Sex-dependent modulation of ultrasonic vocalizations in house mice (Mus musculus musculus)

House mice (Mus musculus) emit ultrasonic vocalizations (USVs), which are surprisingly complex and have features of bird song, but their functions are not well understood. Previous studies have reported mixed evidence on whether there are sex differences in USV emission, though vocalization rate or other features may depend upon whether potential receivers are of the same or opposite sex. We recorded the USVs of wild-derived adult house mice (F1 of wild-caught Mus musculus musculus), and we compared the vocalizations of males and females in response to a stimulus mouse of the same- or opposite-sex. To detect and quantify vocalizations, we used an algorithm that automatically detects USVs (Automatic Mouse Ultrasound Detector or A-MUD). We found high individual variation in USV emission rates (4 to 2083 elements/10 min trial) and a skewed distribution, with most mice (60%) emitting few (≤50) elements. We found no differences in the rates of calling between the sexes overall, but mice of both sexes emitted vocalizations at a higher rate and higher frequencies during opposite- compared to same-sex interactions. We also observed a trend toward higher amplitudes by males when presented with a male compared to a female stimulus. Our results suggest that mice modulate the rate and frequency of vocalizations depending upon the sex of potential receivers.

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abstract: Previously it was shown that male mice, when they encounter female mice or their pheromones, emit ultrasonic vocalizations with frequencies ranging over 30–110 kHz. Here, we show that these vocalizations have the characteristics of song, consisting of several different syllable types, whose temporal sequencing includes the utterance of repeated phrases. Individual males produce songs with characteristic syllabic and temporal structure. This study provides a quantitative initial description of male mouse songs, and opens the possibility of studying song production and perception in an established genetic model organism.

title: Of Mice, Birds, and Men: The Mouse Ultrasonic Song System Has Some Features Similar to Humans and Song-Learning Birds
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title: Ultrasonic vocalizations: A tool for behavioural phenotyping of mouse models of neurodevelopmental disorders
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title: Ultrasonic vocalizations in mouse models for speech and socio-cognitive disorders: insights into the evolution of vocal communication
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title: Translating mouse vocalizations: prosody and frequency modulation 1
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title: The role of ultrasonic vocalizations in mouse communication
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title: Determinants of the mouse ultrasonic vocal structure and repertoire
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title: The contribution of ultrasonic vocalizations to mouse courtship
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title: Unusual Repertoire of Vocalizations in the BTBR T+tf/J Mouse Model of Autism
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title: A Role for Strain Differences in Waveforms of Ultrasonic Vocalizations during Male–Female Interaction
abstract: Male mice emit ultrasonic vocalizations (USVs) towards females during male–female interaction. It has been reported that USVs of adult male mice have the capability of attracting females. Although the waveform pattern of USVs is affected by genetic background, differences among strains with respect to USV and the effects of these differences on courtship behavior have not been analyzed fully. We analyzed USV patterns, as well as actual social behavior during USV recording, in 13 inbred mouse strains, which included laboratory and wild-derived strains. Significant effects of strain were observed for the frequency of USV emission, duration, and frequency of the waveform category. Principal component (PC) analysis showed that PC1 was related to frequency and duration, and PC2–4 were related to each waveform. In the comparison of USV patterns and behaviors among strains, wild-derived KJR mice displayed the highest scores for PC2–4, and female mice paired with KJR males did not emit rejection-related click sounds. It is assumed that the waveforms emitted by KJR males have a positive effect in male–female interaction. Therefore, we extracted waveforms in PC2–4 from the USV recordings of KJR mice to produce a sound file, "HIGH2-4". As a negative control, another sound file ("LOW2-4") was created by extracting waveforms in PC2-4 from strains with low scores for these components. In the playback experiments using these sound files, female mice were attracted to the speaker that played HIGH2-4 but not the speaker that played LOW2-4. These results highlight the role of strain differences in the waveforms of male USVs during male–female interaction. The results indicated that female mice use male USVs as information when selecting a suitable mate.

title: Cross Fostering Experiments Suggest That Mice Songs Are Innate
abstract: Vocal learning is a central functional constituent of human speech, and recent studies showing that adult male mice emit ultrasonic sound sequences characterized as “songs” have suggested that the ultrasonic courtship sounds of mice provide a mammalian model of vocal learning.  We tested whether mouse songs are learned, by examining the relative role of rearing environment in a cross-fostering experiment.  We found that C57BL/6 and BALB/c males emit a clearly different pattern of songs with different frequency and syllable compositions; C57BL/6 males showed a higher peak frequency of syllables, shorter intervals between syllables, and more upward frequency modulations with jumps, whereas BALB/c males produced more “chevron” and “harmonics” syllables. To establish the degree of environmental influences in mouse song development, sons of these two strains were cross-fostered to another strain of parents. Songs were recorded when these cross-fostered pups were fully developed and their songs were compared with those of male mice reared by the genetic parents. The cross-fostered animals sang songs with acoustic characteristics - including syllable interval, peak frequency, and modulation patterns - similar to those of their genetic parents. In addition their song elements retained sequential characteristics similar to those of their genetic parents' songs.  These results do not support the hypothesis that mouse “song” is learned; we found no evidence for vocal learning of any sort under the conditions of this experiment. Our observation that the strain-specific character of the song profile persisted even after changing the developmental auditory environment suggests that the structure of these courtship sound sequences is under strong genetic control. Thus, the usefulness of mouse “song” as a model of mammalian vocal learning is limited, but mouse song has the potential to be an indispensable model to study genetic mechanisms for vocal patterning and behavioral sequences.

title: Mice do not require auditory input for the normal development of their ultrasonic vocalizations
abstract: BackgroundTransgenic mice have become an important tool to elucidate the genetic foundation of the human language faculty. While learning is an essential prerequisite for the acquisition of human speech, it is still a matter of debate whether auditory learning plays any role in the development of species-specific vocalizations in mice. To study the influence of auditory input on call development, we compared the occurrence and structure of ultrasonic vocalizations from deaf otoferlin-knockout mice, a model for human deafness DFNB9, to those of hearing wild-type and heterozygous littermates.ResultsWe found that the occurrence and structure of ultrasonic vocalizations recorded from deaf otoferlin-knockout mice and hearing wild-type and heterozygous littermates do not differ. Isolation calls from 16 deaf and 15 hearing pups show the same ontogenetic development in terms of the usage and structure of their vocalizations as their hearing conspecifics. Similarly, adult courtship 'songs' produced by 12 deaf and 16 hearing males did not differ in the latency to call, rhythm of calling or acoustic structure.ConclusionThe results indicate that auditory experience is not a prerequisite for the development of species-specific vocalizations in mice. Thus, mouse models are of only limited suitability to study the evolution of vocal learning, a crucial component in the development of human speech. Nevertheless, ultrasonic vocalizations of mice constitute a valuable readout in studies of the genetic foundations of social and communicative behavior.

