A humanized version of Foxp2 affects cortico-basal ganglia circuits in mice.

It has been proposed that two amino acid substitutions in the transcription factor FOXP2 have been positively selected during human evolution due to effects on aspects of speech and language. Here, we introduce these substitutions into the endogenous Foxp2 gene of mice. Although these mice are generally healthy, they have qualitatively different ultrasonic vocalizations, decreased exploratory behavior and decreased dopamine concentrations in the brain suggesting that the humanized Foxp2 allele affects basal ganglia. In the striatum, a part of the basal ganglia affected in humans with a speech deficit due to a nonfunctional FOXP2 allele, we find that medium spiny neurons have increased dendrite lengths and increased synaptic plasticity. Since mice carrying one nonfunctional Foxp2 allele show opposite effects, this suggests that alterations in cortico-basal ganglia circuits might have been important for the evolution of speech and language in humans.

The acoustic structure of spider monkey (Ateles geoffroyi) calls is related both to caller goal and arousal.

Analyzing the factors related to the acoustic structure of primate calls is fundamental to identifying the potential information these signals convey, and therefore, their potential function. It is well-accepted that caller arousal is an important driver of acoustic variation in call structure. However, evidence suggests that arousal alone cannot explain the production of calls with different acoustic structures. The "caller goal" framework posits that a call type (e.g., bark and chitter) is a signal which evolved to elicit specific changes on receiver behavior, and a caller's goal, not its arousal state, determines the basic acoustic structure of animal calls. To get a better insight into the effects of caller goal and arousal on the acoustic structure of primate calls, we analyzed the acoustic variation of 382 calls produced by 27 free-ranging spider monkeys (Ateles geoffroyi) in six call contexts representing three caller goals (establishing contact, engage in aggression, and predator presence) across two arousal states (high and low). Discriminant function analyses and linear mixed models showed a strong effect of caller goal on calls' acoustic structure and supported the effect of arousal state on acoustic variation; misclassified calls mainly occurred between the same caller goal categories (e.g., alarm low arousal and alarm high arousal), and acoustic differences between arousal contexts showed the same pattern across the three caller goals (e.g., low center frequency [kHz] values in high arousal contexts). Our results supported the view that caller goal is the primary driver of acoustic difference and showed the effects of caller arousal on other structural differences.

Vocal convergence in a multi-level primate society: insights into the evolution of vocal learning.

The extent to which nonhuman primate vocalizations are amenable to modification through experience is relevant for understanding the substrate from which human speech evolved. We examined the vocal behaviour of Guinea baboons, Papio papio, ranging in the Niokolo Koba National Park in Senegal. Guinea baboons live in a multi-level society, with units nested within parties nested within gangs. We investigated whether the acoustic structure of grunts of 27 male baboons of two gangs varied with party/gang membership and genetic relatedness. Males in this species are philopatric, resulting in increased male relatedness within gangs and parties. Grunts of males that were members of the same social levels were more similar than those of males in different social levels (N = 351 dyads for comparison within and between gangs, and N = 169 dyads within and between parties), but the effect sizes were small. Yet, acoustic similarity did not correlate with genetic relatedness, suggesting that higher amounts of social interactions rather than genetic relatedness promote the observed vocal convergence. We consider this convergence a result of sensory-motor integration and suggest this to be an implicit form of vocal learning shared with humans, in contrast to the goal-directed and intentional explicit form of vocal learning unique to human speech acquisition.

The postnatal development of ultrasonic vocalization-associated breathing is altered in glycine transporter 2-deficient mice.

