Ultrasonic Communication in Rats: Can Playback of 50-kHz Calls Induce Approach Behavior?

Rats emit distinct types of ultrasonic vocalizations, which differ depending on age, the subject's current state and environmental factors. Since it was shown that 50-kHz calls can serve as indices of the animal's positive subjective state, they have received increasing experimental attention, and have successfully been used to study neurobiological mechanisms of positive affect. However, it is likely that such calls do not only reflect a positive affective state, but that they also serve a communicative purpose. Actually, rats emit the highest rates of 50-kHz calls typically during social interactions, like reproductive behavior, juvenile play and tickling. Furthermore, it was recently shown that rats emit 50-kHz calls after separation from conspecifics. The aim of the present study was to test the communicative value of such 50-kHz calls. In a first experiment, conducted in juvenile rats situated singly on a radial maze apparatus, we showed that 50-kHz calls can induce behavioral activation and approach responses, which were selective to 50-kHz signals, since presentation of 22-kHz calls, considered to be aversive or threat signals, led to behavioral inhibition. In two other experiments, we used either natural 50-kHz calls, which had been previously recorded from other rats, or artificial sine wave stimuli, which were identical to these calls with respect to peak frequency, call length and temporal appearance. These signals were presented to either juvenile (Exp. 2) or adult (Exp. 3) male rats. Our data clearly show that 50-kHz signals can induce approach behavior, an effect, which was more pronounced in juvenile rats and which was not selective to natural calls, especially in adult rats. The recipient rats also emitted some 50-kHz calls in response to call presentation, but this effect was observed only in adult subjects. Together, our data show that 50-kHz calls can serve communicative purposes, namely as a social signal, which increases the likelihood of approach in the recipient conspecific.     

Degree of social contact affects the emission of food calls in the common marmoset (Callithrix jacchus)

The aim of this study was to investigate whether the emission of food calls in common marmosets (Callithrix jacchus) is influenced by different social contexts. Food calls are emitted by this species only in the presence of preferred food. If these calls have any communicative function, it may be that individuals produce food calls in order to call family mates toward the food source. If this is the case, the number of calls produced should vary in accordance with the number of family mates present at the moment of the discovery of the food, i.e., the fewer family mates nearby, the more food calls are emitted. This hypothesis was tested with five pairs of common marmosets, by recording the number of food calls emitted in four experimental conditions: 1). isolation: completely isolated from the family mates; 2). visual isolation: separated by a wooden panel from the family mates; 3). visual contact: separated by a wire-mesh from the family mates; and 4). physical interaction: together with the family mates. The results show that the proportion of intervals during which food calls were produced by the pairs was significantly different in the four experimental conditions. It decreased from the isolation and visual isolation condition, through the visual contact condition, reaching the lowest value in the physical interaction condition. The variation observed in the proportion of intervals during which food calls were emitted, in relation to different social contexts, is an indication in favor of the communicative function of this vocalization.     

Blue whales respond to anthropogenic noise

Anthropogenic noise may significantly impact exposed marine mammals. This work studied the vocalization response of endangered blue whales to anthropogenic noise sources in the mid-frequency range using passive acoustic monitoring in the Southern California Bight. Blue whales were less likely to produce calls when mid-frequency active sonar was present. This reduction was more pronounced when the sonar source was closer to the animal, at higher sound levels. The animals were equally likely to stop calling at any time of day, showing no diel pattern in their sensitivity to sonar. Conversely, the likelihood of whales emitting calls increased when ship sounds were nearby. Whales did not show a differential response to ship noise as a function of the time of the day either. These results demonstrate that anthropogenic noise, even at frequencies well above the blue whales' sound production range, has a strong probability of eliciting changes in vocal behavior. The long-term implications of disruption in call production to blue whale foraging and other behaviors are currently not well understood.     