title: Contextual Modulation of Vocal Behavior in Mouse: Newly Identified 12 kHz “Mid-Frequency” Vocalization Emitted during Restraint
abstract: While several studies have investigated mouse ultrasonic vocalizations (USVs) emitted by isolated pups or by males in mating contexts, studies of behavioral contexts other than mating and vocalization categories other than USVs have been limited. By improving our understanding of the vocalizations emitted by mice across behavioral contexts, we will better understand the natural vocal behavior of mice and better interpret vocalizations from mouse models of disease. Hypothesizing that mouse vocal behavior would differ depending on behavioral context, we recorded vocalizations from male CBA/CaJ mice across three behavioral contexts including mating, isolation, and restraint. We found that brief restraint elevated blood corticosterone levels of mice, indicating increased stress relative to isolation. Further, after 3 days of brief restraint, mice displayed behavioral changes indicative of stress. These persisted for at least 2 days after restraint. Contextual differences in mouse vocal behavior were striking and robust across animals. Thus, while USVs were the most common vocalization type across contexts, the spectrotemporal features of USVs were context-dependent. Compared to the mating context, vocalizations during isolation and restraint displayed a broader frequency range, with a greater emphasis on frequencies below 50 kHz. These contexts also included more non-USV vocal categories and different vocal patterns. We identified a new Mid-Frequency Vocalization, a tonal vocalization with fundamental frequencies below 18 kHz, which was almost exclusively emitted by mice undergoing restraint stress. These differences combine to form vocal behavior that is grossly different among behavioral contexts and may reflect the level of anxiety in these contexts.

title: Adult Male Mice Emit Context-Specific Ultrasonic Vocalizations That Are Modulated by Prior Isolation or Group Rearing Environment
abstract: Social interactions in mice are frequently analysed in genetically modified strains in order to get insight of disorders affecting social interactions such as autism spectrum disorders. Different types of social interactions have been described, mostly between females and pups, and between adult males and females. However, we recently showed that social interactions between adult males could also encompass cognitive and motivational features. During social interactions, rodents emit ultrasonic vocalizations (USVs), but it remains unknown if call types are differently used depending of the context and if they are correlated with motivational state. Here, we recorded the calls of adult C57BL/6J male mice in various behavioral conditions, such as social interaction, novelty exploration and restraint stress. We introduced a modulator for the motivational state by comparing males maintained in isolation and males maintained in groups before the experiments. Male mice uttered USVs in all social and non-social situations, and even in a stressful restraint context. They nevertheless emitted the most important number of calls with the largest diversity of call types in social interactions, particularly when showing a high motivation for social contact. For mice maintained in social isolation, the number of calls recorded was positively correlated with the duration of social contacts, and most calls were uttered during contacts between the two mice. This correlation was not observed in mice maintained in groups. These results open the way for a deeper understanding and characterization of acoustic signals associated with social interactions. They can also help evaluating the role of motivational states in the emission of acoustic signals.

title: Communication at the Garden Fence – Context Dependent Vocalization in Female House Mice
abstract: House mice (Mus musculus) live in social groups where they frequently interact with conspecifics, thus communication (e.g. chemical and/or auditory) is essential. It is commonly known that male and female mice produce complex vocalizations in the ultrasonic range (USV) that remind of high-pitched birdsong (so called mouse song) which is mainly used in social interactions. Earlier studies suggest that mice use their USVs for mate attraction and mate choice, but they could also be used as signal during hierarchy establishment and familiarization, or other communication purposes. In this study we elucidated the vocalization behaviour of interacting female mice over an extended period of time under semi-natural conditions. We asked, if the rate or structure of female vocalization differs between different social and non-social contexts. We found that female USV is mainly used in social contexts, driven by direct communication to an unknown individual, the rate of which is decreased over time by a familiarization process. In addition we could show that female mice use two distinct types of USVs, differing in their frequency, which they use differently depending on whether they directly or indirectly communicate with another female. This supports the notion that vocalization in mice is context dependent, driven by a reasonable and yet underestimated amount of complexity that also involves the interplay between different sensory signals, like chemical and auditory cues.

title: Wild mice: an ever-increasing contribution to a popular mammalian model.
abstract: Classical laboratory inbred strains of mice have been extremely helpful for research in immunology and oncology, and more generally, for the analysis of complex traits. Unfortunately, because they all derive from a relatively small pool of ancestors, their genetic polymorphism is rather limited. However, recently strains belonging to different species of Mus have been established from wild progenitors. These are an interesting addition to the arsenal of mouse geneticists, because they can be crossed with classical laboratory strains to produce viable and fertile offspring with a large number of polymorphisms of natural origin. These strains are helpful for making genome annotations because they permit highly refined genotype-phenotype correlations. They also allow the interpretation of molecular variation within a clear evolutionary framework. In this article, we provide examples with the aim of promoting the use of these new strains.

title: The polyphyletic origin of laboratory inbred mice and their rate of evolution
abstract: The analysis of various genetic components in the standard inbred laboratory strains of mice shows that several taxonomic units of the complex species Mus musculus have contributed to their genetic background. These laboratory lines are often taken as archetypes of the mammalian genome and since their genealogy is known for around 80 years they have been used to estimate mutation rates and various other evolutionary parameters. The knowledge of their origins is important if one is to avoid erroneous interpretations. Do they possess haplotypes that could have existed in natural populations of M. musculus domesticus or are they the fruit of artificial recombinations between divergent genomes? We discuss this in the light of various genetic systems.

title: Ultrasonic courtship vocalizations in wild house mice: spectrographic analyses
abstract: House mice emit ultrasonic vocalizations (USVs) during courtship, which are sexually dimorphic and function to attract mates. Spectrographic analyses of laboratory mice show that USVs are surprisingly complex and have features of song. In this study, we conducted the first spectral and temporal analyses of recordings from wild house mice (F1 from wild-caught Mus musculus musculus). Inspection of the spectral shape of syllables shows that the USVs from wild mice can be classified by both frequency and duration, and the most apparent distinction is between low- versus high-frequency calls. High-frequency calls of wild mice seem to be emitted at a much higher frequency range than previously found in some laboratory mice. Interestingly, we found that 20% of males do not vocalize at all, though the reason for their behaviour is unclear. Future studies are needed to determine what kind of information is conveyed in these complex vocalizations, and why some males appear to be non-vocalizers.