KEY POINTS: Newborn mice produce ultrasonic vocalization to communicate with their mother. The neuronal glycine transporter (GlyT2) is required for efficient loading of synaptic vesicles in glycinergic neurons. Mice lacking GlyT2 develop a phenotype that resembles human hyperekplexia and the mice die in the second postnatal week. In the present study, we show that GlyT2-knockout mice do not acquire adult ultrasonic vocalization-associated breathing patterns. Despite the strong impairment of glycinergic inhibition, they can produce sufficient expiratory airflow to produce ultrasonic vocalization. Because mouse ultrasonic vocalization is a valuable read-out in translational research, these data are highly relevant for a broad range of research fields. ABSTRACT: Mouse models are instrumental with respect to determining the genetic basis and neural foundations of breathing regulation. To test the hypothesis that glycinergic synaptic inhibition is required for normal breathing and proper post-inspiratory activity, we analysed breathing and ultrasonic vocalization (USV) patterns in neonatal mice lacking the neuronal glycine transporter (GlyT2). GlyT2-knockout (KO) mice have a profound reduction of glycinergic synaptic currents already at birth, develop a severe motor phenotype and survive only until the second postnatal week. At this stage, GlyT2-KO mice are smaller, have a reduced respiratory rate and still display a neonatal breathing pattern with active expiration for the production of USV. By contrast, wild-type mice acquire different USV-associated breathing patterns that depend on post-inspiratory control of air flow. Nonetheless, USVs per se remain largely indistinguishable between both genotypes. We conclude that GlyT2-KO mice, despite the strong impairment of glycinergic inhibition, can produce sufficient expiratory airflow to produce ultrasonic vocalization.

Baboon vocal repertoires and the evolution of primate vocal diversity.

A remarkable and derived trait of humans is the faculty for language, and considerable research effort has been devoted to understanding the evolution of speech. In contrast to spoken language, which constitutes a (learned) symbolic communication system, the acoustic structure of nonhuman primate vocalizations is largely genetically fixed. Yet, appreciable differences between different genera and species may exist. Environmental conditions, sexual selection, and characteristics of the social system have been invoked to explain these differences. Here, we studied the acoustic variation of call types and vocal repertoires in the genus Papio. Because the genus comprises both stable groups as well as multi-level societies, and reveals striking variation in the degree of aggressiveness from south to north, it constitutes a promising model to assess the link between social system characteristics and vocal communication. We found that, the vocal repertoires of the different species were composed of the same general call types. A quantitative analysis of the acoustic features of the grunts and loud calls of chacma (Papio ursinus), olive (P. anubis), and Guinea (P. papio) baboons showed subtle acoustic differences within call types, however. Social system characteristics did not map onto acoustic variation. We found no correlation between the structure of grunts and geographic distance; the same was true for female loud calls. Only for male loud calls from three populations, call structure varied with geographic distance. Our findings corroborate the view that the structure of nonhuman primate vocalizations is highly conserved, despite the differences in social systems. Apparently, variation in rate and intensity of occurrence of signals, probably due to different behavioral dispositions in species, are sufficient to allow for plasticity at the level of the social relationships, mating patterns, and social organization.

Acoustic variation of spider monkeys' contact calls (whinnies) is related to distance between vocalizing individuals and immediate caller behavior.

Due to several factors such as ecological conditions, group size, and social organization, primates frequently spend time out of visual contact with individuals of their own group. Through the use of long-distance vocalizations, often termed "contact calls," primates are able to maintain contact with out-of-sight individuals. Contact calls have been shown to be individually distinct, and reverberation and attenuation provide information about caller distance. It is less clear, however, whether callers actively change the structure of contact calls depending on the distance to the presumed listeners. We studied this question in spider monkeys (Ateles geoffroyi), a species with complex spatial dynamics (fission-fusion society) that produces highly frequency modulated contact calls, denominated "whinnies." We determined the acoustic characteristics of 566 whinnies recorded from 35 free-ranging spider monkeys that belong to a community located in Mexico, and used cluster analyses, discriminant function analyses, and generalized linear mixed models to assess if they varied in relation to the presumed distance to the listener. Whinnies could be grouped into five subtypes. Since the lowest frequency subtype was mainly produced by spider monkeys that exchanged whinnies at longer distances, and lower frequency calls propagate across longer distances, our results suggest that whinnies vary in order to enhance vocal contact between individuals separated by different distances. Our results also revealed that whinnies convey potential information about caller immediate behaviors and corroborated that these calls are individually distinct. Overall, our results suggest that whinny acoustic variation facilitates the maintenance of vocal contact between individuals living in a society with complex spatial dynamics.

