The Vocal Repertoire of the Bearded Capuchin (Cebidae: Sapajus libidinosus): Implications for Understanding the Complexity of Neotropical Primate Communication

Vocal communication is an essential aspect of primate social behaviour. The bearded capuchin <i>Sapajus libidinosus</i> is endemic to Brazil, and some studies have described specific vocalisation types for this species; however, there is still no complete description of its vocal repertoire. Thus, this study aimed to describe the vocal repertoire of a group of <i>S. libidinosus</i> living in the<i></i>Parque Nacional de Brasília, a protected area in the Cerrado area of Central Brazil. We carried out focal samplings and recording of vocalisations of members of an <i>S. libidinosus</i> troop in different behavioural contexts. The call analyses revealed 25 different types of vocalisations, and each call presented significant structural variation. We grouped these vocalisations according to the context of the emission or acoustic structure into the following categories: contact calls (contact note, infant babbling, trill, teeth- and lip-smacking, and sirena); foraging calls (chihui, grgr, and patinado); whistle series (food-associated, long-distance, and intergroup encounter); aggressive calls (aggressive contact note, ascending rapid staccato, cough cough, and pip); calls in response to aggression (scream, squeal, and pulsed scream), sexual display calls (chuck and raspy oestrous call), and stress-related calls (alarm call/bark, hiccup, hip, double hip, and wah wah). <i>S. libidinosus</i> presented a very rich vocal repertoire, revealing a pattern consistent with the repertoire of other capuchin monkey species. This is the first comprehensive description of the<i> S. libidinosus</i> vocal repertoire and highlights the complexity of neotropical primate communication.

How long does it take to know a species? Redescription, vocalization, and chigger mites infestation pattern in the centenary Brachycephalus garbeanus (Anura: Brachycephalidae)

Although we celebrate the centennial of Brachycephalus garbeanus’ discovery, little progress has been done on understanding this species’ biology apart from a few morphological and ecological studies, which includes its redescription based on three specimens from the type-series, microhabitat use, sexual dimorphism in body size, and feeding habits. This species is endemic to the Serra dos Órgãos Mountain range, in the state of Rio de Janeiro, southeastern Brazil. Here we redescribe B. garbeanus based on a wide sampling, including its advertisement and aggressive calls, and also the chigger mites infestation pattern. The advertisement call is longer than 25.8 s with pulsed notes series emitted at an average rate of 2.3 notes/s and 14.1 pulses/s; long inter-note interval with 320 ms; notes with distinctly short pulses (1 to 16 ms); low dominant frequency for this genus (3.0-5.4 kHz) and presence of four harmonics. This species is often parasitized by chigger mites of Hannemania, with a prevalence of infection of 67%, mainly affecting the ventral body surface. Females had a higher prevalence of parasites than males and there was no correlation found between the size of specimens and the number of parasites. Our study, provides an important and overdue taxonomical contribution, including a large amount of novel information for B. garbeanus.

Do male Boana goiana (Lutz, 1968) (Anura: Hylidae) discriminate between the calls of neighbours and strangers?

Neighbour-stranger discrimination is an important mechanism in social behaviour, as it allows the individual to avoid the high energetic costs of repeated agonistic interactions with neighbours. In some anuran species, the owners of territories respond more aggressively towards strangers than neighbours. Here, we investigated whether gladiator frog, Boana goiana, males discriminate between neighbours and strangers. This is a lek-breeding species; therefore, it does not defend fixed territories which are associated with a specific resource. We conducted a playback field experiment with a repeated-measures design, based on three treatments: (i) neighbour’s call in initial position, (ii) stranger’s call in initial position, and (iii) neighbour’s call in new position. We did not observe any systematic modification in the acoustic properties (call duration, dominant frequency, repetition rate) of the advertisement and short aggressive calls of B. goiana males given in response to our playback treatments. Our results indicate that B. goiana males do not exhibit vocally mediated ‘dear enemy’ relationships. We discuss the possible ecological and social factors that may have impeded the evolution of ‘dear enemy’ relationships in this species.

Function analysis of the calls of Dendropsophus microps of the Campos do Jordão State Park, São Paulo, Brazil

In this study, we describe the calls emitted by Dendropsophus microps, a species of frog in the family Hylidae, in Serra da Mantiqueira, Campos do Jordão, São Paulo, Brazil, and evaluate their functions in the social context using playback experiments. Between October 2016 and November 2017, 15 males of D. microps were recorded. Six hundred and five calls were analyzed and the existence of five types of call compositions was verified: simple call “A normal”; compound call “Af”; shorter “A” call + longer “A” call; “A + Af” calls; and simple call “B”; demonstrating the presence of compound calling in the vocalization structure. One thousand, six hundred and seventeen calls were recorded during the playback experiment in response to the 5 previously constructed stimuli. The “B” call was the most emitted in response to stimuli. The “A”, “Af”, “AA” and “AAf” stimuli caused visual signaling. We recorded a series of 4 to 5 “A” calls during agonistic interactions. Call "B" was identified as an advertisement call and calls "A", "Af", "AA" and "AAf" as aggressive calls. The presence of visual communication in addition to the acoustic communication of these individuals was also observed. The findings increase knowledge of the calling repertoire of this species and can be used in the future in other behavioral and taxonomic studies.

