Behavioural responses of male ruffed grouse (Bonasa umbellus,L.) to playbacks of drumming displays

Birds use a variety of sounds in their courtship displays, but the majority of behavioural studies have focused on vocalizations. In contrast, little is known about how non‐vocal sounds, or sonations, are used, even though many avian species produce them. The ruffed grouse (Bonasa umbellus) is a useful species to examine non‐vocal sounds because they lack vocal components in their courtship and rely on a non‐vocal sound to attract mates and defend their territory. Their courtship display, known as “drumming,” is created by the wings, and the number of pulses and speed (pulse rate) varies significantly among males. Anecdotal evidence suggested that males can affect the drumming behaviour of neighbouring males in drumming “duels” in an analogous way to song contests. Here, we test whether males do respond to the playback of drumming sounds of an unfamiliar male. Using a portable speaker system, we played recordings of drumming displays to males that were actively drumming themselves. Throughout each playback, we recorded the drumming behaviour of target males so that we could assess whether drumming activity changes following a playback as well as whether males change the speed of their display. Overall, male grouse were equally likely to approach the speaker or continue drumming following a playback. For those males that continued drumming, their drumming pulse rate was significantly faster following playbacks, but they drummed less often. These results indicate that male ruffed grouse do respond to drumming sounds, but the specific response differs among males. Because the differential response was not related to colour phase or whether a male was drumming in proximity to other males, we suggest that the response of individuals likely varies with other traits, such as hormone levels or behavioural syndrome.     

Ruffed Grouse Bonasa umbellus habitat selection in a spatially complex forest: evidence for spatial constraints on patch selection

Drumming display sites of male Ruffed Grouse Bonasa umbellus serve as activity centres and occur in a variety of forest types and age classes. We used a case‐control study design and model selection to evaluate a set of predictions about habitat constraints placed upon Grouse given the habitat where their breeding season activity centres were located. We located 110 individual Grouse activity centres near Cloquet, Minnesota, between 2002 and 2005, and 40 activity centres at two other sites in northern Minnesota in 2005. Our most parsimonious model indicated that Ruffed Grouse used logs more than other potential drumming structures (e.g. stumps, dirt mounds or roots) and sites with a higher density of shrubs as compared with unused sites. Predicted values from this model correlated with observed values from independently sampled areas. Structures used by Grouse for their drumming display were characterized by a greater density of aspen stems than unused sites when in young aspen and mature pine, but not when in other forest types. The patterns of habitat selection that we observed supported predictions (1) that the differences in habitats at larger spatial scales (e.g. forest stands or breeding territories) may impose certain constraints on specific sites selected for their drumming display, and (2) that some of these constraints may vary by forest type.     

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Courtship displays are typically comprised of the same behavioral pattern, or patterns, repeated several times by males. Both the quantity and quality of the displays produced by a given male bird are not, however, constant. The number and/or quality of displays can decrease over time, indicating fatigue, or males can increase the number and/or quality as they display more, indicating a warm-up period. Although there is evidence for fatigue or warm-up periods for many types of courtship displays, data on motor components of avian courtship are scant, despite how commonly they are used. Here, we test whether drumming, a non-vocal motor display, in male ruffed grouse (Bonasa umbellus) changes in relation to the number of displays executed. Using a large number of recordings, our linear mixed models yielded a significant effect of cumulative number of drumming displays on the number of wingbeats per second, referred to as pulse rate. Across males, pulse rate is slowest when males begin drumming each day and increases until approximately 50 drumming displays have been produced. The rate of increase is also modulated by the nighttime low temperature such that cooler conditions are associated with lower pulse rates and a slower increase in pulse rate relative to the cumulative number of displays. Further, the maximum pulse rate recorded and average pulse rate after 50 displays is inversely correlated with body mass such that larger males are slower than smaller males. We suggest that the daily changes in pulse rate likely reflect a warm-up period based upon the effects of cumulative drumming count and temperature on pulse rate. Whether these dynamic changes in the production of a motor display are informative to female grouse is unknown. However, we propose that daily changes in how motor displays are performed may be a common feature of avian courtship that has gone relatively unnoticed, despite the potential for motor performance to be a trait that is important for female mate choice.     

