Although dolphins (Tursiops truncatus) have been trained to match numbers and durations of human vocal bursts [] and reported to spontaneously match computer-generated whistles [], spontaneous human voice mimicry has not previously been demonstrated. The first to study white whale (Delphinapterus leucas) sounds in the wild, Schevill and Lawrence [] wrote that “occasionally the calls would suggest a crowd of children shouting in the distance”. Fish and Mowbary [] described sound types and reviewed past descriptions of sounds from this vociferous species. At Vancouver Aquarium, Canada, keepers suggested that a white whale about 15 years of age, uttered his name “Lagosi”. Other utterances were not perceptible, being described as “garbled human voice, or Russian, or similar to Chinese” by R.L. Eaton in a self-published account in 1979. However, hitherto no acoustic recordings have shown how such sounds emulate speech and deviate from the usual calls of the species. We report here sound recordings and analysis which demonstrate spontaneous mimicry of the human voice, presumably a result of vocal learning [], by a white whale.

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After seven years in our care (see the Supplemental Information ), a white whale called NOC began, spontaneously, to make unusual sounds. We interpreted the whale’s vocalizations as an attempt to mimic humans. Whale vocalizations often sounded as if two people were conversing in the distance just out of range for our understanding. These ‘conversations’ were heard several times before the whale was identified as the source. The whale lived among a group of dolphins and socialized with two female white whales. The whale was exposed to speech not only from humans at the surface — it was present at times when divers used surface-to-diver communication equipment (see Supplemental Information ). The whale was recognized as the source of the speech-like sounds when a diver surfaced outside this whale’s enclosure and asked “Who told me to get out?” Our observations led us to conclude the “out” which was repeated several times came from NOC.

4 Fish M.P.

Mowbray W.H. Production of underwater sound by the White Whale or Beluga, Delphinapterus leucas (Pallus). Figure 1 Acoustic record of human speech and whale speech-like sound. Show full caption (A) Human speech from a tape recorded voice track analyzed with Audacity (an on-line open source sound editor). (B) Whale speech-like sounds recorded with a B&K microphone in air and displayed in water-fall mode on the SD 350 digital spectrum Analyzer (Scientific Atlanta). As soon as NOC was identified as the source of these sounds, we recorded his speech-like episodes both in air and underwater ( Supplemental Information ). Recordings revealed an amplitude rhythm similar to human speech. Although there was variation, vocal bursts averaged about three per second ( Figure 1 ). The rhythm of vocal bursts also reminded us of human speech. Intervals between bursts were generally of 0.05 to 0.5 seconds. Fundamental frequencies were in the range of 200 to 300 Hz — similar to human speech and several octaves lower than the whale’s usual sounds []. Spectral characteristics with multiple harmonics were unlike usual whale sounds but not unlike those of the human voice. The greatest energy in each burst was seldom in the fundamental but usually in the second to fourth harmonic. Unlike echolocation clicks, ordinary pulse bursts, and whistle-like sounds, the production of speech-like sounds involved marked inflation of first one and then the other vestibular sac. This was readily observed on the surface of the whale’s head and may have been necessary to emphasize lower frequencies of the speech-like sounds. In usual white whale sounds, such extreme inflation of these sacs is not evident.

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Carder D.A. Nasal pressure and sound production in an echolocating white whale, Delphinapterus leucas. 6 Ridgway S.H.

Carder D.A. Nasal pressure and sound production in an echolocating white whale, Delphinapterus leucas. 7 Cranford T.W.

Amundin M.

Norris K.S. Functional morphology and homology in the odontocete nasal complex. 8 Madsen P.T.

Jensen F.H.

Carder D.

Ridgway S. Dolphin whistles: a functional misnomer revealed by heliox breathing. White whales make sounds by pressurizing the nasal cavities []. The evidence for this has come from whales and dolphins trained to accept rapid response pressure catheters ( Supplemental Information ) into the nasal cavities and sacs. With catheters in place, animals performed a task that required them to echolocate to detect a target in the environment. When targets were detected, the animal vocalized to indicate detection. During the task, nasal cavity pressure could be leaked by variable opening of the catheter. With large leaks in the nasal cavity, air rushed out through the catheter. Air pressure could not drive the phonic lips and no sound could be produced []. One set of phonic lips sits atop each nasal cavity []. Passing pressurized air from the nasal cavities through phonic lips causes vibrations in the lips resulting in sounds including echolocation clicks, pulse bursts and fast vibrations called whistles [].

6 Ridgway S.H.

Carder D.A. Nasal pressure and sound production in an echolocating white whale, Delphinapterus leucas. 7 Cranford T.W.

Amundin M.

Norris K.S. Functional morphology and homology in the odontocete nasal complex. 9 Watkins W.A. The harmonic interval: fact or artifact in spectral analysis of pulse trains. 8 Madsen P.T.

Jensen F.H.

Carder D.

Ridgway S. Dolphin whistles: a functional misnomer revealed by heliox breathing. 7 Cranford T.W.

Amundin M.

Norris K.S. Functional morphology and homology in the odontocete nasal complex. After recording several epochs of speech-like sounds, we decided to put the behavior on signal. After a trainer’s signal the whale was rewarded for making the speech-like sounds. This allowed us to study the mechanism of speech-like sound production. The whale accepted pressure catheters [] into his vestibular sacs above and into the nasal cavity below the phonic lips []. With catheters in place, the whale was signaled to ‘speak’. Pressure increases preceded each vocal episode. As each vocal burst ended pressure fell (see Supplemental Figure S1 ). Pressure increases in the nasal cavities ranged from 200 to 500 mmHg; pressure in the vestibular sacs was under 200 mmHg. Harmonic intervals indicated that the humanoid sounds resulted from modulation of a pulse rate []. Helium breathing experiments have shown that dolphin sounds are produced by pulse rate variation []. Because of the similarity of nasal and phonic lip structure between white whales and dolphins [], we conclude the same mechanism applies. Our whale mimicked human sounds by varying his nasal tract pressure and making concurrent muscular adjustments of the vibrating phonic lips while over-inflating vestibular sacs.

4 Fish M.P.

Mowbray W.H. Production of underwater sound by the White Whale or Beluga, Delphinapterus leucas (Pallus). The speech-like behavior subsided after about four years. After the whale matured, we no longer heard speech-like sounds. However, NOC remained quite vocal. He produced typical echolocation pulses with peak frequencies between 60 and 120 kHz, whistles with fundamental frequencies of 2 to 10 kHz and various pulse burst sounds previously described as “squawks, rasps, yelps or barks” [].