Male serrate-legged treefrogs adjust competition strategies according to visual or chemical cues from females

ABSTRACTThere is increasing evidence that many anurans use multimodal cues to detect, discriminate and/or locate conspecifics and thus modify their behaviors. To date, however, most studies have focused on the roles of multimodal cues in female choice or male–male interactions. In the present study, we conducted an experiment to investigate whether male serrate-legged small treefrogs (Kurixalus odontotarsus) used visual or chemical cues to detect females and thus altered their competition strategies in different calling contexts. Three acoustic stimuli (advertisement calls, aggressive calls and compound calls) were broadcast in a randomized order after a spontaneous period to focal males in one of four treatment groups: combined visual and chemical cues of a female, only chemical cues, only visual cues and a control (with no females). We recorded the vocal responses of the focal males during each 3 min period. Our results demonstrate that males reduce the total number of calls in response to the presence of females, regardless of how they perceived the females. In response to advertisement calls and compound calls, males that perceived females through chemical cues produced relatively fewer advertisement calls but more aggressive calls. In addition, they produced relatively more aggressive calls during the playback of aggressive calls. Taken together, our study suggests that male K. odontotarsus adjust their competition strategies according to the visual or chemical cues of potential mates and highlights the important role of multisensory cues in male frogs' perception of females.

Acoustic variability among male gladiator frogs, Boana goiana (Lutz, 1968) (Anura: Hylidae): an 18-year analysis across several reproductive seasons

Male anurans emit different call types in specific social contexts. Such calls represent a communication pathway for species recognition, mate choice, and male-male competition mediation. The acoustic parameters of these calls can be under directional and/or stabilizing selection due to female choice, which influences intra- and inter-individual call variation. Herein, we investigated the inter-year variation of the advertisement and aggressive calls of the gladiator frog Boana goiana, analysing a temporal series encompassing 18 years of sampling (1996-2014). We measured and analysed the following acoustic parameters: call duration, call repetition rate, number of pulses, pulse duration, pulse repetition rate, and dominant frequency. For both call types, the dominant frequency was classified as a static parameter (CVintra < 5%), while call duration was a dynamic parameter (CVintra > 12%). The advertisement call of B. goiana presents the attributes that could allow individual recognition in the chorus, and we suggest that the aggressive calls might also be important for the individual recognition process. Pulse duration of the advertisement and aggressive calls decreased over the years, as well as the repetition rate of the aggressive calls, which could be related to male body size decrease over the years probably related to habitat alteration. This study provides data on the variation of anuran acoustic features over the longest time span ever analysed. Such studies are less invasive and useful for conservation purposes, since they can detect changes in the reproductive behaviour of populations that might be under environmental modification pressure.

Function of a multimodal signal: a multiple-hypotheses test using an electromechanical robot

1. Many animal species communicate using multimodal signals, which are composed of two or more components emitted and interpreted through different sensory modalities. The main types of selective pressures leading to the evolution of multimodal signals are: (1) content-based, when combined components convey information about the signaller, (2) efficacy-based, when combined components increase the efficacy of signal transmission or processing, and (3) inter-signal interaction, when combined components act in concert to elicit a receiver’s response that differs from the response to either components alone.2. We experimentally tested predictions of five competing hypotheses about the selective pressures leading to the evolution of an audiovisual display (aggressive calls + toe flags) emitted during agonistic male-male interactions of the Neotropical frog Crossodactylus schmidti. 3. To simulate these agonistic interactions in the field, we built an electromechanical robot that emitted acoustic and visual stimuli, either combined or in isolation. We assessed male receiver’s responses to the stimuli types in terms of occurrence and frequency of signals emission.4. The hypothesis that received most support was the context hypothesis, which states that one signal provides a context in which a receiver can interpret and respond to a second signal. The main findings supporting this hypothesis are: (1) the receiver’s response to the acoustic and visual stimuli were non-redundant; (2) the multimodal stimulus magnified the receiver’s response; and (3) the frequency of aggressive notes and toe flags covaried in the receiver’s response to the multimodal stimulus.5. We suggest that the addition of toe flags to aggressive calls modulates male-male interactions by providing to the receiver a new context for the interpretation and response to the acoustic signal. This new context may be motivation to fight for territory possession, level of aggressiveness, or intent of territory defence or invasion. Our study provides one of the few evidences of a context function of a multimodal signal with a modulation effect in animal contests. Moreover, our results draw attention to the role of inter-signal selection on the evolution of multimodal signals in species living in heterogeneous habitats, where efficacy-based selection is often considered as a major driver.