Vocalizations are widely used for communication between animals. Mice use a large repertoire of ultrasonic vocalizations (USVs) in different social contexts. During social interaction recognizing the partner's sex is important, however, previous research remained inconclusive whether individual USVs contain this information. Using deep neural networks (DNNs) to classify the sex of the emitting mouse from the spectrogram we obtain unprecedented performance (77%, vs. SVM: 56%, Regression: 51%). Performance was even higher (85%) if the DNN could also use each mouse's individual properties during training, which may, however, be of limited practical value. Splitting estimation into two DNNs and using 24 extracted features per USV, spectrogram-to-features and features-to-sex (60%) failed to reach single-step performance. Extending the features by each USVs spectral line, frequency and time marginal in a semi-convolutional DNN resulted in a performance mid-way (64%). Analyzing the network structure suggests an increase in sparsity of activation and correlation with sex, specifically in the fully-connected layers. A detailed analysis of the USV structure, reveals a subset of male vocalizations characterized by a few acoustic features, while the majority of sex differences appear to rely on a complex combination of many features. The same network architecture was also able to achieve above-chance classification for cortexless mice, which were considered indistinguishable before. In summary, spectrotemporal differences between male and female USVs allow at least their partial classification, which enables sexual recognition between mice and automated attribution of USVs during analysis of social interactions.

Vocalizations are a widespread means of communication in the animal kingdom. Mice use a large repertoire of ultrasonic vocalizations (USVs) in different social contexts, for instance courtship, territorial dispute, dominance and mother-pup interaction. Previous studies have pointed to differences in the USVs in different context, sexes, strains and individuals, however, in many cases the outcomes of the analyses remained inconclusive. We here provide a more general approach to automatically classify USVs using deep neural networks (DNN). We classified the sex of the emitting mouse (C57Bl/6) based on the vocalization’s spectrogram, reaching unprecedented performance (~84% correct) in comparison with other techniques (Support Vector Machines: 64%, Ridge regression: 52%). Vocalization characteristics of individual mice only contribute mildly, and sex-only classification reaches ~78%. The performance can only partially be explained by a set of classical shape features, with duration, volume and bandwidth being the most useful predictors. Splitting estimation into two DNNs, from spectrograms to features (57-82%) and features to sex (67%) does not reach the single-step performance. In summary, the emitter’s sex can be successfully predicted from their spectrograms using DNNs, excelling over other classification techniques. In contrast to previous research, this suggests that male and female vocalizations differ in their spectrotemporal structure, recognizable even in single vocalizations.

Ambra1 is linked to autophagy and neurodevelopment. Heterozygous Ambra1 deficiency induces autism-like behavior in a sexually dimorphic manner. Extraordinarily, autistic features are seen in female mice only, combined with stronger Ambra1 protein reduction in brain compared to males. However, significance of AMBRA1 for autistic phenotypes in humans and, apart from behavior, for other autism-typical features, namely early brain enlargement or increased seizure propensity, has remained unexplored. Here we show in two independent human samples that a single normal AMBRA1 genotype, the intronic SNP rs3802890-AA, is associated with autistic features in women, who also display lower AMBRA1 mRNA expression in peripheral blood mononuclear cells relative to female GG carriers. Located within a non-coding RNA, likely relevant for mRNA and protein interaction, rs3802890 (A versus G allele) may affect its stability through modification of folding, as predicted by in silico analysis. Searching for further autism-relevant characteristics in Ambra1+/- mice, we observe reduced interest of female but not male mutants regarding pheromone signals of the respective other gender in the social intellicage set-up. Moreover, altered pentylentetrazol-induced seizure propensity, an in vivo readout of neuronal excitation-inhibition dysbalance, becomes obvious exclusively in female mutants. Magnetic resonance imaging reveals mild prepubertal brain enlargement in both genders, uncoupling enhanced brain dimensions from the primarily female expression of all other autistic phenotypes investigated here. These data support a role of AMBRA1/Ambra1 partial loss-of-function genotypes for female autistic traits. Moreover, they suggest Ambra1 heterozygous mice as a novel multifaceted and construct-valid genetic mouse model for female autism.

