Observation and analysis of sonar signal generation in the bottlenose dolphin (Tursiops truncatus): Evidence for two sonar sources

Vocal performance affects metabolic rate in dolphins: implications for animals communicating in noisy environments

“…Comparisons of costs between smaller terrestrial endotherms and larger marine dolphins are also complicated by other differences including sound production anatomy. For example, the nasal complex structures involved in sound production in dolphins appear to be orders of magnitude greater in mass than the vibrating membranes of the larynx of similar-sized mammals (Cranford et al, 2011). Teasing out the individual processes involved in sound production to relate to energetic cost, such as powering the lungs to produce sound, activating the sound-producing muscles and adjusting the vocal tract, is complex and better understood in some terrestrial taxa than in dolphins (Titze and Riede, 2010).…”

“…Although Green et al (1980) present sectional data of the bottlenose dolphin nasal region, many of the photographs are not sufficient in detail to accurately determine the volume of these sound-producing muscles to estimate mass [specifically, the palatopharyngeal muscle is cut off ventrally in multiple sections and two sections in the series (17 and 18), which include the nasal plug muscle, are not shown in Green et al (1980)]. Other muscles are likely involved as well but their activity during sound generation has not been measured Ridgway et al, 1980;Cranford et al, 2011). Therefore, with the currently available data, we cannot determine whether the same relationship reported by Ophir et al (2010) holds true in dolphins.…”

“…2F). Higher energy vocalizations from increased vocal effort likely necessitate higher energy requirements in muscles that actuate the sound-producing organs (Cranford et al, 2011), thereby resulting in higher metabolic costs. Although dolphin B produced squawks, we assume that the results are applicable to whistling dolphins as well, given that the two sound types are likely produced by the same sound-production mechanisms and the lack of a significant result in the whistle data is attributed to a restricted range of vocal performance of dolphin A.…”

“…Vocal responses to noise are well documented in many whale and dolphin species, including increases in whistle repetition rate in bottlenose dolphins during boat approaches (Tursiops truncatus; Buckstaff, 2004) and increases in call amplitude as noise levels increase in endangered killer whales (Orcinus orca; Holt et al, 2009) and North Atlantic right whales (Eubalaena glacialis; Parks et al, 2011). While mammalian sound production is most often accomplished by the larynx, odontocetes (toothed whales and dolphins) produce sound in the nasal complex (Cranford et al, 2011). They also face physiological challenges related to the aquatic lifestyle including a limited oxygen supply while diving.…”

Comparative anatomical study of sound production and reception systems in the common dolphin (Delphinus delphis) and the harbour porpoise (Phocoena phocoena) heads

“…Anatomy of echolocation organs was extensively studied (e.g. Amundin, 1991;Cranford, 2000;Cranford, Amundin, & Norris, 1996;Cranford et al, 2011;McKenna, Cranford, & Pyenson, 2011;Norris, 1964). According to Cranford et al (1996), soundwaves are originated from the nasal respiratory system which the Monkeys Lips/Dorsal Bursae (MLDB) complex is part.…”