413
Songs of humpback whales are typically recorded close to a whale in order to
maximize the signal-to-noise ratio. However, when sounds are recorded at large
distances from any whale, a number of whales singing may sound as in a chorus,
although they do not sing in unison on the same portion of a song (Au et al. 2000).
The most studies bring acoustic information only by spectrograms (Fig. 15.4)
(eg. Payne and McVay 1971; Winn et al. 1981; Arraut and Velliard 2004). The evolution in the study of the humpback whale frequency range is proportional with the
advance in technology. The initial studies reported song range between up to
5–8 kHz (Payne and McVay 1971; Winn et al. 1971), and thereafter it goes up to
15–24 kHz (Helweg et al. 1992; Au et al. 2000, 2001, 2006; Fristrup et al. 2003).
Mercado et al. (2003) measured acoustic patterns in humpback whale songs
recorded in Hawaiian waters during four consecutive years (1992–1995) to determine whether subcomponents of songs differ in their detectability after long-range
propagation. Such analyses can provide important insights into the functions of
humpback whale songs.
Singing whales most often are reported to be alone (Winn and Winn 1978; Tyack
1981) although there are exceptions (Baker and Herman 1984). It is generally
accepted that singing is performed by males in tropical breeding areas, where calves
are being born and seasonal gonadal activity is high (Chittleborough 1955; Payne
and McVay 1971).
This work aims to describe humpback whale songs in a wide geographic scale in
the Brazilian breeding ground which includes the core area of Abrolhos Bank and
the adjacent North Coast, comparing song form in different marine landscapes,
adapting the Acoustic Ecology concept of Truax (1999), who define it as the study
of relations between biological organisms and their sonic environment, or
soundscape.
15.2 Material and Methods
15.2.1 Study Area
This study was conducted from 2005 to 2010, at the Northeastern Brazilian coast
during the breeding season (July to October) of the Southwestern Atlantic Ocean
humpback whale population, known as Breeding Stock A (BSA) by the International
Whaling Commission (IWC 1998). Humpback whale songs were recorded along
the study area, grouped in two main regions: Abrolhos Bank (16–19° S, 37–39° W)
and North Coast (11–14° S, 37–38° W) (Fig. 15.5).
The Abrolhos Bank is very known as the oceanographic environment with the
broadest extension of the Brazilian continental shelf, providing shallow and warm
waters, and when the largest coral reef aggregation of the entire Southwestern
Atlantic Ocean is located (Ekau and Knoppers 1999), making this place a hotspot
for marine conservation and a reference for the humpback whale research as the
core area for the species distribution along the Brazilian coast (Andriolo et al. 2006;
Wedekin et al. 2010).
15 The Spreading Message in a Noisy World: Song Behavior and Acoustic Ecology…
Songs of humpback whales are typically recorded close to a whale in order to
maximize the signal-to-noise ratio. However, when sounds are recorded at large
distances from any whale, a number of whales singing may sound as in a chorus,
although they do not sing in unison on the same portion of a song (Au et al. 2000).
The most studies bring acoustic information only by spectrograms (Fig. 15.4)
(eg. Payne and McVay 1971; Winn et al. 1981; Arraut and Velliard 2004). The evolution in the study of the humpback whale frequency range is proportional with the
advance in technology. The initial studies reported song range between up to
5–8 kHz (Payne and McVay 1971; Winn et al. 1971), and thereafter it goes up to
15–24 kHz (Helweg et al. 1992; Au et al. 2000, 2001, 2006; Fristrup et al. 2003).
Mercado et al. (2003) measured acoustic patterns in humpback whale songs
recorded in Hawaiian waters during four consecutive years (1992–1995) to determine whether subcomponents of songs differ in their detectability after long-range
propagation. Such analyses can provide important insights into the functions of
humpback whale songs.
Singing whales most often are reported to be alone (Winn and Winn 1978; Tyack
1981) although there are exceptions (Baker and Herman 1984). It is generally
accepted that singing is performed by males in tropical breeding areas, where calves
are being born and seasonal gonadal activity is high (Chittleborough 1955; Payne
and McVay 1971).
This work aims to describe humpback whale songs in a wide geographic scale in
the Brazilian breeding ground which includes the core area of Abrolhos Bank and
the adjacent North Coast, comparing song form in different marine landscapes,
adapting the Acoustic Ecology concept of Truax (1999), who define it as the study
of relations between biological organisms and their sonic environment, or
soundscape.
15.2 Material and Methods
15.2.1 Study Area
This study was conducted from 2005 to 2010, at the Northeastern Brazilian coast
during the breeding season (July to October) of the Southwestern Atlantic Ocean
humpback whale population, known as Breeding Stock A (BSA) by the International
Whaling Commission (IWC 1998). Humpback whale songs were recorded along
the study area, grouped in two main regions: Abrolhos Bank (16–19° S, 37–39° W)
and North Coast (11–14° S, 37–38° W) (Fig. 15.5).
The Abrolhos Bank is very known as the oceanographic environment with the
broadest extension of the Brazilian continental shelf, providing shallow and warm
waters, and when the largest coral reef aggregation of the entire Southwestern
Atlantic Ocean is located (Ekau and Knoppers 1999), making this place a hotspot
for marine conservation and a reference for the humpback whale research as the
core area for the species distribution along the Brazilian coast (Andriolo et al. 2006;
Wedekin et al. 2010).
15 The Spreading Message in a Noisy World: Song Behavior and Acoustic Ecology…