BEHAVIORAL SIGNIFICANCE OF UNDERWATER VOCALIZATIONS OF CAPTIVE LEOPARD SEALS, HYDURGA LEPTONYX

Two groups of underwater vocalizations were identified in a three-year study of two captive leopard seals, Hydurga leptonyx (one female and one male at Taronga Zoo, Sydney). This was supplemented by recordings over three months from a male at Marineland, New Zealand. The sexual state of the seals at Taronga was deduced from serum hormonal concentrations: the female was considered to be in estrus at specific times during the breeding season. The seal at Marineland, New Zealand was assumed to be sexually mature on the basis of size and age. Of 12 different underwater sound types recorded, six were produced by the seals at Taronga Zoo during agonistic interactions (local calls) and were heard through most of the year. The other six sound types were produced by lone seals. These broadcast calls were produced by the female only when sexually receptive, and by the mature male during December and January, months believed to be the breeding season of wild leopard seals. We propose that underwater acoustic behavior is important in the mating system of this species, and that broadcast calls are used by mature females to advertise their sexual receptivity, and possibly by mature males in search of mates.     

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.     

Vocalizations of bearded seals (Erignathus barbatus) and their influence on the soundscape of the western Canadian Arctic

The soundscape is a crucial habitat feature for marine mammals. This study investigates the contribution of bearded seal vocalizations to the soundscape in the western Canadian Arctic, and also the vocal characteristics of bearded seals relative to sea ice conditions. Passive acoustic data were recorded near Sachs Harbour between August 2015 and July 2016. Sound pressure levels (SPL) in the 50–1,000 Hz and 1–10 kHz bands increased as the total duration of all bearded seal vocalizations increased, and this relationship was moderated by sea ice concentration. Bearded seals in this region had an overlapping vocal repertoire with bearded seals in other areas of the Arctic, and had seven additional vocalizations that have not been previously documented for this region. This study is the first detailed assessment of the influence of bearded seal calls on SPL, which shows the high potential of bearded seals to influence underwater sound levels during the mating season. Bearded seals live in a changing Arctic seascape, and their influence on the soundscape may shift as sea ice continues to diminish. It is imperative that acoustic monitoring continues within the Arctic, and this study provides a baseline for future monitoring as the Arctic continues to change.     

VOCAL INDIVIDUALITY IN MOTHER AND PUP SOUTH AMERICAN FUR SEALS, ARCTOCEPHALUS AUSTRALIS

South American fur seals breeding in Peru are subjected to levels of maternal aggression, and subsequent pup mortality, that are higher than has been reported for any other otariid species. For mothers and pups to maintain contact with each other, a mutual recognition system should exist to facilitate reunion and avoid misdirection of maternal effort. We recorded vocalizations of mothers and pups at Punta San Juan, Peru, during the 1994 and 1995 breeding seasons. Sixteen acoustic variables were measured from a total of 560 calls from 15 mothers and 13 pups. Multivariate analysis showed that calls were variable in several acoustic dimensions. While calls of both mothers and pups showed low variability within and high variability among individuals, mothers' calls were more individualistic. On average, discriminant-function analysis correctly assigned 60% of pup calls and 70% of mother calls to the individual that produced them. Characteristics of the fundamental frequency were most important for distinguishing among mothers, while pup calls, which typically contained less harmonic structure, could be differentiated by formant-like frequency ranges. Thus, calls of mother and pup South American fur seals appear to exhibit sufficient stereotypy to allow for recognition and discrimination among individuals.     

