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.     

Observational learning of a left-right behavioral asymmetry in mice (Mus musculus)

B6D2F1 hybrid mice that were allowed to observe a trained female mouse open a pendulum door to the right (or to the left) to enter a food compartment later solved this problem faster than pupils that had been placed behind a visual barrier. Male pupils that had observed a "left-handed" teacher performed sinistrally; males that had observed a "right-handed" model performed dextrally. Female pupils did not exhibit their demonstrator's laterality. Observational learning may provide a means to maintain certain lateralized behaviors. Such social learning may lead to the emergence of local traditions and to the cultural diffusion of behavioral asymmetries.     

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.     

Partial mediation of strange-male-induced pregnancy blocks by sexual activity in mice (Mus musculus)

Novel male house mice (Mus musculus) can disrupt early pregnancy in females. Previous research focused on pheromonal rather than behavioral mediation of this phenomenon. In Experiment 1, novel males were housed with females shortly after insemination. Litter production was negatively correlated with the males' sexual activity. Experiment 2 replicated this finding with a larger sample. In Experiment 3, females were exposed to castrated males. Testosterone-treated males completely blocked pregnancy, whereas untreated males did not. In Experiment 4, castrated testosterone-treated males were presented at intervals after insemination. Pregnancy was totally blocked at Days 3 and 4 and mostly blocked at Days 1 and 2 but was less affected at Days 5 and 6. In Experiment 5, females were exposed through a wire-mesh grid to castrated males. Pregnancies occurred in all conditions, even with testosterone-treated males. These data suggest a role for sexual activity in male-induced pregnancy blocks.     

Alcohol-induced conditioned aversion: genotypie specificity in mice (Mus musculus).

Acetaldehyde poisoning from ethanol ingestion may lead to aversion to ethanol among DBA mice but not among C57s, since the former are relatively deficient in aldehyde dehydrogenase activity. The present study paired ingestion of saccharin with a single intraperitoneal injection of one of four concentrations of ethanol for DBA/2J and C57BL/6J mice. Subjects were then given a two-bottle saccharin versus water preference test for 10 days. Substitution of saccharin for the taste of ethanol resulted in avoidance of saccharin with all concentrations of ethanol by DBAs but not by C57s, consistent with the conditioned taste aversion paradigm as a model for genetically mediated ethanol avoidance.     

The introduction of a group of alien mice (Mus musculus L.) into hierarchically organized groups of five male mice

Groups of 3 male or female Mus musculus were introduced into hierarchically organized colonies of 5 male mice for a period of 8 days. The colonies were of 2 kinds; high-level aggressive (HLA), which had been set up 3 days prior to the introduction of the aliens, and low-level aggressive (LLA), which had been established for 21 days before strangers were introduced. Both males and anestrous females were attacked, but males were attacked 5 times more frequently than females. In HLA colonies most of the attacks on the aliens were by the dominant; in LLA colonies there was no difference in the behavior of dominant and subordinate mice toward strangers. Both aggression toward aliens and intracolony aggression declined over the 8 day experimental period. In HLA colonies the dominant mouse mounted females 5 times more frequently than did either his subordinates or male mice in the LLA colonies. In HLA colonies aliens huddled with subordinates to form a single colony with 1 dominant and 7 subordinates. In LLA colonies alien males remained as a discrete group spatially separated in the cage. Female aliens were incorporated into the main colony. In all cases dominant male mice made more attacks on aliens as compared with familiar mice.     

Bitter avoidance in guinea pigs (Cavia porcellus) and mice (Mus musculus and Peromyscus leucopus)

Rejection of bitter substances is common in many species and may function to protect an animal from ingestion of bitter-tasting toxins. Since many plants are bitter, it has been proposed that high tolerance for bitterness would be adaptive for herbivores. Earlier studies conducted on herbivorous guinea pigs (Cavia porcellus) have been used to support this proposal. We tested guinea pigs with bitter plant secondary metabolites (salicin, caffeine, quinine hydrochloride) and bitter protein hydrolysates (two types of hydrolyzed casein, hydrolyzed soy) in a series of two-choice preference tests. For comparison, we tested two nonherbivorous mouse species (Mus musculus and Peromyscus leucopus). Guinea pigs did show weaker avoidance of quinine hydrochloride than did the mice, confirming predictions generated from earlier work. However, guinea pigs had similar responses to caffeine as did Peromyscus. Both of these species showed weaker avoidance responses than Mus to 10 mM caffeine. For salicin, guinea pigs were the only species to avoid it at 10 mM and their preference scores at this concentration were significantly lower than for the two mice species. Guinea pigs avoided all of the protein hydrolysates more strongly than the other species. Responses to the protein hydrolysates did not reflect the patterns observed with the simple bitter compounds, suggesting that other properties of these complex stimuli may be responsible for guinea pig avoidance of them. Our results suggest caution in accepting, without further empirical support, the premise that guinea pigs (and herbivores in general) have a generalized reduced bitter sensitivity.     

