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[[File:Beluga Whale Tadoussac Quebec Canada Luca Galuzzi 2005.jpg|thumb|<span lang="en" dir="ltr" class="mw-content-ltr">Beluga whales surfacing near Tadoussac, Quebec, Canada. Photograph by Luca Galuzzi, 2005 (CC BY-SA 2.5).</span>]]

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The '''beluga whale''' (''Delphinapterus leucas''), also called the '''beluga''' or '''white whale''', is a toothed whale of Arctic and sub-Arctic waters. It belongs to the family Monodontidae, whose only other living species is the narwhal (''Monodon monoceros'').<ref name="IUCN">Lowry, L.; Reeves, R.; and Laidre, K. (2017). [https://doi.org/10.2305/IUCN.UK.2017-3.RLTS.T6335A50352346.en ''Delphinapterus leucas'']. ''The IUCN Red List of Threatened Species'' 2017: e.T6335A50352346.</ref> The Japanese name ''shiro-iruka'' literally means “white dolphin,” but the beluga is not a member of Delphinidae, the taxonomic family usually called the oceanic dolphins.
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Adult belugas are immediately recognizable by their white skin, rounded forehead, absence of a dorsal fin, and unusually flexible neck. They are highly social and produce an extensive repertoire of whistles, pulsed calls, and clicks. Their conspicuous vocal activity gave rise to the nickname “canary of the sea.” Sound is not a decorative feature of beluga life: it is a principal medium for maintaining social contact, locating prey, and navigating water that may be dark, turbid, or covered by ice.<ref name="NOAA-species">NOAA Fisheries. [https://www.fisheries.noaa.gov/species/beluga-whale Beluga whale]. Retrieved 22 September 2026.</ref>
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== Taxonomy and name ==
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The beluga is an odontocete, or toothed whale. ''Delphinapterus leucas'' is the sole living species in the genus ''Delphinapterus''. Together, belugas and narwhals form Monodontidae.<ref name="IUCN" /> Although everyday language does not always follow taxonomic boundaries, this distinction matters: “whale” and “dolphin” are overlapping common-language labels, whereas Monodontidae and Delphinidae are separate biological families.
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== Appearance and Arctic adaptations ==
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[[File:Beluga size comparison.png|thumb|Size comparison between an average human and a beluga whale. Illustration by Chris huh (CC BY-SA 3.0).]]
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Newborn belugas are dark grey. Their colour becomes progressively lighter as they mature, and adults are white. NOAA reports a maximum length of about 4.9 metres (16 feet), an average mass of about 1,430 kilograms (3,150 pounds), and a lifespan that may reach 90 years.<ref name="NOAA-species" /> Size varies by sex and population, so these figures should not be read as a single fixed adult size.
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Several anatomical features suit life in cold, ice-associated habitats. A thick blubber layer can account for as much as about 40 percent of body mass. Instead of a projecting dorsal fin, the animal has a tough dorsal ridge, reducing the obstruction presented when it swims beneath ice. Unlike most cetaceans, a beluga's cervical vertebrae are not fused; it can turn and nod its head without rotating its entire body. This mobility is useful in shallow water, among ice, and while feeding near the seafloor.<ref name="NOAA-species" />
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The rounded forehead contains the '''melon''', a mass of specialized fatty tissue involved in transmitting and shaping sound. Facial muscles can alter the visible contour of a beluga's melon. The mouth contains approximately 32–40 teeth, adapted for grasping rather than chewing prey.<ref name="NOAA-species" />
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Belugas undergo a conspicuous seasonal moult. In summer, they may enter relatively warm, shallow estuaries and rub against coarse gravel, helping shed the outermost skin layer.<ref name="NOAA-species" />
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== Distribution and habitat ==
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Belugas occur across Arctic and sub-Arctic regions of Alaska, Canada, Greenland, Norway, and Russia. They use a wide range of habitats, including offshore waters, continental shelves, bays, estuaries, fjords, and river mouths; some enter rivers. Many populations make seasonal movements associated with sea ice, prey, reproduction, and summering areas, while others are comparatively resident.<ref name="NOAA-species" /><ref name="IUCN" />
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The species is capable of both shallow coastal foraging and deep diving. Recorded dives can approach 1,000 metres and last about 25 minutes, although ordinary behaviour is not defined by those maxima.<ref name="NOAA-species" /> Sea ice is both habitat and hazard: it can offer shelter from killer whales, but moving ice can also restrict access to breathing openings or trap groups in small areas of open water.