WEDDELL SEAL UNDERWATER CALLING RATES DURING THE WINTER AND SPRING NEAR MAWSON STATION, ANTARCTICA

Underwater vocalization monitoring and surveys, both on ice and underwater, were used to determine if Weddell seals ( Leptonychotes weddellii ) near Mawson Station, Antarctica, remain under the fast ice during winter within close range of breeding sites. Daytime and nighttime underwater calling rates were examined at seven breeding sites during austral winter and spring to identify seasonal and diel patterns. Seals rarely hauled out at any of the sites during winter, although all cohorts (adult males, females, and juveniles) were observed underwater and surfacing at breathing holes throughout winter (June–September) and spring (October–December). Seal vocalizations were recorded during each sampling session throughout the study ( n = 102 daytime at seven sites collectively, and n = 5 24-h samples at each of two sites). Mean daytime calling rate was low in mid-winter (July) (mean = 18.9 ± 7.1 calls/min) but increased monthly, reaching a peak during the breeding season (November) (mean = 62.6 ± 15.7 calls/min). Mean nighttime calling rate was high throughout the winter and early spring (July–October) with mean nocturnal calling rate in July (mean = 61.8 ± 35.1 calls/min) nearly equal to mean daytime calling rate in November (during 24-h daylight). Reduced vocal behavior during winter daylight periods may result from animals utilizing the limited daylight hours for nonvocal activities, possibly feeding.     

Weddell seal in-air call sequences made with closed mouths

Weddell seals (Leptonychotes weddelli) near Davis, Antarctica, produce a number of in-air vocalizations during the breeding season. With mouth and nostrils closed, pups and adults of both sexes produce at least 8 call types. Many of these are similar in nature to the sounds made underwater. Calls range from long, high frequency (>5 kHz) whistles to short, low frequency (<0.2 kHz) grunts. Individual call elements are often repeated and up to 6 call types are strung together in highly variable sequences.     

Polar bear responses to the underwater vocalizations of ringed seals

Summary Two captive polar bears were exposed to six different marine mammal vocalizations, in an attempt to determine if polar bears would selectively respond to the underwater vocalization of their primary prey, ringed seals. Vocalizations were played to each bear for a total of eight minutes while their behavioral responses were observed. An analysis of activity indicated that the bears displayed a significantly stronger response to ringed seals' vocalizations. It is theorized that the ability to recognize the underwater vocalizations of their primary prey would increase a bear's probability of a successful capture when a ringed seal rises to breath at an ice bound breathing hole.     

Year-round acoustic detection of bearded seals (Erignathus barbatus) in the Beaufort Sea relative to changing environmental conditions, 2008–2010

Bearded seals (Erignathus barbatus) are pan-Arctic pinnipeds that are often seen in association with pack ice, and are known for their long, loud trills, produced underwater primarily in the spring. Acoustic recordings were collected from August 2008 to August 2010 at two locations and a single year (2008–2009) at a third location, in the western Beaufort Sea. Three recorders in 2008–2009 had a 30 % duty cycle and a bandwidth of 10–4,096 Hz. One recorder in 2009–2010 had a 45 % duty cycle and a bandwidth of 10–4,096 Hz and the second had a 20 % duty cycle and bandwidth of 10–8,192 Hz. Spectrograms of acoustic data were examined for characteristic patterns of bearded seal vocalizations. For each recorder, the number of hours per day with vocalizations was compared with in situ water temperature and satellite-derived daily sea ice concentrations. At all sites, bearded seals were vocally active year-round. Call activity escalated with the formation of pack ice in the winter and the peak occurred in the spring, coinciding with mating season and preceding breakup of the sea ice. There was a change in the timing of seasonal sea ice formation and retreat between the two consecutive years that was reflected in the timing of peak bearded seal call activity. This study provides new information on fall and winter bearded seal vocal behavior and the relationship between year-round vocal activity and changes in annual sea ice coverage and in situ water temperature.     