title: Affiliative Behavior, Ultrasonic Communication and Social Reward Are Influenced by Genetic Variation in Adolescent Mice
abstract: Social approach is crucial for establishing relationships among individuals. In rodents, social approach has been studied primarily within the context of behavioral phenomena related to sexual reproduction, such as mating, territory defense and parental care. However, many forms of social interaction occur before the onset of reproductive maturity, which suggests that some processes underlying social approach among juvenile animals are probably distinct from those in adults. We conducted a longitudinal study of social investigation (SI) in mice from two inbred strains to assess the extent to which genetic factors influence the motivation for young mice to approach one another. Early-adolescent C57BL/6J (B6) mice, tested 4–6 days after weaning, investigated former cage mates to a greater degree than BALB/cJ (BALB) mice, irrespective of the sex composition within an interacting pair. This strain difference was not due to variation in maternal care, the phenotypic characteristics of stimulus mice or sensitivity to the length of isolation prior to testing, nor was it attributable to a general difference in appetitive motivation. Ultrasonic vocalization (USV) production was positively correlated with the SI responses of mice from both strains. Interestingly, several USV characteristics segregated with the genetic background of young mice, including a higher average frequency and shorter duration for the USVs emitted by B6 mice. An assessment of conditioned place preference responses indicated that there was a strain-dependent difference in the rewarding nature of social contact. As adolescent mice aged, SI responses gradually became less sensitive to genetic background and more responsive to the particular sex of individuals within an interacting pair. We have thus identified a specific, genetic influence on the motivation of early-adolescent mice to approach one another. Consistent with classical theories of motivation, which propose a functional relationship between behavioral approach and reward, our findings indicate that reward is a proximal mechanism through which genetic factors affect social motivation during early adolescence.

title: Freezing urine reduces its efficacy for eliciting ultrasonic vocalizations from male mice
abstract: Studies on chemosensory communication generally rely on using samples of emanations that have been frozen for convenience, and assume that freezing has no detrimental effects. Female urine triggers courtship ultrasonic vocalizations (USVs) in male mice, and in this study, we examined whether freezing urine affects males' USV responses. We used wild-derived house mice (Mus musculus musculus), and recorded males' USVs after being presented samples of fresh versus frozen urine. We found that males emitted significantly fewer USVs when presented with frozen versus fresh urine, and furthermore, males were no longer able to discriminate the scent of familiar versus unfamiliar females after samples were frozen. Our findings indicate that freezing alters the bioactivity of urinary compounds both by reducing its potential to elicit behavioral responses from receivers (male courtship USVs) and eliminating important information about senders (familiarity). Freezing may denature the major urinary proteins (MUPs) released in rodent urine that play an important role in chemical communication. Our results raise concerns about the negative results of studies utilizing frozen samples for studying chemical signals.

title: Ultrasonic courtship vocalizations in wild house mice, Mus musculus musculus

abstract: Adult house mice produce ultrasonic vocalizations (USVs) that are sexually dimorphic and have features of song. To test whether USVs play a role in sexual courtship, we examined how males produce USVs following exposure to scent from conspecifics of different sexes and ages, and also females' attraction to recorded playbacks of males' USVs. We studied wild-derived house mice (F1 from wild-caught Mus musculus musculus) since previous work has almost exclusively been on domesticated strains. Males produced USVs in response to female but not to male or immature female urinary scent, and males responded at a higher rate to urine from novel than familiar females. Males' prior social experience had no effect on their USV responses to fresh female urine, corroborating studies with laboratory mice. When presented with playbacks, females were more attracted to USVs of novel males, and showed a preference for unfamiliar nonkin versus familiar siblings. Our results support the idea that male USVs function as courtship behaviour to attract mates, and extend several previous findings on laboratory strains to wild house mice. We also show that USVs are highly diverse among males, but further experiments are needed to determine whether these vocalizations play a role in social (individual, sibling or kin) recognition, inbreeding avoidance or other forms of mate choice.

title: Spectrographic analyses reveal signals of individuality and kinship in the ultrasonic courtship vocalizations of wild house mice
abstract: Male house mice produce ultrasonic vocalizations (USVs) during courtship; however, it is unclear why males produce USVs and what information their calls communicate. In laboratory mice, male USVs are attractive to females . They appear to facilitate mating and coordinate copulation behavior [3,4] perhaps because USVs provide information about males' quality or compatibility. In our studies on wild house mice (Mus musculus musculus), we found that females can discriminate the USVs of unrelated males versus siblings . In this study we conducted spectrographic and temporal analyses on recordings of courtship USVs of wild males. We found evidence that males' vocalizations contain signatures of individuality and kinship. The individuality of males' USVs could be due to differences in the filter function of the vocal tract or differences of the vocal apparatus, which might directly influence the temporal and spectral features of vocalizations. Further studies are needed to determine the consistency of individual USVs over longer periods of time and across contexts, and whether the familial effects we found are due to genetic relatedness, social learning (imprinting), or both.

title: Female odors evoke ultrasounds from male mice
abstract: Four experiments investigated the stimulus properties of female mice that influence ultrasound production by adult males. Female urine alone was less effective in evoking ultrasounds than was the female in male-female pairs. Visual cues were not necessary, since there was no difference in the incidence or latency of ultrasounds from male-female pairs when tested in light and dark conditions. A presently unspecified chemical cue produced by females, whose effectiveness is mediated by olfaction, was sufficient to evoke ultrasounds from male mice. The role of this chemical cue in a multimodal sequential communicative chain is discussed.

title: Pheromonal regulation of male mouse ultrasonic courtship (Mus musculus)
abstract: Biochemicals from several sites on the body of female house mice (Mus musculus) were found to elicit 70-kHz ultrasonic calls from male mice. Experiment 1 demonstrated that an anaesthetized female wrapped in an odour-impermeable plastic bag elicited ultrasounds from males when either the front or rear of their body was left exposed. In experiment 2 cotton swabs rubbed on the face and cheeks of females but not from males elicited ultrasonic calls from males. The results of experiment 3 suggested that female vaginal odours also elicit calls. Experiments 4 and 5 demonstrated that males will also emit ultrasounds in response to female but not male urine. The source and chemical nature of this 'ultrasound-releasing pheromone' remain to be discovered.