Social,contextual, and individual factors affecting the occurrence and acoustic structure of drumming bouts in wild chimpanzees (Pan troglodytes)

The production of structured and repetitive sounds by striking objects is a behavior found not only in humans, but also in a variety of animal species, including chimpanzees (Pan troglodytes). In this study we examined individual and social factors that may influence the frequency with which individuals engage in drumming behavior when producing long distance pant hoot vocalizations, and analyzed the temporal structure of those drumming bouts. Male chimpanzees from Budongo Forest, Uganda, drummed significantly more frequently during travel than feeding or resting and older individuals were significantly more likely to produce drumming bouts than younger ones. In contrast, we found no evidence that the presence of estrus females, high ranking males and preferred social partners in the caller's vicinty had an effect on the frequency with which an individual accompanied their pant hoot vocalization with drumming. Through acoustic analyses, we demonstrated that drumming sequences produced with pant hoots may have contained information on individual identity and that qualitatively, there was individual variation in the complexity of the temporal patterns produced. We conclude that drumming patterns may act as individually distinctive long‐distance signals that, together with pant hoot vocalizations, function to coordinate the movement and spacing of dispersed individuals within a community, rather than as signals to group members in the immediate audience. Am J Phys Anthropol 156:125–134, 2015 © 2014 Wiley Periodicals, Inc.     

The Lombard effect and other noise‐induced vocal modifications: insight from mammalian communication systems

Humans and non‐human mammals exhibit fundamentally similar vocal responses to increased noise, including increases in vocalization amplitude (the Lombard effect) and changes to spectral and temporal properties of vocalizations. Different research focuses have resulted in significant discrepancies in study methodologies and hypotheses among fields, leading to particular knowledge gaps and techniques specific to each field. This review compares and contrasts noise‐induced vocal modifications observed from human and non‐human mammals with reference to experimental design and the history of each field. Topics include the effects of communication motivation and subject‐specific characteristics on the acoustic parameters of vocalizations, examination of evidence for a proposed biomechanical linkage between the Lombard effect and other spectral and temporal modifications, and effects of noise on self‐communication signals (echolocation). Standardized terminology, cross‐taxa tests of hypotheses, and open areas for future research in each field are recommended. Findings indicate that more research is needed to evaluate linkages among vocal modifications, context dependencies, and the finer details of the Lombard effect during natural communication. Studies of non‐human mammals could benefit from applying the tightly controlled experimental designs developed in human research, while studies of human speech in noise should be expanded to include natural communicative contexts. The effects of experimental design and behavioural context on vocalizations should not be neglected as they may impact the magnitude and type of noise‐induced vocal modifications.     

Correlations between hearing and sound production in piranhas

Summary In order to determine whether correlations exist between hearing and the known soundproduction abilities in piranhas (Serrasalmus nattereri), behavioral auditory thresholds were obtained with continuous tones and tone pulses. A new avoidance conditioning method was developed, where fin movements of caged animals were taken as response to a tone. The mean values of the far-field audiogram ranged from –26 dB re. 0.1 Pa at 80 Hz to a low point of about –43 dB between 220–350 Hz and rose to –14 dB at 1500 Hz. The frequency spectrum of typical drumming sounds (barks) covers the range of best hearing (100–600 Hz).Piranhas are able to integrate temporally acoustic signals: in threshold investigations with repeated tone pulses, the thresholds rose approximately exponentially with decreasing pulse duration and repetition rate; thresholds of single pulses were higher with shorter pulses. The temporal patterning of the calls and the temporal integration ability are well correlated in piranhas, optimizing intraspecific detectability and total length of sound production with respect to the fatigue characteristics of drumming muscles and habituation of the neural pacemaker.The lagenae of the piranhas were found to face laterofrontally; this is thought to be a morphological adaptation to sound production, saving the lagenae from excessive strain during activation of the drumming muscles.Abbreviations Cl acoustic condition 1, where a board with the air loudspeaker rested on the experimental tank upon a layer of felt - C2 acoustic condition 2, where the loudspeaker was freely mounted 20 cm above the water surface - d _p pulse duration - f _p pulse repetition rate - D duty cycle     

