Vocalization Rate Research Articles

The effects of 8-OH-DPAT and (�)-pindolol on isolation-induced ultrasonic vocalizations in 3-, 10-, and 14-day-old rats

It has been established that administration of 5-HT1A agonists attenuates the rate of isolation-induced ultrasonic vocalizations (USV) in 10-day-old rat pups. In this study we extended these findings by examining the effects of administration of the serotonergic 1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), and mixed 5-HT1A antagonist/beta adrenergic antagonist, (+/-)-pindolol, in 3-, 10-, and 14-day-old rat pups in order to assess the effect of these drugs from a developmental perspective. At all three ages, 8-OH-DPAT significantly reduced the rate of isolation-induced USV. While only the highest dose (1.0 mg/kg) of 8-OH-DPAT administered to the 10- and 14-day-olds significantly reduced the rate of vocalization, both the 0.1- and 1.0-mg/kg doses significantly attenuated the vocalization rate in the 3-day-olds. Pindolol administration did not alter the rate of USV at any age nor did it block the quieting effect that generally occurs when an anesthetized littermate is placed with the isolated pup. We conclude that 8-OH-DPAT is effective as early as 3 days of age in the quieting of isolation-induced USV and that the regional age-dependent development of 5-HT1A receptors and projections are important factors in the observed differential sensitivity to 8-OH-DPAT administration during development.

The impact of otitis media with effusion on early phonetic inventories: a longitudinal prospective investigation

This prospective investigation examined the effects of otitis media with effusion (OME) on early speech production. Two groups of infants, the otitis media positive (OME+; n=8), and the otitis media negative (OME-; n=8) were defined according to otitis media (OM) history during the first year of life. OM documentation was based on results from tympanometry, pneumatic otoscopy, and behavioural audiometry collected bimonthly beginning at age 2 months. Phonetic transcriptions were completed from infants' recorded babbling samples at 10, 12 and 14 months of age. No differences were found between the two groups on rate of vocalizations (i.e. consonants produced per minute). Differences between the two groups were seen in place and manner of articulation. OME infants produced more bilabial stops than OME- infants who, in turn, produced more alveolar stops and nasals than did their OME+ counterparts. Furthermore, within the OME+ group, children with poorer hearing thresholds showed preference for bilabial stops, whereas children with better hearing thresholds showed more diversity in their phonetic inventories.

The ontogeny of maternal potentiation of the infant rats' isolation call.

Previous studies have shown that preweanling rat pups double or triple their rates of ultrasonic vocalization (USV) when isolated immediately after brief periods of maternal interaction (potentiation). We studied the ontogenetic pattern of USV and other behavioral responses of pups to 3-min periods of isolation in a novel test chamber, from 5 to 25 days postnatal age, before, during, and after 1 min or 5 min of interaction with an anesthetized or an active dam. USV potentiation did not develop until 7-9 days postnatal, a week after the initial isolation and maternal contact quieting responses were well established. Potentiation reached a peak at 13 days, and then declined until all USV responses ceased after 21 days. Other behavioral responses to isolation were not enhanced by maternal interaction at any age. The distinct ontogenetic pattern of this unusual response to maternal separation has implications for understanding its mode of development and possible adaptive value.

The Influence of Olfaction on Potentiation and Inhibition of Ultrasonic Vocalization of Rat Pups

Twelve-day-old isolated rat pups reduce their rates of ultrasonic vocalization (USV) when an anesthetized adult is placed into the test cage, whether the adult is their dam or an unfamiliar male. USV rates remain very low even after removal of the male (inhibition). However, after removal of the dam, pups greatly increase their rates of USV over their first isolation period (potentiation). USV potentiation can be induced by either an awake, normally behaving dam or by one that is anesthetized. To test the role of olfaction in inhibition and potentiation, PND12 pups were rendered anosmic via intranasal infusion of 5% zinc sulphate (ZnSO 4). Control pups were infused with normal saline. After overnight separation from the dam, the USV and other behaviors of pups were recorded during a 6-min test. Each pup was tested during an initial isolation period and a final isolation period. In the first experiment, an anesthetized adult (dam or unfamiliar male) or no companion was placed in contact with the pup during the middle minute. Anosmia prevented both potentiation and inhibition of USV by passive adult contact. Thus, it seems likely that pups use olfactory discrimination as the basis for these two highly differentiated vocal responses to social stimuli. Results from two additional experiments demonstrate that anosmia does not prevent potentiation when the adult dam is active and interacting with the pup on either postnatal day 12 or 8.

