Perception of harmonics in the combination long call of cottontop tamarins, Saguinus oedipus

A number of nonhuman primates produce vocalizations with time-varying harmonic structure. Relatively little is known about whether such spectral information plays a role in call type classification. We address this problem by utilizing acoustic analyses and playback experiments on cottontop tamarins‘ combi nation long call, a species-typical vocalization with a characteristic harmonic structure. Specifically, we used habituation-discrimination experiments to test whether particular frequency components, as well as the relationship between components, have an effect on the perception and classification of long calls. In Condition 1, we show that tamarins classify natural and synthetic exemplars of the long call as perceptually similar, thereby allowing us to use synthetics to manipulate components of this signal precisely. In subsequent conditions, we tested the perceptual salience and discriminability of long calls in which we deleted (1) the second harmonic, (2) the fundamental frequency, or (3) all frequencies above the fundamental; we also examined the effects of frequency mistuning by shifting the second harmonic by 1000 Hz. Following habituation to unmanipulated long calls, tamarins did not respond (transferred habituation) to long calls with either a missing fundamental frequency or the second harmonic, but responded (discriminated) to long calls with the upper harmonics eliminated or with the second harmonic mistuned. These studies reveal the importance of harmonic structure in tamarin perception, and highlight the advantages of using synthetic signals for understanding how particular acoustic features drive perceptual classification in nonhuman primates. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

The units of perception in the antiphonal calling behavior of cotton-top tamarins (Saguinus oedipus): playback experiments with long calls

We investigated how the acoustic structure of the cotton-top tamarin monkey's (Saguinus oedipus) combination long call relates to the antiphonal calling behavior of conspecifics. Combination long calls can function as contact calls and are produced by socially isolated individuals. Often conspecifics respond to these calls with their own long calls. Structurally, these calls are always composed of one or more 'chirps' followed by two or more 'whistles'. We compared the antiphonal calling responses to playbacks of complete, naturally produced long calls versus single whistles or single chirps. Subjects responded significantly more to whole calls than to either syllable-type alone. Thus, our data suggest that, in terms of the antiphonal calling behavior of socially isolated conspecifics, the whole long call is the unit of perception.     

The communicative content of the common marmoset phee call during antiphonal calling

Vocalizations are a dominant means of communication for numerous species, including nonhuman primates. These acoustic signals are encoded with a rich array of information available to signal receivers that can be used to guide species‐typical behaviors. In this study, we examined the communicative content of common marmoset phee calls, the species‐typical long distance contact call, during antiphonal calling. This call type has a relatively stereotyped acoustic structure, consisting of a series of long tonal pulses. Analyses revealed that calls could be reliably classified based on the individual identity and social group of the caller. Our analyses did not, however, correctly classify phee calls recorded under different social contexts, although differences were evident along individual acoustic parameters. Further tests of antiphonal calling interactions showed that spontaneously produced phee calls differ from antiphonal phee calls in their peak and end frequency, which may be functionally significant. Overall, this study shows that the marmoset phee call has a rich communicative content encoded in its acoustic structure available to conspecifics during antiphonal calling exchanges. Am. J. Primatol. 72:974–980, 2010. © 2010 Wiley‐Liss, Inc.     

White-faced capuchin monkeys show triadic awareness in their choice of allies

The social intelligence hypothesis, which holds that social challenges have selected for increased intelligence and social skills, has been supported by evidence that, in catarrhine primates, individuals know about the characteristics of groupmates' social relationships. Evidence for such ‘triadic awareness’ has not been sought for platyrrhine primates, although two platyrrhine genera, capuchins, Cebus, and squirrel monkeys, Saimiri, are among the most highly encephalized primates. We examined patterns of coalitionary recruitment in wild white-faced capuchins, C. capucinus. Analyses have shown that more dominant individuals are more likely to join aggressive coalitions than low-rankers, and that individuals preferentially support those with whom they have stronger affiliative relationships. Data from 110 fights, analysed using simulation techniques that produced distributions of results expected under null hypotheses, revealed that contestants preferentially solicited prospective coalition partners that (1) were dominant to their opponents, and (2) had better social relationships (higher ratios of affiliative/cooperative interactions to agonistic interactions) with themselves than with their opponents. Further analyses showed that soliciting dominant partners could be explained by either of two simpler rules, ‘Solicit an ally that outranks yourself’ or ‘Solicit the highest-ranking available individual’. However, soliciting partners with better social relationships appears to indicate triadic awareness, because subjects did not preferentially solicit the nearby individual with whom they shared the highest-quality social relationship. Effects of relative relationship quality on coalition solicitation decisions were independent of effects of dominance rank.     

