Encounter Calls Research Articles

Network analysis reveals context-dependent structural complexity of social calls in serrate-legged small treefrogs.

Vocal communication plays an important role in survival, reproduction, and animal social association. Birds and mammals produce complex vocal sequence to convey context-dependent information. Vocalizations are conspicuous features of the behavior of most anuran species (frogs and toads), and males usually alter their calling strategies according to ecological context to improve the attractiveness/competitiveness. However, very few studies have focused on the variation of vocal sequence in anurans. In the present study, we used both conventional method and network analysis to investigate the context-dependent vocal repertoire, vocal sequence, and call network structure in serrate-legged small treefrogs Kurixalus odontotarsus. We found that male K. odontotarsus modified their vocal sequence by switching to different call types and increasing repertoire size in the presence of a competitive rival. Specifically, compared with before and after the playback of advertisement calls, males emitted fewer advertisement calls, but more aggressive calls, encounter calls, and compound calls during the playback period. Network analysis revealed that the mean degree, mean closeness, and mean betweenness of the call networks significantly decreased during the playback period, which resulted in lower connectivity. In addition, the increased proportion of one-way motifs and average path length also indicated that the connectivity of the call network decreased in competitive context. However, the vocal sequence of K. odontotarsus did not display a clear small-world network structure, regardless of context. Our study presents a paradigm to apply network analysis to vocal sequence in anurans and has important implications for understanding the evolution and function of sequence patterns.

Communication across multiple sensory modes: quantifying the rich behavioural repertoire of a Neotropical torrent frog

Abstract Anuran communication involves different channels of signal transmission, including acoustic, chemical, seismic, tactile, and visual stimuli. If emitted in combination, the components of the different channels form the multimodal communication, which can be important to reinforce, complement, or transfer fundamental information. This is especially key for species that dwell in noisy environments, such as Hylodes phyllodes. This rheophilic frog species has a complex behavioural repertoire, including acoustic and visual signals. In this study, we quantified and characterized the multimodal communication of this species. We identified and characterized advertisement, territorial, and encounter calls. Additionally, we compared the advertisement calls from the same males when emitted with one or both vocal sacs expanded and found that they differed in temporal and spectral parameters. Hylodes phyllodes performed 16 visual displays, which varied among individuals and populations. We elucidate that visual signalling is easily quantifiable and could be used to compare individuals, populations, and species, as typically done with anuran acoustic signals.

Progression of suicidal ideation to suicidal behavior from a perspective of selected suicidological models.

In clinical practice suicidal ideation (SI) is one of the most commonly encountered symptoms in patients with mental disorders. Such encounter calls for diligent evaluation of suicidal risk. Although the risk factors are widely known, accurate estimation of suicidal risk remains one of the most difficult and most important tasks that clinicians face - especially considering recently collected data showing increase in suicide prevalence in Poland. More thorough estimation of suicidal risk in patients with SI requires taking under consideration not only suicidal risk factors but also factors that are more specific for progression of SI to suicidal behaviors (SB). The review presented in this paper consists of a range of suicidological theories that allow to select a number of groups of factors and mechanisms that are most specific for progression of SI to SB. These groups include: (1) transgression of fear of causing harm and pain to oneself, as well as disintegration of other protective barriers such as (2) decline of social integration with others, feeling of being alienated or abandoned, decline of sense of belongingness, lack of social support, (3) resignation from family and social obligations, (4) dismissing cultural or religious norms, (5) rejection of life goals, values and aspirations that were appreciated earlier, (6) narrowing down in perceived alternatives for suicide, i.e., "tunnel vision", feelings of helplessness and powerlessness, (7) devising in details and accepting simple suicidal plan, especially when such plan is being consolidated through rehearsals and as if "automatized", (8) impulsiveness, (9) accumulation of aggression that may be vented out as suicide, and finally (10) accessibility of means to commit suicide.

Species specificity of temporal processing in the auditory midbrain of gray treefrogs: long-interval neurons.