Singing and mating success in water pipits: one specific song element makes all the difference

Positive correlations between male vocalization and reproductive success have been documented for many animal species. They are usually based on differences between males in vocalization rate, duration or repertoire size. Here, we present probably the first field study linking differences in territorial overlap and mating status to differences in a single, clearly definable song element, the ‘Snarr’. Male water pipits,Anthus spinoletta, with high Snarr scores were mated more often than males with low scores, and their territories overlapped less with those of neighbours. Although correlating positively with male body condition, the frequency of the Snarr did not reflect male age, territory size, territory quality in terms of food and paternal performance. Therefore, it seems unlikely that the higher mating success of males with high Snarr scores results from active female choice of high-quality males; rather, high Snarr scores seem to signal dominance in males. Likely mechanisms that produce the link between vocalization and mating success, and potential costs that prevent some males from producing the Snarr at a higher rate, are discussed.

Visual scanning by common marmosets (Callithrix jacchus): Functional aspects and the specialrrole of adult males

The rates of visual scanning and vocalizations were studied in a group of captive marmosets (Callinthrix jacchus) after the presentation of five different stimuli (artificial flower, playback of long calls, female/male conspecific, stuffed wild cat) in order to assess the function of visual scanning. Only the presentation of a stuffed cat induced a significant response. The adult males in particular increased their scanning rate and all adult individuals decreased their rate of vocalizations. The results indicate that visual scanning in marmosets is an appropriate measure of vigilance which seems to serve the function of predator detection and avoidance. The strong response of adult males suggests that they play a special role in predator detection.

Laterally asymmetrical cell number in a sexually dimorphic nucleus in the gerbil hypothalamus is correlated with vocal emission rates.

A lateralized relationship between the total volume of a discrete area in a hypothalamic, sexually differentiated nucleus (SDApc) and stereotyped vocalization exists in male Mongolian gerbils. In this present study, using unbiased stereological methods, two cytoarchitectural estimates of the SDApc's structure, neuron number, and nuclear volume were found to be sexually differentiated and also laterally asymmetrical in adult males. In ovariectomized females receiving exogenous testosterone, no cytoarchitectural component was asymmetrical. Significantly, the estimate of neuron number, but not nuclear volume, in the left SDApc of males was correlated with vocal emission rate. The authors conclude that a specific, sex-related cytoarchitectural SDApc parameter shows left-right asymmetry, suggesting the SDApc has an intimate role in mediating hemispheric specialization rather than just being an end point index of individual structural variability.

Laterally asymmetrical cell number in a sexually dimorphic nucleus in the gerbil hypothalamus is correlated with vocal emission rates.

Laterally asymmetrical cell number in a sexually dimorphic nucleus in the gerbil hypothalamus is correlated with vocal emission rates.

Vocalizations and other behavioral responses of male cheetahs (Acinonyx jubatus) during experimental separation and reunion trials

In this study we assessed the extent of psychological attachment between male cheetahs living in same sex pairs in zoos by recording the behavior and vocalizations of two male coalitions (siblings and nonsiblings) during four experimental separations and reunions of each coalition. Both coalitions showed higher vocalization rates and walking rates during separations than during reunions, and during separations cheetahs spent less time resting and more time vocalizing, walking, or standing than during baseline observations. Compared to the nonsibling coalition, the sibling coalition showed a significantly higher vocalization rate during separations and more affiliative behavior during reunions. The most common calls emitted during separations were chirps, followed by eeaows and stutters. The chirps showed the highest level of individual distinctiveness. Eeaows comprised a significantly higher percentage of the calls during separations for nonsiblings that for siblings. The only vocalization heard during reunion was the stutter. We hypothesize that chirps emitted during separations communicate desire to reunite, individual identity, and have a structure that facilitates locating the caller. The results of this study suggest that male cheetahs, both sibling and nonsibling, develop strong psychological attachments to each other. The separation of existing coalitions can create stressful conditions for coalition members. We suggest that raising and maintaining coalitions of male cheetahs in coalitions in zoos is a viable husbandry technique. Zoo Biol 17:1–16, 1998. © 1998 Wiley-Liss, Inc.