Vibrational alarm communication in the damp-wood termite Zootermopsis nevadensis

Abstract. Vibrational alarm communication was studied in the New World, damp-wood termite Zootermopsis nevadensis (Isoptera: Termopsidae). Workers and soldiers react to disturbance such as sudden bright light or air currents by drumming their heads against the substratum. This drumming has been described as alarm signalling; its functional significance and perception by the nest mates, however, remained unclear. In the present study we analysed spectral and temporal properties and absolute amplitudes of the vibrational signals and used behavioural responses of the termites to determine the thresholds of the sense of vibration and to find out if and how the termites discriminate the conspecific alarm signals from the background noise.
The drumming signals are trains of pulses of vibrations of the substratum with a pulse repetition rate of about 20 Hz. The carrier frequency depends on the substratum; in the nests studied it was in the range 1–3 kHz. The highest vibrational amplitudes measured close to the signal emitters are usually about 10m/s² (acceleration, RMS). The threshold of the behavioural response is about 1m/s² over a wide range of frequencies (10 Hz to 5 kHz), indicating that the termites can detect these signals as vibrations of the substratum. The animals respond preferentially to temporal patterns similar those of the natural signals; temporal rather than spectral cues seem to be used for signal discrimination.     

Structural Classification of Wild Boar (Sus scrofa) Vocalizations

Determining whether a species' vocal communication system is graded or discrete requires definition of its vocal repertoire. In this context, research on domestic pig (Sus scrofa domesticus) vocalizations, for example, has led to significant advances in our understanding of communicative functions. Despite their close relation to domestic pigs, little is known about wild boar (Sus scrofa) vocalizations. The few existing studies, conducted in the 1970s, relied on visual inspections of spectrograms to quantify acoustic parameters and lacked statistical analysis. Here, we use objective signal processing techniques and advanced statistical approaches to classify 616 calls recorded from semi‐free ranging animals. Based on four spectral and temporal acoustic parameters—quartile Q25, duration, spectral flux, and spectral flatness—extracted from a multivariate analysis, we refine and extend the conclusions drawn from previous work and present a statistically validated classification of the wild boar vocal repertoire into four call types: grunts, grunt‐squeals, squeals, and trumpets. While the majority of calls could be sorted into these categories using objective criteria, we also found evidence supporting a graded interpretation of some wild boar vocalizations as acoustically continuous, with the extremes representing discrete call types. The use of objective criteria based on modern techniques and statistics in respect to acoustic continuity advances our understanding of vocal variation. Integrating our findings with recent studies on domestic pig vocal behavior and emotions, we emphasize the importance of grunt‐squeals for acoustic approaches to animal welfare and underline the need of further research investigating the role of domestication on animal vocal communication.     

The first call note of the Anhui tree frog (Rhacophorus zhoukaiya) is acoustically suited for enabling individual recognition

The effective production of acoustic signals is critically important for intraspecific communication in vocal animals; however, it is also highly time-consuming, energetically demanding and likely to increase predation risks. Thus, we hypothesized that the biological significance of each component of complex acoustic signals would differ serving specific functions and that the first component of such signals would be most important for social signalling and exhibit unique acoustic characteristics because of the precedence effect. To test this hypothesis, we measured temporal and spectral acoustic parameters for each note in the advertisement calls of the Anhui tree frog (Rhacophorus zhoukaiya), a species in which males build mud burrows and call from within these nests. Multivariate analyses including hierarchical cluster analysis and multidimensional scaling were used, based on temporal and spectral acoustic parameters for each of 10 notes/call. These results show that the first call notes form one cluster while the other notes form a second cluster in multidimensional space when the parameters measured were normalized. Furthermore, the temporal and spectral sound attributes of the first call note provide sufficient information for discrimination between different individuals. Moreover, discriminant analysis showed that the fundamental frequency of the first note is sufficient to identify individuals when the data are not normalized. Taken together, these results indicate that the first call note is poised to play an important role in Anhui tree frog vocal communication insofar as the temporal and spectral features provide sufficient information for individual recognition.     

