unknown. The most recent data on balaenopterid populations and behaviors come from studies conducted during seasonal episodes of feeding along
a coastal zone of upwelling (Croll et al. 1999; Gedamke et al. 1999). We will
use blue and fin whales as representative pelagic species.
11.1. Baleen Whale Songs
The term song refers to long, patterned sequences of sounds in which individual sound units are arranged in a hierarchical order (see Payne and
McVay 1971). Songs are typically produced by males during the breeding
season and are assumed to be a male reproductive display. Two coastal
species, humpbacks and bowheads, are known to sing long, patterned combinations of sounds (Payne and McVay 1971; Ljungblad et al. 1982; Würsig
and Clark 1993). These songs are composed of complex vocalizations combined into phrases that are repeated to form themes. In humpbacks, a song
lasts anywhere from 10 to 45 minutes and is composed of up to 7–8 themes,
each consisting of several phrases. The song changes annually, and there is
a great deal of intra- and inter-individual variability. In bowheads, the song
lasts on the order of a minute. It has as many as two themes, with each one
composed from a single phrase. As with humpbacks, bowhead songs change
annually, and there is a high degree of variability such that no two songs
from the same animal are ever exactly the same.
Blue and fin whales produce long, patterned sequences of sounds composed of repetitions of nearly identical 2–3 note phrases (Watkins et al.
1987; Thompson et al. 1992; Clark and Fristrup 1997; Rivers 1997; Moore et
al. 1998; Stafford et al. 1998). There is less inter–annual, intra–individual,
and inter–individual variability for blue and fin whales compared to the
coastal species, but there are measurable differences in vocal features
among populations (Thompson et al. 1992). For fin whales in the northwest
Atlantic ocean, Watkins et al. (1987) used the coincidence between the
seasonal occurrence of these sounds and breeding to suggest that these
are male reproductive displays equivalent to humpback songs. However,
the sex of the animals producing these long, patterned sequences needs to
be determined, and both species are vocally active during the summer
feeding season, which suggests that not all of this vocal activity is related
to breeding (Ljungblad et al. 1998; Croll et al. 2001). Figure 2.5 presents
spectrographic representations of songs for blue, fin, humpback, and
bowhead whales.
11.2. Baleen Whale Calls
For simplicity, we refer to sounds other than songs as calls, with the assumption that the sounds are communicative, produced by males and females,
and not restricted to the reproductive context. By far, the majority of information on whale sounds comes from work on coastal species, where
2. Physical Acoustics of Underwater Sound Communication
37
a coastal zone of upwelling (Croll et al. 1999; Gedamke et al. 1999). We will
use blue and fin whales as representative pelagic species.
11.1. Baleen Whale Songs
The term song refers to long, patterned sequences of sounds in which individual sound units are arranged in a hierarchical order (see Payne and
McVay 1971). Songs are typically produced by males during the breeding
season and are assumed to be a male reproductive display. Two coastal
species, humpbacks and bowheads, are known to sing long, patterned combinations of sounds (Payne and McVay 1971; Ljungblad et al. 1982; Würsig
and Clark 1993). These songs are composed of complex vocalizations combined into phrases that are repeated to form themes. In humpbacks, a song
lasts anywhere from 10 to 45 minutes and is composed of up to 7–8 themes,
each consisting of several phrases. The song changes annually, and there is
a great deal of intra- and inter-individual variability. In bowheads, the song
lasts on the order of a minute. It has as many as two themes, with each one
composed from a single phrase. As with humpbacks, bowhead songs change
annually, and there is a high degree of variability such that no two songs
from the same animal are ever exactly the same.
Blue and fin whales produce long, patterned sequences of sounds composed of repetitions of nearly identical 2–3 note phrases (Watkins et al.
1987; Thompson et al. 1992; Clark and Fristrup 1997; Rivers 1997; Moore et
al. 1998; Stafford et al. 1998). There is less inter–annual, intra–individual,
and inter–individual variability for blue and fin whales compared to the
coastal species, but there are measurable differences in vocal features
among populations (Thompson et al. 1992). For fin whales in the northwest
Atlantic ocean, Watkins et al. (1987) used the coincidence between the
seasonal occurrence of these sounds and breeding to suggest that these
are male reproductive displays equivalent to humpback songs. However,
the sex of the animals producing these long, patterned sequences needs to
be determined, and both species are vocally active during the summer
feeding season, which suggests that not all of this vocal activity is related
to breeding (Ljungblad et al. 1998; Croll et al. 2001). Figure 2.5 presents
spectrographic representations of songs for blue, fin, humpback, and
bowhead whales.
11.2. Baleen Whale Calls
For simplicity, we refer to sounds other than songs as calls, with the assumption that the sounds are communicative, produced by males and females,
and not restricted to the reproductive context. By far, the majority of information on whale sounds comes from work on coastal species, where
2. Physical Acoustics of Underwater Sound Communication
37