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== Feeding, predators, and life history ==
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Belugas are opportunistic predators. Their diet changes with region and season and includes fishes such as salmon, eulachon, cod, and herring, together with squid, octopuses, shrimp, crabs, clams, snails, and marine worms. They forage in the water column and on or near the seabed. Flexible lips and tongue movements allow suction to assist in taking prey, while the teeth hold rather than masticate it.<ref name="feeding">Werth, A. J. (2006). [https://doi.org/10.1644/05-MAMM-A-279R1.1 Mandibular and dental variation and the evolution of suction feeding in Odontoceti]. ''Journal of Mammalogy'' 87(3): 579–588.</ref>
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Known natural predators include killer whales and polar bears. Killer whales can pursue belugas in open water, whereas polar bears may attack animals concentrated at breathing holes or trapped by ice. Humans have also hunted belugas for subsistence over many generations; management and legal conditions differ among regions and populations.<ref name="NOAA-species" />
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Mating generally occurs in late winter or spring. Gestation lasts about 15 months, and most births occur during the following summer. Calves nurse for at least two years. Females usually produce one calf every two or three years, a slow reproductive schedule that limits how quickly a depleted population can recover.<ref name="NOAA-species" />
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== Social life ==
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Beluga group size and composition are flexible. A mother and calf may travel as a pair; small groups can be organized by age, sex, or reproductive state; and hundreds or thousands of whales may assemble seasonally. Genetic and field data from ten Arctic locations showed that most observed social groups were not composed predominantly of close maternal relatives. Belugas regularly associated with close kin, distant kin, and unrelated individuals, consistent with a dynamic, multi-level social system rather than a simple permanent matrilineal “pod.”<ref name="social">O'Corry-Crowe, G.; Suydam, R.; Quakenbush, L.; et al. (2020). [https://doi.org/10.1038/s41598-020-67314-w Group structure and kinship in beluga whale societies]. ''Scientific Reports'' 10: 11462.</ref>
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Such fluid social organization creates an acoustic problem: individuals that cannot see one another still need to coordinate movement, preserve mother–calf contact, and potentially identify familiar companions. Beluga communication must therefore be understood as part of its social ecology, not merely as a list of noises.
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== Acoustic biology ==
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=== Why sound is central ===
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Underwater visibility may be limited by depth, suspended sediment, seasonal darkness, and ice. Sound travels far more effectively than light through many of these environments. Belugas use sound in two broad ways: '''communication''' transmits information between animals, while '''echolocation''' is an active sensing system in which a whale interprets echoes from its own clicks. The same animal and sound-producing anatomy support both systems, but a social call is not simply a form of sonar, and an echolocation click should not automatically be interpreted as a message.
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Like other toothed whales, belugas generate most high-frequency sounds in a complex of air sacs and vibrating tissues in the nasal region rather than with mammalian vocal folds. Acoustic energy passes through the melon, which helps form a forward-projecting beam. Returning echoes are received through sound-conducting tissues associated with the lower jaw and transmitted to the ears.<ref name="cranford">Cranford, T. W.; Amundin, M.; and Norris, K. S. (1996). [https://pubmed.ncbi.nlm.nih.gov/8622183/ Functional morphology and homology in the odontocete nasal complex: implications for sound generation]. ''Journal of Morphology'' 228(3): 223–285.</ref>
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Beluga hearing extends well into the ultrasonic range. In one rehabilitated wild Cook Inlet beluga, auditory-evoked-potential testing found responses across 4–128 kHz and thresholds below 80 dB re 1 µPa over 16–80 kHz. Its results resembled measurements from healthy wild belugas in Bristol Bay.<ref name="hearing">Mooney, T. A.; Castellote, M.; Jones, I.; Rouse, N.; and Goertz, C. E. C. (2020). [https://doi.org/10.1121/10.0002351 Audiogram of a Cook Inlet beluga whale (''Delphinapterus leucas'')]. ''The Journal of the Acoustical Society of America'' 148(5): 3141–3148.</ref> These measurements demonstrate capability, not an identical audiogram for every animal: hearing changes with individual condition, age, and measurement method.