Genetic influences on digging behaviors in mice (Mus musculus) in laboratory and seminatural settings

Digging behaviors of several inbred strains of laboratory mice and some of their crosses were examined in three contexts. In laboratory burrow boxes, C57BL/6Abg mice constructed more sophisticated burrow systems than did BALB/cAbg mice. Their F1 hybrids built burrow systems more complex than either parental strain. The same pattern of genetic influence was observed in an outdoor pen. In an escape task that required digging, BALB/c mice escaped more quickly than did C57BL/6 mice; their F1 hybrids showed dominance toward the BALB/c phenotype. These results indicate that behavioral polymorphisms in digging behavior, which may relate to habitat selection, have a genetic basis. The dominance and overdominance toward the better digging parental strain in each type of task suggest the possible evolutionary importance of these digging behaviors.     

Effects of male social status on reproductive success and on behavior in mice (Mus musculus)

Differences in reproduction as well as in behavior in the presence of females were evaluated according to dominant and subordinate male rank in albino mice, in the temporary absence of each male's antagonist. Dominant males reproduced more successfully than subordinate males. Subordinate males were generally inactive, except for displacement activities, during the first 15 min they were exposed to female partners. These findings suggest that mechanisms other than male-male interference or mating order may be operating or influencing behavior and reproductive results.     

Ultrasonic vocalizations during sex behavior of male house mice (Mus musculus): a description

After placing a female house mouse into the home cage of a male, the occurrences of four behaviors were recorded on separate channels of an event recorder: (1) male sniffing female, (2) male mounting female, (3) male intromitting female, and (4) 70-kHz vocalizations. The amount of vocalizing was greatest shortly after pairing and was associated with the male sniffing the female. After the male began mounting, vocalizations also were associated with mounting. Vocalizations were recorded during intromissions and occasionally occurred coincident with pelvic thrusts. Very few vocalizations were detected when the male was not sniffing or mounting the female. Vocalizations ceased following ejaculation but typically resumed several minutes before the resumption of another mounting sequence. Thus 70-kHz vocalizations appear to be closely linked to male sexual arousal.     

Anxiety and maternal aggression in house mice (Mus musculus): a look at interindividual variability

The hypotheses were tested that mouse motherhood is accompanied by decreased reactivity to aversive stimuli and that female anxiety is inversely related to the probability of displaying intense forms of postpartum aggression. Outbred Swiss female mice were tested for anxiety in a light/dark choice test when virgin, pregnant, or lactating, and then tested for maternal aggression (5-min exposure to a male intruder) on postpartum Day 7. Anxiety declined in pregnant and lactating females when compared with virgin animals. Furthermore, females who displayed higher scores of postpartum fighting were less anxious in the previous test regardless of reproductive stage. Part of interindividual variability in postpartum aggression might thus be related to differences in the extent to which individuals perceive and react to anxiogenic situations. In addition, the higher emotionality characterizing the C57BL/6 and DBA/2 inbred strains may be responsible for the lack of a clear-cut exhibition of maternal aggression in these two strains.     

The reinforcing properties of aggressive vs nonaggressive social interactions in isolated male ICR mice (Mus musculus)

Isolated male ICR mice in a T-maze consistently selected the goal box which enabled them to fight another mouse if the alternative goal box allowed no social interaction (Experiment 1). However, if the alternative choice enabled the isolated mice to interact with another mouse through a mesh screen which prevented fighting, the preference for the opportunity to fight did not appear (Experiment 2). Because the visual, olfactory, and auditory stimuli available through the screen appeared to be as attractive as the stimuli provided by the additional opportunity to fight, it is not necessary to conclude that the stimuli reinforcing the choice behavior in Experiment 1 were provided by fighting. Since there is no compelling reason to conclude that fighting is a primary reinforcer for these isolated mice, it is not necessary to argue that the high incidence of isolation-induced fighting is the reflection of a primary aggressive motive.     