title: Ultrasonic Vocalizations Induced by Sex and Amphetamine in M2, M4, M5 Muscarinic and D2 Dopamine Receptor Knockout Mice
abstract: Adult mice communicate by emitting ultrasonic vocalizations (USVs) during the appetitive phases of sexual behavior. However, little is known about the genes important in controlling call production. Here, we study the induction and regulation of USVs in muscarinic and dopaminergic receptor knockout (KO) mice as well as wild-type controls during sexual behavior. Female mouse urine, but not female rat or human urine, induced USVs in male mice, whereas male urine did not induce USVs in females. Direct contact of males with females is required for eliciting high level of USVs in males. USVs (25 to120 kHz) were emitted only by males, suggesting positive state; however human-audible squeaks were produced only by females, implying negative state during male-female pairing. USVs were divided into flat and frequency-modulated calls. Male USVs often changed from continuous to broken frequency-modulated calls after initiation of mounting. In M2 KO mice, USVs were lost in about 70–80% of the mice, correlating with a loss of sexual interaction. In M5 KO mice, mean USVs were reduced by almost 80% even though sexual interaction was vigorous. In D2 KOs, the duration of USVs was extended by 20%. In M4 KOs, no significant differences were observed. Amphetamine dose-dependently induced USVs in wild-type males (most at 0.5 mg/kg i.p.), but did not elicit USVs in M5 KO or female mice. These studies suggest that M2 and M5 muscarinic receptors are needed for male USV production during male-female interactions, likely via their roles in dopamine activation. These findings are important for the understanding of the neural substrates for positive affect.

title: Female mice ultrasonically interact with males during courtship displays
abstract: During courtship males attract females with elaborate behaviors. In mice, these displays include ultrasonic vocalizations. Ultrasonic courtship vocalizations were previously attributed to the courting male, despite evidence that both sexes produce virtually indistinguishable vocalizations. Because of this similarity, and the difficulty of assigning vocalizations to individuals, the vocal contribution of each individual during courtship is unknown. To address this question, we developed a microphone array system to localize vocalizations from socially interacting, individual adult mice. With this system, we show that female mice vocally interact with males during courtship. Males and females jointly increased their vocalization rates during chases. Furthermore, a female's participation in these vocal interactions may function as a signal that indicates a state of increased receptivity. Our results reveal a novel form of vocal communication during mouse courtship, and lay the groundwork for a mechanistic dissection of communication during social behavior.

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

title: Influence of the female sexual cycle on BALB/c mouse calling behaviour during mating
abstract: Real-time recording technology was used in this study to analyse calling activity during heterosexual encounters in BALB/c mice. The spectrographic analyses revealed distinct types of calls that could be linked to a precise pre-ejaculatory behavioural sequence. In addition, the oestrous cycle of the female was observed to influence the vocalization emission pattern. The recording technology used in this study provides numerous improvements in the characterization description of mice calling behaviour during mating and is expected to be useful in studies of vocal communication in many rodent species.

title: Female Presence and Estrous State Influence Mouse Ultrasonic Courtship Vocalizations
abstract: The laboratory mouse is an emerging model for context-dependent vocal signaling and reception. Mouse ultrasonic vocalizations are robustly produced in social contexts. In adults, male vocalization during courtship has become a model of interest for signal-receiver interactions. These vocalizations can be grouped into syllable types that are consistently produced by different subspecies and strains of mice. Vocalizations are unique to individuals, vary across development, and depend on social housing conditions. The behavioral significance of different syllable types, including the contexts in which different vocalizations are made and the responses listeners have to different types of vocalizations, is not well understood. We examined the effect of female presence and estrous state on male vocalizations by exploring the use of syllable types and the parameters of syllables during courtship. We also explored correlations between vocalizations and other behaviors. These experimental manipulations produced four main findings: 1) vocalizations varied among males, 2) the production of USVs and an increase in the use of a specific syllable type were temporally related to mounting behavior, 3) the frequency (kHz), bandwidth, and duration of syllables produced by males were influenced by the estrous phase of female partners, and 4) syllable types changed when females were removed. These findings show that mouse ultrasonic courtship vocalizations are sensitive to changes in female phase and presence, further demonstrating the context-sensitivity of these calls.

title: Unusual repertoire of vocalizations in adult BTBR T+tf/J mice during three types of social encounters
abstract: BTBR) is an inbred mouse strain that displays social deficits and repetitive behaviors analogous to the first and third diagnostic symptoms of autism. We previously reported an unusual pattern of ultrasonic vocalizations in BTBR pups that may represent a behavioral homolog to the second diagnostic symptom of autism, impaired communication. This study investigated the social and vocal repertoire in adult BTBR mice, to evaluate the role of ultrasonic vocalizations in multiple social situations at the adult stage of development. Three different social contexts were considered: male–female, male–male (resident–intruder) and female–female interactions. Behavioral responses and ultrasonic vocalizations were recorded for BTBR and for the highly social control strain C57BL/6J (B6). No episodes of overt fighting or mating were observed during the short durations of the three different experimental encounters. BTBR displayed lower levels of vocalizations and social investigation in all three social contexts as compared with B6. In addition, the correlation analyses between social investigation and ultrasonic vocalization emission rate showed that in B6 mice, the two variables were positively correlated in all the three different social settings, whereas in BTBR mice, the positive correlation was significant only in the male–female interactions. These findings strongly support the value of simultaneously recording two aspects of the mouse social repertoire: social motivation and bioacoustic communication. Moreover, our findings in adults are consistent with previous results in pups, showing an unusual vocal repertoire in BTBR as compared with B6.

title: Phase-Specific Vocalizations of Male Mice at the Initial Encounter during the Courtship Sequence
abstract: Mice produce ultrasonic vocalizations featuring a variety of syllables. Vocalizations are observed during social interactions. In particular, males produce numerous syllables during courtship. Previous studies have shown that vocalizations change according to sexual behavior, suggesting that males vary their vocalizations depending on the phase of the courtship sequence. To examine this process, we recorded large sets of mouse vocalizations during male–female interactions and acoustically categorized these sounds into 12 vocal types. We found that males emitted predominantly short syllables during the first minute of interaction, more long syllables in the later phases, and mainly harmonic sounds during mounting. These context- and time-dependent changes in vocalization indicate that vocal communication during courtship in mice consists of at least three stages and imply that each vocalization type has a specific role in a phase of the courtship sequence. Our findings suggest that recording for a sufficiently long time and taking the phase of courtship into consideration could provide more insights into the role of vocalization in mouse courtship behavior in future study.