Mother-lamb acoustic recognition in sheep: a frequency coding

Ewes of the domestic sheep ( Ovis aries ) display selective maternal investment by restricting care to their own offspring and rejecting alien young. This trait relies on individual recognition processes between ewes and lambs. Whereas identification at the udder is only olfactory, distance recognition is performed through visual and acoustic cues. We studied the effectiveness and modalities of mutual acoustic recognition between ewes and lambs by spectrographic analysis of their vocal signatures and by playbacks of modified calls in the field. Our results show that ewes and their lambs can recognize each other based solely on their calls. The coding of identity within the vocal signatures, previously unknown in sheep, is similar in lamb and ewe: it uses the mean frequency and the spectral energy distribution of the call, namely the timbre of the call. These results point out a simple signature system in sheep that uses only the frequency domain. This engenders a signal with low information content, as opposed to some highly social birds and mammal species that may integrate information both in the temporal and spectral domains. The simplicity of this system is linked to the roles played by vision and olfaction that corroborate the information brought by the vocal signature.     

At sea vocal repertoire of a foraging seabird

Seabirds spend most of their time at sea, yet our knowledge of their activities and behaviour is limited due to difficulties of in‐situ data collection. In particular, we know virtually nothing about their acoustic communication when at sea. We benefited from the recent development of miniaturised audio‐recording devices to deploy acoustic recorders on breeding Cape gannets Morus capensis to study their vocal activity while foraging. Call sequences were recorded on 1718 occasions, from which acoustic variables were measured on calls with good recording quality. A total of 1348 calls from 18 birds were measured in temporal and frequency domains. Each call was assigned to a behavioural context defined acoustically: sitting on the water, flying, taking off or just before diving. Potential discrimination among calls from different contexts was tested using the random forest algorithm. Within each context, individual stereotypy in the calls was assessed per acoustic variable using a measure of potential of individual coding, and as a combination of variables using a similar multivariate analysis. The acoustic structure differed according to the behavioural context (global accuracy of prediction 75%). Temporal variables (sequence and call duration) were most important to correctly classify the calls among the four contexts. When considering only two contexts, on the water and in the air (merging flying and diving), frequency and spectral variables (percentage of energy below 1200 Hz and fundamental frequency) were of most importance (accuracy 86%). A combination of acoustic variables was necessary to discriminate individuals, but calls from all contexts were not strongly individually distinct (accuracy 41–63%). We provided the first detailed acoustic analysis of a foraging seabird and demonstrated context‐specific acoustic structure in its vocalisations at sea. Our results suggest that seabirds use vocal communication to exchange various types of information that likely improves foraging success.     

Macrogeographic variation in the call of the corncrake Crex crex

This study was conducted to characterise macrogeographic variation in the vocalisation of the corncrake Crex crex, a bird species with a non‐learned and highly stereotyped call. We also examined: 1) whether call characteristics remained stable across successive breeding seasons within two of the study populations and 2) whether call similarity was related to distance between populations. Recordings of 352 males from eight populations were analysed. The analyses focused on variation in 1) temporal characteristics (duration of syllables and intervals, duration of the intervals between consecutive maximal amplitude peaks within syllables, called pulse‐to‐pulse duration (PPD)), and 2) spectral characteristics (minimal and maximal frequency, frequencies below which 25%, 50% and 75% acoustic energy of signal is distributed). We found significant differences in most of the temporal and all of the spectral characteristics between populations. No differences were found in PPD. Significant interannual differences in spectral characteristics were found in both of the populations examined, whereas differences in temporal characteristics were only observed in one population. In general, geographic variation in calls showed clinal distance‐dependence, where distant populations showed larger differences in call than neighbouring populations. Our results show that geographic variation in corncrake calls may be very dynamic in the short term and that within‐population variation may occur on the same scale as between‐population variation. This finding is surprising because call characteristics in non‐learners are essentially inherited, and genetic transmission should be very slow. We suggest that the social interactions between males and/or the specific dispersal patterns of this species and the low site fidelity of adult and young birds may be responsible for such pattern.     