Environmental correlates of vocal communication of wild pygmy marmosets, Cebuella pygmaea

We quantified the acoustic characteristics of the habitats of two wild populations of pygmy marmosets, in Amazonian Ecuador to evaluate their effects on vocal signal structure. We obtained measures of ambient noise, sound attenuation and reverberation through recordings and broadcasts of exemplars of two short-range vocalizations and one long-range vocalization of the marmosets. Ambient noise levels differed among habitats. The calls of pygmy marmosets had frequencies that coincided with relatively quiet regions of the ambient noise spectra of the habitats. The three vocalization types were degraded similarly in all habitats. The two short-range signals, with a pulsatile structure, were more affected by reverberation than was the long-range, less pulsatile vocalization. This degradation could be used by the marmosets to estimate the distance of the caller animals. We obtained data on context of vocalizations from six groups of pygmy marmosets, three from each population, in both the dry and rainy seasons. The use of Trills, J calls and Long calls was related to the distance between the calling animal and the potential receivers suggesting that marmosets are using the calls in a way appropriate to the effects of habitat acoustics. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Efficiency and Significance of Multiple Vocal Signals in Sibling Competition

Animals can compete for resources by displaying various acoustic signals that may differentially affect the outcome of competition. We propose the hypothesis that the most efficient signal to deter opponents should be the one that most honestly reveals motivation to compete. We tested this hypothesis in the barn owl (Tyto alba) in which nestlings produce more calls of longer duration than siblings to compete for priority access to the indivisible prey item their parents will deliver next. Because nestlings increase call rate to a larger extent than call duration when they become hungrier, call rate would signal more accurately hunger level. This leads us to propose three predictions. First, a high number of calls should be more efficient in deterring siblings to compete than long calls. Second, the rate at which an individual calls should be more sensitive to variation in the intensity of the sibling vocal competition than the duration of its calls. Third, call rate should influence competitors’ vocalization for a longer period of time than call duration. To test these three predictions we performed playback experiments by broadcasting to singleton nestlings calls of varying durations and at different rates. According to the first prediction, singleton nestlings became less vocal to a larger extent when we broadcasted more calls compared to longer calls. In line with the second prediction, nestlings reduced vocalization rate to a larger extent than call duration when we broadcasted more or longer calls. Finally, call rate had a longer influence on opponent’s vocal behavior than call duration. Young animals thus actively and differentially use multiple signaling components to compete with their siblings over parental resources.     

Vocal-tract filtering by lingual articulation in a parrot

Human speech and bird vocalization are complex communicative behaviors with notable similarities in development and underlying mechanisms. However, there is an important difference between humans and birds in the way vocal complexity is generally produced. Human speech originates from independent modulatory actions of a sound source, e.g., the vibrating vocal folds, and an acoustic filter, formed by the resonances of the vocal tract (formants). Modulation in bird vocalization, in contrast, is thought to originate predominantly from the sound source, whereas the role of the resonance filter is only subsidiary in emphasizing the complex time-frequency patterns of the source (e.g., but see ). However, it has been suggested that, analogous to human speech production, tongue movements observed in parrot vocalizations modulate formant characteristics independently from the vocal source. As yet, direct evidence of such a causal relationship is lacking. In five Monk parakeets, Myiopsitta monachus, we replaced the vocal source, the syrinx, with a small speaker that generated a broad-band sound, and we measured the effects of tongue placement on the sound emitted from the beak. The results show that tongue movements cause significant frequency changes in two formants and cause amplitude changes in all four formants present between 0.5 and 10 kHz. We suggest that lingual articulation may thus in part explain the well-known ability of parrots to mimic human speech, and, even more intriguingly, may also underlie a speech-like formant system in natural parrot vocalizations.     

Decisions during Phonotaxis in the Bushcricket Requena verticalis (Orthoptera: Tettigoniidae): Do Females Change Direction to Alternative Male Calls?

Female bushcrickets (Requena verticalis, Listroscelidinae, Tettigoniidae) show a preference between male calls that differ in three parameters, temporal structure, frequency and intensity. In a two-choice speaker situation they prefer louder calls, songs in which the upper part of the frequency spectrum occupies higher frequencies and calls with short chirps rather than those with longer chirps. In an experiment females were offered an alternative call while orienting to a model of their conspecific song. The alternative call was demonstrably preferred by females when presented in a paired-speaker trial. Two motivational states were identified where females moved slowly or quickly to a sound source. Movement patterns were associated with the form of stimulus and slow females were discriminatory of male calls while fast females were not. Slow females changed speaker preference when the alternate speaker broadcast a call model with the higher frequency peak or the song model with the shorter chirps. By comparison fast moving females only changed course when the alternative sound source was louder.     