title: 40- and 70-kHz Vocalizations of Mice (Mus musculus) during Copulation
abstract: Ultrasonic vocalizations were tape recorded from five pairs of copulating mice and subjected to spectrographic analysis. As expected, the mice emitted numerous 70-kHz vocalizations. At the beginning of the test, before copulation began, 70-kHz calls were emitted almost continuously, while calls with lower spectrographic frequencies were not observed. Subsequently, bursts of 70-kHz calling generally began shortly before mounts and intromissions and persisted until dismount. Intermixed with these 70-kHz calls were additional vocalizations of about 40 kHz. Calling rates were highest just prior to intromission. Once intromissions began, 70-kHz calls continued at a lower rate until dismount; however, 40-kHz calls occurred infrequently. In a second experiment, the male was found to emit the majority of the 70-kHz calls and all of the 40-kHz calls. When the male was devocalized, few calls were detected, regardless of whether the female was able to call. If the male was not devocalized, high rates of calling were detected, even if the female was devocalized.

title: Female behavior is affected by male ultrasonic vocalizations in house mice
abstract: The effects of male-mouse ultrasonic vocalizations on female preference behavior were investigated using Swiss-Webster mice. Intact females spent more time with an intact tethered male than with a devocalized tethered male during 3-min preference tests. Female preference behavior was similar during estrus and diestrus; but, a preference for the vocalizing male was absent after ovariectomy, and returned following replacement treatment with ovarian hormones. Similar effects on female behavior were obtained using synthetic 70 kHz ultrasounds presented behind one of two devocalized tethered males during preference tests. The results indicate that ultrasounds maintain the female close to the vocalizing male and may facilitate copulation.

title: Female mice respond to male ultrasonic ‘songs’ with approach behaviour
abstract: The ultrasonic vocalizations of mice are attracting increasing attention, because they have been recognized as an informative readout in genetically modified strains. In addition, the observation that male mice produce elaborate sequences of ultrasonic vocalizations (‘song’) when exposed to female mice or their scents has sparked a debate as to whether these sounds are—in terms of their structure and function—analogous to bird song. We conducted playback experiments with cycling female mice to explore the function of male mouse songs. Using a place preference design, we show that these vocalizations elicited approach behaviour in females. In contrast, the playback of whistle-like artificial control sounds did not evoke approach responses. Surprisingly, the females also did not respond to pup isolation calls. In addition, female responses did not vary in relation to reproductive cycle, i.e. whether they were in oestrus or not. Furthermore, our data revealed a rapid habituation of subjects to the experimental situation, which stands in stark contrast to other species' responses to courtship vocalizations. Nevertheless, our results clearly demonstrate that male mouse songs elicit females' interest.

title: Experience restores innate female preference for male ultrasonic vocalizations
abstract: Mouse models are increasingly contributing to our understanding of the neural genetics of sensory processing and memory. For example, strain differences have helped elucidate basic mechanisms of age‐related hearing loss and auditory fear conditioning. Assessing sensory differences arising in acoustic communication contexts is also important for understanding natural audition. While this topic has not been well studied, it is currently being addressed through auditory neuroethological studies in the CBA/CaJ strain, where insights will help lay a foundation for future neural genetic studies. Here, we focus on the responses of adult females to ultrasonic vocalizations of males. We tested a group of female mice in a place‐preference paradigm before and after auditory and olfactory experience with a male. A control group was housed with other female cagemates between trials. All females showed an initial preference for male calls that rapidly decayed over the course of a trial. However, only females that had been pair‐housed with a male during the inter‐trial interval displayed a reinstated interest in male vocalizations, suggesting possible group differences in the assessment of the calls' behavioral relevance. These findings provide a timeframe during which auditory processing of male ultrasounds might be expected to show a difference depending on behavioral relevance, and also suggest an importance of social interactions in maintaining call recognition.

title: Scent-marking displays provide honest signals of health and infection
abstract: Males of many species produce scent marks and other olfactory signals that function to intimidate rivals and attract females. It has been suggested that scent marks provide an honest, cheat-proof display of an individual's health and condition. Here we report several findings that address this hypothesis in wild-derived house mice (Mus musculus domesticus). (1) We exposed males to female odor, which induces an increase in testosterone, and found that sexual stimulation significantly increased the males' scent-marking and the attractiveness of their scent marks to females. (2) We challenged sexually stimulated males with a nonreplicating strain of bacteria (Salmonella enterica C5TS) to activate immunity and found that this significantly decreased the males' scent-marking and the attractiveness of their scent marks to females. (3) We collected scent marks from infected and sham-infected males when they were sexually stimulated or not, and we found that females could significantly discriminate the scent marks of infected versus control males, but only when the males were sexually stimulated. Taken together, our results indicate that male mice modulate their scent-marking display depending on their health and perceived mating opportunities. Increased scent marking enhances males' attractiveness to females, scent marks provide an honest indicator of bacterial infection (and perhaps immune activation), and females are able to assess the health of males more easily when males mark at a high rate.

title: Social status and ultrasonic vocalizations of male mice.
abstract: Dominant male mice (Mus musculus) emit much more 70-kHz ultrasound in response to females than do subordinates. Neither dominant nor subordinate males emit much ultrasound in response to male stimuli. Inhibition of initial courtship by social subordination may be a central factor contributing to the greater reproductive fitness of dominant males.

title: Social Stress Effects on Territorial Marking and Ultrasonic Vocalizations in Mice
abstract: Acute social defeat (SD) leads to transient and persistent physiological and behavioral changes. We examined the effects of acute SD on territorial urine marking and ultrasonic courtship vocalizations in DBA/2 male mice. Both behaviors are considered androgen dependent and are influenced by social status, with dominant mice displaying more of both behaviors. In Experiment 1, male mice that received SD displayed prolonged inhibition of territorial urine marking, relative to nondefeated control mice (NOSD). In addition, territorial marking increased with repeated tests. In Experiment 2, male mice that received 3 successive days of SD displayed fewer ultrasonic courtship vocalizations at 30 min. post-SD1 and 30 min. post-SD2, relative to NOSD mice. In Experiment 2, we also observed decreased territorial marking 4 weeks post-SD. In sum, SD induced prolonged inhibition of territorial marking, but had only transient effects on ultrasonic courtship vocalizations, suggesting that different mechanisms may mediate the maintenance of these behaviors.