Vocalisation and its association with androgens and corticosterone in a night frog (Nyctibatrachus humayuni) with unique breeding behaviour

In anurans, vocalisation is used to communicate within and between the sexes during reproduction. Knowledge of vocal repertoire and its diversity is essential in understanding its significance in sexual selection. In this context, we studied the vocal behaviour of Nyctibatrachus humayuni and quantified the urinary metabolites of androgens and corticosterone to understand the associations among hormones, body condition index and vocalisation. Our results show that males of N. humayuni produce an amplitude‐modulated call consisting of a train of pulses. Interestingly, a high degree of inter‐individual variation was observed in the call parameters. The dominant frequency and pulse interval were negatively correlated with male body size, whereas pulse duration and pulse duty cycle were positively correlated with it. Dominant frequency was negatively correlated with androgens and corticosterone, whereas pulse interval was negatively correlated with corticosterone. Further, pulse duty cycle, pulse duration and pulses per call were positively associated with corticosterone. Surprisingly, none of the acoustic parameters was associated with male body temperature and body condition. A significant variation was evident in the vocal effort, dominant frequency and amplitude of advertisement calls produced under different social situations. Calls produced during territory establishment had lower dominant frequency but higher vocal effort, whereas those produced during courtship had higher amplitude and vocal effort than the calls produced in the absence of a competitor/female. Our results suggest that greater inter‐male variability in the advertisement call of N. humayuni could be important in female choice as it may help females to assess the quality of a male. Further, androgens and corticosterone could be important in modulating crucial parameters of the advertisement call.     

Males’ calls carry information about individual identity and morphological characteristics of the caller in burrowing petrels

Acoustic communication in burrowing petrels has been poorly studied. However, as for many other bird species, acoustic communication seems to play an essential role in social interactions during the breeding season of these seabirds. Bachelor males call from their burrow, likely to attract females, but also when vocally challenged by other males. Calling in the breeding colony exposes petrels to high predation risks and thus it should provide an important benefit. The present study focuses on the informative content of males’ calls in the blue petrel Halobaena caerulea and the Antarctic prion Pachyptila desolata, two monogamous petrel species producing a single egg per year. We tested the hypotheses that acoustic parameters of a male's calls 1) reflect phenotypic characteristics, and 2) bear an individual vocal signature. To do so, we first tested on both species the relationships between seven morphometric measurements and 11 acoustic parameters using multivariate analyses. Second, we performed a between‐class analysis and calculated the potential of individuality coding (i.e. the ratio between intra‐ and inter‐individual variabilities) for acoustic parameters in both spectral and temporal domains. Results show acoustic parameters (especially energy quartiles, call duration, and syllable or phrase rate) reflect the caller's body size, bill morphology and wing morphology in both species. Considering the seeming pertinence of wing morphology, we suggest wing area may be a more relevant trait to consider than wing length when studying soaring birds. The results support the idea that energy quartiles, phrase rate and call duration also code for individual identity. Information carried by males’ calls might play a role in social interactions, such as burrow defence (e.g. male‐male competition, neighbour‐stranger discrimination) and/or female mate choice.     

