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P.L. Tyack and c.w. Clark
3.2 Baleen Whales
About a decade after the definitive experimental demonstration of echolocation in dolphins (Norris et al. 1961), several papers appeared suggesting
that baleen whales might also produce ultrasonic clicks of use for echolocation (Beamish and Mitchell 1971, 1973). However, these should stand as
a cautionary tale about the difficulties of identifying vocalizations from
marine mammals at sea. Most sounds of marine mammals can be heard
much farther away than the animals can be seen. Many animals surface
infrequently and can be difficult to see under the best of circumstances. This
means that a researcher can be following one animal visually, but recording sounds of some other species that is not under observation. Ultrasonic
sounds have been so rarely recorded in the presence of baleen whales, that
it is now thought that these early reports of clicks from baleen whales most
likely represent sounds of odontocetes that were recorded but not seen by
the researchers. Contrary to some earlier reports(Poulter 1968), there is no
evidence that baleen whales echolocate using ultrasonic clicks. The few
experiments investigating how baleen whales avoid artificial obstacles
yielded negative results (Evans and Dreher 1962, Beamish 1978).
Most baleen whales are quite vocal however, and they tend to specialize
in low-frequency sounds, often with most energy below 1kHz. Ketten
(Chapter 2) has shown that the inner ears of baleen whales also indicate
specializations for low-frequency hearing. As was discussed above, these
low frequencies are particularly well suited for propagating over ranges
of many kilometers. Most research on the low-frequency calls of whales
emphasizes their communicative function. While these low frequencies are
not appropriate for the kind of echolocation performed by dolphins, there
are some potential targets of importance to marine mammals that could be
detected by these frequencies, targets such as the swim bladders of fish, the
lungs of marine mammals, and large targets such as the sea floor or sea
surface. As was discussed above, several authors have speculated about the
potential use of low-frequency sounds by baleen whales to explore their
environment, but there is little evidence on this topic.
Signals have been reported from baleen whales that play all of the functional roles described in Section 2.6 on conspecific communication. There
is evidence for contact calls produced by animals that are joining (e.g.,
Clark 1983 for southern right whales, Eubalaena australis) or produced as
members of a dispersed group or herd coordinate their swimming patterns
(e.g., Clark, 1991b, Wtirsig and Clark 1993 for bowhead whales, Balaena
mysticetus). Some sounds of baleen whales are thought to function as threat
displays. For example, "social sounds" are typically heard from competitive
groups of humpback whales, in which adult males are competing for access
to a female (e.g., Silber 1986). The detailed role played by social sounds
within fights is not known, but they tend to be produced more often when
a new whale joins the group. Right whales produce high-intensity, low-
P.L. Tyack and c.w. Clark
3.2 Baleen Whales
About a decade after the definitive experimental demonstration of echolocation in dolphins (Norris et al. 1961), several papers appeared suggesting
that baleen whales might also produce ultrasonic clicks of use for echolocation (Beamish and Mitchell 1971, 1973). However, these should stand as
a cautionary tale about the difficulties of identifying vocalizations from
marine mammals at sea. Most sounds of marine mammals can be heard
much farther away than the animals can be seen. Many animals surface
infrequently and can be difficult to see under the best of circumstances. This
means that a researcher can be following one animal visually, but recording sounds of some other species that is not under observation. Ultrasonic
sounds have been so rarely recorded in the presence of baleen whales, that
it is now thought that these early reports of clicks from baleen whales most
likely represent sounds of odontocetes that were recorded but not seen by
the researchers. Contrary to some earlier reports(Poulter 1968), there is no
evidence that baleen whales echolocate using ultrasonic clicks. The few
experiments investigating how baleen whales avoid artificial obstacles
yielded negative results (Evans and Dreher 1962, Beamish 1978).
Most baleen whales are quite vocal however, and they tend to specialize
in low-frequency sounds, often with most energy below 1kHz. Ketten
(Chapter 2) has shown that the inner ears of baleen whales also indicate
specializations for low-frequency hearing. As was discussed above, these
low frequencies are particularly well suited for propagating over ranges
of many kilometers. Most research on the low-frequency calls of whales
emphasizes their communicative function. While these low frequencies are
not appropriate for the kind of echolocation performed by dolphins, there
are some potential targets of importance to marine mammals that could be
detected by these frequencies, targets such as the swim bladders of fish, the
lungs of marine mammals, and large targets such as the sea floor or sea
surface. As was discussed above, several authors have speculated about the
potential use of low-frequency sounds by baleen whales to explore their
environment, but there is little evidence on this topic.
Signals have been reported from baleen whales that play all of the functional roles described in Section 2.6 on conspecific communication. There
is evidence for contact calls produced by animals that are joining (e.g.,
Clark 1983 for southern right whales, Eubalaena australis) or produced as
members of a dispersed group or herd coordinate their swimming patterns
(e.g., Clark, 1991b, Wtirsig and Clark 1993 for bowhead whales, Balaena
mysticetus). Some sounds of baleen whales are thought to function as threat
displays. For example, "social sounds" are typically heard from competitive
groups of humpback whales, in which adult males are competing for access
to a female (e.g., Silber 1986). The detailed role played by social sounds
within fights is not known, but they tend to be produced more often when
a new whale joins the group. Right whales produce high-intensity, low-