title: Courtship ultrasonic vocalizations and social status in mice
abstract: A series of experiments was conducted to investigate whether the poorer sexual performance of subordinate than dominant male mice, Mus domesticus, was linked to lower sexual motivation. Ultrasonic calls uttered by a male in the presence of a female were used as an index of sexual interest. Males were housed in pairs for 5 days and dominant/subordinate roles were assigned. Subordinates, when tested in their home cage immediately after the removal of the dominant male, uttered more ultrasounds than the latter. When the dominant male was tested before the subordinate, there was no difference in the number of ultrasounds uttered and the subordinates' performance was consistently poorer. The fewer calls recorded when subordinate males were tested after the dominant partner was not associated with less defence/escape behaviour, nor could it be explained as habituation to female odour, as a consequence of being tested after the dominant partner. Within sexually experienced pairs, the urine of dominant males interacting with a female for 3 min reduced the number of ultrasounds uttered by the subordinate in the presence of a female. It is suggested that an inhibitory factor in the dominant male's urine functions as an indirect competitive mechanism when direct competition is prevented by removing the dominant subject.

title: Ultrasonic vocalization by female mice in the presence of a conspecific carrying food cues
abstract: In female mice, Mus domesticus, reunion with a same-sex conspecific is associated with intense ultrasonic vocalization. We examined whether the palatability of a familiar food eaten by a demonstrator mouse and the motivational state of the conspecific observer could modulate the number of ultrasonic calls uttered during female-female interaction in NMRI mice. A pilot study indicated that these calls were uttered almost exclusively by the observer member of the pair. Observers were either food deprived or not deprived and demonstrators were offered either no food, a palatable diet or an unpalatable diet. We monitored both the number of ultrasounds (range 65-75 kHz) uttered and a series of behavioural parameters during the first 3 min of social interaction after 24 h of separation. Observers investigated the nose area of demonstrators fed on the unpalatable diet more than the same area of demonstrators not given food. No differences were found in demonstrators' behaviour. Ultrasonic calls were given immediately after female-female reunion and were affected by both the motivational state of the observer and the salience of the information carried by the conspecific. These results suggest that the motivational state of the observer affects ultrasonic calling towards a demonstrator conspecific. Nondeprived animals produced more calls towards demonstrators fed on palatable food, whereas food-deprived subjects vocalized more to fed conspecifics, independently of the palatability of the food eaten by the demonstrator. We suggest that ultrasonic vocalization in female mice can facilitate proximity with a conspecific and the number of these calls is modulated by the salience of the information carried by the companion.

title: Ultrasonic vocalizing by adult female mice (Mus musculus).
abstract: 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.

title: Spectrographic analysis of the ultrasonic vocalisations of adult male and female BALB/c mice
abstract: In this study, a spectrographic analysis was designed to improve the description of the shape, the modulations, the rate, length and frequencies of BALB/c mouse calls in different behavioural situations. Male and female calls emitted during investigation of cages with clean bedding, soiled with male or female bedding, and during same-sex encounters, were recorded and described. BALB/c male mice uttered different types of vocalisations both when investigating counterpart odour cues and when interacting with same-sex counterparts. BALB/c female mice vocalised solely during same-sex counterpart encounters and it appeared that calls were uttered mainly by the resident females. Male and female mice present a complex array of calls, which seem to be linked to particular behavioural situations. Further studies using this technology may help to improve our understanding of the role of vocal communication in natural rodent populations.

title: The emission and elicitation of mouse ultrasonic vocalizations: The effects of age, sex and gonadal status
abstract: Subject' mice of varying gonadal status (castrate males; intact or neonatally gonadectomized females and males) were paired for 3-min with intact 'stimulus' females and ultrasonic vocalizations were monitored. Vocalization patterns from home cages differed from the test pairings. The results suggested that the age, experience and gonadal status of the subject influenced the vocalizations from the pair. As the source of ultrasonic calls from these vocally intact pairs could not be individually identified, the 'subjects' were paired with a range of ultrasonically silent (inferior laryngeal nerve-transected) stimulus animals. Vocalizations were detected from all combinations of animals. Gonadally intact females were most effective in eliciting ultrasonic vocalizations from the subjects and gonadally intact males were least effective. The responses of castrate males were lower than from intact males. Anesthetized adults of either sex elicited only poor vocalization responses from other adults. Ultrasonic calls have often previously been studied using vocally intact 'subject' and 'stimulus' animals: the present results confirm the difficulty of establishing who is who in such situations.

title: The Structure and Usage of Female and Male Mouse Ultrasonic Vocalizations Reveal only Minor Differences
abstract: Ultrasonic vocalizations (USV) of mice are increasingly recognized as informative dependent variables in studies using mouse models of human diseases. While pup vocalizations primarily serve to re-establish contact with the mother, adult male “songs” were considered to be courtship signals. Alternatively, mouse USVs may generally function as territorial signals. To distinguish between these two hypotheses, we compared the structure and usage of adult male and female USVs in staged resident-intruder encounters. If calls function primarily as courtship signals, males should respond stronger than females, specifically when presented with a female intruder. Refuting this hypothesis, we found that in response to female intruders, females called more than males (228±32 calls/min vs. 71±15 calls/min), and males called more to female than to male intruders (14±7.5 calls/min). There were no significant differences in the acoustic characteristics of the calls given by females and males. To control for the influence of the intruder's behavior on calling, we repeated the experiments using anaesthetized intruders. Again, females produced more calls to female than male intruders (173±17 calls/min vs. 71±15 calls/min), while males called more in response to female than male intruders (39±17 calls/min), and there were no acoustic differences in female and male calls. The vocal activity did not differ significantly with regard to intruder state (awake or anaesthetized), while the acoustic structure exhibited significant differences. Taken together, our findings support the view that calls do not mainly function as courtship signals, although they might serve both a territorial (sex-independent) and a courtship function. The comparison of responses to awake vs. anaesthetized intruders suggests that the latter are sufficient to elicit vocal activity. The subtle acoustic differences, however, indicate that the subject differentiates between intruder states.

