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Air-driven vocal production systems such as those found in mammals, birds, and anurans (frogs and toads) combine pneumatic and mechanical elements in species-specific ways to produce a diversity of communication signals. This study uses bond graphs to model a generalized anuran vocal production system. Bond graphs allow an incremental approach to modeling dynamic physical systems involving different domains. Anurans provide an example of how signal diversity results from variation in the structure and behavior of vocal system elements. This paper first proposes a bond graph model of the integrated anuran vocal system as a framework for future study. It then presents a simulated submodel of the anuran sound source that produces sustained oscillations in vocal fold displacement and air flow through the larynx. The modeling approach illustrated here should prove of general applicability to other biological sound production systems, and will allow researchers to study the biomechanics of vocal production as well as the functional congruence and evolution of groups of traits within integrated vocal systems. [ABSTRACT FROM AUTHOR]

In acoustically advertising anurans the male courtship call elicits species-typical responses from conspecifics - usually phonotactic approach and mate choice in gravid females and an evoked vocal response in adult males. Males in several species, however, are also known to perform phonotaxis, sometimes with the same acoustic preferences as females. Female túngara frogs are known to update their phonotactic approach as male advertisement signals change dynamically in attractiveness. Here we show that males also perform such temporal updating during phonotaxis in response to dynamic playbacks. While males exhibit slower phonotactic approaches than females, their responsiveness to dynamic changes in call complexity does not differ significantly compared to females. These results demonstrate that males are sensitive to the location of preferred call types on a moment-to-moment basis and suggest that similarities between male and female sexual behaviour in anurans might often be overlooked. We suggest that anuran phonotaxis is more widespread and serves different functions in reproductive females and males. Lastly, these temporal updating results suggest that male frogs are highly selective about site selection in a chorus. [ABSTRACT FROM AUTHOR]

It is well known that animal decision-making can be influenced by environmental variables, such as the risk of predation. During the breeding season, nocturnal amphibians encounter a range of environmental conditions at breeding aggregations, including variable ambient light conditions. For nocturnal frogs, illumination is expected to minimize conspicuous movement that might increase predator detection. Previous work has shown that female Physalaemus pustulosus (Cope, 1864) (= Engystomops pustulosus (Cope, 1864)) are sensitive to variation in light levels during mate choice. Here we use an acoustic playback design in which stimuli are adjusted for intensity and complexity during female phonotaxis to show that choosiness is influenced by light level. Frogs were more likely to commit to an initial mate choice despite a dynamic reduction in mate attractiveness under dim light conditions compared with darkness. These results suggest that females are trading off the attractiveness of potential mates with the perceived costs of executing mate choice by committing to an initial decision and thereby reducing assessment time and movement. The dynamic playback design used here provides an approach that could be applied in other systems in which context-dependent decision-making is thought to be important. Il est bien connu que la prise de décisions chez les animaux peut subir l’influence des variables du milieu, comme par exemple, le risque de prédation. Durant la saison de reproduction, les amphibiens nocturnes rencontrent une gamme de conditions environnementales lors de leurs rassemblements de reproduction, en particulier des conditions variables de luminosité. Chez les grenouilles nocturnes, l’illumination devrait réduire les mouvements trop apparents qui pourraient augmenter la détection par les prédateurs. Des travaux antérieurs ont montré que les femelles de Physalaemus pustulosus (Cope, 1864) (= Engystomops pustulosus (Cope, 1864)) sont sensibles à la variation de l’intensité lumineuse durant leur choix de partenaire. Nous utilisons ici un plan d’expérience comportant une rediffusion acoustique dans laquelle l’intensité et la complexité des stimuli sont ajustées durant le phonotactisme de la femelle de manière à montrer que le choix est influencé par l’intensité lumineuse. En lumière faible, les grenouilles sont plus susceptibles de s’engager envers un premier partenaire choisi, malgré une réduction dynamique de l’attrait du partenaire, qu’en obscurité totale. Ces résultats laissent croire que les femelles font un compromis entre l’attrait des partenaires potentiels et les coûts perçus reliés au choix du partenaire; en s’engageant vis-à-vis leur premier choix, elles réduisent le temps d’évaluation et les déplacements. Le plan de rediffusion dynamique utilisé ici fournit une approche qui pourrait servir dans d’autres systèmes dans lesquels la prise de décisions en fonction du contexte est importante. [ABSTRACT FROM AUTHOR]