Vocalizations and other behavioral responses of male cheetahs (Acinonyx jubatus) during experimental separation and reunion trials

In this study we assessed the extent of psychological attachment between male cheetahs living in same sex pairs in zoos by recording the behavior and vocalizations of two male coalitions (siblings and nonsiblings) during four experimental separations and reunions of each coalition. Both coalitions showed higher vocalization rates and walking rates during separations than during reunions, and during separations cheetahs spent less time resting and more time vocalizing, walking, or standing than during baseline observations. Compared to the nonsibling coalition, the sibling coalition showed a significantly higher vocalization rate during separations and more affiliative behavior during reunions. The most common calls emitted during separations were chirps, followed by eeaows and stutters. The chirps showed the highest level of individual distinctiveness. Eeaows comprised a significantly higher percentage of the calls during separations for nonsiblings that for siblings. The only vocalization heard during reunion was the stutter. We hypothesize that chirps emitted during separations communicate desire to reunite, individual identity, and have a structure that facilitates locating the caller. The results of this study suggest that male cheetahs, both sibling and nonsibling, develop strong psychological attachments to each other. The separation of existing coalitions can create stressful conditions for coalition members. We suggest that raising and maintaining coalitions of male cheetahs in coalitions in zoos is a viable husbandry technique. Zoo Biol 17:1–16, 1998. © 1998 Wiley-Liss, Inc.

Five generations of selective breeding for ultrasonic vocalization (USV) responses in N:NIH strain rats.

This article reports on early results from an ongoing selective breeding study in which rats were selected for different rates of ultrasonic vocalization (USV) in response to isolation. Using the N:NIH strain, all litters were screened at 10 (+/- 1) days of age in a 2-min isolation test, and those males and females with the highest (or lowest) rates in each litter were selected for later breeding with like breeders from unrelated litters. A Random line (unselected control) was also bred. In the first selected generation (S1), the Low line diverged from Random line controls, and has maintained significantly lower rates over all generations since. In the S3 generation, the High line diverged significantly from Random line controls, and has shown significantly higher USV rates in each succeeding generation. No line differences were found in other behaviors measured in isolation. Data from a small sample of S5 pups tested at postnatal Days 3, 10, 14, and 18 days showed that individual pups' rates of USV from Day 10 predicted those at Day 14, consistent with findings from an unselected generation. Ambient temperature, modulated by body weight, controlled USV at Day 3, whereas at Days 10 and 14 line accounted for most of the variance in USV. This is the first instance of laboratory selection occurring on the basis of an infantile trait.

Evidence for opioid and nonopioid processes mediating adaptive responses of infant rats that are repeatedly isolated.

Previous research examining the ability of neonatal rats to adapt to repeated isolation demonstrated that an opioid-dependent decline in ultrasonic vocalizations occurred across a series of isolations (Goodwin, Molina, & Spear, 1994). These findings were expanded in the present study. In the first experiment, the decline in vocalization rates was found to result from the release of endogenous opioids throughout the series of isolations. Although naltrexone attenuated the decline in calling rates relative to vehicle-treated subjects, there was still a significant decline in calling rates following opioid receptor blockade. In the second experiment, two injections of naltrexone did not attenuate the decline in calling rates any more than a single injection did, suggesting that there must also be some nonopioid process that modulates this decline. In both experiments, activity levels and, in the first experiment, the amount of body heat lost in the repeatedly isolated subjects declined in a nonnaltrexone reversible manner. In a final study, after calling rates had been suppressed by a series of isolations, a brief exposure to the mother was found to restore baseline calling rates, suggesting the decline is not the consequence of fatigue. The attenuation of vocalization rates, activity, and loss of body heat are adaptive responses of infant rats to isolation; however, of these three, only the attenuation of vocalization rates is consistently modulated by the release of endogenous opioids.

