Diving apart together: call propagation in diving long-finned pilot whales.

Group-living animals must communicate to stay in contact. In long-finned pilot whales, there is a trade-off between the benefits of foraging individually at depth and the formation of tight social groups at the surface. Using theoretical modelling and empirical data of tagged pairs within a group, we examined the potential of pilot whale social calls to reach dispersed group members during foraging periods. Both theoretical predictions and empirical data of tag pairs showed a potential for communication between diving and non-diving group members over separation distances up to 385 m (empirical) and 1800 m (theoretical). These distances match or exceed pilot whale dive depths recorded across populations. Call characteristics and environmental characteristics were analysed to investigate determinants of call detectability. Longer calls with a higher sound pressure level (SPL) that were received in a quieter environment were more often detected than their shorter, lower SPL counterparts within a noisier environment. In a noisier environment, calls were louder and had a lower peak frequency, indicating mechanisms for coping with varying conditions. However, the vulnerability of pilot whales to anthropogenic noise is still of concern as the ability to cope with increasing background noise may be limited. Our study shows that combining propagation modelling and actual tag recordings provides new insights into the communicative potential for social calls in orientation and reunion with group members for deep-diving pilot whales.

Affiliative Contact Calls during Group Travel: Chirp and Wail Vocalization Use in the Male Ring-Tailed Lemur (Lemur catta).

Affiliative vocalizations occur across primate taxa and may be used to maintain spatial cohesion and/or to regulate social interactions in group-living species. For gregarious strepsirhines like the ring-tailed lemur (Lemur catta), with large vocal repertoires and several distinct affiliative vocalizations including the chirp and wail, it is important to understand behavioural usage of these vocalizations to gain insight into their social interactions. To determine whether chirp and wail vocalizations facilitate group cohesion, regulate interactions to achieve socially positive outcomes, and are correlated with differences in individual characteristics such as dominance rank and age, I collected 565 h of focal data on 31 males aged ≥1 year at Beza Mahafaly Special Reserve, Madagascar, from March to July 2010. I found that chirp and wail vocalizations occurred at the highest rates during group-wide travel compared to other behaviours. Although nearest neighbour distance did not influence calling rate, focal animals maintained the same distance or were located closer to nearest neighbours after calling. Both chirp and wail calls were heard in behavioural contexts without agonism rather than agonistic contexts. No relationship was found between male calling rate and dominance rank or age, although the chirp showed a non-significant tendency to be produced at higher rates by younger males. Overall, my results indicated that ring-tailed lemur males of all ages and dominance ranks used both chirp and wail vocalizations as contact calls during group-wide travel events, helping individuals maintain proximity to other group members during movement. Chirp and wail vocalizations may additionally help regulate the caller's social interactions and promote increased tolerance from conspecifics. These findings add to our understanding of the breadth of communication behaviour in wild lemurs, thus furthering our knowledge of the social lives and cognitive abilities of strepsirhines. Through examining the complexity of vocalization use by a living lemur species with a communication system much like early social primates, we gain broad insight into the evolution of primate sociality.

Sex and species recognition by wild male southern white rhinoceros using contact pant calls.

Recognition of information from acoustic signals is crucial in many animals, and individuals are under selection pressure to discriminate between the signals of conspecifics and heterospecifics or males and females. Here, we first report that rhinos use information encoded in their calls to assess conspecifics and individuals of closely related species. The southern (Ceratotherium simum) and critically endangered northern (C. cottoni) white rhinos are the most social out of all the rhinoceros species and use a contact call pant. We found that southern white rhino pant calls provide reliable information about the caller's sex, age class and social situation. Playback experiments on wild territorial southern white rhinoceros males revealed that they responded more strongly to the pant calls of conspecific females compared to the calls of other territorial males. This suggests that pant calls are more important form of communication between males and females than between territorial males. Territorial southern males also discriminated between female and territorial male calls of northern species and reacted more intensively to the calls of northern than southern males. This might be caused by a novelty effect since both species naturally live in allopatry. We conclude that white rhinos can directly benefit from assessing individuals at long distances using vocal cues especially because their eyesight is poor. Pant calls thus likely play a significant role in their social relationships and spatial organization. In addition, better understanding of vocal communication in white rhinos might be helpful in conservation management particularly because of their low reproduction in captivity.