In recently diverged gray treefrogs (Hyla chrysoscelis and H. versicolor), advertisement calls that differ primarily in pulse shape and pulse rate act as an important premating isolation mechanism. Temporally selective neurons in the anuran inferior colliculus may contribute to selective behavioral responses to these calls. Here we present in vivo extracellular and whole-cell recordings from long-interval-selective neurons (LINs) made during presentation of pulses that varied in shape and rate. Whole-cell recordings revealed that interplay between excitation and inhibition shapes long-interval selectivity. LINs in H. versicolor showed greater selectivity for slow-rise pulses, consistent with the slow-rise pulse characteristics of their calls. The steepness of pulse-rate tuning functions, but not the distributions of best pulse rates, differed between the species in a manner that depended on whether pulses had slow or fast-rise shape. When tested with stimuli representing the temporal structure of the advertisement calls of H. chrysoscelis or H. versicolor, approximately 27 % of LINs in H. versicolor responded exclusively to the latter stimulus type. The LINs of H. chrysoscelis were less selective. Encounter calls, which are produced at similar pulse rates in both species (≈5 pulses/s), are likely to be effective stimuli for the LINs of both species.

Quantitative description of the vocal repertoire of the territorial olive frog Babina adenopleura from Taiwan

Anurans communicate using a repertoire of acoustic signals that can be classified as different call types based on differences in both their acoustic properties and the contexts in which they are produced. Descriptions of these repertoires represent a key first step towards understanding the vocal behaviour of any species and provide a critical foundation for comparative bioacoustic studies. In this study of the olive frog, Babina (formerly Rana) adenopleura, a territorial species from subtropical Taiwan, we used focal observations, acoustic recordings and statistical analyses of temporal, spectral and amplitude-related call properties to describe six different call types in the species' vocal repertoire. These call types included a putative advertisement call, territorial call, encounter call, amplectant call, distress call and alarm call. Advertisement calls consisted of four to five discrete notes, and they were the most commonly produced call. Territorial and encounter calls were delivered during interactions with other males; the former is a two-note call, whereas the latter is a distinctly pulsatile signal. Amplectant calls were acoustically similar to territorial calls but were delivered while males were in amplexus. Distress calls were given while the animal was being consumed by a snake, and alarm calls were recorded in response to startling stimuli. With basic descriptions of these call types in hand, we discuss several testable hypotheses for their putative adaptive functions.

Notes on behaviour, communication and reproduction in captive Hyloxalus toachi (Anura: Dendrobatidae), an Endangered Ecuadorian frog

We studied, under laboratory conditions, behavioural traits related to social interactions, parental care and communication in Hyloxalus toachi. This species is diurnal. Females spent most of their time maintaining and defending territories and were more territorial than ♂♂. Male vocalizations included long‐range advertisement calls, two kinds of close‐range courtship calls, aggression calls and sounds produced while attempting to clasp ♀♀. During body contact, ♂♂ and ♀♀ produced encounter calls. Preovipositional amplexus was cephalic and lasted 10–15 minutes. During terrestrial oviposition, the ♂ climbed onto the dorsum of the ♀ in an axillary position, but without clasping the ♀. Fertilization occurred as the eggs were deposited. When oviposition was completed, the ♂ left the ♀, while the ♀ remained close to the clutch for up to 5 hours. The mean clutch size was 11 eggs. Eggs had a mean diameter of 2·4 mm. The incubation time was 13–16 days. During that time, egg attendance and transport of tadpoles to water were performed exclusively by the ♂. Tadpoles were carried on the ♂'s dorsum for up to 5 days. The behaviours and features reported here are useful for interpreting trends in the evolution of dendrobatid behaviour.