The Function of Click Call Emission in Capybaras (Hydrochoerus hydrochaeris)

Contact calls are used to promote cohesion among individuals that live in social groups. Capybaras are very gregarious and often vocalize. This species emits a vocalization known as a click, which has been observed during aggregating and foraging behaviors, suggesting contact or monitoring call function. We carried out a playback experiment to evaluate behavioral responses to the capybara's click call and to a bird call, used as control in ten capybaras. We compared animals' latency to respond to stimuli, the time spent in behavioral patterns, alertness, head orientation toward the sound source, and approach to the sound source. All capybaras responded to the emission of the click call playback. Most of them assumed an alert position, showed head orientation toward the sound source, and approached the sound source. They promptly reacted to the first click call emission, while few reacted to the first bird call emission, used as control. All subjects showed behavioral changes after the second emission of the click call, and some responded to the third emission. Just three individuals answered after the first control emission, while none of them responded to the second and third emission of the playback. Therefore, click call playback promotes prompt behavioral changes in capybaras, including approach to the sound source. These results indicate that this vocalization functions as a contact or monitoring call in the species.     

VOCALIZATION OF TWO PALAEARCTIC SPECIES OF HAMSTER: EVERSMANN HAMSTER ALLOCRICETULUS EVERSMANNI AND GREY HAMSTER CRICETULUS MIGRATORIOS

ABSTRACT

This study compared the vocalization of two sympatrically occurring species of hamster: the Eversmann hamster Allocricetulus eversmann and the Grey hamster Cricetulus migratorius. The animals were tested in conspecific pairs for 5 min. Because of the high level of aggressiveness of both species, the hamsters were separated by a mesh partition, but they had olfactory, visual and acoustic contact. Female and male Eversmann hamsters vocalized more than those of Grey hamsters. This was expressed by emission of low-frequency calls as well as by ultrasounds. The difference in vocalization between the two species was also reflected in the basic structure of ultrasonic vocalizations. Grey hamster high-frequency (ultrasonic) pulses were longer and had larger bandwidths and lower minimum frequencies than Eversmann hamster calls. Within-species comparison of vocalization indicated that males of both species emitted fewer ultrasounds than females did. These differences could have an important role in communication within and between species living in the same area and preferring the same habitats.     

Sound production by the river bullhead, Cottus gobio L. (Cottidae, Teleostei)

Acoustic signals of Cottus gobio consist of knocking sounds produced as single pulses (48 ms) or as trains of 4–6 pulses (230 ms). Frequencies extend up to 3 kHz, but most sound energy is concentrated between 50 and 500 Hz in both sound types. Cottus gobio is solitary, maintains territories, and defends them by threat display, seldom by biting and fighting. Threatening consists of spreading gill covers and fins, darkening, and sound production. Calling is accompanied by a nodding movement of the head, during which the pectoral girdle and the skull are moved rapidly against each other. No difference in ability of sound production was observed between sexes, but males emitted significantly more sounds than females. In the laboratory an increase in vocalization activity was observed between night and day. An increase in the number of encounters and calls was noted when temperatures were raised from 8°C to 13°C. Sound production was registered throughout the year.     

Usage of monophonic and biphonic calls by free-ranging resident killer whales (Orcinus orca) in Kamchatka, Russian Far East

Killer whale discrete calls include types containing an overlapping high-frequency component (biphonic calls) and types without an overlapping high-frequency component (monophonic calls). In the resident killer whales of the Northeast Pacific, biphonic discrete calls exhibit higher source levels than monophonic calls, which suggests different active space and consequently different functions for monophonic and biphonic call types. In this study we investigate the potential communicative functions of monophonic and biphonic discrete calls produced by killer whales from Kamchatka (Northwest Pacific). We analyze how the usage of these calls depends on the number of pods present in the area and type of activity. Our results show that the usage of monophonic and biphonic calls in Kamchatkan killer whales depends on the number of pods in the area and is less dependent on the type of activity. Biphonic calls are more common when more than one pod is present in the area and could therefore function as markers of pod and matriline affiliation, serving mainly as cohesion signals. Monophonic calls dominated the vocalizations when a single pod was present, while in the presence of more than one pod both categories were used in equal proportions.     