Mate choice studies most often examine female preferences based on population responses, thus potentially overlooking individual differences in behavior. Moreover, such studies typically use invariant stimulus conditions to infer preferences. By using population responses and static stimulus presentations, it is difficult to thoroughly understand the complexity of the mate choice process, including variation present between individuals. Here, we investigated phonotactic mate choice behavior in female túngara frogs (Physalaemus pustulosus) in response to temporally dynamic presentations of male advertisement calls. We tested females on repeated trials to examine individual differences and found considerable variation in the extent to which females update their mate choice decisions. Females in our study were bimodally distributed and thus broadly classified as either committed or uncommitted to an initial mate approach. We compared body condition measures of females differing behaviorally and determined that females with larger residual body masses were more committed to initial mate choices than less massive individuals, despite the fact that all females were in reproductive condition and field collected in amplexus. Our results suggest that anuran phonotaxis, once considered to be a highly stereotyped behavior, is more complex and variable than previously thought. [ABSTRACT FROM PUBLISHER]

Acoustic signals produced by most anurans are accompanied by inflation of a conspicuous vocal sac. We presented female túngara frogs, Physalaemus pustulosus, with acoustic playback of the male advertisement call, synchronized with a video playback of vocal sac inflation. Females significantly preferred a stimulus combination including vocal sac inflation over an identical set of stimuli with the vocal sac inflation removed. Neither a moving rectangle bearing the gross contrast and spatiotemporal properties of the vocal sac inflation sequence, nor the image of a noncalling male significantly enhanced the attractiveness of the acoustic stimulus. Both the form and spatiotemporal properties of the vocal sac thus appear to be salient to females. The results indicate that the vocal sac can serve as a visual cue, which may account for the conspicuous pigmentation found on the vocal sacs of males in many species. Gular inflation in synchrony with a call may function to facilitate female localization of individual males in an aggregation. [Copyright &y& Elsevier]

Animal choruses, such as those found in insects and frogs, are often intermittent. Thus, females sampling males in the chorus might have to remember the location of the potential mates' calls during periods of silence. Although a number of studies have shown that frogs use and prefer multimodal mating signals, usually acoustic plus visual, it is not clear why they do so. Here we tested the hypothesis that preference for multimodal signals over unimodal signals might be due to multimodal signals instantiating longer memories than unimodal signals, particularly during the inter‐chorus intervals.We tested this hypothesis in serrate‐legged small treefrogs Kurixalus odontotarsus whose males produce advertisement calls accompanied by conspicuous vocal sac inflation. Females were tested with acoustic and acoustic + visual (video of inflating‐deflating vocal sac) mating calls.We found that females prefer multimodal calls over unimodal, audio‐only calls. Furthermore, multimodal calls are still preferred after a silent period of up to 30 s, a time that spans the average silent period of the chorus. This was not true of unimodal calls.Our results demonstrate that a multimodal signal can engage longer working memory than a unimodal signal, and thus female memory might favour the evolution of multimodal signals in males through sexual selection. Selection might also favour female preference for multimodal signals if longer memory facilitates mate searching and assessment. Our study does not allow us to elucidate the sequence of evolution of this trait and preference. [ABSTRACT FROM AUTHOR]

We analyzed and described quantitative differences in morphology and calls of Physalaemus petersi and P. freibergi, both members of the monophyletic Physalaemus pustulosus species group. We found significant differences between the two species in both morphometric and call parameters. Physalaemus petersi has proportionately longer legs and a narrower dorsum and head than P. freibergi. The calls of P. petersi are higher in frequency and longer than P. freibergi. Discriminant Function Analysis (DFA) of morphometric variables correctly classified 76.7-87.4% of individuals to species. DFA of call variables correctly classified 96.8-100.0% of males to species. Physalaemus petersi is found north of the Río Marañ on and Río Amazonas in eastern Ecuador, northeastern Peru, and southeastern Colombia; P. freibergi is found south of these rivers in Amazonian Brazil, southeastern Peru, and Amazonian Bolivia. Calls and geographic locations are the most reliable means of identifying these species in the field. [ABSTRACT FROM AUTHOR]

