Bottlenose Dolphins

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Bottlenose dolphins produce a extensive variety sounds that are divided into two categories: pulsed emissions, i.e. echolocation clicks and burst-pulsed sounds; and non-pulsed signals, i.e. whistles (Caldwell et al., 1990; Janik, 2013) (Figure 1:2).

Clicks are high-frequency and directional sounds that are used to detect, discriminate and recognize objects in the environment, including potential preys (Caldwell et al., 1990; Janik, 2013). These clicks are used to locate/discriminate an object based on the returning echo, and the system is known as echolocation or biosonar (Griffin, 1958). Bottlenose dolphins produce high-frequency broadband clicks with dominant frequencies generally higher than 50-60kHz (Au, 1993).
Burst-pulse sounds are
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These sounds usually vary from 4 to 15 kHz and may have a social function, such as individual identification (Caldwell et al., 1990; Janik, 2013). Often last less than one second, and can go from one to multiple loop repetition (Figure 1:3), having highly variable frequency modulation contour shapes, from concave to convex, upsweep to downsweep, and with intermediary forms between categories (Bazúa-Durán & Au 2002; Dudzinski et al., 2009). Whistles have different features that can vary depending on the context. For example, in isolation it has been reported that dolphins tend to modify whistle time-frequency parameters, number of loops and emission rate compared with normal situations (Caldwell et al. 1990; Weary and Fraser 1995; Watts and Stookey 2001; Barton, 2006; Esch et al., 2009a; Esch et al.,…show more content…
(1990), signature whistles are stereotyped and individually distinctive whistles, recognizable by the frequency modulation pattern of the contour (Janik et al. 2006), and may be the most commonly whistle type produced by an animal in isolation (Caldwell et al., 1990).
David and Melba Caldwell were the first investigators postulating that signature whistles may represent a unique vocalization, different for each dolphin. These stereotyped whistles seem to be stable for a long time (Sayigh et al. 1990, 2007; Bruck, 2013; Luís et al., 2015), suggesting that these signals may be involved in individual identification (Caldwell & Caldwell, 1965; Tyack 1986; Caldwell et al., 1990; Sayigh et al., 1990; dos Santos et al., 2005).
In isolation, signature whistles may represent 80% to 100% of whistles’ emissions (Caldwell & Caldwell, 1965; Caldwell et al., 1990; Janik & Slater, 1998; Sayigh et al. 2007; Janik et al., 2013).
Signature whistles are probably developed through vocal learning during the first year of a dolphin’s life, and may remain stable throughout an individual’s lifetime (Caldwell & Caldwell, 1979; Caldwell et al. 1990; Sayigh et al. 1990; Janik & Sayigh,
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