Female dunnocks use vocalizations to compete for males

In songbirds, males are usually the more competitive sex and they use vocalizations to attract females and to compete with rival males. When levels of female–female competition were experimentally increased in a population of dunnocks,Prunella modularis, females were predicted to increase their vocalization rates and to use vocalizations in comparable ways to competing males. Females produced tseep calls in territorial conflicts with rival females, and trill calls during the pre-breeding and fertile periods when they were left alone by their mate. Males were more likely to approach trills than tseeps, and females were more likely to trill than tseep in response to the song of their mate. Removal experiments to increase polygyny showed that females produced both types of call more when they were competing for male attention. Three out of 13 polygynous, fertile females also produced complex songs when their mate left to join another female. Songs were produced in the same context as the songs of female alpine accentors,P. collaris, a congener which breeds in large, polygynandrous groups where female competition for mates is intense, and females attract males with song. The possible functions of the mate-attracting trills and songs of females are discussed; in dunnocks they may (1) attract mates away from other females to reduce the likelihood of polygyny, (2) ensure that the male copulates sufficiently to cross a helping threshold, and (3) enable the female to assess future levels of parental care from her mate.

Potentiation and inhibition of ultrasonic vocalization of rat pups: regulation by social cues.

Eight- and 11- to 12-day-old rat pups were tested in isolation and in the presence of an anesthetized adult under cold conditions. Pups of both ages reduced rates of ultrasonic vocalization (USV) when an adult was placed into the test cage, independent of whether the adult was their dam or an unrelated male. However, after removal of the dam, pups greatly increased their rates of USV over their first isolation period and in comparison with control pups. USV rates remained low after removal of the male. The temperature challenges faced by the pups in the two experimental conditions were the same. These phenomena are better explained by a hypothesis that postulates USV rate as being multiply determined, including by social cues, rather than a theory that considers thermal challenge only.

Male detention affects extra-pair copulation frequency and pair behaviour in western bluebirds

Male western bluebirds,Sialia mexicanashow patterns of mate following consistent with mate guarding. The hypothesis that males prevent extra-pair copulations by guarding their mates was tested using 1-h male detention experiments. Males were caged on territory in view of the female, visually occluded on territory or removed from the territory altogether (visually+vocally occluded). Extra-pair males were more likely to join females within 15m and attempt to copulate with them in the three detention treatments than in treatments where males were captured and released or not manipulated at all. Detention also increased the number of females accepting one or more extra-pair copulations. The increased frequency of extra-pair copulations was not caused by movement of females away from their nests, nor by increased rates of vocalization by resident males or females. Extra-pair events occurred shortly after the resident male was caught, suggesting that extra-pair copulations can occur during brief lapses in mate following. Intruding males were usually neighbours with mates and nests of their own. Half intruded when their own mates were at peak receptivity, suggesting that males leave their own fertile mates to seek extra-pair copulations. Detained males did not compensate for detention by increasing the frequency with which they copulated with their mates after they were returned to the territory. Acceptance of extra-pair copulations by females did not increase with the number of extra-pair copulation attempts and females were no more likely to participate in extra-pair copulations when resident males were visually occluded than when they were visually present. Only half of the females that experienced extra-pair copulation attempts accepted one or more extra-pair copulations. Although male detention resulted in an increase in the frequency of extra-pair copulations in western bluebirds, females appeared to be selective about participating in extra-pair matings.

Androgenic Effects on Hypothalamic Asymmetry in a Sexually Differentiated Nucleus Related to Vocal Behavior in Mongolian Gerbils

The relationship between courtship ultrasound emission rates and the volume of a discrete, sex-related, hypothalamic nucleus, the sexually dimorphic area, pars compacta (SDApc), in male and neonatally androgenized female gerbils is lateralized. Unbiased stereological estimates of neuron number and nuclear and neuropil volume are also laterally asymmetric in male SDApcs. In this study sexual differentiation and lateral asymmetry of stereologically assessed cytoarchitectural SDApc components, and their relationship to male-typical behaviors, including vocal emission, were examined in masculinized females. Female neonates received a single injection of testosterone propionate (TP) or control vehicle (Control) and were then implanted with silastic cannulae of testosterone at 65 days of age. Total SDApc volume, neuron number, nuclear volume, and neuropil volume had significantly greater values in TP compared to Control females. Neuron number was laterally asymmetric in TP females, since the left SDApc contained a greater number of smaller neurons, possibly interneurons, than the right. Courtship vocal emission and two other behaviors were masculinized in TP females. Left SDApc total volume and, most significantly, left neuron number, were correlated with vocal rates. No other lateralized correlations between behaviors and stereological estimates were found. It was concluded that various stereological parameters and the lateralization of vocal behavior and brain asymmetry depend on the early sexually differentiating effects of androgens. It is suggested that in gerbils, androgens have a role in the survival of interneurons in a laterally asymmetric hypothalamic nucleus which is an index of vocal control.