title: A Role for Ultrasonic Vocalisation in Social Communication and Divergence of Natural Populations of the House Mouse (Mus musculus domesticus)
abstract: It has long been known that rodents emit signals in the ultrasonic range, but their role in social communication and mating is still under active exploration. While inbred strains of house mice have emerged as a favourite model to study ultrasonic vocalisation (USV) patterns, studies in wild animals and natural situations are still rare. We focus here on two wild derived mouse populations. We recorded them in dyadic encounters for extended periods of time to assess possible roles of USVs and their divergence between allopatric populations. We have analysed song frequency and duration, as well as spectral features of songs and syllables. We show that the populations have indeed diverged in several of these aspects and that USV patterns emitted in a mating context differ from those emitted in same sex encounters. We find that females vocalize not less, in encounters with another female even more than males. This implies that the current focus of USVs being emitted mainly by males within the mating context needs to be reconsidered. Using a statistical syntax analysis we find complex temporal sequencing patterns that could suggest that the syntax conveys meaningful information to the receivers. We conclude that wild mice use USV for complex social interactions and that USV patterns can diverge fast between populations.

title: Evidence for an audience effect in mice: male social partners alter the male vocal response to female cues
abstract: Mice (Mus musculus) form large and dynamic social groups and emit ultrasonic vocalizations in a variety of social contexts. Surprisingly, these vocalizations have been studied almost exclusively in the context of cues from only one social partner, despite the observation that in many social species the presence of additional listeners changes the structure of communication signals. Here, we show that male vocal behavior elicited by female odor is affected by the presence of a male audience – with changes in vocalization count, acoustic structure and syllable complexity. We further show that single sensory cues are not sufficient to elicit this audience effect, indicating that multiple cues may be necessary for an audience to be apparent. Together, these experiments reveal that some features of mouse vocal behavior are only expressed in more complex social situations, and introduce a powerful new assay for measuring detection of the presence of social partners in mice.  Mice modify their vocalizations in response to audiences, but not to simple social stimuli, constituting a novel paradigm for measuring the influence of social cues.

title: Automatic mouse ultrasound detector (A-MUD): A new tool for processing rodent vocalizations
abstract: House mice (Mus musculus) emit complex ultrasonic vocalizations (USVs) during social and sexual interactions, which have features similar to bird song (i.e., they are composed of several different types of syllables, uttered in succession over time to form a pattern of sequences). Manually processing complex vocalization data is time-consuming and potentially subjective, and therefore, we developed an algorithm that automatically detects mouse ultrasonic vocalizations (Automatic Mouse Ultrasound Detector or A-MUD). A-MUD is a script that runs on STx acoustic software (S_TOOLS-STx version 4.2.2), which is free for scientific use. This algorithm improved the efficiency of processing USV files, as it was 4–12 times faster than manual segmentation, depending upon the size of the file. We evaluated A-MUD error rates using manually segmented sound files as a ‘gold standard’ reference, and compared them to a commercially available program. A-MUD had lower error rates than the commercial software, as it detected significantly more correct positives, and fewer false positives and false negatives. The errors generated by A-MUD were mainly false negatives, rather than false positives. This study is the first to systematically compare error rates for automatic ultrasonic vocalization detection methods, and A-MUD and subsequent versions will be made available for the scientific community.

title: Ultrasonic vocalizations emitted during dyadic interactions in female mice: A possible index of sociability?
abstract: Despite the evidence that ultrasonic vocalizations are a consistent component of the behavioural repertoire of female mice, only few studies have investigated this phenomenon. In this paper, we reported new data about ultrasonic vocalisations emitted during female-female mice social encounters. In particular, we first showed that the resident female utters a considerable number of 70 kHz calls and that the number of calls seems to be modulated by the motivational state of the emitter during the estrous cycle: sexually receptive females emitted fewer ultrasonic vocalizations than non-receptive ones in the presence of a female intruder. A strong positive correlation linked the number of calls and the time spent by the resident sniffing the intruder female. Moreover, the number of calls uttered during interaction with an unknown female partner significantly decreased with pregnancy and ageing. Secondly we reported that 1-year-old female mice showed a reduction of ultrasonic calls in the presence of a partner they had been exposed to, only if the re-exposure (test) occurred 30 min after the previous presentation. If the test was performed with a delay of 60 min, the number of calls emitted did not decrease. These results confirm that ultrasonic vocalizations emitted during social interaction with a female conspecific can be used as an index of social recognition and can be useful to detect age-related disruption of social memory in female mice.

title: Is sexual selection defined by dimorphism alone? A reply to Padian and Horner.
abstract: In their letter in response to our article in TREE , Padian and Horner  make three main points, the two most relevant concerning firstly the definition of sexual selection itself and secondly, the issue of how we might test for its presence in fossils organisms. Their third point pertains to species recognition and is addressed by Mendelson and Shaw .

title: Volitional exaggeration of body size through fundamental and formant frequency modulation in humans
abstract: Several mammalian species scale their voice fundamental frequency (F0) and formant frequencies in competitive and mating contexts, reducing vocal tract and laryngeal allometry thereby exaggerating apparent body size. Although humans’ rare capacity to volitionally modulate these same frequencies is thought to subserve articulated speech, the potential function of voice frequency modulation in human nonverbal communication remains largely unexplored. Here, the voices of 167 men and women from Canada, Cuba, and Poland were recorded in a baseline condition and while volitionally imitating a physically small and large body size. Modulation of F0, formant spacing (∆F), and apparent vocal tract length (VTL) were measured using Praat. Our results indicate that men and women spontaneously and systemically increased VTL and decreased F0 to imitate a large body size, and reduced VTL and increased F0 to imitate small size. These voice modulations did not differ substantially across cultures, indicating potentially universal sound-size correspondences or anatomical and biomechanical constraints on voice modulation. In each culture, men generally modulated their voices (particularly formants) more than did women. This latter finding could help to explain sexual dimorphism in F0 and formants that is currently unaccounted for by sexual dimorphism in human vocal anatomy and body size.

