Wild Female House Mice Research Articles

Male scent but not courtship vocalizations induce estrus in wild female house mice

Exposure to males or male urinary scent can induce and accelerate the rate of female estrous cycling in house mice ("Whitten effect"), and this response has been replicated many times since its discovery over 60 years ago. Here, we tested whether exposing female mice to recordings of male courtship ultrasonic vocalizations (USVs) induces estrous cycling, and whether exposure to both male scent and USVs has a stronger effect than to either of these stimuli alone. We conducted our study with 60 wild-derived female house mice (Mus musculus musculus). After singly housing females for 14 days, we monitored estrous stages via vaginal cytology for two weeks while isolated from males or male stimuli. We continued monitoring estrus for two more weeks during experimental exposure to one of four different types of stimuli: (1) clean bedding and background noise playback (negative control); (2) recordings of male USVs (16 min per day) and clean bedding (male USV treatment); (3) soiled male bedding and background noise playback (male odor treatment; positive control); or (4) male USVs and soiled male bedding (male odor and USV treatment). Females were then paired with males to test whether any of the four treatments influenced female reproduction (especially latency to birth). We confirmed that exposure to male odor increased female cycling, as expected, but exposure to recordings of male USVs had no effect on estrus. Females exposed to both USVs and odor went through more cycles compared to controls, but did not differ significantly from exposure to male odor (and background noise). After pairing females with a male, females showing male odor-induced cycling produced their first litter sooner than controls, whereas USVs did not have such an effect. This is the first study to our knowledge to show that male odor induces estrus in wild house mice and to show functional effects on reproduction. Our results do not support the hypothesis that male vocalizations induce female estrus, although we suggest other approaches that could be used to further test this hypothesis.

Male Scent But Not Courtship Vocalizations Induce Estrus in Wild Female House Mice

Male Scent But Not Courtship Vocalizations Induce Estrus in Wild Female House Mice

Nest defense and survival of offspring in highly aggressive wild Canadian female house mice

Nest defense behavior was examined in wild female house mice ( Mus domesticus) that were derived from a stock initially trapped in Alberta, Canada. The first objective was to determine whether behavior toward pups prior to mating was related to the intensity of postpartum aggression in a variety of social situations. Therefore, prior to the experiments we screened virgin females for their behavior toward a newborn pup [60% of the females exhibited infanticide and 40% were noninfanticidal: 7% were parental (retrieved and hovered over the pup) and 33% ignored the pup]. Infanticidal and noninfanticidal females were then mated with males and used in four experiments. In Experiment 1 the females were housed individually prior to delivery, while in Experiment 2 the females were allowed to remain with their mates; in both situations all females successfully reared litters of similar sizes. Male and female intruders (that had all exhibited infanticide when previously tested with a pup) were placed separately into a test cage containing a lactating female during the first four days after delivery. Regardless of the presence of the stud male, previously infanticidal females were more aggressive (exhibited more attacks per min) toward both male and female intruders than were previously noninfanticidal females; infanticidal females also exhibited more of both forms of attack (offensive and defensive) and also attacked with greater intensity than did noninfanticidal females. The number of attacks toward intruders of both sexes increased for both infanticidal and noninfanticidal females between Day 1–4 postpartum, but very high rates of attack were observed on all days by the lactating females, including the day of delivery. In Experiments 3 and 4 only the most aggressive (previously infanticidal) females were tested. In Experiment 3, two unrelated, unfamiliar females were mated separately and then were housed together just prior to delivery, which was planned to occur 3–4 days apart. In 5 of the 15 cages, all pups disappeared on the day of delivery of the second female to deliver her litter. In the remaining 10 cages, it appeared that none of the pups produced by the 20 females were killed. Thus, in this experiment, 66% of pups survived to Day 4 postpartum. In Experiment 4, two previously infanticidal female siblings, which had been housed together since birth, were placed together with a stud male. In all 9 cages only one female became pregnant and delivered pups, but only 3 litters survived to Day 4 (no litters were observed being attacked during intruder tests). In contrast to kin-selection theory and our expectation that a sibling would contribute to communal rearing and nest defense, housing siblings together thus resulted in the lowest overall reproductive success ( 3 18 ; 17% of the females produced litters that survived to Day 4 postpartum) of any of the social conditions examined. We discuss the implications for social structure and population dynamics of the extremely high aggresiveness and infanticidal tendency, regardless of kinship, of females from this stock of wild mice.

Environmental influences on the preferences of wild female house mice for males of differing t-complex genotypes.

Twenty-five percent of wild house mice are heterozygous (+/t) for a deleterious, recessive mutation at the t complex. In previous studies we have demonstrated that wild female house mice can discriminate +/+ from +/t males and show strong preferences for the odors of males who do not carry t mutations. In the present study we examine the extent to which preferences of +/+ female mice are influenced by the genotype of their parents and or littermates. Our data indicate that when +/+ females are reared by two +/+ parents, they exhibit strong preferences for the odors of +/+ males. In contrast, when a +/+ female is reared by one +/+ and one +/t parent she shows no preference for males of either genotype. A second experiment using mice carrying recombinant chromosomes indicates that the genes responsible for the parental (or family) odor cue are not the deleterious t mutations per se but rather other genes linked to these mutations.

Analysis of a genetic recognition system in wild house mice.

