Marathon callers: acoustic variation during sustained calling in treefrogs (original) (raw)
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Ethology Ecology and Evolution
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Calling in gray treefrog choruses: Modifications and mysteries
The Journal of the Acoustical Society of America, 2013
Frogs are well known model systems in the study of communication for investigating the influences of noise on both signaling behavior and auditory processing. The best-studied frogs in this regard are two sister-species in the Hyla versicolor species complex (H. versicolor and H. chrysoscelis). Males of both species produce loud, pulsatile advertisement calls that function to attract females. In the competitive social environment of a breeding chorus, males commonly shift to producing longer calls (with more pulses) at slower rates when the level of competition increases. These behavioral modifications can be evoked in controlled laboratory experiments using playbacks of calls and chorusshaped noise. In contrast to birds and mammals, however, there is no evidence that males increase the amplitude of their vocalizations (the Lombard Effect) in response to increasing noise levels. In addition, current evidence suggests that males do not necessarily profit significantly from producing longer calls at slower rates in terms of increasing their overall attractiveness to females, overcoming interference by overlapping calls, or increasing the detectability of their calls in noise. Despite the robust and directional nature of call modifications in noise, the evolutionary function of these modifications remains obscure.
The Advertisement Call of the European Treefrogs (Hyla arborea): A Multilevel Study of Variation
Ethology, 2002
In this study, we analysed the patterns of variation of the European treefrog's advertisement call at four levels of organization: within individuals, within populations, among populations of the same species, and among dierent species of the same clade. At the within-individual level, call acoustic properties are distinguished into static and dynamic properties. At the withinpopulation level, two sources of call variation were analysed: temperature and body size. Temperature aects both temporal and spectral properties of the call. Body size mostly aects spectral properties. At the between-population level, calls do not show signi®cant dierences with respect to temporal properties, but they do dier in two spectral (and stereotyped) properties: the fundamental frequency and the dierence in amplitude between dominant and fundamental frequencies. Finally, at the between-species level, call dierences are much more conspicuous: they involve both spectral and temporal and both static and dynamic properties. At all four levels, body size is associated with call variation, explaining 11% of the dierences among populations of the same species and 73% of the dierences among species of the same clade. On the basis of these results, we hypothesize that patterns of variation of call acoustic properties, their constraints, and their biological functions are intrinsically associated. We discuss the role that such an association might play in the evolution of acoustic signals.
Vocal Communication In a Neotropical Treefrog, Hyla Ebraccata: Aggressive Calls
Behaviour, 1984
We studied the vocal communication of Hyla ebraceata in central Panama. The advertisement call of this species consists of a pulsed buzz-like primary note which may be given alone or followed by 1-4 secondary click notes. Primary notes are highly stereotyped, showing little variation within or among individuals in dominant frequency, duration, pulse repetition rate or rise time. Males calling in isolation give mostly single-note calls. They respond to playbacks of conspecific calls by increasing calling rates and the proportion of multi-note calls, and by giving synchronized calls 140-200 ms after the stimulus begins. Responses to conspecific advertisement calls are usually given immediately after the primary note of the leading call, but the primary note of the response often overlaps with the click notes of the leading call. Experiments with synthetic signals showed that males synchronize to any type of sound of the appropriate frequency (3 kHz), regardless of the fine structure of the stimulus. Playbacks of synthetic calls of variable duration showed that males do not synchronize well to calls less than 150 ms long, but they do to longer calls (200-600 ms). The variance in response latency increased with increasing stimulus duration, but modal response times remained at around 140-200 ms. Similar results were obtained in experiments with synthetic calls having a variable number of click notes. Males showed no tendency to increase the number of click notes in their calls in response to increasing stimulus duration or increasing number of clicks in the stimulus. Females preferred three-note to one-notecalls in two-choice playback experiments, whether these were presented in alternation, or with the one-note call leading and the three-note call following. Females showed no preference for leader or follower calls when both were one-note. When two-note calls were presented with the primary note of the follower overlapping the click note of the leader, females went to calls in which click notes were not obscured. Our results indicate that male H. ebraeeata respond to other males in a chorus in ways which enhance their ability to attract mates.
