguiculatus)

We examined the responses of male and female gerbils housed in opposite- or same-sex pairs to the urine odors from their cage-mate and those of an unfamiliar gerbil of the same sex. Gerbils housed in mated pairs spent more time investigating the odor of their partner. They also emitted more modulated ultrasonic vocalizations in the presence of their partner's odor than in the presence of the unfamiliar odor. Gerbils housed in same-sex pairs did not respond differentially to the odor of their cage-mate. There were sex differences in the frequency of ventral scent-marking and modulated vocalizations, with males showing more of these behaviors than females. The urine odor of the gerbil's mate can thus be discriminated from those of other gerbils. Recognition of individual odors may promote affiliative behavior and reduce aggression, thus playing an important role in pair maintenance in gerbils.     

An ephemeral sex pheromone in the urine of female house mice (Mus domesticus).

From previous research, the ultrasonic vocalizations of male mice (Mus domesticus) to female mouse urine were hypothesized to be learned as a result of classical conditioning during adult heterosexual encounters. According to this interpretation, a previously neutral conditioned stimulus in female urine comes to elicit vocalizations as a result of its association with some other unknown unconditioned stimulus associated with adult females. However, the research from which this hypothesis was derived utilized urine collected from females housed in metabolic cages. Three experiments further examined the classical conditioning hypothesis using two types of female urine: (i) metabolic-cage-collected urine and (ii) freshly voided urine. Experiment 1 demonstrated that, in contrast to vocalizations to metabolic-cage-collected urine, adult heterosexual experience was not necessary for males to vocalize to freshly voided female urine. In addition, unlike metabolic-cage-collected urine (Experiment 3), freshly voided urine remained a potent stimulus for eliciting vocalizations during repeated testing (Experiments 2 and 3). Finally, freshly voided urine appeared to cause a previously neutral stimulus (cotton swab) to acquire ultrasound eliciting properties (Experiment 2). We suggest from these findings that two chemosignals that elicit vocalizations from males may exist in female mouse urine: (i) a potent, but volatile or easily degraded, unconditioned stimulus to which males vocalize without sexual experience and (ii) a nonvolatile, chemically stable conditioned stimulus.     

Sex differences in adolescent suicides in Norway, 1990-1992

All suicides in persons under 20 years in Norway in the time period 1990-1992 (99 males, 30 females) were included in a postmortem case-control study with seven controls for each suicide, focusing on gender differences. Few sex differences between the suicide completers were evident, in spite of the difference in suicide rates (M/F rate ratio = 3.0). Females more often attempted suicide (p = .05), more often wrote farewell notes (p = .03), and used less violent suicide methods (ns). The adjusted risk for suicide related to affective disorders (Female OR = 22,1; Male OR = 24.0, both p = .000) and disruptive disorders (female OR = 14,7, ns; male OR = 5.0, p = .002) differed little, as did the effect of frequent use of alcohol or substances (female OR = 0.4, ns; male OR = 0.4, ns).     

Developmental expression of defensive responses during exposure to conspecific adults in preweanling rats (Rattus norvegicus).

I examined preweanling rats' (Rattus norvegicus) expression of ultrasounds and secretion of ACTH when exposed to unfamiliar adult male rats or to their mothers. Pups at 7 days of age produced similar levels of ultrasonic vocalization near both unfamiliar males and mothers. However, these pups could discriminate familiar from unfamiliar adults because ACTH was significantly higher in pups near adult males than in those near mothers. At 14 days of age, pups avoided adult males but not their mothers; therefore, adult males represented a significant threat. Importantly, 14-day-old rats significantly reduced ultrasound production only when near adult males. Pups at 21 days of age no longer emitted ultrasounds when socially isolated or when near conspecific adults. In addition, 14- and 21-day-old rats produced similar elevated ACTH levels across stimulus conditions. Results show significant changes in preweanling rats' responses to conspecific adults.     