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=== Whistles, pulsed calls, and combined calls ===
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There is no single universal “dictionary” for beluga sounds. Classification depends on the research question, recording bandwidth, population, and analyst. A useful acoustic division is:
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* '''Whistles''' are comparatively continuous, narrowband tonal signals. Their frequency contours may rise, fall, remain level, or change direction several times.
* '''Pulsed calls''' are trains of brief broadband pulses. At slow repetition rates, separate impulses may be audible; at high rates, the train can be perceived as a buzz, squawk, or creak. “Burst-pulsed” describes this rapidly repeated region rather than a separate sound-producing organ.
* '''Combined calls''' contain simultaneous or closely integrated tonal and pulsed components.
* '''Echolocation clicks''' are short, broadband, strongly directional pulses used principally for active sensing. During a rapid sequence they may sound like a buzz to a human listener, but their timing and beam direction differ from many social pulsed calls.
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NOAA outreach material groups the repertoire more broadly as whistles, social calls, and echolocation clicks.<ref name="NOAA-sound">NOAA Fisheries (2023). [https://www.fisheries.noaa.gov/alaska/outreach-and-education/5-facts-about-how-belugas-use-sound 5 facts about how belugas use sound].</ref> Both schemes are useful as long as their categories are not treated as interchangeable.
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=== Repertoire: diversity without a universal codebook ===
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One foundational study recorded belugas summering in Cunningham Inlet, Canada, from 1981 to 1983. Researchers sorted 807 tonal calls and whistles into 16 contour types and classified 436 pulsed sounds as click series, pulsed tones, or noisy vocalizations. The measured whistles had mean frequencies from 2.0 to 5.9 kHz and durations from 0.25 to 1.95 seconds; pulsed tones had mean pulse-repetition rates from about 204 to 1,289 pulses per second.<ref name="sjare">Sjare, B. L., and Smith, T. G. (1986). [https://doi.org/10.1139/z86-063 The vocal repertoire of white whales, ''Delphinapterus leucas'', summering in Cunningham Inlet, Northwest Territories]. ''Canadian Journal of Zoology'' 64(2): 407–415.</ref> These are measurements from a particular place, season, recording system, and classification method—not fixed limits for the species.
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A 2023 analysis of endangered Cook Inlet belugas classified 1,633 vocalizations into 1,264 whistles (77 percent), 354 pulsed calls (22 percent), and 15 combined calls (1 percent), producing a catalogue of 41 call types. Automated classification methods agreed substantially, but not perfectly, with human classification.<ref name="brewer">Brewer, A. M.; Castellote, M.; Van Cise, A. M.; Gage, T.; and Berdahl, A. M. (2023). [https://doi.org/10.1121/10.0022516 Communication in Cook Inlet beluga whales: describing the vocal repertoire and masking of calls by commercial ship noise]. ''The Journal of the Acoustical Society of America'' 154(5): 3487–3505.</ref> Differences between catalogues can reflect genuine population variation as well as equipment, sampling, and analytical choices. A call-type number is therefore an output of a study, not a final count of everything a beluga can say.