The Energetics of Acoustic Signaling in Anurans and Insects

SYNOPSIS. This review focuses on the energetics of advertisementcalls in frogs and insects (mostly ensiferans). I also reviewa number of methodological questions relating to the most appropriateways to normalize metabolic rates for calling animals and tocalculate efficiency of sound production Although the mechanism of sound production is very differentin these groups (vocalization vs. stridulation), net metaboliccosts normalized to mass are similar among species producingthe most conspicuous calls. Features of the call that interactto determine energetic cost include repetition rate, call duration,and intensity (sound pressure level). Anurans tend to producelouder (more intense) calls while ensiferans tend to producesound during a greater proportion of the calling bout. All evidencesuggests that advertisement calls are produced aerobically andthe aerobic costs are similar or exceed the aerobic (but notnecessarily total costs) of terrestrial locomotion The pattern of radiated sound tends to be constant within aspecies and can be predicted to some degree from characteristicsof an animal's acoustic radiator. Efficiency of sound production(acoustic power/net metabolic power) is low (0.05 to 6%) andvariable when compared to locomotion ({small tilde} 10–20%).From the present sample it appears that frogs are more efficientthan ensiferans, but as more katydids are studied this trendmay not hold. Of the factors that have been identified as determiningefficiency the most important are the match between the sizeof the radiator and wavelength radiated, the absorption propertiesof the environment immediately around the animal, and the presenceor absence of structures such as baffles and acoustic burrows     

Sound amplification by means of a horn-like roosting structure in Spix's disc-winged bat

While sound is a signal modality widely used by many animals, it is very susceptible to attenuation, hampering effective long-distance communication. A strategy to minimize sound attenuation that has been historically used by humans is to use acoustic horns; to date, no other animal is known to use a similar structure to increase sound intensity. Here, we describe how the use of a roosting structure that resembles an acoustic horn (the tapered tubes that form when new leaves of plants such as Heliconia or Calathea species start to unfurl) increases sound amplification of the incoming and outgoing social calls used by Spix''s disc-winged bat (Thyroptera tricolor) to locate roosts and group members. Our results indicate that incoming calls are significantly amplified as a result of sound waves being increasingly compressed as they move into the narrow end of the leaf. Outgoing calls were faintly amplified, probably as a result of increased sound directionality. Both types of call, however, experienced significant sound distortion, which might explain the patterns of signal recognition previously observed in behavioural experiments. Our study provides the first evidence of the potential role that a roost can play in facilitating acoustic communication in bats.     

Variations in underwater vocalizations of Weddell seals (Leptonychotes weddelli) at the Vestfold Hills as a measure of breeding population discreteness

Weddell seal vocalizations from Davis Station showed similarities to those from McMurdo Sound and Palmer Peninsula, but none were identical. One vocalization, DD1, was unique to Davis Station. At all sites trills, or territorial defense calls, were the most common and had more types than other calls. Chugs, an aggressive sound, were common at all sites. Weddell seal calls from Davis Station showed similarities to sounds from McMurdo by sharing the use of prefixes and suffixes. Sounds from Davis Station shared the use of both ascending and descending trills and whistles with calls from Palmer Peninsula.Commonalities in underwater vocalizations may indicate the degree of mixing between breeding populations, in which case, Weddell seals in the Davis area probably are from a breeding population distinct from those at either McMurdo Sound or Palmer Peninsula.     

Parental alarm calls suppress nestling vocalization

Evolutionary models suggest that the cost of a signal can ensure its honesty. Empirical studies of nestling begging imply that predator attraction can impose such a cost. However, parents might reduce or abolish this cost by warning young of the presence of danger. We tested, in a controlled field playback experiment, whether alarm calls cause 5-, 8- and 11-day-old nestlings of the white-browed scrubwren, Sericornis frontalis, to suppress vocalization. In this species, nestlings vocalize when parents visit the nest ('begging') and when they are absent ('non-begging'), so we measured effects on both types of vocalization. Playback of parental alarm calls suppressed non-begging vocalization almost completely but only slightly reduced begging calls during a playback of parental feeding calls that followed. The reaction of nestlings was largely independent of age. Our results suggest two reasons why experiments ignoring the role of parents probably overestimate the real cost of nestling vocalizations. Parents can warn young from a distance about the presence of danger and so suppress non-begging vocalizations that might otherwise be overheard, and a parent's presence at the nest presumably indicates when it is safe to beg.     

Long‐term monitoring of captive red drum Sciaenops ocellatus reveals that calling incidence and structure correlate with egg deposition

In the present study, quantitative data were collected to clarify the relationship between calling, call structure and eggs produced in a captive population of red drum Sciaenops ocellatus. Sciaenops ocellatus were held in four tanks equipped with long‐term acoustic loggers to record underwater sound throughout a simulated reproductive season. Maximal sound production of captive S. ocellatus occurred when the photoperiod shifted from 13·0 to 12·5 h of light, and the water temperature decreased to c. 25° C. These captive settings are similar to the amount of daylight and water temperatures observed during the autumn, which is the primary spawning period for S. ocellatus. Sciaenops ocellatus exhibited daily patterns of calling with peak sound production occurring in the evenings between 0·50 h before dark and 1·08 h after dark. Spawning occurred only on evenings in which S. ocellatus were calling, and spawning was more productive when S. ocellatus produced more calls with longer durations and more pulses. This study provides ample evidence that sound production equates to spawning in captive S. ocellatus when calls are longer than 0·8 s and contain more than seven pulses. The fact that more calling, longer calls and higher sound pressure levels are associated with spawns that are more productive indicates that acoustic metrics can provide quantitative information on spawning in the wild.     