title: Vocal signalling of male southern elephant seals is honest but imprecise
abstract: In the most common models of communication, it is assumed that animals provide reliable information about phenotype, and hence can settle competitive contests without physical interactions like fights. This assumption has rarely been tested for wild mammals. Recent studies of mammals have revealed relationships of vocal attributes to age and body size. Here, we analyse relationships of frequency attributes of agonistic vocalizations to phenotype (age, body size, proboscis size and agonistic behaviour) in males of the southern elephant seal, Mirounga leonina, a species with intense male competition for access to females, and in which vocalizations are used frequently to settle male–male contests. We analysed formant structure and vocal tract size, and found that nasal and oral components of the vocal tract contribute separately to vocal formants; hence, the male's proboscis serves to elongate the vocal tract. We also found that formants in the upper part of the frequency spectrum (fourth and fifth in particular) and formant dispersion convey significant information about age, size and resource holding potential at large, and, therefore, can be honest signals of a vocalizer's phenotype. Explained variance was statistically significant in our study and in similar studies but was not high, so formant structure cannot serve as the sole basis of acoustic assessment. Other possible sources of information exchanged in elephant seal contests are nonvocal acoustic signals (e.g. vibrations) and optical displays.

title: Black and White Colobus Monkey (Colobus guereza) Roars as a Source of Both Honest and Exaggerated Information About Body Mass
abstract: Formant dispersion, the average spacing, in Hz, between the resonant frequencies of a vocalization, has been predicted to provide honest information about signaler body size. Previous descriptions of black and white colobus monkey (Colobus guereza, ‘‘guereza’’) roars, however, suggest a formant dispersion that is far lower than expected for an animal its size, and could effectively exaggerate its body size. Nonetheless, recent research on red deer shows that even when the formant positions of vocalizations effectively exaggerate body size, they may still provide honest cues within a species. We investigate whether the frequency bands observed in the spectrograms of guereza roars represent formants, and whether roar formant dispersion and/or individual formants provide honest information about body size (specifically, body mass) relative to conspecifics, although perhaps not relative to other species. We document coordinated vertical movements in the frequency bands of guereza roars and show that these bands move independently of fundamental frequency, indicating that they represent formants. We show, for captive adult male guerezas, that signaler body mass significantly predicts roar formant dispersion, even for randomly selected calls. Body mass also predicts formants 2 and 3, but the relationships are not as strong as with formant dispersion. Our roar formant dispersion calculations predict a vocal tract length of approx. 29 cm, but anatomically determined guereza vocal tract length is much smaller: approx. 7–8 cm. Videotaped roars revealed no laryngeal movement during roars, but rather inflation of the subhyoid air sac. We measured the volume of this air sac (approx. 10 cm 3 ) and speculate that it may function in roars to exaggerate body size, relative to other species.

title: A domain-specific opposite-sex bias in human preferences for manipulated voice pitch
abstract: Women's preferences for masculine characteristics in men's voices and men's preferences for feminine characteristics in women's voices are thought to reflect adaptations that identify high-quality (e.g. healthy) mates. Consistent with this proposal, we found that men had stronger preferences than women for women's voices with raised pitch (i.e. feminized female voices) and that women had stronger preferences than men for men's voices with lowered pitch (i.e. masculinized male voices). Importantly, however, no such opposite-sex bias was evident for attributions of dominance to voices with raised and lowered pitch; men's and women's voices with lowered pitch were perceived to be more dominant than those with raised pitch and these effects were equivalent for male and female listeners. Collectively, our findings suggest that preferences for voice pitch may function, at least in part, to identify high-quality mates and show that opposite-sex biases in preferences for voice pitch cannot be explained simply by greater general sensitivity to manipulated pitch in opposite-sex voices than in own-sex voices.

title: Preferences for Very Low and Very High Voice Pitch in Humans
abstract: Manipulations of voice pitch have been shown to alter attractiveness ratings, but whether preferences extend to very low or very high voice pitch is unknown. Here, we manipulated voice pitch in averaged men's and women's voices by 2 Hz intervals to create a range of male and female voices speaking monopthong vowel sounds and spanning a range of frequencies from normal to very low and very high pitch. With these voices, we used the method of constant stimuli to measure preferences for voice. Nineteen university students (ages: 20–25) participated in three experiments. On average, men preferred high-pitched women's voices to low-pitched women's voices across all frequencies tested. On average, women preferred men's voices lowered in pitch, but did not prefer very low men's voices. The results of this study may reflect selection pressures for men's and women's voices, and shed light on a perceptual link between voice pitch and vocal attractiveness.

title: Men's voices as dominance signals: vocal fundamental and formant frequencies influence dominance attributions among men
abstract: Men's vocal folds and vocal tracts are longer than those of women, resulting in lower fundamental frequency (F0) and closer spacing of formant frequencies (formant dispersion, Df) in men than in women. The evolutionary reasons for these sex differences are uncertain, but some evidence implicates male dominance competition. Previous manipulations of F0 and Df affected perceptions of dominance among men. However, because these acoustic dimensions were manipulated simultaneously, their relative contributions are unclear. In unscripted recordings of men speaking to a competitor, we manipulated F0 and Df independently and by similar perceptual amounts to examine effects on social and physical dominance ratings. Recordings lowered in either F0 or Df were perceived as being produced by more dominant men than were the respective raised recordings. Df had a greater effect than did F0, and both Df and F0 tended to affect physical dominance more than social dominance, although this difference was significant only for Df.

title: Female urine-induced male mice ultrasonic vocalizations, but not scent-marking, is modulated by social experience
abstract: Despite the evidence for a communicative function of rodent scent marks and ultrasonic vocalizations, relatively little is known about the impact of social factors on these two forms of communication. Here, we tested the effects of two important social factors, prior exposure to a female and freshness of female urine, on male scent marks and ultrasonic vocalizations elicited by female urine. We also asked whether a recently reported strain difference between the highly social strain C57BL/6J (B6) and the mouse model of autism BTBR T+tf/J (BTBR) herein is specifically seen in response to female urine or also detectable in response to male urine traces. Results show that the emission of female urine-elicited ultrasonic vocalizations was dependent on previous female experience, while scent-marking behavior was not affected. A positive correlation was detected between scent-marking behavior and ultrasonic calling in the most biologically relevant context, male mice exposed to fresh female urine after female experience. Correlations were less prominent or missing in less biologically relevant contexts, e.g. in male mice exposed to fresh female urine without previous female experience, indicating that previous female experience is affecting both the emission of female urine-elicited ultrasonic vocalizations and the correlation between olfactory and acoustic communication. The strain difference in scent-marking behavior and ultrasonic calling between B6 and BTBR appears to be specific to female urine-elicited behavior as it was not seen in response to male urine traces, highlighting the relevance of the social context in which mouse communication is evaluated.