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=== Contact calls, group cohesion, and identity ===
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The most intensively studied candidate contact signal is a stereotyped broadband pulsed sound often labelled '''Type A'''. In observations of a captive social group, Type A calls formed 24–97 percent of recorded vocalizations during situations in which contact was especially important—including separation, reunion, isolation, births, and the death of a calf—but only 4.4 percent during ordinary sessions. Researchers divided 2,835 Type A calls into five acoustic variants. The variants were not unique signatures of single animals: some were shared by a mother and her offspring.<ref name="contact">Vergara, V.; Michaud, R.; and Barrett-Lennard, L. (2010). [https://doi.org/10.46867/ijcp.2010.23.03.08 What can captive whales tell us about their wild counterparts? Identification, usage, and ontogeny of contact calls in belugas (''Delphinapterus leucas'')]. ''International Journal of Comparative Psychology'' 23(3): 278–309.</ref>
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The timing of calls also matters. In the same study, adults sometimes exchanged Type A calls antiphonally—that is, one animal's call was followed within a short interval by another's. During the first three months of one calf's life, half of its mother's Type A calls occurred within two seconds of a calf call. Temporal association alone does not prove that every sequence is a deliberate exchange, but the context and repeated patterns support a role in maintaining contact.<ref name="contact" />
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Evidence from free-ranging whales strengthens, but does not close, the case for vocal identity cues. During 14 natural entrapments in a shallow channel at Cunningham Inlet, contact calls accounted for 61 percent of vocalizations from temporarily isolated whales, compared with 10 percent in the free-ranging herd. Researchers catalogued 87 complex contact-call types and found that the number of distinctive types increased with the number of entrapped animals. They described this as preliminary evidence for vocal signatures in wild belugas.<ref name="wild-contact">Vergara, V., and Mikus, M.-A. (2019). [https://doi.org/10.1111/mms.12538 Contact call diversity in natural beluga entrapments in an Arctic estuary: preliminary evidence of vocal signatures in wild belugas]. ''Marine Mammal Science'' 35(2): 434–465.</ref>
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It is tempting to call such signals “names,” but that claim goes beyond the present evidence. The research supports context-linked contact calls, call matching, learned variants, and possible individual distinctiveness. Demonstrating a name-like referential system would require stronger evidence that receivers treat a signal as a stable label for a particular individual across contexts.
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=== Vocal development and learning ===
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Beluga calves do not begin life with the adult repertoire fully formed. A longitudinal study of one captive male recorded low-energy broadband pulse trains within his first hour after birth. Rudimentary whistles appeared at about two weeks, whistle production increased substantially in the second month, and mixed tonal–pulsed calls became consistent at about four months. The calf's calls gradually became more stereotyped over months and years.<ref name="development">Vergara, V., and Barrett-Lennard, L. G. (2008). [https://doi.org/10.1578/AM.34.1.2008.123 Vocal development in a beluga calf (''Delphinapterus leucas'')]. ''Aquatic Mammals'' 34(1): 123–143.</ref>
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By 20 months, that calf produced a contact-call variant closely resembling calls used by his mother and older half-sister.<ref name="contact" /> This is evidence of prolonged vocal development and learning within a social environment. Because the original developmental record concerned one captive calf, it should not be converted into a rigid developmental timetable for all wild belugas.
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=== Echolocation: active acoustic sensing ===
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In echolocation, a beluga emits a click and interprets the returning echo. Echo delay carries information about range; changes in level and spectrum can contribute information about target size, shape, orientation, motion, and material. The whale can adjust click rate, level, spectrum, and beam direction as it approaches or examines a target. Echolocation supports navigation, obstacle avoidance, and prey detection where vision alone is unreliable.<ref name="NOAA-sound" />
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Beluga biosonar is flexible rather than mechanically fixed. In a controlled study of one trained male, ambient noise in Kaneohe Bay was 12–17 dB higher than in San Diego Bay. In the quieter environment, the whale's echolocation signals peaked mainly at 40–60 kHz with bandwidths of 15–25 kHz. In the noisier environment, peaks shifted to 100–120 kHz, bandwidths widened to 20–40 kHz, and signal intensity rose by as much as 18 dB. The authors interpreted this as adaptation of the emitted signal to the acoustic environment.<ref name="adaptation">Au, W. W. L.; Carder, D. A.; Penner, R. H.; and Scronce, B. L. (1985). [https://doi.org/10.1121/1.392341 Demonstration of adaptation in beluga whale echolocation signals]. ''The Journal of the Acoustical Society of America'' 77(2): 726–730.</ref> The result is an instructive case study, not a species-wide rule derived from a large sample.
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=== How the sounds are studied ===
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Researchers record belugas with hydrophones, inspect waveforms and spectrograms, measure features such as duration, peak frequency, bandwidth, contour, and pulse-repetition rate, and compare those measurements with observed behaviour. Passive acoustic recorders can operate when visual surveys are impossible, revealing seasonal presence and calling activity. Tags carried temporarily by a whale can add movement and received-level data, while synchronized hydrophone arrays can help localize a caller.
