• Changes in vocal repertoire of the Hawaiian crow, Corvus hawaiiensis, from past wild to current captive populations

      Tanimoto, Ann M.; Hart, Patrick J.; Pack, Adam A.; Switzer, Richard A.; Banko, Paul C.; Ball, Donna L.; Sebastián-González, Esther; Komarczyk, Lisa; Warrington, Miyako H. (2017)
      ...We compared the vocal repertoire of three of the last four wild 'alalā pairs from the early 1990s to three current captive pairs on the Island of Hawai'i to determine how acoustic behaviour has been affected by changes in their social and physical environment. Over 18 h of recordings from wild breeding pairs were analysed and compared with 44 h from captive breeding pairs....
    • Influence of season and social context on male giant panda (Ailuropoda melanoleuca) vocal behaviour

      Charlton, Benjamin D.; Owen, Megan A.; Zhou, Xiaoping; Zhang, Hemin; Swaisgood, Ronald R. (2019)
      Documenting the different social and behavioural contexts that vocalisations are produced in remains an important step towards understanding the functional relevance of specific call types in a given species’ vocal repertoire. In this study we investigated whether seasonal differences and the presence or absence of male and female conspecifics influence the production of male giant panda vocal signals. To this end, captive male giant pandas were observed during and outside of the breeding season in three social contexts: only male conspecific neighbours, only female conspecific neighbours, and a context with no neighbours. We found that males were more likely to bleat, chirp, honk and moan during the breeding season, and showed a tendency to growl more outside of the reproductive period. The contextual analysis revealed that bleats were more likely to be produced by males when opposite-sexed conspecifics are in close attendance during the breeding season. Conversely, males were more likely to chirp when neighboured by males than females or no neighbours. In addition, males were more likely to honk in the absence of neighbouring conspecifics during the breeding season, raising the possibility that these calls function to signal location and gain the attention of potential mates. Moans were produced more often when male giant pandas had male than female neighbours during the breeding season, which may reflect mild aggression towards these same-sexed rivals, whereas the production of barks and growls did not vary according to season or the sex of conspecific neighbours. Our findings underscore the importance of male giant panda bleats for coordinating reproduction and promoting contact with potential mating partners in this non-gregarious species, and yield fresh insights into the function of male honks that warrant further investigation. They also provide a basis for comparison with free-ranging giant panda vocal behaviour that could potentially inform conservation efforts.
    • Lifetime changes in vocal syntactic complexity of rock hyrax males are determined by social class

      Demartsev, Vlad; Kershenbaum, Arik; Ilany, Amiyaal; Barocas, Adi; Weissman, Yishai; Koren, Lee; Geffen, Eli (2019)
      The ontogeny of quality-based signals has been studied in numerous animal systems but the degradation of vocal signals with age has received much less attention. Investigating age-related changes in quality-based acoustic signals and the associated social processes (e.g. rank changes, competition intensity) can expand our understanding of the information content of signals and their perception by receivers....
    • Male European badger churrs: Insights into call function and motivational basis

      Charlton, Benjamin D.; Newman, Chris; Macdonald, David W.; Buesching, Christina D. (2020)
      Determining the contexts of emission and information content of vocal signals can yield insights into the function of different call types, and remains an important step towards understanding the diversification of mammalian vocal repertoires. In this study, we used infra-red video cameras and remote audio recorders to document seasonal and contextual variation in male European badger (Meles meles) churr production over a 24-month period, and acoustic analysis based on source-filter theory to examine whether churr acoustic structure varies according to the caller’s arousal state and identity….
    • Male-male affiliation and cooperation characterize the social behavior of the large-bodied pitheciids, Chiropotes and Cacajao: A review

      Gregory, Tremaine; Bowler, Mark (2016)
      …In this review of recent studies of male-male social interactions in Chiropotes and Cacajao, we posit that the ability to maintain large groups in these genera may be related to the affiliative and perhaps coalitionary relationships between males, who may or may not be related. Affiliative male-male relationships may allow for monopolization of groups of females and facilitate group cohesion by reducing intragroup aggression; however data on male-male interactions with identified individuals will be required to determine patterns of affiliation, while genetic studies may be the most practical way of determining dispersal patterns for these genera….
    • Signalling behaviour is influenced by transient social context in a spontaneously ovulating mammal