Do sexual calls in female black capuchin monkeys (Sapajus nigritus) vary with fertility? An acoustic analysis.

Females across a range of animal taxa produce vocalizations and signals uniquely associated with periods of mating. While such signals may ultimately function to increase female attractivity to males, conflicting findings challenge the extent to which these signals co-vary in accordance with the probability of conception. Female black capuchin monkeys (Sapajus nigritus) display an elaborate repertoire of both vocal and visual components as part of their socio-sexual behavior, and previous analyses have shown that the rates of production of visual, but not vocal, components provide graded information on female ovulation. It remains possible, however, that the acoustic parameters of these sexual calls, rather than their rate of productions, co-vary with female fertility. To test this, we analyzed structural and temporal call parameters from estrous calls and post-copulatory calls recorded over five consecutive mating seasons in 12 sexually mature females at Iguazú National Park, Argentina. Calls given during the fertile phase of the female ovarian cycle were compared with those given during the non-fertile phase, as determined by profiles of female reproductive hormones. Similarly, within the fertile phase, we tested whether temporal or spectral acoustic parameters of calls gradually change with the approach of ovulation. We did not find any significant relationship between call parameters and the two measures of female fertility in either female estrous calls or post-copulatory calls. However, some differences between pre- and post-copulatory calls were apparent. Overall, our results indicate that sexual calls in black capuchin females do not provide precise information about the timing of ovulation, but may allow listeners to make probabilistic inferences about whether copulations have taken place. This, combined with previous findings, suggests that females in our study may use signals in different modalities to convey information about their fertility and sexual behavior with varying degrees of precision.

Charting the neglected West: The social system of Guinea baboons.

OBJECTIVES: Primate social systems are remarkably diverse, and thus play a central role in understanding social evolution, including the biological origin of human societies. Although baboons have been prominently featured in this context, historically little was known about the westernmost member of the genus, the Guinea baboon (Papio papio). MATERIAL AND METHODS: Here, we summarize the findings from the first years of observations at the field site CRP Simenti in the Niokolo Koba National Park in Senegal. RESULTS: Guinea baboons reveal a nested multi-level social organization, with reproductive units comprising one "primary" male, one to several females, young, and occasionally "secondary" males at the base of the society. Three to five units form "parties," which team up with other parties to form a "gang." Different gangs have largely overlapping home ranges and agonistic interactions between different parties or gangs are rare. Some but not all strongly socially bonded males are highly related, and population genetic and behavioral evidence indicate female-biased dispersal. Females play an important role in intersexual bond formation and maintenance, and female tenure length varies between a few weeks to several years. DISCUSSION: While the social organization resembles that of hamadryas baboons (P. hamadryas), the social structure differs considerably, specifically in terms of low male aggressiveness and female freedom. Despite substantial differences in social organization and social structure, the acoustic structure of Guinea baboon vocalizations does not differ substantially from that of other baboon taxa. With its multi-level organization, stable bonds between males and females, as well as a high-degree of male-male cooperation and tolerance, Guinea baboons constitute an intriguing model for reconstructing human social evolution.

Social interactions and activity patterns of old Barbary macaques: Further insights into the foundations of social selectivity.