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Every recording system imposes limits. A digital system sampled at 44.1 kHz cannot represent frequencies above approximately 22.05 kHz, and the usable limit may be lower if the hydrophone, preamplifier, or recorder rolls off earlier. A 96 kHz system has a theoretical Nyquist limit of 48 kHz, but even that does not capture the entire hearing or echolocation range reported for belugas. Older or bandwidth-limited recordings may therefore preserve the audible portion of a call while omitting ultrasonic structure. Caller identification is another difficulty: in a group, a visible animal rarely provides an obvious external cue at the instant it makes a sound.<ref name="contact" />
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Spectrogram categories are also human analytical constructs. A cluster that looks distinct to an analyst is biologically meaningful only if its production, context, or perception differs for the whales. Strong interpretation therefore combines acoustics with behaviour, individual attribution, developmental records, controlled experiments, or playback studies rather than relying on sound shape alone.
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== Noise, masking, and communication space ==
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'''Masking''' occurs when background sound reduces the detectability of a biologically relevant signal. It does not require physical hearing damage: a healthy animal can fail to detect a call when noise overlaps it in frequency and time. For a social species, the result is a smaller '''communication space'''—the area over which a call remains audible to an intended receiver.
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A propagation model for endangered St. Lawrence belugas combined measured noise, hearing data, and source levels from tagged wild whales and whales in human care. Estimated median communication ranges for adult and sub-adult contact calls were more than 18 times those of newborn calls. Vessel noise reduced the adult and sub-adult ranges by 57 and 53 percent, respectively, and the median modeled range of a newborn call in vessel noise was only 170 metres.<ref name="active-space">Vergara, V.; Wood, J.; Lesage, V.; et al. (2021). [https://doi.org/10.33265/polar.v40.5521 Can you hear me? Impacts of underwater noise on communication space of adult, sub-adult and calf contact calls of endangered St. Lawrence belugas]. ''Polar Research'' 40: 5521.</ref> These are modelled ranges under study-specific conditions, not universal distances, but they identify a particular vulnerability: young calves produce quieter calls while remaining dependent on contact with their mothers.
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The Cook Inlet repertoire study reached a complementary result. In the 0–12 kHz band, common call types were partly masked by distant commercial ship noise and completely masked by nearby ship noise.<ref name="brewer" /> Belugas may alter calling behaviour, level, or frequency in noise, but compensation has limits and may carry energetic or informational costs. More intense sound can also disturb behaviour or, at sufficiently high exposure, injure hearing.<ref name="NOAA-species" />
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== Conservation ==
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The IUCN assessed the beluga globally as Least Concern in 2017, but a global category can conceal severe local declines.<ref name="IUCN" /> Populations are geographically, genetically, and behaviourally differentiated, and threats are not evenly distributed. The Cook Inlet distinct population segment, for example, is listed as endangered under the United States Endangered Species Act; NOAA's current abundance estimate is about 331 animals.<ref name="NOAA-species" />
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Major pressures include climate-driven changes to sea ice and prey, underwater noise, contaminants, habitat alteration, disease, entanglement, harassment, and unsustainable removal in some contexts. Reduced sea ice may also increase shipping and industrial access while allowing killer whales to enter areas that formerly provided belugas with refuge. Conservation therefore requires population-specific management and protection of both physical habitat and acoustic habitat.
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== External media ==
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* [https://www.fisheries.noaa.gov/alaska/outreach-and-education/5-facts-about-how-belugas-use-sound NOAA Fisheries: “5 Facts About How Belugas Use Sound”] includes short examples of call categories and echolocation clicks.
* [https://commons.wikimedia.org/wiki/File:Beluga_vocalizations.ogg Beluga vocalizations] is a 16-second recording distributed by NOAA and hosted on Wikimedia Commons.
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== References ==
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[[Category:Marine mammals{{#translation:}}]]
[[Category:Bioacoustics{{#translation:}}]]
[[Category:Animal communication{{#translation:}}]]
[[Category:Echolocation{{#translation:}}]]

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