Female competition for availability of males in insects: the Nezara viridula (Linnaeus, 1758) model

Multimodal communication in solitary stinkbugs enables them to meet, mate and copulate. Many plant‐dwelling species exchange information during the calling phase of mating behavior using substrate‐borne vibratory signals. A female‐biased gender ratio induces rivalry and competition for a sexual partner. Female competition for males, first described among Heteroptera in three stinkbug species, revealed species specific differences and opened the question of plasticity in individually emitted temporal and frequency signal characteristics during calling and rival alternation. To address this question and gain an insight into the mechanisms underlying stinkbug female rivalry, we compared the characteristics of alternated signals in the southern green stinkbug Nezara viridula (Linnaeus, 1758) (Hemiptera: Pentatomidae). Compared to male rivalry, female rivalry is more complex, lasts longer and runs through successive phases by a combination of different song types. The male pheromone triggers alternation between females, producing song pulses that occasionally overlap each other. One female initiates the rivalry by changing individual pulses into pulse trains of three different types. The competing female alternates with pulses of changed temporal characteristics at lower levels of rivalry and by varying the frequency characteristics of pulse trains at higher levels. During female rivalry, the male either stops responding or occasionally emits calling and courtship signals in response to the female that has produced signals of steady temporal characteristics. Female rivalry shows complex and species specific patterns of information exchange at different levels with a broad‐range variation of temporal and frequency characteristics of, until now, unidentified vibratory emissions.     

Responses of male cricket frogs (Acris crepitans) to attenuated and degraded advertisement calls

We examined the vocal and non‐vocal responses of male cricket frogs (Acris crepitans) to conspecific advertisement calls that had been attenuated or degraded by reducing the depth of amplitude modulation (AM). Both are characteristic of changes to the call as it is transmitted through natural habitats. As stimulus calls became more intense or less degraded, male cricket frogs gradually decreased their call rate and increased the number of call groups and pulse groups in their calls, changes indicative of increased aggressive interactions. At the higher intensities and lower degradation levels, the probability that males would shift to one of two non‐vocal behavioral responses, attacking the perceived intruder or ceasing calling and abandoning the call site, gradually increased. The results show that differences in signal attenuation and AM degradation levels are perceived by males and trigger both vocal and non‐vocal behavioral responses consistent with their use in evaluating the distance to a challenging male. Furthermore, the results indicate that the male responses are graded, increasing as intensity rises and degradation falls, and hierarchical, with vocal responses preceding behavioral responses over the range of intensities and degradation levels presented.     

Calling at the highway: The spatiotemporal constraint of road noise on Pacific chorus frog communication

Loss of acoustic habitat due to anthropogenic noise is a key environmental stressor for vocal amphibian species, a taxonomic group that is experiencing global population declines. The Pacific chorus frog (Pseudacris regilla) is the most common vocal species of the Pacific Northwest and can occupy human‐dominated habitat types, including agricultural and urban wetlands. This species is exposed to anthropogenic noise, which can interfere with vocalizations during the breeding season. We hypothesized that Pacific chorus frogs would alter the spatial and temporal structure of their breeding vocalizations in response to road noise, a widespread anthropogenic stressor. We compared Pacific chorus frog call structure and ambient road noise levels along a gradient of road noise exposures in the Willamette Valley, Oregon, USA. We used both passive acoustic monitoring and directional recordings to determine source level (i.e., amplitude or volume), dominant frequency (i.e., pitch), call duration, and call rate of individual frogs and to quantify ambient road noise levels. Pacific chorus frogs were unable to change their vocalizations to compensate for road noise. A model of the active space and time (“spatiotemporal communication”) over which a Pacific chorus frog vocalization could be heard revealed that in high‐noise habitats, spatiotemporal communication was drastically reduced for an individual. This may have implications for the reproductive success of this species, which relies on specific call repertoires to portray relative fitness and attract mates. Using the acoustic call parameters defined by this study (frequency, source level, call rate, and call duration), we developed a simplified model of acoustic communication space–time for this species. This model can be used in combination with models that determine the insertion loss for various acoustic barriers to define the impact of anthropogenic noise on the radius of communication in threatened species. Additionally, this model can be applied to other vocal taxonomic groups provided the necessary acoustic parameters are determined, including the frequency parameters and perception thresholds. Reduction in acoustic habitat by anthropogenic noise may emerge as a compounding environmental stressor for an already sensitive taxonomic group.     