Human aging is accompanied by a decrease in social activity and a narrowing in social networks. Studies in nonhuman primates may provide valuable comparative insights in which way aging impacts social life, in the absence of cultural conventions and an awareness of a limited lifetime. For female Barbary macaques at "La Forêt des Singes" in Rocamadour, France, we previously reported an age-associated decrease in active grooming time and network size. Here, we aimed to extend these findings by investigating in which way physical decline, spatial proximity, and aggression vary with age in female Barbary macaques. We analyzed >1,200 hr of focal observations for 46 females aged 5-29 years. As expected, older females engaged less frequently in challenging locomotor activity, such as climbing or running, than younger ones. The previously reported decrease in grooming time was not due to shorter grooming bout duration. Instead, active grooming bouts lasted even longer, which discounts the idea that manual fatigue explains the shift in grooming pattern. We found that older females tended to be spatially reclusive and that they were less frequently the targets of aggression. Although older females showed aggressive behaviors at similar rates as younger females, the proportion of low-level aggression (i.e., threats) increased with age. We suggest that these threats are not simply a signal of dominance, but also function to deter approaches by others. Overall, these findings are in line with the idea that older females aim to avoid potentially negative interactions, specifically if these are costly. In sum, these findings support the idea that shifts in female Barbary macaques' grooming activity, do not simply result from physical deterioration, but are instead due to a higher selectivity in the choice of social partners.

Vocal repertoire of long-finned pilot whales (Globicephala melas) in northern Norway.

The knowledge of the vocal repertoire of pilot whales is very limited. In this paper, the vocal repertoire of long-finned pilot whales recorded during different encounters in the Vestfjord in northern Norway between November 2006 and August 2010 are described. Sounds were analysed using two different methods: (1) an observer-based audio-visual inspection of FFT-derived spectrograms, with which, besides a general variety of clicks, buzzes, nonharmonic sounds, and whistles, 129 different distinct call types and 25 subtypes were distinguished. These call types included pulsed calls and discrete structured whistles varying from simple to highly complex structures composed of several segments and elements. In addition, ultrasonic whistles previously not described for pilot whales were found. In addition to the diversity of single calls, call sequences consisting of repetitions and combinations of specific call types were recorded and (2) a parametric approach that permitted the confirmation of the high variability in pilot whale call structures was developed. It is concluded that the pilot whale vocal repertoire is among the most complex for the mammalian species and the high structural variability, along with call repetitions and combinations, require a closer investigation to judge their importance for vocal communication.

Are simakobu (Simias concolor) loud calls energetically costly signals?

OBJECTIVES: Male vocal displays play an important role in sexual selection in many species. If there are costs or constraints, calls may convey honest information about the caller. We studied the loud calls of male simakobu (Simias concolor), a sexually dimorphic primate that resides in one-male groups, on Siberut Island, Indonesia. MATERIALS AND METHODS: We combined behavioral and ecological data with acoustic analysis to determine the influence of energy costs and status on calling effort. Based on all-day follows (n = 107) and loud-call recordings (n = 186), we determined how calling rates and durations varied in relation to short-term (time of day, temperature, travel distance) and long-term (fruit availability, physical condition) measures of energy availability and expenditure. RESULTS: We found that males avoided calling at the hottest times of the day, and produced shorter calls at higher temperatures, supporting the hypothesis that calls are influenced by thermoregulation costs. A peak of longer duration calls just before sunrise, however, could not be explained by energy constraints, but we hypothesize that this pattern is related to the fact that dawn calls occur in choruses, motivating males to call longer than their neighbors. Contrary to predictions, calling rates increased with decreasing fruit availability and did not appear to be energetically costly. DISCUSSION: We hypothesize that calling rates instead reflect strategies involving feeding and/or mate competition, signaling the motivation, rather than fighting ability, of the caller. Overall, results only weakly support the hypothesis that the timing and duration-but not rate-of simakobu loud calls are influenced by energy costs. Am J Phys Anthropol 161:44-52, 2016. © 2016 Wiley Periodicals, Inc.

Vocal communication in a complex multi-level society: constrained acoustic structure and flexible call usage in Guinea baboons.

