temporal features, to converge on group mates’ calls. Juvenile horseshoe
bats alter the resting frequency of CF echolocation pulses to be more
similar to their mothers’ (Table 4.2). Humpback whales match the themes
they sing to those that other whales are singing, although the nature of this
process and how heavily it relies on learned acquisition or social modification remain to be explained. In all of these cases, social modification
increases similarity and may facilitate recognition of individuals and group
mates. Bottlenose dolphins may modify whistle signatures to be either more
or less similar to certain other individuals, although who is copied is inconsistent. Decreased similarity may facilitate individual recognition, whereas
increased similarity may facilitate social cohesion. No uncontested evidence
demonstrates that primates socially modify vocalization structure, although
they may learn correct usage of vocalizations through social interactions.
Social modification appears to be more common in birds than in mammals,
although mammals have been less well-studied so this pattern may reflect
an experimental bias.
For several mammals, individual signatures are socially modified. These
individually distinctive calls function as contact calls (e.g., lesser spearnosed bats), sonar signals (e.g., moustache bats; Table 4.2), or territorial
advertisements (kangaroo rats; Table 4.2). Social modification occurs quite
frequently in group signatures for both birds and mammals (Tables 4.1 and
4.2). In addition, dialect variation in song of two bird species (Anna’s hummingbird and budgerigar) and one mammal species (humpback whale)
appears to arise, at least in part, from social modification.
5.1.3. General Principles that Can Be Derived from These Patterns
Social modification may be more widespread because it is a simpler mechanism than learned acquisition with respect to required motor, perceptual,
and neural substrates, or because social modification is less risky in an
evolutionary sense. Normal vocal development is more certain than with
learned acquisition, but enough flexibility in motor control, perceptual discrimination, and neural processing can be retained to allow vocalizations
to be fine-tuned to the social circumstances. The apparent predominance
of social modification may also result from our patterns of investigation.
Research into call learning in birds and mammals is much less welldeveloped than song learning in oscine birds, and we have yet to work out
the mechanism of call sharing and dialect variation in many cases. Demonstrating learned acquisition is more complex than demonstrating social
modification, so we may just have more known instances of the latter. More
work to elucidate mechanisms in taxa where vocal learning occurs is warranted. However, this work is not without obstacles and will require creativity in experimental design. Deafening is both unethical and likely to be
unproductive in taxa such as bats and odontocetes that rely on hearing for
navigation. Social isolation is less extreme but can produce abnormal
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J.W. Boughman and C.F. Moss
bats alter the resting frequency of CF echolocation pulses to be more
similar to their mothers’ (Table 4.2). Humpback whales match the themes
they sing to those that other whales are singing, although the nature of this
process and how heavily it relies on learned acquisition or social modification remain to be explained. In all of these cases, social modification
increases similarity and may facilitate recognition of individuals and group
mates. Bottlenose dolphins may modify whistle signatures to be either more
or less similar to certain other individuals, although who is copied is inconsistent. Decreased similarity may facilitate individual recognition, whereas
increased similarity may facilitate social cohesion. No uncontested evidence
demonstrates that primates socially modify vocalization structure, although
they may learn correct usage of vocalizations through social interactions.
Social modification appears to be more common in birds than in mammals,
although mammals have been less well-studied so this pattern may reflect
an experimental bias.
For several mammals, individual signatures are socially modified. These
individually distinctive calls function as contact calls (e.g., lesser spearnosed bats), sonar signals (e.g., moustache bats; Table 4.2), or territorial
advertisements (kangaroo rats; Table 4.2). Social modification occurs quite
frequently in group signatures for both birds and mammals (Tables 4.1 and
4.2). In addition, dialect variation in song of two bird species (Anna’s hummingbird and budgerigar) and one mammal species (humpback whale)
appears to arise, at least in part, from social modification.
5.1.3. General Principles that Can Be Derived from These Patterns
Social modification may be more widespread because it is a simpler mechanism than learned acquisition with respect to required motor, perceptual,
and neural substrates, or because social modification is less risky in an
evolutionary sense. Normal vocal development is more certain than with
learned acquisition, but enough flexibility in motor control, perceptual discrimination, and neural processing can be retained to allow vocalizations
to be fine-tuned to the social circumstances. The apparent predominance
of social modification may also result from our patterns of investigation.
Research into call learning in birds and mammals is much less welldeveloped than song learning in oscine birds, and we have yet to work out
the mechanism of call sharing and dialect variation in many cases. Demonstrating learned acquisition is more complex than demonstrating social
modification, so we may just have more known instances of the latter. More
work to elucidate mechanisms in taxa where vocal learning occurs is warranted. However, this work is not without obstacles and will require creativity in experimental design. Deafening is both unethical and likely to be
unproductive in taxa such as bats and odontocetes that rely on hearing for
navigation. Social isolation is less extreme but can produce abnormal
200
J.W. Boughman and C.F. Moss