Sex differences in aggressive behavior in a marsupial,the gray short-tailed opossum (Monodelphis domestica)

In male and female gray short-tailed opossums (Monodelphis domestica), same-sex interactions were characterized by high levels of threat behavior (open-mouth postures and screeching vocalizations). Actual fighting behavior (biting, locking, and tumbling) was seen almost exclusively in male-male interactions. In male-female interactions, females showed high levels of threat behavior and males showed little aggressive behavior of any kind. Clicking vocalizations, submissive behavior in marsupials, were displayed almost exclusively by males. These findings are discussed with respect to the uses of auditory and olfactory communication in marsupials.     

Role of the ultrasonic vocalization of the female rat (Rattus norvegicus) in sexual behavior

Both male and female rats vocalize ultrasonically during mating. Whereas male calls are known to facilitate female proceptive behavior, the female mating call has not been studied beyond spectrographic analysis. In this article, a series of experiments were done to examine the effects of the female's mating call on rat mating behavior. In the first experiment, females copulated with intact males before and after surgical devocalization. In the second experiment, intact females copulated twice with a male: once when they were able to hear and once when they were temporarily deafened with a medical ear mold. In the third experiment, tape recorded ultrasounds were placed in the presence of devocalized females while they were copulating with intact males. In the control condition, tape hiss was presented. In each experiment, it was observed that the female darted more if communication were disrupted (i.e., female devocalized or male deafened). Playback partially reduced darting to control levels. No other behavior was affected consistently across all experiments. Female calls might facilitate self-regulation of mating behavior, or they might focus the male's attention on her proceptive behaviors. It is also possible that the female calls could alter the stimulus properties of the male's behavior, indirectly affecting her own behavior.     

An analysis of some sensitizing agents in the pathogenesis of stress-induced gastric erosive disease

Prior surgical implantation of a venous catheter sensitized rats to coldimmobilization stress. Three of six catheterized females succumbed during the stress. The remaining rats fell into two groups in terms of their core temperature at the end of the stress period: Male uncatheterized rats had higher temperatures than rats in the other three groups. No relation was found between catheter patency and magnitude of hypothermia. Degree of gastric disease paralleled the core temperature findings in that the male uncatheterized rats had significantly fewer gastric erosions than the rats in the other three groups. Additionally, a robust effect of gender was found with uncatheterized females showing more hypothermia and more gastric disease than uncatheterized males. A subsequent experiment was conducted to evaluate whether anesthesia or wearing the protective spring was responsible in part for the sensitization seen. Here, the gender difference was less although females consistently averaged lower core temperatures after stress than did males. Despite similar core temperatures after stress, females that were prepared with the protective spring apparatus developed more gastric disease than female controls or similarly treated males. Thus, the additional sensitization exhibited by females in the first experiment may relate to the fact that both catheterization and the taping procedure were sensitizers while only catheterization was a sensitizer for males.     

A comparison of adult women's and men's ascriptions of negative traits to the same and opposite sex

College students (N=135), ranging from 19 to 55 years of age, were studied to determine their sex stereotypes. Results from the present study indicated that adult males were significantly more negative than adult females in their evaluations of both sexes. One possible explanation that may be offered to account for these findings is that current emphasis of female rights may be causing negativistic reactions on the part of males toward both sex groups.     

Interference risk and the function of dynamic shifts in calling in the gray treefrog (Hyla versicolor)

Male gray treefrogs call to attract females under challenging acoustic conditions. At higher chorus densities, there is considerable background noise and a good chance that a male's calls will often be overlapped by calls of other individuals. Call overlap may reduce the probability of mating because females prefer calls with internal pulse structure that is not obscured. With increases in acoustic stimulation, males lengthen call duration while simultaneously reducing call rate such that "pulse effort" changes little. In our study, we tested the "interference risk hypothesis." This proposes that males change call duration so that, on average, there will be a sufficient number of pulses and interpulse intervals clear of acoustic interference per call to attract a female. However, female choice experiments employing call alternatives of different durations, rates, intensity levels, and degrees of call overlap refuted this hypothesis. Our results leave open the possibilities that the dynamic shift in the two components of pulse effort are related to the problem of call detection in a noisy environment or are responses by males to the perceived threat of competition for females.     