Begging to differ: scrubwren nestlings beg to alarm calls and vocalize when parents are absent

Nestling birds face a dilemma: they can increase parental provisioning by begging more intensively, but by doing so may also increase their risk of predation. Nestlings could deal with this dilemma by reducing begging intensity after parents have warned them of a nearby predator. We therefore tested experimentally whether nestling scrubwrens, Sericornis frontalis, increase begging intensity with hunger but reduce it after adult alarm calls. Single 5- and 8-day-old nestlings were temporarily taken into the laboratory for playback experiments. Over a 90-min period of food deprivation we simulated parental visits every 10 min by playing back adult feeding calls. Hungrier nestlings begged louder and longer to simulated parental visits, but contrary to expectation did not beg less if they had previously heard playback of alarm calls, and even begged to the alarm calls themselves. The results were similar for both ‘mobbing’ and ‘flee’ alarm calls. Nestlings also gave distinctive calls in the 10-min interval between simulated parental visits, and the number of these calls increased with hunger and after playback of alarm calls. We suggest that nestlings acquire the ability to respond appropriately to alarm calls late in the nestling period and that therefore parents might be selected to avoid alarm calling when defending young nestlings.Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.      

The evolution of nonhuman primate loud calls: Acoustic adaptation for long-distance transmission

Many nonhuman primates produce species-typical loud calls used to communicate between and within groups over long distances. Given their observed spacing functions, primate loud calls are likely to show acoustic adaptations to increase their propagation over distance. Here we evaluate the hypothesis that primates emit loud calls at relatively low sound frequencies to minimize their attenuation. We tested this hypothesis within and between species. First, we compared the frequencies of loud calls produced by each species with those of other calls from their vocal repertoires. Second, we investigated the relationship between loud call frequency and home range size across a sample of primate species. Comparisons indicated that primates produce loud calls at lower frequencies than other calls within their vocal repertoires. In addition, a significant negative relationship exists between loud call frequency and home range size among species. The relationship between call frequency and range size holds after controlling for the potentially confounding effects of body size and phylogeny. These results are consistent with the hypothesis that nonhuman primates produce loud calls at relatively low frequencies to facilitate their transmission over long distances.     

Who cares who calls? Selective responses to the lost calls of socially dominant group members in the white‐faced capuchin (Cebus Capucinus)

In many social mammals and birds, soft vocalizations are habitually produced during dispersed moving and foraging, the function being to maintain contact and regulate spacing between group members. In some species, much louder calls are given sporadically by specific individuals when they become separated from the group, or 'lost'. The function of these calls has seldom been specifically tested, particularly among social primates, but is often assumed to involve regaining contact with the group based on a combination of individually distinctive calls and antiphonal responses to them from within the group. To test these assumptions, we conducted research on two groups of white-faced capuchins (Cebus capucinus) in Costa Rica. We analyzed 82 bouts of 'lost' calls given by 13 different adult individuals when separated from the group and the antiphonal responses they elicited. Lost calls were individually distinctive and were answered in 35% of calling episodes. Answers were selective: dominant males and females were answered more than were subordinate callers of either sex. As a result, dominant callers relocated and returned to the group more quickly than did subordinate callers. We discuss the potential proximate motivations for, and ultimate benefits of, such selective answering of dominant group members.     

Antiphonal call timing in marmosets is behaviorally significant: interactive playback experiments

Studies of primate vocal communication systems have generally focused on vocalizations and the information they convey to conspecifics. But the vocalizations are not the only sources of information. Aspects of each species vocal behaviors are likely to be communicatively rich as well. During vocal interactions, for example, the latency delay between the calls could communicate an important message to the signal receiver, such as an interest and willingness to socialize. Here we employed novel, interactive playback software to address this issue in the antiphonal calling behavior of common marmosets. In these experiments, we parametrically varied the latency delay of antiphonal call stimuli and measured its effects on subjects’ resultant vocal behavior. Results showed that marmosets produced successively fewer antiphonal call responses during test conditions with increasing latency delays. Moreover, although subjects produced significantly more antiphonal than spontaneous calls in conditions with antiphonal call timing delays up to 9 s, a longer delay resulted in a significant decline in calling. These data suggest that antiphonal call timing is a salient cue for maintaining antiphonal calling interactions and may be used by marmosets to determine whether a subsequent call is produced in response to or independently of their own.     

