335
13.1.5 S. guianensis Acoustic Repertoire
Odontocetes developed a sophisticated biosonar system that provides accurate
information even in dark environments, in which case it would not be possible for a
normal vision system, because their emitted signals penetrate and pass through
objects causing reflections, which are received by them again and so the information
is processed and interpreted by the central nervous system (Ary et al. 2016).
As other species of dolphins, S. guianensis presents an acoustic repertoire, usually divided into three categories (Richardson et al. 1995): whistles and two types of
pulsed sounds (a variety of calls which may contain gargle) and the clicks for echolocation (Norris et al. 1994; Monteiro-Filho and Monteiro 2001; Rossi-Santos et al.
2008).
The whistles have been reported in several studies around the Brazilian coast,
being basically pure tones and can have some harmonics and frequency values ranging from 1.05 kHz (Deconto and Monteiro-Filho 2016) with records up to 66.7 kHz
(Andrade et al. 2015) (Fig. 13.11a, b) has already been registered harmonics with
frequencies up to 136 kHz (May-Collado and Wartzok 2009).
Some studies indicate that the behavior of animals and social group size can
interfere in the parameters of whistles (Erber and Simão 2004) and are often associated with social behavior, to maintain vocal or physical contact between the dolphins (Tyack 2008; Andrade et al. 2015), allowing group cohesion and individual
recognition (Monteiro-Filho and Monteiro 2001; Figueiredo and Simon 2009) and
is therefore considered a social vocalization (Caldwell and Caldwell 1968; Sayigh
et al. 1990; Smolker et al. 1993).
Pulsed calls, presents a wide variation in the frequency parameters, duration and
intensity, always occurring with harmonics (Fig. 13.11c, d). The frequency parameters of these sounds have been described between 0.7 kHz and 5 kHz, with duration
varying between 0.02 and 0.9 s. As the whistles, pulsed calls are associated with
social communication, but usually in groups’ vocalizations (Monteiro-Filho and
Monteiro 2001).
Another sound already registered, ‘gargles’ are similar to pulsed calls and therefore classified by some authors in the same category (Fig. 13.11e) (Monteiro-Filho
et al. 2008; Garcia 2009). Gargles are characterized by a long, low frequency notes,
about 0.3 kHz, containing 2 harmonics and average duration of 3 s, reaching 20 s
(Monteiro-Filho and Monteiro 2001). Gargles were described only in Cananéia
estuary (Monteiro-Filho and Monteiro 2001) and in Caravelas estuary (Garcia
2009). These sounds were associated with groups containing calves and interacting
in shallower waters as estuarine areas.
Clicks are basically related with navigation and prey detection, vocalization and
echolocation (eg Kellogg et al. 1953; Kellogg 1958; Pilleri 1990). They are characterized by a sequence of pulsed sounds with registered frequency range ranging
from 0.1 kHz to 43.62 kHz (Deconto and Monteiro-Filho 2016) (Fig. 13.11f) having
been described with the highest occurrence in foraging activity (Monteiro-Filho and
Monteiro 2001).
13 Anthropogenic Noise and Guiana Dolphins (Sotalia guianensis) in Brazil…
13.1.5 S. guianensis Acoustic Repertoire
Odontocetes developed a sophisticated biosonar system that provides accurate
information even in dark environments, in which case it would not be possible for a
normal vision system, because their emitted signals penetrate and pass through
objects causing reflections, which are received by them again and so the information
is processed and interpreted by the central nervous system (Ary et al. 2016).
As other species of dolphins, S. guianensis presents an acoustic repertoire, usually divided into three categories (Richardson et al. 1995): whistles and two types of
pulsed sounds (a variety of calls which may contain gargle) and the clicks for echolocation (Norris et al. 1994; Monteiro-Filho and Monteiro 2001; Rossi-Santos et al.
2008).
The whistles have been reported in several studies around the Brazilian coast,
being basically pure tones and can have some harmonics and frequency values ranging from 1.05 kHz (Deconto and Monteiro-Filho 2016) with records up to 66.7 kHz
(Andrade et al. 2015) (Fig. 13.11a, b) has already been registered harmonics with
frequencies up to 136 kHz (May-Collado and Wartzok 2009).
Some studies indicate that the behavior of animals and social group size can
interfere in the parameters of whistles (Erber and Simão 2004) and are often associated with social behavior, to maintain vocal or physical contact between the dolphins (Tyack 2008; Andrade et al. 2015), allowing group cohesion and individual
recognition (Monteiro-Filho and Monteiro 2001; Figueiredo and Simon 2009) and
is therefore considered a social vocalization (Caldwell and Caldwell 1968; Sayigh
et al. 1990; Smolker et al. 1993).
Pulsed calls, presents a wide variation in the frequency parameters, duration and
intensity, always occurring with harmonics (Fig. 13.11c, d). The frequency parameters of these sounds have been described between 0.7 kHz and 5 kHz, with duration
varying between 0.02 and 0.9 s. As the whistles, pulsed calls are associated with
social communication, but usually in groups’ vocalizations (Monteiro-Filho and
Monteiro 2001).
Another sound already registered, ‘gargles’ are similar to pulsed calls and therefore classified by some authors in the same category (Fig. 13.11e) (Monteiro-Filho
et al. 2008; Garcia 2009). Gargles are characterized by a long, low frequency notes,
about 0.3 kHz, containing 2 harmonics and average duration of 3 s, reaching 20 s
(Monteiro-Filho and Monteiro 2001). Gargles were described only in Cananéia
estuary (Monteiro-Filho and Monteiro 2001) and in Caravelas estuary (Garcia
2009). These sounds were associated with groups containing calves and interacting
in shallower waters as estuarine areas.
Clicks are basically related with navigation and prey detection, vocalization and
echolocation (eg Kellogg et al. 1953; Kellogg 1958; Pilleri 1990). They are characterized by a sequence of pulsed sounds with registered frequency range ranging
from 0.1 kHz to 43.62 kHz (Deconto and Monteiro-Filho 2016) (Fig. 13.11f) having
been described with the highest occurrence in foraging activity (Monteiro-Filho and
Monteiro 2001).
13 Anthropogenic Noise and Guiana Dolphins (Sotalia guianensis) in Brazil…