99 research outputs found

    Vocal Repertoire, Social Structure and Feeding Preferences of Australian and Antarctic Killer Whales (Orcinus orca)

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    This thesis aimed to improve the understanding of killer whale populations in the Australian and Antarctic regions. Visual surveys, photo-identification and passive acoustic recordings were combined to study these populations. This study describes the call repertoire of killer whales found in Australian and Antarctic waters, presents an acoustic comparison between sympatric ecotypes in Antarctic waters and investigates the sociality and feeding preferences of killer whales in the Bremer Sub-Basin

    Icelandic herring-eating killer whales feed at night

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    This study was funded by an Icelandic Research Fund (i. Rannsóknasjóður, grant number 120248042) supported by a Marie Curie Fellowship.Herring-eating killer whales debilitate herring with underwater tail slaps and likely herd herring into tighter schools using a feeding-specific low-frequency pulsed call (‘herding’ call). Feeding on herring may be dependent upon daylight, as the whales use their white underside to help herd herring; however, feeding at night has not been investigated. The production of feeding-specific sounds provides an opportunity to use passive acoustic monitoring to investigate feeding behaviour at different times of day. We compared the acoustic behaviour of killer whales between day and night, using an autonomous recorder deployed in Iceland during winter. Based upon acoustic detection of underwater tail slaps used to feed upon herring we found that killer whales fed both at night and day: they spent 50% of their time at night and 73% of daytime feeding. Interestingly, there was a significant diel variation in acoustic behaviour. Herding calls were significantly associated with underwater tail slap rate and were recorded significantly more often at night, suggesting that in low-light conditions killer whales rely more on acoustics to herd herring. Communicative sounds were also related to underwater tail slap rate and produced at different rates during day and night. The capability to adapt feeding behaviour to different light conditions may be particularly relevant for predator species occurring in high latitudes during winter, when light availability is limited.Publisher PDFPeer reviewe

    Calls produced by Ecotype C killer whales (Orcinus orca) off the Eckstroem Iceshelf, Antarctica

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    Killer whales (Orcinus orca) are highly social top predators distributed throughout the worldʼs oceans. They are divided into different ecotypes according to foraging specializations, phenotype, and social organization. For Northern Hemisphere killer whale ecotypes, acoustic behaviour has been shown to relate to foraging strategies and social organization. In contrast to the intensively studied Northern Hemisphere ecotypes, distribution patterns, social structures, and acoustic behaviour of the Southern Hemisphere killer whale ecotypes are poorly known. One of the Southern Hemisphere ecotypes, the Antarctic Ecotype C killer whale, is known to occur in regions with dense pack ice. The limited accessibility of these areas make passive acoustic monitoring (PAM) methods a very effective investigation tool to derive information on ecotype-specific abundance and distribution. During 2 d in February 2013, it was possible to collect concurrent visual and acoustic information of Ecotype C killer whales off the Antarctic continent. From these events, a call type catalogue was compiled. The 2,238 examined calls were subjectively classified into 26 discrete call types. Ten percent of the examined calls were re-classified by two additional independent observers to examine robustness of the classification. Mean classification accordance among observers was 68%. Most call types were composed of more than one call part. Sixty-five percent of all call types were monophonic, and 35% were biphonic. Almost two-third of all call types started with a short, broadband pulse. The variability within call types was relatively high. The Ecotype C vocal repertoire contained typical acoustic features such as biphonation, high call complexity, and generally high variability in frequency modulation. For future studies, the distinct characteristics of some of the call types described herein could potentially serve as acoustic markers for PAM-based differentiation of killer whale ecotypes in the Southern Ocean

    Whistles of Sympatric Species of Bottlenose Dolphins (Tursiops truncatus) and Spotted Dolphins (Stenella frontalis) in the Bahamas: Acoustic Characteristics and Contextual Use

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    Bottlenose and spotted dolphins in the Bahamas frequently interact in social, socio-sexual, and aggressive encounters, and whistles are thought to play a key role in their communication. Concurrent vocal and behavioral recordings of wild sympatric species of Atlantic spotted dolphins (Stenella frontalis) and Atlantic bottlenose dolphins (Tursiops truncatus) were collected from three Bahamas populations, and the acoustic parameters, structure, and contextual use of their whistles were analyzed. The mean acoustic parameters of spotted dolphins in the Bimini and White Sand Ridge Bahamas populations were higher in frequency than those of bottlenose dolphins, but bottlenose dolphins produced whistles that had higher delta and maximum frequencies than those of spotted dolphins. Bottlenose dolphins produced proportionately more rise-type calls and convex calls than spotted dolphins did, and spotted dolphins displayed greater use of amplitude-modulated whistles. Differences in acoustic parameters between these two sympatric species may enable them to differentiate between conspecifics and non-conspecifics. As with all odontocete species examined so far, the two whistle parameters with the highest intraspecific variability in these populations were duration and number of inflection points, which may aid in individual differentiation or identification. Whistle acoustic parameters were also found to vary with behavioral context and group composition in spotted dolphins. Specifically, significantly more whistles produced by dolphin groups comprised mainly or entirely of calves and younger juveniles were amplitude modulated, and had significantly higher frequency parameters, especially during people-oriented behavioral states. Whistles with amplitude modulation and higher frequencies may provide cues about the age and emotive state of the animals producing them. Biphonation, the simultaneous production of two sounds, is a commonly occurring phenomena in the Bahamas Atlantic spotted dolphins. Bitonal whistles have very rarely been reported in any species of dolphin, but both burst-pulse whistles and bitonal whistles have been recorded in this population. Bitonal whistles are produced far more frequently by adults than by sexually immature dolphins, while burst-pulse whistles are produced more often in younger rather than older animals. Biphonal components of whistles may provide cues as to identity, age, and social role in spotted dolphin whistles