The vocal sac is a visually conspicuous attribute of most male frogs, but its role in visual communication has only been demonstrated recently in diurnally displaying frogs. Here we characterized the spectral properties of the inflated vocal sac of male túngara frogs (Physalaemus pustulosus), a nocturnal species, and túngara visual sensitivity to this cue across reproductive state and sex. We measured the spectral and total reflectance of different male body regions, including inflated and non-inflated vocal sacs, along with samples of the visual background against which males are perceived. Inflated vocal sacs were the most reflective of all body parts, being one log unit more reflective than background materials. We utilized an optomotor drum with black stripes and stripes that mimicked the spectral reflectance of the inflated vocal sacs with various nocturnal light intensities to measure the visual sensitivity thresholds of males, non-reproductive females and reproductive females. All three groups exhibited visual sensitivities corresponding to intensities below moonless conditions in open habitats or at the edge of secondary tropical forests. Reproductive females exhibited the greatest visual sensitivity of all groups, and were significantly more sensitive than non- reproductive females. Though the mechanism for this physiological difference between reproductive and non-reproductive females is unknown, it is consistent with previously observed patterns of light-dependent phonotaxic behavior in túngaras. We suggest that the visual ecology of the vocal sac; especially in nocturnal frogs, offers a rich source for investigations of visual ecology and physiological regulation of vision. [ABSTRACT FROM AUTHOR]

In most anurans, the production of advertisement calls is accompanied by the inflation of a vocal sac. Current functions of the vocal sac, however, are not fully understood, although several hypotheses have been proposed. One hypothesis suggests that the vocal sac decreases the intercall interval (i.e., increases call rate) by reinflating the lungs more rapidly than is possible with the buccal pump. We investigate this hypothesis by analyzing audio and video recordings of calling túngara frogs. We compare the first two call bouts emitted by an originally uninflated male. The first call bout requires lung inflation via buccal pumping, but in the second, the male is already inflated because of capture of air and reinflation of the lungs by the vocal sac. Lung inflation to typical field levels requires 26–51 buccal pumps, which takes at least 4.4 s. This estimate is more than 2.5 times the typical intercall interval with lung reinflation via a vocal sac (ca. 1.7 s). Evidence from phonotaxis tests demonstrates that these differences in intercall intervals are salient to females and that female Physalaemus pustulosus prefer the shorter intercall interval/higher call rate. Acoustic analyses demonstrate that the first call of bout 1, which requires buccal pumping, is usually shorter, of lower amplitude, and spans a smaller frequency range than the first call of bout 2, which does not require buccal pumping. Because females prefer longer, more intense calls, these results suggest that the vocal sac not only increases call rate but also allows males to produce more calls of increased attractiveness to females. [ABSTRACT FROM AUTHOR]

The human music faculty might have evolved from rudimentary components that occur in non-human animals. The evolutionary history of these rudimentary perceptual features is not well understood and rarely extends beyond a consideration of vertebrates that possess a cochlea. One such antecedent is a preferential response to what humans perceive as consonant harmonic sounds, which are common in many animal vocal repertoires. We tested the phonotactic response of female túngara frogs (Physalaemus pustulosus) to variations in the frequency ratios of their harmonically structured mating call to determine whether frequency ratio influences attraction to acoustic stimuli in this vertebrate that lacks a cochlea. We found that the ratio of frequencies present in acoustic stimuli did not influence female response. Instead, the amount of inner ear stimulation predicted female preference behaviour. We conclude that the harmonic relationships that characterize the vocalizations of these frogs did not evolve in response to a preference for frequency intervals with low-integer ratios. Instead, the presence of harmonics in their mating call, and perhaps in the vocalizations of many other animals, is more likely due to the biomechanics of sound production rather than any preference for 'more musical' sounds. [ABSTRACT FROM AUTHOR]