6. Summary
We have reviewed data on call learning in birds and mammals for calls that
function as individual or group signatures and dialects and focused on call
learning rather than song learning. We distinguished two forms of vocal
learning—learned acquisition and social modification. We began by predicting when vocal learning was expected and detailing the evidence
necessary to demonstrate that vocalizations were learned. Studies should
exclude or control factors that can produce patterns similar to those induced by learning, including maturation, body size, genetics, population
structure, and local ecology. We then presented case studies for three functional levels: (1) individual signatures: lesser spear-nosed bats, bottlenose
dolphins, and Japanese and rhesus macaques; (2) group signatures: chickadees, budgerigars, greater spear-nosed bats, killer whales, and pygmy
marmosets; and (3) dialects: Amazon parrots, hummingbirds, humpback
whales, and tamarins.
Learned acquisition of calls is rare in mammals although fairly common
in birds. Social modification is more common in both mammals and birds.
Social modification of group signatures is particularly prevalent. Too little
data are available to carefully test the validity of song-learning theories for
call learning. This area should receive further attention to evaluate the
necessity of sensorimotor input, the existence and duration of critical
periods, and the possibility of selective attrition. Social interaction is clearly
necessary for most species. The study of call learning in mammals and birds
has much promise. Not only can it provide critical insight into the neural,
perceptual, and motor mechanisms that underlie vocal learning across taxa,
but also into the ecological and behavioral factors that favor its evolution.
These questions will benefit from putting vocal-learning studies squarely
in a phylogenetic framework. Vocal learning also has potential to give
us insight into cultural evolution and help us understand how the dual
processes of genetic and cultural change influence biological evolution and
diversity.
Acknowledgments. We thank Kari and Kisi Bohn for help in preparing the
figures. Thanks also to Kisi Bohn and the editors, A. Megela-Simmons and
R. Fay, for valuable comments on an earlier version of this chapter. This
work was supported by NSF and NIH grants to CFM. JWB was supported
by an NIH training grant in The Comparative and Evolutionary Biology of
Hearing, an NSF–NATO postdoctoral fellowship, and an NSF International
Research Fellowship.
References
Andrew RJ (1962) Evolution of intelligence and vocal mimicking. Science 137:
585–589.
4. Comparative Vocal Learning
209
We have reviewed data on call learning in birds and mammals for calls that
function as individual or group signatures and dialects and focused on call
learning rather than song learning. We distinguished two forms of vocal
learning—learned acquisition and social modification. We began by predicting when vocal learning was expected and detailing the evidence
necessary to demonstrate that vocalizations were learned. Studies should
exclude or control factors that can produce patterns similar to those induced by learning, including maturation, body size, genetics, population
structure, and local ecology. We then presented case studies for three functional levels: (1) individual signatures: lesser spear-nosed bats, bottlenose
dolphins, and Japanese and rhesus macaques; (2) group signatures: chickadees, budgerigars, greater spear-nosed bats, killer whales, and pygmy
marmosets; and (3) dialects: Amazon parrots, hummingbirds, humpback
whales, and tamarins.
Learned acquisition of calls is rare in mammals although fairly common
in birds. Social modification is more common in both mammals and birds.
Social modification of group signatures is particularly prevalent. Too little
data are available to carefully test the validity of song-learning theories for
call learning. This area should receive further attention to evaluate the
necessity of sensorimotor input, the existence and duration of critical
periods, and the possibility of selective attrition. Social interaction is clearly
necessary for most species. The study of call learning in mammals and birds
has much promise. Not only can it provide critical insight into the neural,
perceptual, and motor mechanisms that underlie vocal learning across taxa,
but also into the ecological and behavioral factors that favor its evolution.
These questions will benefit from putting vocal-learning studies squarely
in a phylogenetic framework. Vocal learning also has potential to give
us insight into cultural evolution and help us understand how the dual
processes of genetic and cultural change influence biological evolution and
diversity.
Acknowledgments. We thank Kari and Kisi Bohn for help in preparing the
figures. Thanks also to Kisi Bohn and the editors, A. Megela-Simmons and
R. Fay, for valuable comments on an earlier version of this chapter. This
work was supported by NSF and NIH grants to CFM. JWB was supported
by an NIH training grant in The Comparative and Evolutionary Biology of
Hearing, an NSF–NATO postdoctoral fellowship, and an NSF International
Research Fellowship.
References
Andrew RJ (1962) Evolution of intelligence and vocal mimicking. Science 137:
585–589.
4. Comparative Vocal Learning
209