BACKGROUND: To understand the evolution of acoustic communication in animals, it is important to distinguish between the structure and the usage of vocal signals, since both aspects are subject to different constraints. In terrestrial mammals, the structure of calls is largely innate, while individuals have a greater ability to actively initiate or withhold calls. In closely related taxa, one would therefore predict a higher flexibility in call usage compared to call structure. In the present study, we investigated the vocal repertoire of free living Guinea baboons (Papio papio) and examined the structure and usage of the animals' vocal signals. Guinea baboons live in a complex multi-level social organization and exhibit a largely tolerant and affiliative social style, contrary to most other baboon taxa. To classify the vocal repertoire of male and female Guinea baboons, cluster analyses were used and focal observations were conducted to assess the usage of vocal signals in the particular contexts. RESULTS: In general, the vocal repertoire of Guinea baboons largely corresponded to the vocal repertoire other baboon taxa. The usage of calls, however, differed considerably from other baboon taxa and corresponded with the specific characteristics of the Guinea baboons' social behaviour. While Guinea baboons showed a diminished usage of contest and display vocalizations (a common pattern observed in chacma baboons), they frequently used vocal signals during affiliative and greeting interactions. CONCLUSIONS: Our study shows that the call structure of primates is largely unaffected by the species' social system (including grouping patterns and social interactions), while the usage of calls can be more flexibly adjusted, reflecting the quality of social interactions of the individuals. Our results support the view that the primary function of social signals is to regulate social interactions, and therefore the degree of competition and cooperation may be more important to explain variation in call usage than grouping patterns or group size.

Bioacoustic field research: a primer to acoustic analyses and playback experiments with primates.

Acoustic analyses of primate vocalizations as well as playback experiments are staple methods in primatology. Acoustic analyses have been used to investigate the influence of factors such as individuality, context, sex, age, and size on variation in calls. More recent studies have expanded our knowledge on the effects of phylogenetic relatedness and the structure of primate vocal repertoires in general. Complementary playback experiments allow direct testing of hypotheses regarding the attribution of meaning to calls, the cognitive mechanisms underpinning responses, and/or the adaptive value of primate behavior. After briefly touching on the historical background of this field of research, we first provide an introduction to recording primate vocalizations and discuss different approaches to describe primate calls in terms of their temporal and spectral properties. Second, we present a tutorial regarding the preparation, execution, and interpretation of field playback experiments, including a review of studies that have used such approaches to investigate the responses to acoustic variation in calls including the integration of contextual and acoustic information, recognition of kin and social relationships, and social knowledge. Based on the review of the literature and our own experience, we make a number of recommendations regarding the most common problems and pitfalls. The power of acoustic analyses typically hinges on the quality of the recordings and the number of individuals represented in the sample. Playback experiments require profound knowledge of the natural behavior of the animals for solid interpretation; experiments should be conducted sparingly, to avoid habituation of the subjects to the occurrence of the calls; experimenter-blind designs chosen whenever possible; and researchers should brace themselves for long periods of waiting times until the appropriate moments to do the experiment arise. If all these aspects are considered, acoustic analyses and field playback experiments provide unique insights into primate communication and cognition.

Proximate factors underpinning receiver responses to deceptive false alarm calls in wild tufted capuchin monkeys: is it counterdeception?

Previous research demonstrates that tufted capuchin monkeys use terrestrial predator alarm calls in a functionally deceptive manner to distract conspecifics when feeding on contestable resources, although the success of this tactic is limited because listeners frequently ignore these calls when given in such situations. While this decreased response rate is suggestive of a counterstrategy to deception by receivers, the proximate factors underpinning the behavior are unclear. The current study aims to test if the decreased response rate to alarm calls in competitive contexts is better explained by the perception of subtle acoustic differences between predator-elicited and deceptive false alarms, or by receivers varying their responses based on the context in which the signal is received. This was tested by first examining the acoustic structure of predator-elicited and deceptive false alarms for any potentially perceptible acoustic differences, and second by comparing the responses of capuchins to playbacks of each of predator-elicited and false alarms, played back in noncompetitive contexts. The results indicate that deceptive false alarms and predator-elicited alarms show, at best, minimal acoustic differences based on the structural features measured. Likewise, playbacks of deceptive false alarms elicited antipredator reactions at the same rate as did predator-elicited alarms, although there was a nonsignificant tendency for false alarms to be more likely to elicit escape reactions. The lack of robust acoustic differences together with the high response rate to false alarms in noncompetitive contexts suggests that the context in which the signal is received best explains receiver responses. It remains unclear, however, if listeners ascribe different meanings to the calls based on context, or if they generally ignore all signals in competitive contexts. Whether or not the decreased response rate of receivers directly stems from the deceptive use of the calls cannot be determined until these latter possibilities are rigorously tested.