Vocalisations of the bigeye Pempheris adspersa: characteristics, source level and active space.

Fish sounds are an important biological component of the underwater soundscape. Understanding species-specific sounds and their associated behaviour is critical for determining how animals use the biological component of the soundscape. Using both field and laboratory experiments, we describe the sound production of a nocturnal planktivore, Pempheris adspersa (New Zealand bigeye), and provide calculations for the potential effective distance of the sound for intraspecific communication. Bigeye vocalisations recorded in the field were confirmed as such by tank recordings. They can be described as popping sounds, with individual pops of short duration (7.9±0.3 ms) and a peak frequency of 405±12 Hz. Sound production varied during a 24 h period, with peak vocalisation activity occurring during the night, when the fish are most active. The source level of the bigeye vocalisation was 115.8±0.2 dB re. 1 µPa at 1 m, which is relatively quiet compared with other soniferous fish. Effective calling range, or active space, depended on both season and lunar phase, with a maximum calling distance of 31.6 m and a minimum of 0.6 m. The bigeyes' nocturnal behaviour, characteristics of their vocalisation, source level and the spatial scale of its active space reported in the current study demonstrate the potential for fish vocalisations to function effectively as contact calls for maintaining school cohesion in darkness.

Bioacoustic differentiation of calls in the chiffchaff complex.

The chiffchaff complex is a group of common forest bird species, notorious for the number of cryptic taxa recently discovered, being a great example of speciation in action. Vocalizations have been crucial to unveil its hidden diversity. In this study we quantitatively analyze the acoustic characteristics of their calls with permutational analysis of variance, canonical variate analysis and a self-organizing map, to determine their variability and differences. We related these differences with the geographical and genetic distances between taxonomic groups, by means of Pearson correlations. We used recordings from Xeno-canto, an open database of bird vocalizations. Inter-taxa distances based on call traits were broadly consistent with geographic distances but not correlated with genetic distances. The Iberian Chiffchaff (Phylloscopus ibericus), presumably the most ancient lineage, was the most central in the variation space, while the Siberian Chiffchaff (P. collybita tristis) was the most peripheric and also very uniform, in contrast with the Canarian Chiffchaff (P. canariensis) highly variable, as expected by the "character release hypothesis" on islands. Calls proved to be an excellent tool, especially amenable for non-biased mathematical analyses which, combined with the wide availability of records in Xeno-canto, greatly facilitates the widespread use of this methodology in a wide range of species and geographical areas.

Social Behavior and Ultrasonic Vocalizations in a Genetic Rat Model Haploinsufficient for the Cross-Disorder Risk Gene Cacna1c.

The top-ranked cross-disorder risk gene CACNA1C is strongly associated with multiple neuropsychiatric dysfunctions. In a recent series of studies, we applied a genomically informed approach and contributed extensively to the behavioral characterization of a genetic rat model haploinsufficient for the cross-disorder risk gene Cacna1c. Because deficits in processing social signals are associated with reduced social functioning as commonly seen in neuropsychiatric disorders, we focused on socio-affective communication through 22-kHz and 50-kHz ultrasonic vocalizations (USV). Specifically, we applied a reciprocal approach for studying socio-affective communication in sender and receiver by including rough-and-tumble play and playback of 22-kHz and 50-kHz USV. Here, we review the findings obtained in this recent series of studies and link them to the key features of 50-kHz USV emission during rough-and-tumble play and social approach behavior evoked by playback of 22-kHz and 50-kHz USV. We conclude that Cacna1c haploinsufficiency in rats leads to robust deficits in socio-affective communication through 22-kHz and 50-kHz USV and associated alterations in social behavior, such as rough-and-tumble play behavior.

Studying Socio-Affective Communication in Rats through Playback of Ultrasonic Vocalizations.