Behaviors of Swiss-Webster and C57/BL/6N sin mice in a fear/defense test battery

When confronted by an approaching threat stimulus (experimenter or laboratory rat), Swiss-Webster mice show initial flight, followed by freezing and defensive vocalization and biting, the latter only when escape is blocked. These defense patterns resemble those of the wild rat, suggesting that mice of this strain do not show the reductions in flight and defensive threat/attack that are typical of laboratory rats. C57/BL/6N Sin strain mice showed fewer avoidances to an approaching predator, as well as reduced vocalization and defensive biting, a pattern more similar to that of laboratory rats. As with rats, female mice appeared to be more defensive to a predator. They showed greater reactivity to dorsal contact and more frequent defensive biting and jump attacks than males of the same strains. These patterns of defensive behaviors suggest that, although strain differences in defense are substantial, laboratory mice are suitable for, and may offer several advantages in, the study of the genetic, endocrine, and pharmacological basis of antipredator defense. © 1995 Wiley-Liss, Inc.     

Analysis of ultrasonic vocalizations emitted by residents during aggressive encounters among rats (Rattus norvegicus)

This investigation was concerned with the extent to which aggressive resident rats emit 40-70-kHz vocalizations and the effect of these signals on intruders. In Experiment 1, deafened and intact intruder males were given two encounters with resident animals. Deafened intruders engaged in a higher duration of immobile or freezing postures than intact animals. Experiment 2 indicated that the augmentation of freezing found among deafened intruders was not due to an inability to detect ultrasounds made by residents since intruders encountering devocalized resident males showed no reliable differences in specific motor patterns from intruders paired with intact residents. The results further demonstrated that 40-70-kHz vocalizations are produced almost entirely by intruding animals since there were no significant changes in occurrence of these calls when resident males were devocalized. Under the constraints of the testing procedures employed, the role of ultrasonic communication during the initial formation of agonistic relations could not be determined experimentally.     

Affiliation and aggression as related to gender in domestic chicks (Gallus gallus).

Social discrimination in male and female domestic chicks (Gallus gallus) was investigated by using (a) latencies of approach response, (b) simultaneous free choice, and (c) intersubject aggressive-pecking tests. In approach-response tests, females showed shorter latencies when tested with cagemates than when tested with strangers, whereas males showed shorter latencies when tested with strangers than when tested with cagemates. In simultaneous-choice tests, females spent more time near a cagemate, whereas males spent more time near a strange chick. In aggressive-pecking tests, both sexes pecked more at strangers than at cagemates; aggressive pecking at strangers, however, was higher in males than in females. It is argued that gender effects in social discrimination can be accounted for in terms of stronger social attachment in females and aggressive responses in males.     

Three last letters identify most female first names

The last spelled letter often indicates the sex of first names. Most female names end with the last letter a, e, or i. Female names are distinctive and therefore easy to identify because of the small number of predominantly female endings. Most male names end with one of 19 last letters. Two last letters, h and y, occur with similar frequency for both sexes. The cultural tradition of higher status for men contributes to the avoidance of predominantly female last letters for male names. A female name with a predominantly male last letter therefore occurs more often than a male name with a predominantly female last letter. The findings were obtained from the 500 most frequent first names given to males and females in Pennsylvania in 1990.     

Exploring the Relationship between Psychopathy and Helping Behaviors in Naturalistic Settings: Preliminary Findings

This study examined the helping behavior of participants with high (High-P; 15 males, 13 females) and low (Low-P; 14 males, 16 females) psychopathic traits without their awareness. In the first of three tests, we found Low-P participants offered more help to an apparently lost female confederate than High-P participants. In the second test, High-P compared to Low-P males offered more help to an “injured” female experimenter, the reverse was true for females. In the third test, High-P compared to Low-P females offered more help to a female confederate who had apparently dropped papers they were carrying; whereas the reverse was true for males. Our preliminary findings indicate that context, gender and psychopathic traits interact and impact helping behavior.