Wild female house mice have strong preferences for odors of male mice whose t-complex genotype is +/+ rather than for males carrying deleterious mutations (+/t) at the t complex. In this review of a large number of studies examining the basis for this preference, we suggest the following: first, preferences of +/+ females are greatly influenced by environmental factors and probably do not have a large genetic component: second, preferences of +/t females are less dependent upon environmental factors and hence may have a strong genetic component: third, the lethal factors within the t complex are involved in both the production of the cue by males and the expression of the preference in females: and fourth, there may be a second gene or genes within the t complex involved in the expression of female preference.

Long-term effects of accelerated or delayed sexual maturation on reproductive output in wild female house mice (Mus musculus).

The effects of acceleration and delay of puberty in female house mice on survival and reproduction were tested using 6 experimental groups: (1) control females mated at the time of first oestrus, (2) females mated at weaning, (3) females treated with male urine starting at weaning and mated at first oestrus, (4) females housed in groups and mated at first oestrus, (5) females housed alone, treated with urine from grouped females and mated at first oestrus, and (6) females housed alone and mated at 68 days of age. Females caged with males at weaning or treated with male urine and mated at puberty had lower rates of survival to 180 days of age, but did not differ in rates of fertility from mice in the other four treatments. Those females that were housed with males from weaning or treated with male urine also had smaller total numbers of litters, fewer total young, and smaller average litter sizes than did females for which the age of mating was delayed, by grouping or treatment with urine from grouped females, or by being held until age 68 days before mating. Control females mated at first oestrus generally were intermediate or did not differ from the male treatments on these dependent variables. There were no differences in the average number of female young/litter across the 6 treatments. However, females that were delayed in age of first mating had significantly more male young/litter than did females that were accelerated in their sexual development or control females.(ABSTRACT TRUNCATED AT 250 WORDS)

Kin recognition and choice of males by wild female house mice (Mus musculus).

Kin recognition and choice of males by wild female house mice (Mus musculus).

Infanticide and parental behavior in wild female house mice: Effects of ovariectomy, adrenalectomy and administration of oxytocin and prostaglandin F 2α

We have previously observed that about 60% of virgin, wild female house mice (Mus musculus), that were the offspring of wild mice trapped in Missouri, exhibited infanticide when a single 2-day-old pup was placed into each female's home cage. But, by the end of pregnancy, there was a significant increase (to 90%) in the proportion of wild female mice that exhibited infanticide. At parturition, infanticide was inhibited and parental behavior was induced in all females. In the present study we examined the influence of ovarian and adrenal hormones, as well as two hormones associated with pregnancy and parturition: oxytocin and prostaglandin F 2α (PGF), in regulating infanticide and parental behavior in wild female house mice. The presence or absence of gonadal and adrenal hormones did not influence the frequency of infanticidal behavior in adult female mice. Subcutaneous injections of either oxytocin or PGF inhibited infanticide in previously infanticidal pregnant females 1 hr after injection, but only oxytocin served to also facilitate parental behavior (most PGF-treated females left the pup untouched). Oxytocin, but not PGF, was effective in inhibiting infanticide in previously infanticidal virgin females. These findings suggest that, by themselves, ovarian and adrenal hormones do not mediate the exhibition of infanticide by wild female mice, but the lack of response to PGF in virgin females suggests that endocrine changes during pregnancy (possibly changes in steroids) may modulate the inhibitory effects of PGF on infanticide.

Kin recognition and choice of males by wild female house mice (Mus musculus).

Kin recognition and choice of males by wild female house mice (Mus musculus).

The influence of reproductive state on infanticide by wild female house mice (Mus musculus)

The majority of female mice (Mus musculus) from laboratory stocks are spontaneously parental. In contrast, the majority of adult wild female house mice exhibit infanticide (the killing of preweanling young), but the frequency with which infanticide is observed varies as a function of age and reproductive state. Prepubertal females were less likely to exhibit infanticide (39%) than were adult virgin females (61%). The frequency of infanticide increased during pregnancy, with over 90% of females exhibiting infanticide just before parturition. But, after parturition, previously infanticidal females cared for their own litters. When lactating female mice were tested after two days of separation from their own nursing young for their behavior toward a novel newborn pup on either the tenth or twenty-fifth day after parturition, the proportion of the females that exhibited infanticide was not significantly different from that of adult virgin females (about 60%). After only two hours of separation from their own nursing young on the tenth day after parturition, however, all females continued to exhibit parental behavior toward a novel pup.

Puberty delay by a urinary cue from female house mice in feral populations.

Urine produced by wild female house mice, living in high- and low-density populations and confined to areas within a highway cloverleaf, was tested for its ability to delay puberty in juvenile female mice. Only urine collected from females in the dense population at its maximum density delayed puberty in test females. Urine collected when the population was less dense, or from a population that remained sparse, failed to delay puberty. These results suggest that a urinary factor present at high densities may delay puberty and thus help to slow further population growth.

Oestrous synchronization and pregnancy blocking in wild house mice (Mus musculus).

Summary. In wild female house mice a skewed distribution of vaginal plugs on the days following pairing indicates an oestrous synchronization (Whitten effect) correlated with the presence of the male. Inseminated wild house mice were exposed to strange males or subjected to various types of cage changes and handling during the pre-implantation period. The strange males produced a significant reduction in pregnancy rates (Bruce effect). Changes in the physical environment produced comparable reductions in the absence of a strange male.