Song behaviour and reproductive strategies in a duetting wren, Thryothorus nigricapillus: I. Removal experiments

Mate removal experiments were conducted to test the hypotheses that vocal duetting functions in pair bond maintenance and/or territory defence in the bay wren, Thryothorus nigricapillus, in the Republic of Panama. Males and females were observed while in established pairs, while alone after mate removal and following the arrival of a new mate. Duet repertoires and precision of duet performance were then compared in birds singing with old and new mates. Another experiment in which males were exchanged between two territories was similarly analysed. These experiments demonstrated that (1) individual repertoires and duet precision do not change following a change in mates, refuting the pair bond maintenance hypothesis, and (2) unpaired birds do not lose their territories, failing to support the hypothesis that duets are necessary for territory defence. Analysis of vocalization rates suggested that male and female songs serve different functions. Male vocal behaviour was sensitive to male mating status: when males were alone, their vocalization rates dramatically increased. However, males answered the songs of a new mate less frequently than they did those of their original mate. These results suggest that unpaired males sing to attract females and that males might use participation in duets to assess new mates. The function of duetting by males in established pairs remains unclear. Female song rates were unaffected by female mating status, suggesting that female songs may be directed to conspecific females. Results also indicated that territory residency may play a more important role in mate acquisition for males than it does for females.

Responses of chimpanzees to habituation and tourism in the Kibale Forest, Uganda

This study monitored the impact of habituation and tourism on a community of chimpanzees in the Kibale Forest, Uganda. From February 1992 to June 1993, chimpanzees' initial reactions to contacts with human observers were recorded together with other factors such as numbers of observers present and the method used to locate the chimpanzees. On 54 occasions with various numbers of observers (and/or tourists) present, activity rates were recorded for the observed individuals. Numbers of observers present (up to five) had no impact on the chimpanzees' initial reaction, and the only significant change in activity caused by higher numbers of observers (up to 15) was an increasing vocalisation rate. As visitor satisfaction declines with groups of more than six to eight people it is suggested that tourist groups viewing chimpanzees should be kept at a maximum number of 10 (including guides).

Identification, vocal rating, and acoustical measurement of acted emotion

A series of studies of eight acted emotions compared acoustical measurements, respondents’ identifications, and vocal ratings. Predictions were made as to which of these three approaches would be most accurate in differentiating between emotions within a pair. Emotion pairs were classified as logically similar and/or perceptibly similar. Logically similar emotion pairs (such as sadness/depression or anger/hate) were better distinguished by vocal/acoustic analysis. Perceptibly similar but logically dissimilar emotions (such as anger, fear, and joy) were better distinguished by respondents’ identifications. Multivariate statistics were used to compare the respondents’ identification space, and vocal rating space, and the acoustical measurement space.

Castration affects the emission of an ultrasonic vocalization in a nocturnal primate, the grey mouse lemur ( Microcebus murinus)

Male primates have evolved particular displays to advertise male fitness. In nocturnal prosimians it was assumed that such displays (vocal advertisement, marking behaviour) are hormonally dependent and influenced by olfactory cues of a receptive female. To test this assumption mouse lemur males of different gonadal status (males castrated as adults, normal males), or of varying olfactory input (males vomeronasalectomized or bulbectomized as adults) were paired with intact “stimulus” preoestrous females and vocalization, vocal rates, and marking behaviours were monitored. The vocal rate of only one particular vocalization, the “trill” advertisement call, was sexually dimorphic and changed depending on gonadal status. Vocalization rate declined significantly in sexually experienced, castrated males, as did their marking behaviour. There was, however, no significant correlation between either calling rate or marking behaviour and plasma testosterone levels in gonadally intact males. Neither vomeronasalectomy nor bulbectomy had a significant effect on trill calling rate or marking behaviour. Results imply that testicular hormones have a greater impact on advertisement calling and marking motivation than olfactory information of preoestrous females. In contrast to rodents, ultrasonic calling rate seems to be not only dependent on gonadal status, but also on social experience.