Isolated catatonia-like executive dysfunction in mice with forebrain-specific loss of myelin integrity.

A key feature of advanced brain aging includes structural defects of intracortical myelin that are associated with secondary neuroinflammation. A similar pathology is seen in specific myelin mutant mice that model 'advanced brain aging' and exhibit a range of behavioral abnormalities. However, the cognitive assessment of these mutants is problematic because myelin-dependent motor-sensory functions are required for quantitative behavioral readouts. To better understand the role of cortical myelin integrity for higher brain functions, we generated mice lacking Plp1, encoding the major integral myelin membrane protein, selectively in ventricular zone stem cells of the mouse forebrain. In contrast to conventional Plp1 null mutants, subtle myelin defects were restricted to the cortex, hippocampus, and underlying callosal tracts. Moreover, forebrain-specific Plp1 mutants exhibited no defects of basic motor-sensory performance at any age tested. Surprisingly, several behavioral alterations reported for conventional Plp1 null mice (Gould et al., 2018) were absent and even social interactions appeared normal. However, with novel behavioral paradigms, we determined catatonia-like symptoms and isolated executive dysfunction in both genders. This suggests that loss of myelin integrity has an impact on cortical connectivity and underlies specific defects of executive function. These observations are likewise relevant for human neuropsychiatric conditions and other myelin-related diseases.

Acoustic structure of male loud-calls support molecular phylogeny of Sumatran and Javanese leaf monkeys (genus Presbytis).

BACKGROUND: The degree to which loud-calls in nonhuman primates can be used as a reliable taxonomic tool is the subject of ongoing debate. A recent study on crested gibbons showed that these species can be well distinguished by their songs; even at the population level the authors found reliable differences. Although there are some further studies on geographic and phylogenetic differences in loud-calls of nonhuman primate species, it is unclear to what extent loud-calls of other species have a similar close relation between acoustic structure, phylogenetic relatedness and geographic distance. We therefore conducted a field survey in 19 locations on Sumatra, Java and the Mentawai islands to record male loud-calls of wild surilis (Presbytis), a genus of Asian leaf monkeys (Colobinae) with disputed taxanomy, and compared the structure of their loud-calls with a molecular genetic analysis. RESULTS: The acoustic analysis of 100 surili male loud-calls from 68 wild animals confirms the differentiation of P.potenziani, P.comata, P.thomasi and P.melalophos. In a more detailed acoustic analysis of subspecies of P.melalophos, a further separation of the southern P.m.mitrata confirms the proposed paraphyly of this group. In concordance with their geographic distribution we found the highest correlation between call structure and genetic similarity, and lesser significant correlations between call structure and geographic distance, and genetic similarity and geographic distance. CONCLUSIONS: In this study we show, that as in crested gibbons, the acoustic structure of surili loud-calls is a reliable tool to distinguish between species and to verify phylogenetic relatedness and migration backgrounds of respective taxa. Since vocal production in other nonhuman primates show similar constraints, it is likely that an acoustic analysis of call structure can help to clarify taxonomic and phylogenetic relationships.

Mice do not require auditory input for the normal development of their ultrasonic vocalizations.

BACKGROUND: Transgenic 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. RESULTS: We 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. CONCLUSION: The 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.

Introducing the Software CASE (Cluster and Analyze Sound Events) by Comparing Different Clustering Methods and Audio Transformation Techniques Using Animal Vocalizations.