A REVISION OF ODONTOPHRYNUS BARRIOI (ANURA: NEOBATRACHIA): MORPHOLOGY, OSTEOLOGY, VOCALIZATIONS, AND GEOGRAPHIC DISTRIBUTION

The present paper provides diagnostic characters from external morphology and osteology that reinforce the specific recognition of the frog Odontophrynus barrioi, describes its advertisement and encounter calls, and extends its distribution range. Odontophrynus barrioi is distinguished from all other species of the genus principally by the large size of adults, great number of irregularly arranged postorbital and temporal glands, lack of both a light vertebral line and keratinous spines, alary process of the premaxilla short and wide, pterygoid process of the maxilla well developed, and high preorbital process of the maxilla. The advertisement call consists of a trill of a single repeated and pulsed note with a low dominant frequency. The encounter call consists of only one note of similar frequency as the advertisement call, but longer in time duration. We report new records of O. barrioi from Catamarca, La Rioja, and San Juan Provinces (Argentina), that increase considerably the range of this previously poorly known species.

Territorial vocal behavior in hybrid smooth froglets, Geocrinia laevis complex (Anura: Myobatrachidae)

Males of the parapatically distributed myobatrachid frogs Geocrinia laevis and G. victoriana have highly divergent advertisement calls. Furthermore, the two species differ strongly in the complexity of their vocal repertoires, with males of G. victoriana possessing, and those of G. laevis lacking, a distinct territorial vocalization (encounter call). We investigated the territorial vocal behavior of males in a persistent natural hybrid population. Most hybrid males possessed encounter calls functionally equivalent to those of G. victoriana, that were produced following exposure to playback of recorded advertisement calls presented at >110 dB peak sound pressure level. The territorial acoustic responses were not associated with an index of hybridity derived from the structure of the advertisement call, suggesting genetic and functional decoupling of the two components of the vocal repertoire; i.e., advertisement calls and encounter calls. This decoupling may be the result of sexual selection favouring those hybrids with pronounced territorial behavior and the associated vocalization, regardless of the structure of their advertisement calls.

Temporal bone anatomy in Panthera tigris

Preliminary findings suggest that members of Panthera tigris subspecies may rely on low-frequency acoustic cues when communicating with conspecifics either in the field or in captivity. This view is supported by the observation that individuals are sensitive to tone bursts in the 300–500-Hz range and produce significant acoustic energy in an overlapping frequency band in the case of close encounter roars. Other utterances within the vocal repertoire of tigers also contain, and are often dominated by, low frequency acoustic energy that can extend into the infrasonic range. Efforts to determine temporal bone correlates of P. tigris bioacoustical features were recently initiated using computerized tomography to assess key aspects of middle and inner ear morphology from a small set of adult Siberian tigers (P. tigris altaica) and one neonate. Obvious peripheral auditory specializations were not observed and structures comprising the auditory periphery were consistent with the anatomical character of felids generally. Although cochlear dimensions appeared to be adultlike, or nearly so, in the case of the neonate, other temporal bone features were grossly immature. The relationship between acoustic sensitivity, the spectral character of a subset of close encounter calls and cochlear dimensions will be considered.

Reproductive biology of Hyla goiana (Anura, Hylidae)

Male-male and male-female interactions, reproductive habitat, and vocalizations of Hyla goiana B. Lutz, 1968 a member of H. polytaenia species group, are described. Three groups of calling males were surveyed along a small stream, at the Estação de Pesquisa e Desenvolvimento Ambiental de Galheiro, Perdizes municipality, State of Minas Gerais, Brazil. The mean distance between the nearest calling neighbors was 2.7 m, in accordance with an uniform distribution. Clutches (mean 180 eggs) were deposited in the stream, submerged and attached to plants. In two observed courtships the female moved towards a calling male that rapidly clasped her. In the male-male interaction, the males emitted advertisement and encounter calls and then engaged in physical combat. The males have a prepollical fang-like spine on each hand and several of them were observed with scratches on dorsum. The advertisement call consists of alternating harsh notes and a trilled of brief notes. The frequency of the call is lower than that of H. aff. polytaenia and H. cipoensis B. Lutz, 1968. The clutch characteristics of H. goiana are similar to those described for H. polytaenia Cope, 1870 and H. cipoensis.