      Owen, Megan A.; Swaisgood, Ronald R.; Zhou, Xiaoping; Blumstein, Daniel T. (2016)
      ...Using female giant pandas at the Wolong Breeding Centre in Sichuan, China, we explored the interaction between social context and reproductive status on signalling and maintenance behaviours. To do so, we used linear mixed models and an information-theoretic approach to assess the temporal relationship between signalling behaviours and the timing of first mating....
    • The acoustic structure of male giant panda bleats varies according to intersexual context

      Charlton, Benjamin D.; Keating, Jennifer L.; Rengui, Li; Huang, Yan; Swaisgood, Ronald R. (2015)
      ...These results show that acoustic features of male giant panda bleats have the potential to signal the caller's motivational state, and suggest that males increase the rate of fundamental frequency modulation in bleats when they are alone to maximally broadcast their quality and promote close-range contact with receptive females during the breeding season...
    • The “Law of Brevity” in animal communication: Sex-specific signaling optimization is determined by call amplitude rather than duration

      Demartsev, Vlad; Gordon, Naomi; Barocas, Adi; Bar Ziv, Einat; Ilany, Tchia; Goll, Yael; Ilany, Amiyaal; Geffen, Eli (2019)
      The efficiency of informational transfer is one of the key aspects of any communication system. The informational coding economy of human languages is often demonstrated by their almost universal fit to Zipf's “Law of Brevity,” expressing negative relationship between word length and its usage frequency. Animal vocal systems, however, provided mixed results in their adherence to this relationship, potentially due to conflicting evolutionary pressures related to differences in signaling range and communicational needs. To examine this potential parallel between human and animal vocal communication, and also to explore how divergent, sex-specific, communicational settings affect signaling efficiency within a species, we examined the complete vocal repertoire of rock hyraxes (Procavia capensis). As male and female hyraxes differ in their sociality levels and male hyraxes vocal repertoire is dominated by sexual advertisement songs, we hypothesized that sex-specific vocal repertoires could be subjected to different signaling optimization pressures. Our results show that the sexes differ in repertoire size, call usage, and adherence to coding efficiency principles. Interestingly, the classic call length/call usage relationship is not consistently found in rock hyraxes. Rather, a negative relationship between call amplitude and call usage is found, suggesting that the efficiency of the vocal repertoire is driven by call amplitude rather than duration. We hypothesize that, in contrast to human speech that is mainly intended for short distance, the need for frequent long-range signaling shapes an animal's vocal repertoire efficiency according to the cost of call amplitude rather than call length. However, call duration may be a secondary factor affecting signaling efficiency, in cases where amplitude is under specific selection pressures, such as sexual selection.
    • Vocal behaviour predicts mating success in giant pandas

      Charlton, Benjamin D.; Martin-Wintle, Meghan S.; Owen, Megan A.; Zhang, Hemin; Swaisgood, Ronald R. (2018)
      Surprisingly little is known about how mammal vocal signals are used to achieve behavioural synchrony in the lead up to copulation. The ability to signal short-term fluctuations in arousal levels and behavioural intention is likely to be particularly important for synchronizing mating behaviour in asocial species, which must overcome their natural avoidance and aggressive tendencies to mate. Here, we examined vocal behaviour during breeding encounters in captive giant pandas (Ailuropoda melanoleuca) to gain a greater understanding of how close-range vocal signalling mediates reproduction in this asocial, and conservation-dependent species. Our results revealed that the occurrence of different giant panda vocalizations and acoustic variation within these calls is predictive of successful encounters leading to copulation, as opposed to unsuccessful encounters that do not. In addition, key differences were detected between vocalizations produced during and just prior to copulation. These findings illustrate that vocal exchanges are crucial for achieving behavioural synchrony and signalling intention to mate in giant pandas, and could also provide a valuable tool for breeding programmes, helping conservation managers to assess the likelihood of breeding introductions leading to copulation or potentially injurious failure.
    • Vocal repertoire and signal characteristics of 'Alalā, the Hawaiian Crow (Corvus hawaiiensis)

      Tanimoto, Ann M.; Hart, Patrick J.; Pack, Adam A.; Switzer, Richard A. (2017)
      The critically endangered Hawaiian Crow or ′Alalā (Corvus hawaiiensis) is currently extinct in the wild and the remaining 115 individuals are being captively managed on Hawai′i and Maui Islands by the Zoological Society of San Diego. Here we provide the first comprehensive analysis of the vocal repertoire of this species....