433
Pacific coasts of South America, bringing important information on temporal variation in the humpback whale songs to this area.
Winn and Winn (1978) suggested that because low frequencies within humpback
whale songs are attenuated less than high frequencies during propagation, higher
frequency units might be used for transmission over short ranges whereas lower
frequency units might be used for longer ranges. Mercado and Frazer (1999) add to
this notion that it also depends on the depth where whales sing, because in shallow
water environments in Hawaii, the lowest frequencies they produce do not propagate as far as the higher frequencies they produce). Mercado et al. (2003) also
pointed out that no single frequency will propagate optimally to all positions within
the water column. Thus, increasing the range of produced frequencies could increase
the number of positions within a shallow water environment from which the sound
could be detected.
Another possible argument to the high variability found in the form of humpback
whale song in the Brazilian coast (present study) could be related to the high capacity of copying in humpbacks, controlling changes over time that can abruptly be
modified (Noad et al. 2000), which suggest that individual whales select patterns
and units to include in songs based on their recent experience, or kept in use during
next seasons (Payne and Payne 1985; Cato 1991; Mercado et al. 2005). Furthermore,
Mercado et al. (2005) discuss on song copying by humpback whales as being an
open process in the spectral domain in that specific frequencies could be utilized
by each different individual, within or across years, and that species-specific constraints determine song form and regionalization. These affirmations could, in part,
explain the present results on the diversity of song structure between the two regions,
the Abrolhos Bank and the North Coast of our study area.
Sequences of alternating tonal and pulsed units in humpback whale songs also
could be possibly related to internalized ‘inhale’ and ‘exhale’ of air during sound
production (Mercado et al. 2003). Further studies involving size estimation in the
two regions of our study area could help to elucidate the matter of body size and
song diversity, comparing song production among individuals of different sizes.
Despite the high variability within and between seasons, some song components
are said to recur for over decades (Payne and Payne 1985; Mercado et al. 2003)
indicating important features that may be maintained during time to build an effective communication system.
15.4.2.1 Song Form Diversity and Function
It is still debated the complete role that songs serve for (revised in Parsons et al.
2008). The behavior that accompanies singing indicates that it probably plays a part
in courtship analogous to the role of singing in birds (Tyack 1981). Some authors say
that it is primarily for inter- and intra-sexual advertisement, informing females about
the location and reproductive fitness of singers, and informing other males about the
location of singers to produce spacing among multiple singers (reviewed by Helweg
et al. 1992; Clapham 1996), or advertising the fitness of males (Darling and Bérubé
15 The Spreading Message in a Noisy World: Song Behavior and Acoustic Ecology…
Pacific coasts of South America, bringing important information on temporal variation in the humpback whale songs to this area.
Winn and Winn (1978) suggested that because low frequencies within humpback
whale songs are attenuated less than high frequencies during propagation, higher
frequency units might be used for transmission over short ranges whereas lower
frequency units might be used for longer ranges. Mercado and Frazer (1999) add to
this notion that it also depends on the depth where whales sing, because in shallow
water environments in Hawaii, the lowest frequencies they produce do not propagate as far as the higher frequencies they produce). Mercado et al. (2003) also
pointed out that no single frequency will propagate optimally to all positions within
the water column. Thus, increasing the range of produced frequencies could increase
the number of positions within a shallow water environment from which the sound
could be detected.
Another possible argument to the high variability found in the form of humpback
whale song in the Brazilian coast (present study) could be related to the high capacity of copying in humpbacks, controlling changes over time that can abruptly be
modified (Noad et al. 2000), which suggest that individual whales select patterns
and units to include in songs based on their recent experience, or kept in use during
next seasons (Payne and Payne 1985; Cato 1991; Mercado et al. 2005). Furthermore,
Mercado et al. (2005) discuss on song copying by humpback whales as being an
open process in the spectral domain in that specific frequencies could be utilized
by each different individual, within or across years, and that species-specific constraints determine song form and regionalization. These affirmations could, in part,
explain the present results on the diversity of song structure between the two regions,
the Abrolhos Bank and the North Coast of our study area.
Sequences of alternating tonal and pulsed units in humpback whale songs also
could be possibly related to internalized ‘inhale’ and ‘exhale’ of air during sound
production (Mercado et al. 2003). Further studies involving size estimation in the
two regions of our study area could help to elucidate the matter of body size and
song diversity, comparing song production among individuals of different sizes.
Despite the high variability within and between seasons, some song components
are said to recur for over decades (Payne and Payne 1985; Mercado et al. 2003)
indicating important features that may be maintained during time to build an effective communication system.
15.4.2.1 Song Form Diversity and Function
It is still debated the complete role that songs serve for (revised in Parsons et al.
2008). The behavior that accompanies singing indicates that it probably plays a part
in courtship analogous to the role of singing in birds (Tyack 1981). Some authors say
that it is primarily for inter- and intra-sexual advertisement, informing females about
the location and reproductive fitness of singers, and informing other males about the
location of singers to produce spacing among multiple singers (reviewed by Helweg
et al. 1992; Clapham 1996), or advertising the fitness of males (Darling and Bérubé
15 The Spreading Message in a Noisy World: Song Behavior and Acoustic Ecology…