Through-ice communication by Weddell seals may not be practicable

Possible communication between territorial male Weddell seals (Leptonychotes weddellii) under the ice with females on the ice was investigated. In-air and underwater recordings of underwater calls were made at three locations near Davis, Antarctica. Most underwater calls were not detectable in air, often because of wind noise. In-air call amplitudes of detectable calls ranged from 32–74 dB re. 20 Pa at 86 Hz down to 4–38 dB re. 20 Pa at 3.6 kHz. Most of these would be audible to humans. Only 26 of 582 amplitude measurements (from 230 calls) ranged from 5 dB to a maximum of 15 dB above the minimum harbour-seal (Phoca vitulina) in-air detection threshold. Seals on the ice could likely hear a few very loud underwater calls but only if the caller was nearby and there were no wind noises. The low detectability of underwater calls in air likely precludes effective communication between underwater seals and those on the ice.     

Evaluating the function of the male harbour seal, Phoca vitulina, roar through playback experiments

The aim of this study was to evaluate the role of vocalizations produced during the breeding season by the male harbour seal, an aquatically breeding pinniped. During the spring of 1999, playback experiments were conducted at eight locations in Elkhorn Slough, California, U.S.A. Through an underwater speaker, we presented male harbour seals with three acoustic stimuli: a long-duration, low-frequency roar (LL), a short-duration, high-frequency roar (SH) and amplified water noise (control). Male responses to the playback boat were characterized by increased approach rates and aggressive flipper slapping during 62.5% of SH sessions (N=8), 25% of LL sessions (N=8) and 0% of control sessions (N=8). No more than one identifiable seal responded during each playback location. We observed no responses by female harbour seals to playbacks. We conclude from these experiments that territorial male harbour seals use roars given by intruders to locate and challenge intruders.     

Underwater calling rates of harp and Weddell seals as a function of hydrophone location

Stereo recordings of harp seal (Pagophilus groenlandicus) and Weddell seal (Leptonychotes weddellii) underwater vocalizations were made near breeding groups using separations between two hydrophones of 159–339 m. Within a large herd, harp seal call numbers varied slightly between channels. Counts of Weddell seal calls were higher near a small herd on the ice than 159–180 m away. Repeat counts of harp seal calls by a single observer differed significantly. Source levels of Weddell seal calls varied and higher amplitude calls would be detected up to 2 orders of magnitude farther away than quieter calls. Hydrophone location (especially near small groups), observer variability and call source level differences will bias the use of monitoring underwater seal vocalizations to index locations, population size or underwater behaviours. Using hydrophone arrays and multiple observers may mitigate these problems. Accepted: 15 September 2000     

Ultrasonic vocalization of the female rat (Rattus norvegicus) during mating

The characterization and frequency of occurrence of ultrasonic vocalizations produced by females rats (Rattus norvegicus) during copulation were investigated. By devocalizing one member of a male-female pair, it was demonstrated that female rats produce complex, brief 40–70-kHz vocalizations during copulation. These calls shared common structural characteristics with those produced by males and occurred with similar frequency. The female-produced vocalizations were controlled by a hormone-sensitive mechanism; ovariectomized females exhibited few, if any, vocalizations without exposure to ovarian hormones. The implications of these findings are discussed with respect to previous results and to the role of these vocalizations in rodent communication.     

Dialects in southern Rocky Mountain pikas, Ochotona princeps (Lagomorpha)

This work quantifies the geographic variation (dialects) in the vocalizations of southern Rocky Mountain pikas and presents data on the vocal responses of pikas to playback of recorded vocalizations of two dialects. Pika vocalizations were tape-recorded in twenty-six locations in Wyoming, Colorado, Utah and New Mexico. Two dialects (based on duration of note and frequency of fundamental) were found in short calls. One dialect was north of the Colorado River (dialect A), and the other was south of the Colorado River (dialect B). There was seasonal variation in the incidence of vocalizations with a peak of songs in late spring and a peak of short calls in late summer. Results of this study indicate that acoustic characteristics of vocalizations could be a useful taxonomic tool in the genus Ochotona.     