Acoustic variability and distinguishability among mouse ultrasound vocalizations.

Auditory neurobiology has benefited significantly from ethological approaches using acoustic communication signals. Developing an ethological model in a genetically manipulable system such as the mouse would enhance the ability to investigate the processing, learning, and recognition of sounds. Characterizing the basic acoustic structure of mouse vocalizations would help lay a foundation for such a future study. Towards this goal, ultrasound vocalizations emitted by isolated mouse pups and pairs of adult males and females have been digitally recorded and examined. Previous work suggests that these calls may have communicative significance. An analysis of the natural variability in their spectral content, median frequency, duration, and repetition period reveals acoustic structure that could be used for recognizing the calls. Other parameters, like the rate of frequency modulation, may also be informative, but have not been examined. Pup isolation calls develop systematically between postnatal day 5 and 12 towards a more stereotyped vocalization--contracting from a wide range of values into narrower clusters of frequency and duration, and shifting from longer to shorter repetition periods. Most significantly, pup isolation and adult encounter calls fall into two distinct spectral and temporal categories, making it possible for a receiver to acoustically distinguish between them, and to potentially categorically perceive them along those dimensions.

Individual and Contextual Variation in Thomas Langur Male Loud Calls

AbstractIndividual and contextual differences in male loud calls of wild Thomas langurs (Presbytis thomasi) were studied in northern Sumatra, Indonesia. Loud calls were given in the following contexts: morning calls, vocal responses to other groups, between‐group encounter calls and alarm calls. Loud call spectrograms were analysed for a large number of variables. With discriminant analyses, 14 variables were found to be important in distinguishing individuals and contexts. Loud calls were assigned to the correct individual in 95.6% of the cases (91.8% with ‘leave‐one‐out’ validation) and to the correct context in 52.2% of the cases (39.0% with ‘leave‐one‐out’ validation). Further analyses with two‐way anovas showed significant differences in both temporal and frequency variables between individuals and contexts. Loud calls seemed to differ between the contexts in functionally meaningful ways, relating to the distance of the intended receivers and to the urgency of the message. Observation showed that females in the caller's group collected infants more often in the between‐group encounter context and in the alarm call context than in the vocal exchange context. These differential responses suggest that the monkeys also perceive the measurable differences in loud call characteristics between the various contexts.

Calling and plasticity in Pacific Treefrog choruses

Male Pacific treefrogs (Hyla regilla) use advertisement and encounter calls to regulate intermale spacing within breeding choruses. Encounter calls are produced when a neighbor’s advertisement calls exceed a threshold amplitude. These aggressive thresholds are plastic; males resume advertisement calling (i.e., accommodate) to repeated presentation of advertisement calls at amplitudes 4–8 dB above their aggressive threshold. Correspondingly, a male’s aggressive threshold for the advertisement call is positively correlated with the maximum amplitude of neighbors advertisement calls measured at his position. The aggressive thresholds of males for the encounter call are also plastic but not correlated with the maximum call amplitude of their neighbors. This disjunction stems from the fact that males in stable choruses are not regularly exposed to suprathreshold encounter calls. Accommodation to one call type fails to significantly alter a male’s aggressive threshold to the other call type, which suggests that the two call types are processed by discrete neural filters. Plasticity of aggressive thresholds and aggressive signalling appears to be important in balancing the costs and benefits of aggressive behaviors. In phonotaxic studies, females show a strong preference for the advertisement call over the encounter call. Prolonged encounter calling would therefore decrease a male’s chance of mating.