    Physical constraints of cultural evolution of dialects in killer whales

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    Data collection was supported by a variety of organizations, including the Russian Fund for the Fundamental Research (Grant No. 15-04-05540), the Rufford Small Grants Fund, Whale and Dolphin Conservation, the Fundação para a Ciência e a Tecnologia (Grant No. SFRH/BD/30303/2006), Russell Trust Award of the University of St. Andrews, the Office of Naval Research, the Icelandic Research Fund (i. Rannsóknasjóður), the National Geographic Society Science and Exploration Europe (Grant No. GEFNE65-12), Vancouver Aquarium Marine Science Centre, the Canadian Ministry of Fisheries and Oceans, and the North Gulf Oceanic Society.Odontocete sounds are produced by two pairs of phonic lips situated in soft nares below the blowhole; the right pair is larger and is more likely to produce clicks, while the left pair is more likely to produce whistles. This has important implications for the cultural evolution of delphinid sounds: the greater the physical constraints, the greater the probability of random convergence. In this paper the authors examine the call structure of eight killer whale populations to identify structural constraints and to determine if they are consistent among all populations. Constraints were especially pronounced in two-voiced calls. In the calls of all eight populations, the lower component of two-voiced (biphonic) calls was typically centered below 4 kHz, while the upper component was typically above that value. The lower component of two-voiced calls had a narrower frequency range than single-voiced calls in all populations. This may be because some single-voiced calls are homologous to the lower component, while others are homologous to the higher component of two-voiced calls. Physical constraints on the call structure reduce the possible variation and increase the probability of random convergence, producing similar calls in different populations.PostprintPeer reviewe

    The Sarasota Dolphin Whistle Database : a unique long-term resource for understanding dolphin communication

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    Funding for data collection and analysis over the years has been provided by the National Science Foundation, The Royal Society of London, Dolphin Quest, Adelaide M. and Charles B. Link Foundation, Marine Mammal Commission, National Oceanic and Atmospheric Administration, Earthwatch Institute, Protect Wild Dolphins Fund of the Harbor Branch Oceanographic Institute, Grossman Family Foundation, WHOI Ocean Life Institute, Vulcan Machine Learning Center for Impact, and the Allen Institute for Artificial Intelligence. Current support for PT’s involvement is provided by the Office of Naval Research Grants N00014-18-1-2062 and N00014-20-1-2709 through a subaward from Carnegie Mellon University. Current support for LS’s involvement is provided by the Adelaide M. & Charles B. Link Foundation and Dolphin Quest.Common bottlenose dolphins (Tursiops truncatus) produce individually distinctive signature whistles that are learned early in life and that help animals recognize and maintain contact with conspecifics. Signature whistles are the predominant whistle type produced when animals are isolated from conspecifics. Health assessments of dolphins in Sarasota, Florida (USA) provide a unique opportunity to record signature whistles, as dolphins are briefly separated from conspecifics. Recordings were first made in the mid 1970’s, and then nearly annually since 1984. The Sarasota Dolphin Whistle Database (SDWD) now contains 926 recording sessions of 293 individual dolphins, most of known age, sex, and matrilineal relatedness. The longest time span over which an individual has been recorded is 43 years, and 85 individuals have been recorded over a decade or more. Here we describe insights about signature whistle structure revealed by this unique and expansive dataset. Signature whistles of different dolphins show great variety in their fundamental frequency contours. Signature whistle types (with ‘whistle type’ defined as all whistles visually categorized as sharing a particular frequency modulation pattern) can consist of a single stereotyped element, or loop (single-loop whistles), or of multiple stereotyped loops with or without gaps (multi-loop whistles). Multi-loop signature whistle types can also show extensive variation in both number and contour of loops. In addition, fundamental frequency contours of all signature whistle types can be truncated (deletions) or embellished (additions), and other features are also occasionally incorporated. However, even with these variable features, signature whistle types tend to be highly stereotyped and easily distinguishable due to the extensive variability in contours among individuals. In an effort to quantify this individual distinctiveness, and to compare it to other species, we calculated Beecher’s Information Statistic and found it to be higher than for any other animal signal studied so far. Thus, signature whistles have an unusually high capacity to convey information on individual identity. We briefly review the large range of research projects that the SDWD has enabled thus far, and look ahead to its potential to answer a broad suite of questions about dolphin communication.Publisher PDFPeer reviewe

    Tuvan Throat Singing: The Globalization of the Tuvan Spirit

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