DEVELOPMENT OF DISPLAY BEHAVIOR IN YOUNG CAPTIVE BEARDED SEALS

In this study of the ontogeny of vocal behavior in captive bearded seals, Erignathus barbatus , (three males and three females), only males exhibited vocal displays. The onset of display behavior coincided with sexual maturity. Males exhibited three types of dive displays associated with the performance of vocalizations. Vocalizing individuals were frequently attended by another male that maintained passive muzzle contact with the vocalizing male. These interactions were non-aggressive and might play a role in the establishment of a social hierarchy or they might allow the attendee to obtain "near-field" vocal information from the displaying male. Captive males' vocalizations resembled those of males in the wild. However, display dives were shorter, and fewer vocalization types were documented among the captive males compared to bearded seals in the wild. The capacity of the captive males for producing well-formed, long calls with large frequency changes was also significantly less than for wild males. These capacities will likely develop further as the males grow older. Individual capacity for vocal production appears to develop gradually, showing plasticity in form development over time.     

Comparative assessment of amphibious hearing in pinnipeds

Auditory sensitivity in pinnipeds is influenced by the need to balance efficient sound detection in two vastly different physical environments. Previous comparisons between aerial and underwater hearing capabilities have considered media-dependent differences relative to auditory anatomy, acoustic communication, ecology, and amphibious life history. New data for several species, including recently published audiograms and previously unreported measurements obtained in quiet conditions, necessitate a re-evaluation of amphibious hearing in pinnipeds. Several findings related to underwater hearing are consistent with earlier assessments, including an expanded frequency range of best hearing in true seals that spans at least six octaves. The most notable new results indicate markedly better aerial sensitivity in two seals (Phoca vitulina and Mirounga angustirostris) and one sea lion (Zalophus californianus), likely attributable to improved ambient noise control in test enclosures. An updated comparative analysis alters conventional views and demonstrates that these amphibious pinnipeds have not necessarily sacrificed aerial hearing capabilities in favor of enhanced underwater sound reception. Despite possessing underwater hearing that is nearly as sensitive as fully aquatic cetaceans and sirenians, many seals and sea lions have retained acute aerial hearing capabilities rivaling those of terrestrial carnivores.     

Ultrasonic Vocalizations Emitted by Flying Squirrels

Anecdotal reports of ultrasound use by flying squirrels have existed for decades, yet there has been little detailed analysis of their vocalizations. Here we demonstrate that two species of flying squirrel emit ultrasonic vocalizations. We recorded vocalizations from northern (Glaucomys sabrinus) and southern (G. volans) flying squirrels calling in both the laboratory and at a field site in central Ontario, Canada. We demonstrate that flying squirrels produce ultrasonic emissions through recorded bursts of broadband noise and time-frequency structured frequency modulated (FM) vocalizations, some of which were purely ultrasonic. Squirrels emitted three types of ultrasonic calls in laboratory recordings and one type in the field. The variety of signals that were recorded suggest that flying squirrels may use ultrasonic vocalizations to transfer information. Thus, vocalizations may be an important, although still poorly understood, aspect of flying squirrel social biology.     

Significance of temporal and spectral acoustic cues for sexual recognition in Xenopus laevis

As in many anurans, males of the totally aquatic species, Xenopus laevis, advertise their sexual receptivity using vocalizations. Unusually for anurans, X. laevis females also advertise producing a fertility call that results in courtship duets between partners. Although all X. laevis calls consist of repetitive click trains, male and female calls exhibit sex-specific acoustic features that might convey sexual identity. We tested the significance of the carrier frequency and the temporal pattern of calls using underwater playback experiments in which modified calls were used to evoke vocal responses in males. Since males respond differently to male and female calls, the modification of a key component of sexual identity in calls should change the male's response. We found that a female-like slow call rhythm triggers more vocal activity than a male-like fast rhythm. A call containing both a female-like temporal pattern and a female-like carrier frequency elicits higher levels of courtship display than either feature alone. In contrast, a male-like temporal pattern is sufficient to trigger typical male-male encounter vocalizations regardless of spectral cues. Thus, our evidence supports a role for temporal acoustic cues in sexual identity recognition and for spectral acoustic cues in conveying female attractiveness in X. laevis.     