Claustrophobia, the well-known fear of being trapped in narrow/closed spaces, is often considered a conditioned response to traumatic experience. Surprisingly, we found that mutations affecting a single gene, encoding a stress-regulated neuronal protein, can cause claustrophobia. Gpm6a-deficient mice develop normally and lack obvious behavioral abnormalities. However, when mildly stressed by single-housing, these mice develop a striking claustrophobia-like phenotype, which is not inducible in wild-type controls, even by severe stress. The human GPM6A gene is located on chromosome 4q32-q34, a region linked to panic disorder. Sequence analysis of 115 claustrophobic and non-claustrophobic subjects identified nine variants in the noncoding region of the gene that are more frequent in affected individuals (P=0.028). One variant in the 3′untranslated region was linked to claustrophobia in two small pedigrees. This mutant mRNA is functional but cannot be silenced by neuronal miR124 derived itself from a stress-regulated transcript. We suggest that loosing dynamic regulation of neuronal GPM6A expression poses a genetic risk for claustrophobia.

Comparative analyses used to reconstruct the evolution of traits associated with the human language faculty, including its socio-cognitive underpinnings, highlight the importance of evolutionary constraints limiting vocal learning in non-human primates. After a brief overview of this field of research and the neural basis of primate vocalizations, we review studies that have addressed the genetic basis of usage and structure of ultrasonic communication in mice, with a focus on the gene FOXP2 involved in specific language impairments and neuroligin genes (NL-3 and NL-4) involved in autism spectrum disorders. Knockout of FoxP2 leads to reduced vocal behavior and eventually premature death. Introducing the human variant of FoxP2 protein into mice, in contrast, results in shifts in frequency and modulation of pup ultrasonic vocalizations. Knockout of NL-3 and NL-4 in mice diminishes social behavior and vocalizations. Although such studies may provide insights into the molecular and neural basis of social and communicative behavior, the structure of mouse vocalizations is largely innate, limiting the suitability of the mouse model to study human speech, a learned mode of production. Although knockout or replacement of single genes has perceptible effects on behavior, these genes are part of larger networks whose functions remain poorly understood. In humans, for instance, deficiencies in NL-4 can lead to a broad spectrum of disorders, suggesting that further factors (experiential and/or genetic) contribute to the variation in clinical symptoms. The precise nature as well as the interaction of these factors is yet to be determined.

Autism spectrum disorder (ASD) is a frequent neurodevelopmental disorder characterized by variable clinical severity. Core symptoms are qualitatively impaired communication and social behavior, highly restricted interests and repetitive behaviors. Although recent work on genetic mutations in ASD has shed light on the pathophysiology of the disease, classifying it essentially as a synaptopathy, no treatments are available to date. To develop and test novel ASD treatment approaches, validated and informative animal models are required. Of particular interest, in this context are loss‐of‐function mutations in the postsynaptic cell adhesion protein neuroligin‐4 and point mutations in its homologue neuroligin‐3 (NL‐3) that were found to cause certain forms of monogenic heritable ASD in humans. Here, we show that NL‐3‐deficient mice display a behavioral phenotype reminiscent of the lead symptoms of ASD: reduced ultrasound vocalization and a lack of social novelty preference. The latter may be related to an olfactory deficiency observed in the NL‐3 mutants. Interestingly, such olfactory phenotype is also present in a subgroup of human ASD patients. Tests for learning and memory showed no gross abnormalities in NL‐3 mutants. Also, no alterations were found in time spent in social interaction, prepulse inhibition, seizure propensity and sucrose preference. As often seen in adult ASD patients, total brain volume of NL‐3 mutant mice was slightly reduced as assessed by magnetic resonance imaging (MRI). Our findings show that the NL‐3 knockout mouse represents a useful animal model for understanding pathophysiological events in monogenic heritable ASD and for developing novel treatment strategies in this devastating human disorder.

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.

Studies on primate vocalisation have revealed different types of alarm call systems ranging from graded signals based on response urgency to functionally referential alarm calls that elicit predator-specific reactions. In addition, alarm call systems that include both highly specific and other more unspecific calls have been reported. There has been consistent discussion on the possible factors leading to the evolution of different alarm call systems, among which is the need of qualitatively different escape strategies. We studied the alarm calls of free-ranging saddleback and moustached tamarins (Saguinus fuscicollis and Saguinus mystax) in northeast Peru. Both species have predator-specific alarm calls and show specific non-vocal reactions. In response to aerial predators, they look upwards and quickly move downwards, while in response to terrestrial predators, they look downwards and sometimes approach the predator. We conducted playback experiments to test if the predator-specific reactions could be elicited in the absence of the predator by the tamarins' alarm calls alone. We found that in response to aerial alarm call playbacks the subjects looked significantly longer upwards, and in response to terrestrial alarm call playbacks they looked significantly longer downwards. Thus, the tamarins reacted as if external referents, i.e. information about the predator type or the appropriate reaction, were encoded in the acoustic features of the calls. In addition, we found no differences in the responses of S. fuscicollis and S. mystax whether the alarm call stimulus was produced by a conspecific or a heterospecific caller. Furthermore, it seems that S. fuscicollis terrestrial alarm calls were less specific than either S. mystax terrestrial predator alarms or either species' aerial predator alarms, but because of the small sample size it is difficult to draw a final conclusion.