Active choice, passive attraction and the cognitive machinery of acoustic preferences

Female preferences for loud calls are widespread among animals that communicate acoustically, but their ‘strategic’ role is still controversial. According to the ‘passive attraction’ hypothesis, females are more likely to respond to loud calls simply because these calls are more effective at stimulating their acoustic receptors and primary neurons. The ‘active choice’ hypothesis, however, assumes that females use sound intensity as a cue to assess the power and location of sound sources and to respond accordingly. To test which hypothesis could best explain the preference for loud calls of female green toads, Bufo viridis, we carried out multitrial discrimination experiments, in which females were given a choice between two stimuli differing in either the power or the distance of their sources or both. In the laboratory, females could discern differences in intensity caused by differences in power or location of the acoustic sources. This ability increased in field experiments, when the speakers and receivers were further apart than in the laboratory experiments. Phonotactic behaviour did not vary significantly between females, but did within females: in their second trial, females were more likely to approach the closer speaker than in the first trial. These findings suggest that sound intensity plays a more complex role in female mate choice than that recognized by the passive attraction hypothesis. To understand female preferences and, ultimately, mate choice, attention should be focused directly on the computational processes of the female's central nervous system.     

Sensory-motor interactions modulate a primate vocal behavior: antiphonal calling in common marmosets

A fundamental issue in neuroscience pertains to how different cortical systems interact to generate behavior. One of the most direct ways to address this issue is to investigate how sensory information is encoded and used to produce a motor response. Antiphonal calling is a natural vocal behavior that involves individuals producing their species-specific long distance vocalization in response to hearing the same call and engages both the auditory and motor systems, as well as the cognitive neural systems involved in decision making and categorization. Here we present results from a series of behavioral experiments investigating the auditory–vocal interactions during antiphonal calling in the common marmoset (Callithrix jacchus). We manipulated sensory input by placing subjects in different social contexts and found that the auditory input had a significant effect on call timing and propensity to call. Playback experiments tested the significance of the timing of vocal production in antiphonal calling and showed that a short latency between antiphonal calls was necessary to maintain reciprocal vocal interactions. Overall, this study shows that sensory-motor interactions can be experimentally induced and manipulated in a natural primate vocal behavior. Antiphonal calling represents a promising model system to examine these issues in non-human primates at both the behavioral and neural levels.     

Acoustic signals of baby black caimans

In spite of the importance of crocodilian vocalizations for the understanding of the evolution of sound communication in Archosauria and due to the small number of experimental investigations, information concerning the vocal world of crocodilians is limited. By studying black caimans Melanosuchus niger in their natural habitat, here we supply the experimental evidence that juvenile crocodilians can use a graded sound system in order to elicit adapted behavioral responses from their mother and siblings. By analyzing the acoustic structure of calls emitted in two different situations (‘undisturbed context’, during which spontaneous calls of juvenile caimans were recorded without perturbing the group, and a simulated ‘predator attack’, during which calls were recorded while shaking juveniles) and by testing their biological relevance through playback experiments, we reveal the existence of two functionally different types of juvenile calls that produce a different response from the mother and other siblings. Young black caimans can thus modulate the structure of their vocalizations along an acoustic continuum as a function of the emission context. Playback experiments show that both mother and juveniles discriminate between these ‘distress’ and ‘contact’ calls. Acoustic communication is thus an important component mediating relationships within family groups in caimans as it is in birds, their archosaurian relatives. Although probably limited, the vocal repertoire of young crocodilians is capable of transmitting the information necessary for allowing siblings and mother to modulate their behavior.     

Conspicuous males suffer higher predation risk: visual modelling and experimental evidence from lizards

Colour pattern variation is a striking and widespread phenomenon. Differential predation risk between individuals is often invoked to explain colour variation, but empirical support for this hypothesis is equivocal. We investigated differential conspicuousness and predation risk in two species of Australian rock dragons, Ctenophorus decresii andC. vadnappa . To humans, the coloration of males of these species varies between ‘bright’ and ‘dull’. Visual modelling based on objective colour measurements and the spectral sensitivities of avian visual pigments showed that dragon colour variants are differentially conspicuous to the visual system of avian predators when viewed against the natural background. We conducted field experiments to test for differential predation risk, using plaster models of ‘bright’ and ‘dull’ males. ‘Bright’ models were attacked significantly more often than ‘dull’ models suggesting that differential conspicuousness translates to differential predation risk in the wild. We also examined the influence of natural geographical range on predation risk. Results from 22 localities suggest that predation rates vary according to whether predators are familiar with the prey species. This study is among the first to demonstrate both differential conspicuousness and differential predation risk in the wild using an experimental protocol. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.      