Neural mechanisms of call recognition in Pacific treefrogs

Pacific treefrogs, Hyla regilla, use advertisement and encounter calls in their acoustic communication. These two call types differ primarily in the rate that pulses are repeated; at 17<th>°C, pulse repetition rates (PRRs) for advertisement and encounter calls are about 100 pulses/s and 30 pulses/s, respectively. Behavioral studies indicate that two discrete channels exist for processing these communication signals. Because sound pulses in these two call types are highly similar in spectral and temporal structure, the PRR selectivity of the advertisement filter is likely to result from an analysis of interpulse interval. Behavioral studies support the hypothesis that temporal integration might underlie this analysis. As a neural correlate to the behavioral studies, toral neurons have been recorded that respond selectively to PRRs found in the advertisement call. These cells fail to respond to encounter call PRRs. In support of the integration hypothesis, these units only respond after a threshold number of correct interpulse intervals have been presented; the average PRR is largely irrelevant. The interval-counting process can be reset by a single inappropriate interval. In the most selective cases, a single interval that is slightly longer or shorter than the optimal interval can reset the integration process. [Work supported by NIDCD.]

Atividade reprodutiva de Physalaemus signifer (Anura, Leptodactylidae) em ambiente temporário

The breeding activity of Physalaemus signifer (Girard, 1853) was monitored from July 1999 to July 2000 in a temporary pond in Palmital, Municipality of Saquarema, State of Rio de Janeiro, Atlantic Rain Forest, Brazil. Males were sexually actives only in four nights, arriving at the pond on the early rainy season. Males in amplexus were larger and spent more nights in the reproductive aggregation than solitary ones. The number of nights was correlated with the mass of the males. Males adopted satellite behavior as alternative tactic for mate acquisition. Changes between calling and satellite tactics were observed in different nights. Calling males were not larger and heavier than satellite ones. Satellite behavior seemed to be related with the order of arrival on the pond. Size and mass of males did not influence the results of fights. Resident males won the majority of agonistics combats. Three types of vocalizations are described: advertisement, territorial, and encounter calls.

Pacific treefrogs use temporal integration to differentiate advertisement from encounter calls

Male Pacific treefrogs, Hyla regilla, use advertisement and encounter calls in their reproductive communication. Encounter calls are produced when a male hears either advertisement or encounter calls at amplitudes that exceed his aggressive threshold for that call type, and they are believed to play a role in male spacing in a chorus. Aggressive thresholds of males for advertisement and encounter calls are plastic; males resume advertisement calling (i.e. accommodate) after repeated exposure to either advertisement or encounter calls that exceed their aggressive thresholds for that call type. Presentation of one call type does not elevate a male's aggressive threshold for the other call type, indicating that discrete neural ‘channels’ exist for processing advertisement versus encounter calls. Because these calls are spectrally highly similar, it is likely that they are differentiated in the central auditory system on the basis of their different temporal structure; pulses are repeated in advertisement and encounter calls at rates of approximately 100 pulses/s and 30 pulses/s, respectively. The present study tested whether consecutive advertisement-type interpulse intervals (IPIs) are required to activate the filter for advertisement calls. Males were accommodated to synthetic stimuli that differed in the proportion of advertisement versus encounter IPIs. Aggressive thresholds of males for the encounter call and advertisement call (monophasic type) were elevated 450% and 58%, respectively, following accommodation to a stimulus that had nine of each IPI type, arranged in an alternating sequence. Aggressive thresholds for the monophasic advertisement call were elevated 151%, however, when males were accommodated with stimuli that had two sets of eight to nine consecutive advertisement IPIs; consistent with previous work, aggressive thresholds for the encounter call were not significantly elevated. Aggressive thresholds for the advertisement call are typically elevated approximately four-fold following accommodation with that call type. These findings are consistent, therefore, with the hypothesis that several consecutive advertisement IPIs are required to activate the ‘advertisement channel’; if consecutive advertisement IPIs were not required, the stimulus that consisted of the same number of advertisement and encounter IPIs should have induced comparable elevations of the aggressive thresholds of males for advertisement and encounter calls. Selective filters for the advertisement call, therefore, appear to integrate information across many consecutive ‘correct’ IPIs. This integration process may contribute to a female's call preference.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .

Territory Defense Strategy of the Wrinkled Frog, Rana rugosa

The advertisement call of anurans functions to attract potential mates. The dominant frequency of an advertisement call is generally getting lower with increased snout-vent length (SVL) of the caller Rana rugosa has an advertisement call tilth a particularly high frequency modulation. We conducted a playback experiment to verify the function of frequency modulation, and investigated the territorial behavior of the frog. The frog has five types of territory defense strategy. Strategy choice depended on the caller`s SVL. Small males became satellites or lowered the dominant frequency of their advertisement call, whereas large males actively defended their territory with encounter calls. In response to high frequency (1107 Hz) playback, the frogs lowered their advertisement call frequency, and towered them further in response to the low frequency (1028 Hz) playback. In addition, the number of pulses in a call was increased in response to the playback. These results indicate that the frog avoids physical conflict with competitors by selecting a territory defense strategy suitable for the caller`s size, and by lowering its call frequency to disguise its SVL.

Female choice and plasticity of male calling behaviour in the Pacific treefrog

Male Pacific treefrogs, Hyla regilla , use advertisement and encounter calls to regulate intermale spacing within breeding choruses. When either type of call produced by a neighbour is detected above a particular amplitude, a resident frog responds aggressively by producing encounter calls. These ‘aggressive thresholds’ differ for the two call types and are plastic: males rapidly resume advertisement calling (accommodate) following repeated presentation of these calls above their aggressive threshold. We tested the hypothesis that this plasticity is the result of female preference for the advertisement call over the encounter call. Female choice was tested in a two-speaker phonotaxis assay with alternating presentation of the two call types. Of the 12 females that met our criteria for demonstrating a phonotaxic response, each approached the speaker playing the advertisement call rather than the encounter call. This strong female preference for the advertisement call supports our hypothesis, and suggests that the plasticity in male calling behaviour allows males to maximize the time spent in producing advertisement calls to attract a female by rapidly adjusting their aggressive behaviour to changes in male spacing within choruses.

Plasticity of mating calls inhyla japonica(Amphibia: Hylidae)

Hyla japonica males were observed to produce two distinctively different types of mating calls: advertisement call to attract conspecific females and encounter call to keep off potential competitor males. Whereas advertisement calls were organized in bouts of calls or notes, encounter calls were usually produced as separate calls. Encounter calls were much longer and had more pulses per call than advertisement calls. However dominant frequencies or pitches of the two calls did not differ significantly. Hyla Japonica males exhibited considerable plasticity in their calling behavior. They altered both qualitative and quantitative properties of their calls in response to other calling males. Sometimes, they even switched from producing advertisement calls to encounter calls. Advertisement calls produced by chorusing males were shorter in duration and thus move calls per bout than those produced by lone males. Males also produced much lower-pitched calls when calling together with other males. Considering that low pitch calls are often Highly correlated with body size, it is possible that H. japonica males may try to generate deceptive calls to indicate the size greater than the actual.

GRADED CALL VARIATION IN THE ASIAN CRICKET FROG RANA NICOBARIENSIS

ABSTRACT We describe the vocal repertoire of the Asian cricket frog Rana nicobariensis for the first time. Three structurally-distinct call types exist: advertisement calls, aggressive calls and encounter calls. Compound calls consisting of both advertisement and aggressive elements were also recorded. A remarkable feature of communication in this species is the highly variable advertisement call which shows a 20-fold variation in duration, comprising 1–25 notes. In natural choruses, the duration of the advertisement call is inversely related to the distance between a focal male and its closest calling neighbour. In playback experiments, males clearly responded to stimuli containing different numbers of notes by adjusting the number of notes emitted. However, they did not match the stimulus precisely, and were inhibited from calling by a stimulus consisting of a continuous train of notes. Different proportions of each call type were recorded during playbacks at different distances; aggressive and encounter calls were increasingly emitted at closer distances. Our results suggest that a graded communication system has evolved in Rana nicobariensis, in which the best call for a male to use at any moment depends on the type of calls being emitted by other males in the chorus.