Unsupervised clustering algorithms are widely used in ecology and conservation to classify animal sounds, but also offer several advantages in basic bioacoustics research. Consequently, it is important to overcome the existing challenges. A common practice is extracting the acoustic features of vocalizations one-dimensionally, only extracting an average value for a given feature for the entire vocalization. With frequency-modulated vocalizations, whose acoustic features can change over time, this can lead to insufficient characterization. Whether the necessary parameters have been set correctly and the obtained clustering result reliably classifies the vocalizations subsequently often remains unclear. The presented software, CASE, is intended to overcome these challenges. Established and new unsupervised clustering methods (community detection, affinity propagation, HDBSCAN, and fuzzy clustering) are tested in combination with various classifiers (k-nearest neighbor, dynamic time-warping, and cross-correlation) using differently transformed animal vocalizations. These methods are compared with predefined clusters to determine their strengths and weaknesses. In addition, a multidimensional data transformation procedure is presented that better represents the course of multiple acoustic features. The results suggest that, especially with frequency-modulated vocalizations, clustering is more applicable with multidimensional feature extraction compared with one-dimensional feature extraction. The characterization and clustering of vocalizations in multidimensional space offer great potential for future bioacoustic studies. The software CASE includes the developed method of multidimensional feature extraction, as well as all used clustering methods. It allows quickly applying several clustering algorithms to one data set to compare their results and to verify their reliability based on their consistency. Moreover, the software CASE determines the optimal values of most of the necessary parameters automatically. To take advantage of these benefits, the software CASE is provided for free download.

Concordance between vocal and genetic diversity in crested gibbons.

BACKGROUND: Gibbons or small apes are, next to great apes, our closest living relatives, and form the most diverse group of contemporary hominoids. A characteristic trait of gibbons is their species-specific song structure, which, however, exhibits a certain amount of inter- and intra-individual variation. Although differences in gibbon song structure are routinely applied as taxonomic tool to identify subspecies and species, it remains unclear to which degree acoustic and phylogenetic differences are correlated. To trace this issue, we comparatively analyse song recordings and mitochondrial cytochrome b gene sequence data from 22 gibbon populations representing six of the seven crested gibbon species (genus Nomascus). In addition, we address whether song similarity and geographic distribution can support a recent hypothesis about the biogeographic history of crested gibbons. RESULTS: The acoustic analysis of 92 gibbon duets confirms the hypothesised concordance between song structure and phylogeny. Based on features of male and female songs, we can not only distinguish between N. nasutus, N. concolor and the four southern species (N. leucogenys, N. siki, N. annamensis, N. gabriellae), but also between the latter by applying more detailed analysis. In addition to the significant correlation between song structure and genetic similarity, we find a similar high correlation between song similarity and geographic distance. CONCLUSIONS: The results show that the structure of crested gibbon songs is not only a reliable tool to verify phylogenetic relatedness, but also to unravel geographic origins. As vocal production in other nonhuman primate species appears to be evolutionarily based, it is likely that loud calls produced by other species can serve as characters to elucidate phylogenetic relationships.

Adult but not juvenile Barbary macaques spontaneously recognize group members from pictures.

For group-living animals, it is crucial to distinguish one's own group members from those of other groups. Studies applying operant conditioning revealed that monkeys living in relatively small groups are able to recognize their own group members when tested with photographs of group members and other conspecifics. Employing a simple looking time paradigm, we here show that Barbary macaques living in two social groups comprising 46 and 57 individuals, respectively, at the enclosure 'La Forêt des Singes' at Rocamadour are able to spontaneously distinguish photographs of members of their own group from those depicting animals that belong to another group. This ability appears to develop with age, as juveniles did not discriminate between members of their own group and another group, although they showed generally more interest in the pictures than did adults. Juveniles frequently displayed picture directed behaviours such as lip-smacking, touching and sniffing in both conditions, indicating that the stimuli were highly salient to them. In conclusion, it appears that at least adult monkeys are able to memorize the faces of a large number of individuals. Whether the difference in behaviour is based on individual recognition of one's own group members or simply the discrimination based on familiarity remains unresolved. However, both mechanisms would be sufficient for group membership identification.