Genetic Relationships of Ornamental Cultivars of Ginkgo biloba Analyzed by AFLP Techniques

Eight primer combinations that produced clear and a large number of polymorphic bands were screened from 64 EcoR I/Mse I primer combinations (Mse I fluorescent labeled). The genetic relationships of 21 ornamental cultivars of Ginkgo biloba L. from the United States of America, Holland, Japan, France, and China were analyzed. These primer combinations produced a total of 1 119 bands, 229 specific loci (including 54 absent bands, and 175 monomorphic bands). Among them, 983 polymorphic bands (PPB), accounting for 88%, were detected. The percentage of identification per primer combination was as high as 100%. The average PPB of 14 foreign cultivars was 35.86% and the average PPB of seven domestic cultivars was 31.51%. Genetic similarity coefficient (SC) among all cultivars varied from 0.4899 to 0.8499, and all cultivars were divided into the four clusters when SC was set at 0.7300. The cultivars from the same origin did not fall into the same group. The cultivars from France and China were classified into three groups. According to the comprehensive analyses based on specific loci, similarity coefficient, and clustering results, eight cultivars ‘Fastigiata’, ‘Tit’, ‘Tubifolia’, ‘Daeryinxing’, ‘Variegata’, ‘Horizontalis, ‘Pendula’, and ‘Yiyuanyeziyinxing’ were considered to be important germplasms of ornamental cultivars of Ginkgo biloba.     

Calls out of chaos: the adaptive significance of nonlinear phenomena in mammalian vocal production

Recent work on human vocal production demonstrates that certain irregular phenomena seen in human pathological voices and baby crying result from nonlinearities in the vocal production system. Equivalent phenomena are quite common in nonhuman mammal vocal repertoires. In particular, bifurcations and chaos are ubiquitous aspects of the normal adult repertoire in many primate species. Here we argue that these phenomena result from properties inherent in the peripheral production mechanism, which allows individuals to generate highly complex and unpredictable vocalizations without requiring equivalently complex neural control mechanisms. We provide examples from the vocal repertoire of rhesus macaques, Macaca mulatta, and other species illustrating the different classes of nonlinear phenomena, and review the concepts from nonlinear dynamics that explicate these calls. Finally, we discuss the evolutionary significance of nonlinear vocal phenomena. We suggest that nonlinear phenomena may subserve individual recognition and the estimation of size or fluctuating asymmetry from vocalizations. Furthermore, neurally ‘cheap’ unpredictability may serve the valuable adaptive function of making chaotic calls difficult to predict and ignore. While noting that nonlinear phenomena are in some cases probably nonadaptive by-products of the physics of the sound-generating mechanism, we suggest that these functional hypotheses provide at least a partial explanation for the ubiquity of nonlinear calls in nonhuman vocal repertoires.     

Begging in the absence of sibling competition in Wilson’s storm-petrels, Oceanites oceanicus

Begging displays of nestlings in multichick broods can signal both hunger and competitive ability. Studies of begging in species with single-chick broods exclude the influence of nestling competition and may provide especially useful models for the study of signalling during parent-offspring conflict. However, there is no evidence that chicks signal hunger by begging in the absence of sibling competition. I tested predictions of signalling models in a species with single-chick broods, the Wilson's storm-petrel. Chicks used two types of begging calls, ‘rhythmic’ calls and ‘long’ calls. I found that chicks conveyed information about their current body condition by begging. When their body condition was low, chicks increased the number and frequency of long begging calls, as well as the frequency of rhythmic calling. Parents responded to increased begging by regurgitating larger meals. The study thus demonstrates that the begging system can work in the absence of nestling competition. Chicks also called in the absence of their parents, but in this context they used only rhythmic calls and there was no correlation with current body condition. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Two auditory filter systems determine the calling behavior of the fire-bellied toad: a behavioral and neurophysiological characterization

Summary Male fire-bellied toads,Bombina bombina, are stimulated into calling by conspecific mating calls. They tend to synchronize their activity with other calling individuals, which leads to antiphonal calling. Behavioral physiological experiments revealed the existence of two different auditory filter systems which influence this acoustic behavior. One filter system is tuned to the recognition of conspecific mating calls, the other is part of a circuit that controls an acoustic jamming avoidance reaction. The two filter systems differ in several properties: filter bandwidth, threshold, and time constant. Neurophysiological recordings in the midbrain and the thalamus show that the filter characteristics can be explained by the coding properties of auditory neurons in these two brain nuclei.     