What makes wild chimpanzees wake up at night?

I examined the possible cause of night awakening among wild chimpanzees (Pan troglodytes) in Mahale Mountains National Park, Tanzania. Chimpanzee vocalizations and activity-related sounds (CVSs) were used to indicate awakening because I was unable to visually observe them. Over a 5-night observation period, CVSs (n = 128) were heard every night, and most (n = 91) were observed within 5 min of previous CVSs. Chimpanzees use CVSs as social communication to maintain spatial contact with other chimpanzees who occasionally travel at night. The first sound in a sequence of CVSs (CVS bout) was heard immediately following the vocalization or sound of another animal (n = 11), defecation or urination by a chimpanzee (n = 7), or unknown (n = 19). CVS bouts were longer when preceded by defecation or urination than when preceded by the vocalization or sound of other animals or an unknown factor. This suggests that the degree of wakefulness varies according to the possible cause of the disturbance. CVSs at night may be provoked by various factors, and awakening during the night is probably common among diurnal primates.     

Search behaviour and mate choice by female field crickets, Gryllus integer

The search tactics that females might employ to find a suitable mate impose different cognitive demands on searchers and some theoretical models of search behaviour presuppose that females are able to recall encountered males and return to mate with a previously sampled individual. In this study, I exposed female field crickets, Gryllus integer, to male calls either sequentially or simultaneously from two speakers in a three-arm radial maze. Subjects that were exposed to the two calls in sequence and allowed to move to the location of each call returned, in the absence of any audible signal, to the location of the call initially encountered. Subjects allowed to walk to the location of only one of two simultaneously active speakers before playback of both calls was terminated were as likely to move, in the absence of any audible signal, to the never-active speaker as to the location of the other male call. These subjects were also more likely to search all three arms of the maze and searched for a longer time than females exposed to calls sequentially. Thus, female G. integer probably do not construct a spatial representation of the locations of potential mates from the calls of males that advertise concurrently. The results of this study suggest, however, that female G. integer are able to recall previously encountered males under some conditions and may potentially employ a search tactic that is more complicated than a simple instantaneous comparison of the qualities of males that are actively calling. Copyright 1999 The Association for the Study of Animal Behaviour.     

Echolocation calls and communication calls are controlled differentially in the brainstem of the bat Phyllostomus discolor

Background  

Echolocating bats emit vocalizations that can be classified either as echolocation calls or communication calls. Neural control of both types of calls must govern the same pool of motoneurons responsible for vocalizations. Electrical microstimulation in the periaqueductal gray matter (PAG) elicits both communication and echolocation calls, whereas stimulation of the paralemniscal area (PLA) induces only echolocation calls. In both the PAG and the PLA, the current thresholds for triggering natural vocalizations do not habituate to stimuli and remain low even for long stimulation periods, indicating that these structures have relative direct access to the final common pathway for vocalization. This study intended to clarify whether echolocation calls and communication calls are controlled differentially below the level of the PAG via separate vocal pathways before converging on the motoneurons used in vocalization.     

Antipredator Responses to a Previously Neutral Sound by Free-living Adult Golden-mantled Ground Squirrels, Spermophilus lateralis (Sciuridae)

I investigated whether free-living adult golden-mantled ground squirrels ( Spermophilus lateralis ) could learn to associate a novel sound with the appearance of a predator. Using a classical conditioning protocol, I presented adult squirrels with a novel tone followed by the appearance of a model hawk. After repeated trials, I again measured the squirrels' behavioral responses to the tone and compared them with their pretraining responses. Individuals that experienced the tone paired with the hawk responded with antipredator behavior of longer duration after pairing than before and these responses were indistinguishable from responses to natural, conspecific alarm calls. By examining the process, rather than simply the pattern, of call recognition ontogeny, this study provides new evidence for a mechanism by which animals can develop the ability to respond to both conspecific and heterospecific calls.