Rats are able to produce ultrasonic vocalizations (USVs). Such USVs are an important component of the rat social behavior repertoire and serve distinct communicative functions as socio-affective signals. Depending on the emotional valence of the situation, juvenile and adult rats utter (1) aversive 22-kHz USVs conveying an appeasing and/or alarming function; or (2) appetitive 50-kHz USVs, which act as social contact calls, amongst others. A 50-kHz USV radial maze playback paradigm that allows assessment of the behavioral responses displayed by the recipients in a highly standardized manner has been developed. In this newly developed paradigm, a rat is exposed individually to playback of natural 50-kHz USVs and appropriate acoustic control stimuli using an acoustic presentation system for ultrasound. By this means, it has been consistently shown that 50-kHz USVs lead to social approach behavior in the recipient, supporting the notion that they serve an affiliative function as social contact calls.

Repeatability in the contact calling system of Spix's disc-winged bat (Thyroptera tricolor).

Spix's disc-winged bat (Thyroptera tricolor) forms cohesive groups despite using an extremely ephemeral roost, partly due to the use of two acoustic signals that help individuals locate roost sites and group members. While the calls that aid in group cohesion are commonly used, some bats rarely or never produce them. Here, we examine whether the differences observed in the contact calling behaviour of T. tricolor are repeatable; that is, whether individual differences are consistent. We recorded contact calls of individuals in the field and rates and patterns of vocalization. To determine whether measured variables were consistent within individuals, we estimated repeatability (R), which compares within-individual to among-individual variance in behavioural traits. Our results show that repeatability for call variables was moderate but significant, and that repeatability was highest for the average number of calls produced (R=0.46-0.49). Our results demonstrate important individual differences in the contact calling behaviour of T. tricolor; we discuss how these could be the result of mechanisms such as frequency-dependent selection that favour groups composed of individuals with diverse vocal strategies. Future work should address whether changes in social environment, specifically group membership and social status, affect vocal behaviour.

The stability of the vocal signature in phee calls of the common marmoset, Callithrix jacchus.

Phee calls were recorded from five captive common marmosets on three occasions. An initial recording session was followed by further sessions 1-12 days later, and finally, 12 months after the initial sample. Sonograms from the first recordings were measured using one duration and five frequency parameters, and significant differences between individuals were found for all six parameters. Discriminant function analysis was then applied to classify each call to a particular individual, witn a resulting classification accuracy of 97.27%. Analysis of the second and third recordings demonstrated accurate classification to the same caller using the measurements obtained from the initial sample. The accuracy remained high despite intra-individual differences in acoustic structure among the three recording periods. Such differences may well reflect proximate changes in the underlying arousal state of the caller. Stability over time in the vocal signature of the phee call supports the view that this vocalization may be important in signalling individual identity over long distances, in a habitat where visual contact is limited. © 1993 Wiley-Liss, Inc.

Early learning of discrete call variants in red crossbills: implications for reliable signaling.

The identification of appropriate companions and mates is essential to both speciation and the maintenance of species through prezygotic isolation. In many birds, social assortment is mediated by vocalizations learned through imitation. When imitative vocal learning occurs throughout life, emergent shared signals reflect current social associations. However, when vocal and genetic variation arises among populations, shared learned signal variants have a potential to reflect cultural or genetic origin and to limit social and reproductive intermixing, provided that signal learning occurs prior to dispersal. The red crossbill (Loxia curvirostra) is a bird species in which discrete contact call variants are associated with morphological variation, raising the possibility that learned calls play a role in limiting intermixing. I examined the process of early call learning to determine if contact call variants have a potential to limit intermixing in crossbills. I conducted a captive playback study to nestlings to evaluate potential learning predispositions. I also cross-fostered nestlings to adoptive adult pairs of either their own or a different call variant than their biological parents to assess the degree of vocal learning plasticity. Results show that young crossbills imitate the call structures of adoptive parents, generating shared family-specific calls, which could facilitate family cohesion. Learning processes that generate family-specific calls could also ensure that discrete call variants are transmitted across generations, making call variants reliable signals of crossbills' morphological and genetic backgrounds.