24
w.w.L. Au
the top portion of its head and sounds enter through the lower jaw, making
it very difficult to align both portions of the dolphin's head toward a very
close target.
Despite the many observations and reports of burst pulse sounds in the
literature, there is a paucity of quantitative description of these sounds.
Burst pulse sounds may occur as often as whistles in a wide variety of
species. The burst pulse sounds of S. frontalis are discussed by Herzing in
Chapter 5. Squawks occurred separately and continuously with echolocation in T. truncatus, either immediately before or immediately after echolocation (Herzing 1988). Whistles were commonly found overlapping
squawks or at the beginning or end of squawks. Squawks and squeals have
been observed in head-to-head and agnostic and open-mouth encounters
and in play. Buzz in threat and sex yelp in precopulatory behavior have also
been reported. High-intensity, broadband cracks or pops have also been
observed in alarm and fright behavior, in agonistic encounters, aggressive,
and head-to-head open-mouth encounters, often accompanied by head
nodding, shaking, and arching (Herzing 1988).
Nonwhistling porpoise like P. phocoena must adjust the repetition rate
of their click signals in order to produce communication or social sounds.
Amundin (1991) studied the social sounds produced by five subadult males
and one subadult female P. phocoena in a pool and described these sounds
for different behavioral contexts. He was able to identify six different calls
based on the repetition rate patterns and relate these patterns to the behavioral state of the porpoises.
Most investigators attribute the emission of clicks by sperm whales,
P. catodon to an echolocation function, however, Watkins and Schevill
(1977) have been able to detect certain patterns within click trains that
suggest that sperm whale may use clicks in a social context. The pattern of
clicks in a coda was usually about 0.5 to 1.5 s in duration and was repeated
from two to six or more times, almost exactly at variable intervals of a few
seconds or minutes. The spectra of the clicks within a coda were similar, and
successive codas had the same click repetition patterns and similar frequency emphasis. Codas may serve as unique individual identifiers since
they were easily separated by human listeners and presumably other sperm
whales could easily identify different coda patterns. According to Watkins
and Schevill (1977), codas from different whales within acoustic contact
were remarkably varied. This suggests to them that P. catodon use codas as
purposefully chosen identifications sufficiently varied from all other whales
in an area over a particular time period. The use of codas by sperm whales
is discussed in more detail by Tyack and Clark (Chapter 4).
4.4.4 Geographic Difference and Dialect
It is appropriate to begin this section with a discussion of the distinction
between geographical difference and dialect. Geographical differences are
w.w.L. Au
the top portion of its head and sounds enter through the lower jaw, making
it very difficult to align both portions of the dolphin's head toward a very
close target.
Despite the many observations and reports of burst pulse sounds in the
literature, there is a paucity of quantitative description of these sounds.
Burst pulse sounds may occur as often as whistles in a wide variety of
species. The burst pulse sounds of S. frontalis are discussed by Herzing in
Chapter 5. Squawks occurred separately and continuously with echolocation in T. truncatus, either immediately before or immediately after echolocation (Herzing 1988). Whistles were commonly found overlapping
squawks or at the beginning or end of squawks. Squawks and squeals have
been observed in head-to-head and agnostic and open-mouth encounters
and in play. Buzz in threat and sex yelp in precopulatory behavior have also
been reported. High-intensity, broadband cracks or pops have also been
observed in alarm and fright behavior, in agonistic encounters, aggressive,
and head-to-head open-mouth encounters, often accompanied by head
nodding, shaking, and arching (Herzing 1988).
Nonwhistling porpoise like P. phocoena must adjust the repetition rate
of their click signals in order to produce communication or social sounds.
Amundin (1991) studied the social sounds produced by five subadult males
and one subadult female P. phocoena in a pool and described these sounds
for different behavioral contexts. He was able to identify six different calls
based on the repetition rate patterns and relate these patterns to the behavioral state of the porpoises.
Most investigators attribute the emission of clicks by sperm whales,
P. catodon to an echolocation function, however, Watkins and Schevill
(1977) have been able to detect certain patterns within click trains that
suggest that sperm whale may use clicks in a social context. The pattern of
clicks in a coda was usually about 0.5 to 1.5 s in duration and was repeated
from two to six or more times, almost exactly at variable intervals of a few
seconds or minutes. The spectra of the clicks within a coda were similar, and
successive codas had the same click repetition patterns and similar frequency emphasis. Codas may serve as unique individual identifiers since
they were easily separated by human listeners and presumably other sperm
whales could easily identify different coda patterns. According to Watkins
and Schevill (1977), codas from different whales within acoustic contact
were remarkably varied. This suggests to them that P. catodon use codas as
purposefully chosen identifications sufficiently varied from all other whales
in an area over a particular time period. The use of codas by sperm whales
is discussed in more detail by Tyack and Clark (Chapter 4).
4.4.4 Geographic Difference and Dialect
It is appropriate to begin this section with a discussion of the distinction
between geographical difference and dialect. Geographical differences are