The acoustic structure of loud calls (“wahoos”) recorded from free-ranging male baboons (Papio cynocephalus ursinus) in the Moremi Game Reserve, Botswana, was examined for differences between and within contexts, using calls given in response to predators (alarm wahoos), during male contests (contest wahoos), and when a male had become separated from the group (contact wahoos). Calls were recorded from adolescent, subadult, and adult males. In addition, male alarm calls were compared with those recorded from females. Despite their superficial acoustic similarity, the analysis revealed a number of significant differences between alarm, contest, and contact wahoos. Contest wahoos are given at a much higher rate, exhibit lower frequency characteristics, have a longer “hoo” duration, and a relatively louder “hoo” portion than alarm wahoos. Contact wahoos are acoustically similar to contest wahoos, but are given at a much lower rate. Both alarm and contest wahoos also exhibit significant differences among individuals. Some of the acoustic features that vary in relation to age and sex presumably reflect differences in body size, whereas others are possibly related to male stamina and endurance. The finding that calls serving markedly different functions constitute variants of the same general call type suggests that the vocal production in nonhuman primates is evolutionarily constrained.

This study provides an overview of the vocalizations of Barbary macaques, Macaca sylvanus. Spectrographic displays of calls are presented along with photographs of the accompanying facial gestures. We give a general description of the contexts in which the different calls are uttered, with special regard to the age and sex of the caller. The vocal repertoire of Barbary macaques mainly consists of screams, shrill barks, geckers, low-frequency pants and grunts, with gradation occurring within and between call types. The spectrograms document that typically, Barbary macaques produce series of several consecutive calls. The influence of habitat, social structure and phylogenetic descent on the morphology of the repertoire and call diversity are discussed in comparison to other species.

We studied variation in the loud barks of free‐ranging female chacma baboons (Papio cynocephalus ursinus) with respect to context, predator type, and individuality over an 18‐month period in the Moremi Game Reserve, Botswana. To examine acoustic differences in relation to these variables, we extracted a suite of acoustic parameters from digitized calls and applied discriminant function analyses. The barks constitute a graded continuum, ranging from a tonal, harmonically rich call into a call with a more noisy, harsh structure. Tonal barks are typically given when the signaler is at risk of losing contact with the group or when a mother and infant have become separated (contact barks). The harsher variants are given in response to large predators (alarm barks). However, there are also intermediate forms between the two subtypes which may occur in both situations. This finding is not due to an overlap of individuals' distinct distributions but can be replicated within individuals. Within the alarm bark category, there are significant differences between calls given in response to mammalian carnivores and those given in response to crocodiles. Again, there are intermediate variants. Both alarm call types are equally different from contact barks, indicating that the calls vary along different dimensions. Finally, there are consistent, significant differences among different individuals' calls. However, individual identity in one call type cannot directly be inferred from knowledge of the individuals' call characteristics in the other. In sum, the barks of female baboons potentially provide rich information to the recipients of these signals. The extent to which baboons discriminate between alarm and contact barks, and classify calls according to context and/or acoustic similarity will be described in a subsequent paper.

In order to test whether 'coo' calls of young rhesus macaques, Macaca mulatta, undergo same modifications during early development, and to explore which factors may influence these changes, we studied the ontogeny of their contact call, the 'coo' call. Vocalizations were recorded during brief periods of social separation. Infants were either raised with their mothers and other conspecifics, or separated from their mothers at birth and housed in a nursery with other infants. We recorded calls uttered in the separation context from 20 infants. We digitized the first 50 calls of a given series and subjected them to a Fourier transform. From each frequency-time spectrum, we extracted 65 acoustic parameters using a software program (LMA 5.9). We then used a cluster analysis to separate the 'coo' calls from other call types. With increasing age, the 'coos' dropped in pitch and became more even. The course of amplitude became more constant and the call duration increased slightly. Nevertheless, we found a high intra-individual variation throughout the 5mo. Neither rearing condition nor sex had any apparent influence on age-related changes in 'coo' structure. With one exception, all parameters that correlated with age could be explained by variation in weight. Therefore, we conclude that growth is the main factor accounting for the observed changes.

