4. Acoustic Communication in Whales and Dolphins
191
regular clicks. Sperm whales dive at rates of 1 to 4m/s (Watkins et al. 1993).
They have enormous momentum because they weigh up to 30 to 40 metric
tons. It would take a diving whale some time to slow its descent. A depthsounding sonar would be of obvious utility for early warning of the
approaching sea floor for an animal that takes some time to slow its dive.
Resolution of how sperm whales use slow clicks and whether they actually
respond to bottom echoes will have to rely upon future research.
Sperm whales spend most of their time diving, but often in the late afternoon they spend a few hours at the surface, resting and socializing (Whitehead and Weilgart 1991). Especially when they are socializing, sperm whales
also produce distinctive rhythmic patterns of clicks, called codas, often
in exchanges between individual whales (Watkins and Schevill 1977). All
of the papers on sperm whale codas suggest a communicative function,
and most suggest a role as a recognition signal. The limited data currently
available on codas suggest a variety of potential recognition functions,
including individual, group, and regional identification. While Watkins
and Schevill (1977) described codas as individually distinctive, they also
described an exchange in which each whale matched the coda of the
other whale. Moore et al. (1993) described two shared coda patterns that
comprised more than 50% of the codas from many individual whales
within many different groups recorded over a large part of the southeast
Caribbean. Weilgart and Whitehead (1993) described different shared coda
patterns for sperm whales off the Galapagos, and Weilgart and Whitehead
(1997) described geographical variation in the proportional usage of different codas. More work is needed to track coda usage of individual sperm
whales, within groups, and over large areas, but the current evidence suggests possible variety in usage for individual, group, and regional identification that is consistent with the variety of recognition problems posed by
sperm whale societies.
Sperm whales also produce fast series of clicks, called creaks. Creaks last
about a second, with click repetition rates of about 20 clicks per second.
Some authors have suggested that these creaks may be used in echolocation for prey and may be analogous to the terminal buzz produced by a bat
after it has detected a moth and is closing in to capture it. Such an analogy
has also been made for another marine mammal, the narwhal, M. monoceros, by Miller et al. (1995). When sperm whales are diving and presumably
foraging, they do occasionally interrupt their regular clicks with creaks
(Gordon 1987). This pattern is consistent with the interpretation that
creaks may represent use of echolocation during a prey capture. However,
Whitehead and Weilgart (1991) found that creaks were more likely to occur
when sperm whales were socializing at the surface than when they were
foraging at depth, and creaks tended more often to be associated with
codas than with regular clicks. This suggests that at least some fast series
of clicks are social signals like codas, and might even best be thought of as
representing a type of coda.
191
regular clicks. Sperm whales dive at rates of 1 to 4m/s (Watkins et al. 1993).
They have enormous momentum because they weigh up to 30 to 40 metric
tons. It would take a diving whale some time to slow its descent. A depthsounding sonar would be of obvious utility for early warning of the
approaching sea floor for an animal that takes some time to slow its dive.
Resolution of how sperm whales use slow clicks and whether they actually
respond to bottom echoes will have to rely upon future research.
Sperm whales spend most of their time diving, but often in the late afternoon they spend a few hours at the surface, resting and socializing (Whitehead and Weilgart 1991). Especially when they are socializing, sperm whales
also produce distinctive rhythmic patterns of clicks, called codas, often
in exchanges between individual whales (Watkins and Schevill 1977). All
of the papers on sperm whale codas suggest a communicative function,
and most suggest a role as a recognition signal. The limited data currently
available on codas suggest a variety of potential recognition functions,
including individual, group, and regional identification. While Watkins
and Schevill (1977) described codas as individually distinctive, they also
described an exchange in which each whale matched the coda of the
other whale. Moore et al. (1993) described two shared coda patterns that
comprised more than 50% of the codas from many individual whales
within many different groups recorded over a large part of the southeast
Caribbean. Weilgart and Whitehead (1993) described different shared coda
patterns for sperm whales off the Galapagos, and Weilgart and Whitehead
(1997) described geographical variation in the proportional usage of different codas. More work is needed to track coda usage of individual sperm
whales, within groups, and over large areas, but the current evidence suggests possible variety in usage for individual, group, and regional identification that is consistent with the variety of recognition problems posed by
sperm whale societies.
Sperm whales also produce fast series of clicks, called creaks. Creaks last
about a second, with click repetition rates of about 20 clicks per second.
Some authors have suggested that these creaks may be used in echolocation for prey and may be analogous to the terminal buzz produced by a bat
after it has detected a moth and is closing in to capture it. Such an analogy
has also been made for another marine mammal, the narwhal, M. monoceros, by Miller et al. (1995). When sperm whales are diving and presumably
foraging, they do occasionally interrupt their regular clicks with creaks
(Gordon 1987). This pattern is consistent with the interpretation that
creaks may represent use of echolocation during a prey capture. However,
Whitehead and Weilgart (1991) found that creaks were more likely to occur
when sperm whales were socializing at the surface than when they were
foraging at depth, and creaks tended more often to be associated with
codas than with regular clicks. This suggests that at least some fast series
of clicks are social signals like codas, and might even best be thought of as
representing a type of coda.