Differences between male,female and juvenile haddock (Melanogrammus aeglefinus L.) sounds

Female and juvenile haddock make sounds, as well as males. Examination of the sounds from different sexes indicates that the sound waveform is a function of fish maturity and it is gender-specific. Immature fish sounds were found to be made up of two pulses with similar frequencies and opposite polarities. Females produced two pulses with the same polarity, the first pulse having a higher frequency than the second. The acoustic characteristics of juvenile, female and male haddock sounds are compared. Sexual dimorphism in the mass of the drumming muscle mass has also been investigated. Female haddock possess less well-developed drumming muscles than males throughout the whole year. A significant difference in drumming muscle mass was observed not only in males but also in females at different seasons. A positive relation between drumming muscle mass and fish size has been highlighted in both male and female fish. The physical parameters of the sound units emitted by juveniles, females and males, which are likely affected by physiological condition and maturity stage, are discussed in relation to the sound-producing mechanism.     

Vocal Signature in Wild Infant Chimpanzees

A large array of communication signals supports the fission/fusion social organization in chimpanzees, and among them the acoustic channel plays a large part because of their forest habitat. Adult vocalizations convey social and ecological information to their recipients allowing them to obtain cues about an ongoing event from calls only. In contrast to adult vocalizations, information encoded in infant calls had been hardly investigated. Studies mainly focused on vocal development. The present article aims at assessing the acoustic cues that support individual identity coding in infant chimpanzees. By analyzing recordings performed in the wild from seven 3‐year‐old infant chimpanzees, we showed that their calls support a well‐defined individual vocal signature relying on spectral cues. To assess the reliability of the signature across the calls of an individual, we defined two subsets of recordings on the basis of the characteristics of the frequency modulation (whimpers and screams) and showed that both call types present a reliable vocal signature. Early vocal signature may allow the mother and other individuals in the group to identify the infant caller when visual contact is broken. Chimpanzee mothers may have developed abilities to cope with changing vocal signatures while their infant, still vulnerable, gains in independence in close habitat. Am. J. Primatol. 75:324‐332, 2013. © 2012 Wiley Periodicals, Inc.     

Sound production in the Ponto‐Caspian goby Neogobius fluviatilis and acoustic affinities within the Gobius lineage: implications for phylogeny

The aim of this study was to describe the vocal repertoire of the Ponto‐Caspian goby Neogobius fluviatilis and to compare the acoustic properties of this species with those of other soniferous Mediterranean gobies belonging to the Gobius lineage. Vocalizations and associated behaviours were recorded under controlled aquarium conditions in female and male N. fluviatilis. Sound emission was elicited by means of ‘intruder tests’, using an individual of the same or opposite sex as an intruder, and recording sounds using a hydrophone placed 20 cm from the shelter used as a nest for the resident fish. Five acoustic properties, including spectral and temporal properties, were measured from 13 individuals. The vocal repertoire of the species consisted of sequences of short vocalizations during both agonistic and reproductive intraspecific interactions. The wave form of each sound resolved in a pure sine wave composed of rapidly repeated pulses. Sounds lasted about 200 ms, showing an average fundamental frequency of about 80 Hz. Sound properties did not differ between reproductive and the aggressive contexts, and the general structure of sounds was highly stereotyped. The individual means of three acoustic independent traits characterizing the sounds of seven species of the Gobius lineage, including N. fluviatilis, were then entered in a discriminant function analysis to assess how well species could be differentiated on the basis of acoustics, and their degree of affinities. The results suggested that the pulse repetition rate of the sounds, i.e. the relative tonal/pulsatile nature of the sounds, was the most important property in differentiating the species, and that this trait may contain a high level of phylogenetic signal, as the species producing tonal sounds clustered together, in line with the results of recent molecular phylogenic studies. The results were discussed in light of the geological and phylogeographical events believed to have driven the diversification of European gobies.