We examined vocalizations of Barbary macaques, Macaca sylvanus, given in response to a dog, in two populations, at Rocamadour, France, and Salem, Germany. Calls were recorded from 16 individuals in Rocamadour and 23 individuals in Salem. Despite an overall similarity, an acoustic analysis revealed significant differences in the call structure between populations. To test the perceptual salience of these acoustic differences, we conducted playback experiments in both populations in which calls from the own or the other population were broadcast. The overall response pattern did not differ significantly between the populations with regard to the origin of the call. However, subjects responded slightly, but significantly longer after playback of calls from the other group. Although call function apparently determined the general response of subjects, they none the less discriminated between calls from different origins. These results suggest a small but possibly meaningful plasticity in call production. Copyright 1998 The Association for the Study of Animal Behaviour.

The vocal behavior of Barbary macaques (Macaca sylvanus) was studied in an outdoor enclosure at Rocamadour, France. Ad libitum recordings were made across a broad array of socioecological contests from 92 individually identified subjects from all age-sex classes. From the recordings, 8479 calls were sampled and submitted to a Fourier transform. A custom software program was used to determine 35 acoustic parameters describing the call in terms of its frequency and time dynamics. On these parameters a cluster analysis was used to examine the acoustic morphology of the Barbary macaque vocal repertoire. The analysis revealed a highly graded structure with intergraded variations between different clusters ('call types'). There were clear age-related preferences in usage of different clusters, but animals of all ages were potentially able to produce the whole array of call types. The major sex difference was a differential use of certain call types in specific situations. Despite a clear sex dimorphism in body size no significant sex differences in the acoustic structure of calls in adults was found. There were no unidirectional relationships between the acoustic structure of a call and the context in which it was uttered, although call usage was more specific in some contexts than in others. The results suggest that the major factor underlying the variation in acoustic structure reflect the internal state of the caller.

Semi-free-ranging Barbary macaques (Macaca sylvanus) were observed to utter distinctive calls after disturbances in the surroundings (e.g. presence of a predator, occurrence of some unusual phenomenon). These calls differed from calls given in other contexts. Most of these calls were uttered in a serial manner, some of which lasted as long as the corresponding context. The aim of this study was to determine the object-related specificity of calls and variation of acoustic parameters within a call series. The analysis revealed that acoustic features of calls varied among contexts. Within one apparently homogeneous context, both temporal and frequency characteristics shifted gradually. Furthermore, the disturbance calls clearly differed between individuals. To examine the disturbance calls' meaning, playback experiments were conducted in which alarm calls and disturbance calls were presented. After playback of an alarm call, subjects typically showed an escape response, whereas, in response to disturbance calls, they most often scanned the surroundings. Juvenile animals generally showed stronger responses than adults.

Barbary macaques (Macaca sylvanus) show an increase in vocal activity at dusk. This investigation showed that these vocalizations were mainly produced by juveniles from six to 18 months of age, during their attempts to achieve body contact with their mothers, thereby building up a sleeping cluster. The "dusk calling" consisted of protracted sequences of variable vocal patterns which always ceased when the juvenile joined its preferred sleeping cluster. The length of the sequences corresponded to the time it took the juvenile to be accepted into a sleeping cluster. One-year-old juveniles exhibited the highest vocal activity. The similarity of the results obtained in two outdoor enclosures in France and of those in the field (Morocco) indicated that dusk calling is common to this species, and not a behavior unique to captive animals. © Wiley-Liss, Inc.

Sleeping cluster composition and distribution were studied in a semi-free-ranging population of 174 Barbary macaques (Macaca sylvanus) in Rocamadour/France. Over a period of 2 months 341 sleeping clusters comprising 754 animals were recorded as animals left the sleeping trees. To control for nocturnal activities five observation periods were conducted, each of which covered a complete night. Sleeping partners were selected from a particular set of individuals. From night to night there was considerable fluctuation among the individuals, which finally formed a sleeping cluster. Preferred size of sleeping clusters was two and three individuals per cluster. The majority of females spent the nights in body contact to infants or female juveniles; whereas males either slept alone or with older male juveniles. Adult males and females never shared a sleeping cluster. During the night the animals showed hardly any locomotive and vocal activity. Sleeping clusters remained stable until dissociation the next morning. © 1992 Wiley-Liss, Inc.