VOCAL REPERTOIRE OF WILD BREEDING ORANGE-WINGED PARROTS AMAZONA AMAZONICA IN AMAZONIA

ABSTRACT

The vocal repertoire of Amazona amazonica during its breeding season has been recorded from wild individuals in Santa Bárbara do Pará, Pará State, Brazil. At individual nests, we continuously recorded vocalizations and behaviour for four hours in the early morning and three hours in the late afternoon, three times a week throughout the breeding season. We identified nine vocalizations that we classified in three behavioural categories: (1) Flight call—emitted when parrots arrive in the nest area; (2) Perched contact calls—two different vocalizations, one of them related to feeding, were emitted when the pair was perched in the nest area and interacted socially between themselves or with other individuals; (3) Aggressive calls—emitted when birds were in a dangerous situation, i.e. alarm (three types of calls), agonistic contact and distress calls (two types of call). The Orange-winged Parrot is a highly social species and the complexity of its social interactions is reflected in the diversity of its vocal repertoire.     

The significant features of Japanese macaque coo sounds: a psychophysical study

Japanese macaques, Macaca fuscata, were trained with a positive reinforcement operant procedure to discriminate smooth early high and smooth late high coo sounds recorded during Green's (1975) field study of the speices' vocal repertoire. Subjects labelled the various tokens by maintaining contact with a response device for calls from one category and by breaking contact for those of the second call type. After the completion of discrimination training, the generalization of the operant behaviour to novel natural and synthetic vocalizations was measured. Initial generalization tests established that macaques would respond appropriately both to natural vocalizations and to computer-synthesized prototypes representing the smooth early high-smooth late high contrast. In subsequent tests, individual acoustic features were removed from the synthetic prototypes to determine the minimal elements of functional coo sounds. These tests suggested that those sounds are distinguished by the predominant direction of their frequency change which, in turn, is determined by the temporal position of their highest frequency.     

Neighbor effects in marmosets: social contagion of agonism and affiliation in captive Callithrix jacchus

Researchers have demonstrated the neighbor effect for affiliative and agonistic neighbor vocalizations in captive chimpanzees. We extend the investigation of the neighbor effect to New World monkeys, Callithrix jacchus. We collected data on vocalizations and behaviors of 31 focal individuals and concurrent neighbor vocalization within three behavioral categories: intragroup and intergroup aggression and intragroup affiliation. We investigated whether there was an influence of neighbor vocalizations on focal behavior within the same behavioral category. For data analysis we used approximate randomization of paired‐sample t‐tests. We found that marmosets performed intergroup aggressive behavior (bristle, anogenital present for neighbor loud shrill only) for significantly longer, and emitted significantly more intergroup agonistic vocalizations (twitter, loud shrill), at a high frequency of intergroup agonistic neighbor vocalizations (twitter, loud shrill) than at low. The marmosets were also significantly more likely to engage in bristle behavior immediately after hearing a neighbor intergroup aggressive call (twitter, loud shrill) than directly beforehand. High neighbor intragroup agonistic calls (chatter) were associated with significantly longer spent in related behavior (composite of: attack, chase, steal food). Affiliative behaviors (share food, grooming invite) were engaged in by marmosets for significantly longer at higher frequencies of affiliative neighbor chirp calls than at low. Marmosets were also significantly more likely to perform food sharing and active affiliative contact immediately after rather than before hearing a neighbor chirp call. Our findings suggest that neighbor vocalizations influence marmoset behavior through social contagion and indicate that the neighbor effect for affiliation and aggression generalizes to the marmoset. Am. J. Primatol. 72:549–558, 2010. © 2010 Wiley‐Liss, Inc.