Repeated tests of intermale aggression in mice (Mus musculus) are influenced by housing and test conditions

Young adult male Binghamton Heterogenous (HET) mice were housed either individually or in groups of four, in two-tiered cages for 11 days before their agonistic behavior was observed. Pairs of male mice were tested 3 min each day for 9 consecutive days. Agonistic behavior was observed in two-tiered cages in which there were either clean pine shavings or shavings soiled by young adult female HET mice. Housing and shaving conditions interactively influenced aggression observed over the course of testing. That is, when individually housed mice were tested with clean shavings and when group-housed mice were tested with female-soiled shavings, agonistic behavior decreased over days, but when isolated mice were tested in soiled shavings and when group-housed mice were tested in clean shavings, aggression increased over the course of the 9-day test period.     

Maternal aggression toward infanticidal males of different social status in wild house mice (Mus musculus domesticus)

Maternal aggression was examined in wild female mice (Mus musculus domesticus) derived from animals trapped in Alberta, Canada. Lactating females were tested for their behavior toward intruder males during the time of postpartum estrus while housed in a two-cage apparatus containing a defensible nest area. Prior to being used as intruders, sexually naive males were screened for their behavior toward a newborn pup (83% exhibited infanticide). Only infanticidal males were then housed in pairs and allowed to establish a dominance hierarchy. Dominance status was further verified by a urine marking test. The dominant and subordinate infanticidal males were then placed into a lactating female's cage and observed for 1 hr. The test was terminated immediately when a male began to attack the pups. Lactating females attacked the males in both groups, but subordinate males received more intense attacks than dominant males. Dominant males elicited significantly more fear/defense behavior than subordinate intruders. All of the dominant males and only one submissive male attacked the pups. Females were thus successful in blocking infanticide only by infanticidal subordinate males. Since females do not persist in attacking males with high fighting ability, one function of maternal aggression could be to assess the fighting, and resource holding, potential of a future mate. © 1994 Wiley-Liss, Inc.     

Learning to cope with two different food distributions: the performance of house mice (Mus musculus domesticus)

Search abilities of mice (Mus musculus domesticus) were evaluated using an arena closed by a ceiling in which 9 food sources (which mice could reach standing on their hind legs) could be arranged according to 2 configurations: a 3 x 3 square matrix and 3 clusters each containing 3 food sources. Testing conditions prevented olfactory and visual cues from being left after visits to food sources, and mice were able to choose alternative routes between food sources. Results showed that mice were more efficient with the matrix than with the cluster configuration. Sex differences were observed: Females improved their performance with both configurations, whereas males improved only with the matrix one. Mice did not develop evident search strategies that would minimize task complexity. Comparison with data published on capuchin monkeys revealed differences, with monkeys performing better with the cluster configuration than with the matrix and applying searching strategies.     

Social dominance, reproduction, and release of the maturation-delaying chemosignal in the urine of female house mice (Mus musculus)

Five experiments were performed to investigate the effects of social status in groups of female mice on reproduction and on the release or urinary chemosignals that accelerate or delay the onset of sexual maturation in young females. Treatment of young female mice with urine from bottom-ranking mice in groups of 5 adult females resulted in delays in puberty comparable to those produced by treatment with urine pooled from females housed at moderate to high densities. Treatment of young females with urine from top-ranking females from the same groups resulted in ages for puberty not different from those of control females treated with water. There was an interaction between the social rank of a female and the stages of the estrous cycle with respect to the presence in the urine of chemosignals from grouping that delay puberty and estrus that accelerate puberty. Within groups of 5 adult mice, top-ranking females were in estrus more frequently than bottom-ranking females. Individually caged adult females treated with urine from top-ranking females were in estrus more frequently than females treated with urine from bottom-ranking females. When grouped females were separated into individual cages and mated, there was differential reproductive success: More top-ranking females conceived and bore litters than bottom-ranking females. Bottom-ranking females produced more female pups, relative to top- and middle-ranking females.