Acoustic and Temporal Variation in Gelada (<Emphasis Type="Italic">Theropithecus gelada</Emphasis>) Loud Calls Advertise Male Quality

Many animals rely on information from vocal signals to assess potential competitors and mates. For example, in primates, males use loud calls to assess rivals when the acoustic properties of the calls reliably indicate the condition or quality of the sender. Here, we investigate whether the loud calls of male geladas (Theropithecus gelada) function as a quality signal. Gelada males produce loud calls during ritualistic chases with rival males. Given the physically taxing nature of these displays, we hypothesize that variation in the acoustic properties of loud calls reliably signal male stamina or competitive ability. To test this hypothesis, we examined whether the acoustic properties of the gelada loud call varied in relation to individual, age, status, and exhaustion. Specifically, we examined 12 call parameters (e.g., fundamental frequency) and 3 bout parameters (e.g., number of calls per bout), that have been previously shown to vary across condition in male primates. We found that several acoustic features varied consistently across age and status such that males deemed higher quality in gelada society (e.g., high status) produced more calls per bout, produced calls that were lower in overall frequency measures, and exhibited a greater vocal range. In addition, we found that similar acoustic features varied with exhaustion; after a long chase event, males produced both fewer calls per bout and calls with higher spectral measures. Results from this study are consistent with the hypothesis that gelada loud calls are quality signals, contributing to the growing evidence that primates may use acoustic information to assess the quality of a rival or a potential mate.     

Tritrichomonas foetus from domestic cats and cattle are genetically distinct

The genetic relationship amongst Tritrichomonas foetus isolated from domestic cats and cattle was investigated by DNA sequencing of the internal transcribed region of the ribosomal DNA unit and the TR7/TR8 variable-length repeat. The results reject the hypothesis that T. foetus from domestic cats is genetically identical to T. foetus in cattle. We suggest recognition of a ‘cat genotype’ and a ‘cattle genotype’ of T. foetus. Review of public nucleotide repositories revealed that the ‘cat genotype’ has not been isolated from cattle nor the ‘cattle genotype’ recovered from cats. However, at least one cat isolate has been shown to induce disease in experimentally infected cattle. We conclude that these genotypes fall within the single species T. foetus.     

Rye oxidative stress under long term Al exposure

Aluminium (Al) toxicity decreases plant growth. Secale cereale L. is among the most Al-tolerant crop species. In order to study the response to Al-long term exposure, two rye genotypes with different Al sensitivity (‘D. Zlote’ and ‘Riodeva’) were exposed to 1.11 and 1.85 mM Al and the antioxidant responses were followed for 2 and 3 weeks in roots and leaves. Al toxicity signals, such as a severe decrease in root growth, occurred sooner in ‘Riodeva.’ The antioxidant response was dependent on the genotype, the organ, Al concentration and the exposure period. Al-exposed roots of ‘D. Zlote’ showed earlier enhancements of APX, SOD and G-POX activities than those of ‘Riodeva.’ ‘D. Zlote’ roots showed stimulation of the AsA–GSH cycle after the second week (when root growth inhibition was less severe), while later (when severe root growth inhibition was observed), oxidation of AsA and GSH pools was observed. In leaves of both genotypes, CAT, SOD and G-POX activities increased with Al exposure. In these leaves, the effect of AsA–GSH was time dependent, with maximum oxidation at the second week, followed by recovery. We confirmed that the oxidation state of AsA and GSH pools is involved in the detoxification of Al-induced oxidative stress. Moreover, our data demonstrate that the production of ROS does not correlate with the Al-induced root growth decrease. Finally, the differences observed over time indicate that long term exposure may provide additional information on rye sensitivity to Al, and contribute to a better understanding of this species’ mechanisms of Al tolerance.