Treefrogs adjust their acoustic signals in response to harmonics structure of intruder calls
Behavioral Ecology, 2021
Spectral properties of animal acoustic signals may help individuals to assess the characteristics of rivals and to adjust their competitive strategies in territorial disputes. Thus, we hypothesized that the distribution of energy across frequency bands in anuran calls determines behavioral responses in male–male competition. Using playback experiments, we investigated the relevance of the harmonic calls in the acoustic communication of the treefrog Dendropsophus minutus. We exposed territorial males to three synthetic acoustic stimuli composed of aggressive notes: 1) standard call (all harmonics and peak frequency corresponding to the second band); 2) inverted-energy call (all harmonics and peak frequency corresponding to the first band); and 3) concentrated-energy call (all energy contained in the second harmonic). Males responded aggressively to all stimuli, mainly by increasing the rate and duration of their aggressive notes. However, when exposed to stimuli with different harmon...
Journal of Herpetology, 2013
We evaluated the hypothesis that adjustments in call duration made by male Gray Treefrogs render their calls less easily masked in noise and so facilitate communication with females in choruses. We also tested whether shifts in male call duration and rate can be elicited through changes in the level of filtered background noise. We found that males increased the number of pulses in their calls while lowering call rate with elevations in noise level in a fashion similar to that reported during broadcasts of calls. In phonotaxis tests with females using unmodulated or modulated background noise and calls (10, 20, 30, or 40 pulses long) presented at either unequal or equal rates, we failed to find significant differences in noise levels at call recognition thresholds for calls of different duration. However, calls were detected more easily (i.e., noise levels at recognition thresholds were higher) when the noise background was modulated as compared to unmodulated. Our results and those of an earlier study by our laboratory indicate that changes in vocal behavior made by males of Hyla versicolor in response to changes in the calling of other males and background noise within choruses likely do not function to lessen the problems of signal detection or degradation due to interference. Accordingly, a small advantage accruing to males because of an inherent, albeit context-dependent, female preference for long calls (even at low call rates) may account for the dynamic calling behavior of male Gray Treefrogs.
Female mate choice in treefrogs static and dynamic acoustic criteria
Patterns of variation in the acoustic properties of advertisement calls of several species of treefrogs (family Hylidae) are related to patterns of female preferences for these same properties. Properties were unequivocally classified as static or dynamic based on within-male variability during bouts of calling. Static properties are highly stereotyped within males and between males in natural populations. Dynamic properties often change by as much as 100% during single bouts of calling; dynamic properties are usually much more variable among males in natural populations than are static properties. An analysis of the calling performance of individual males over the course of a breeding season indicated that at least one dynamic property, pulse number (or call duration) in Hyla versicolor, was sufficiently repeatable to differentiate between males. Playback experiments that employed synthetic calls showed that: (1) females exhibit patterns of preferences that should result in selection that is stabilizing or weakly directional on static properties, and highly directional on dynamic properties; and (2) the overall attractiveness of a signal is affected by variation in both static and dynamic properties. Similar results were found in laboratory and field studies of other taxa, primarily anurans and insects. Patterns of variability in call properties of males and in female preferences are discussed in terms of proximate mechanisms and theoretical models of the evolution of female choice.
PeerJ, 2017
The evolution of exaggerated vocal signals in anuran species is an important topic. Males and females have both evolved the ability to discriminate communication sounds. However, the nature of sexual dimorphism in cognition and sensory discrimination and in the evolution and limitation of sexual signal exaggeration remain relatively unexplored. In the present study, we used male calls of varied complexity in the serrate-legged small treefrog,, as probes to investigate how both sexes respond to variations in call complexity and how sex differences in signal discrimination play a role in the evolution of sexual signal exaggeration. The compound calls of maleconsist of a series of one or more harmonic notes (A notes) which may be followed by one or more short broadband notes (B notes). Male playback experiments and female phonotaxis tests showed that increasing the number of A notes in stimulus calls elicits increased numbers of response calls by males and increases the attractiveness ...
Why stop calling? A study of unison bout singing in a Neotropical treefrog
Animal Behaviour, 1991
Chorusing males of the Neotropical treefrog, Hyla microcephala, call in distinct bouts punctuated by periods of silence, known as unison bout singing. Previous studies of the calling energetics of frogs do not support the idea that males periodically stop calling because of high muscle lactate levels. Three additional hypotheses of why calling periodically ceases were tested. A two-stimulus female choice experiment failed to support the hypothesis that females prefer males that call cyclically. Playback experiments with males in the field rejected the hypothesis that males stop calling because of high ambient noise. Rather, data indirectly supported the hypothesis that males cease calling to save energy. Male H. microcephala adjust the timing of notes in their multi-note calls when interrupted by notes of other males. The flexibility of note timing was tested by interrupting males with call-triggered computer-generated advertisement calls of 20-1000 ms. The vocal behaviour of the frogs reduced acoustic interference significantly for most stimulus durations and probably allows males to minimize note overlap with their closest neighbours in the chorus while continuing to call when chorus noise levels are high.