contour; therefore, the processes that influenced contour development had
clearly taken place before the end of the first year and the start of their
study, which agrees with McCowan and Reiss (1995b). Sayigh et al. (1990)
hypothesized that because females may continue to associate with their
mothers for many years, distinctive signature whistles may facilitate accurate individual identification. Males disperse and thus may not face the
same constraints; rather, they suggested that similar whistles may facilitate
kin recognition. For this latter interpretation to be plausible, all males
should have imitated their mothers, and this was not the case (Sayigh et al.
1990, 1995). The occurrence of shared whistles in captive repertoires further
complicates interpreting the results of these two studies. It seems quite
likely that both females and males shared some whistles with mothers and
produced others that were individually distinctive. Individuals need to be
recorded in a large number of sessions, preferably in multiple contexts,
before one can be sure that the entire repertoire is cataloged.
Data on sharing of whistles among social companions are somewhat
conflicting. Most studies suggest that infants only occasionally copy their
mother, who is their primary social partner during the first few years of life
(Sayigh et al. 1990, 1995; Reiss and McCowan 1993; McCowan and Reiss
1995b). Yet other studies show sharing of whistles among other types of
companions (Connor and Smolker 1995; McCowan et al. 1998) and even
apparent imitation of a trainer’s whistle (Tyack 1997). Currently, it is
unclear who serves as the primary tutor and why.
Three males in a coalition increased the similarity of their whistles as the
tenure of their coalition lengthened (Fig. 4.2; Smolker 1993; Smolker and
Pepper 1999). Given the information on the potential size of repertoires
and the extent of shared calls, it is unclear whether males socially modified
existing whistles to increase similarity, acquired novel whistle types, or
increased their use of a particular whistle already in their repertoire.
Because of the possibility that convergence results from changing use rather
than the generation of novel whistles, Smolker and Pepper (1999) did not
demonstrate vocal learning in the sense outlined by Janik and Slater (1997)
(e.g., acquisition of novel calls or modulation of call frequency characteristics). However, it seems quite likely that the whistle type these males
used depended on their social affiliation, which meets the criterion for
vocal learning that we use. The contribution of by-product distinctiveness
to variation among individuals in these shared whistles should be studied.
Dolphins have been trained operantly to match a whistle of a particular
contour presented as a stimulus (Richards et al. 1984; Reiss and McCowan
1993). This requires vocal flexibility and auditory–vocal feedback to achieve
matching. Such work demonstrates remarkable intrinsic cognitive and vocal
abilities, but does not tell us much about the context, function, or extent of
vocal flexibility in nature.
The work on dialects in dolphins has produced conflicting results. One
study found evidence of geographic variation at both the microgeographic
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J.W. Boughman and C.F. Moss
clearly taken place before the end of the first year and the start of their
study, which agrees with McCowan and Reiss (1995b). Sayigh et al. (1990)
hypothesized that because females may continue to associate with their
mothers for many years, distinctive signature whistles may facilitate accurate individual identification. Males disperse and thus may not face the
same constraints; rather, they suggested that similar whistles may facilitate
kin recognition. For this latter interpretation to be plausible, all males
should have imitated their mothers, and this was not the case (Sayigh et al.
1990, 1995). The occurrence of shared whistles in captive repertoires further
complicates interpreting the results of these two studies. It seems quite
likely that both females and males shared some whistles with mothers and
produced others that were individually distinctive. Individuals need to be
recorded in a large number of sessions, preferably in multiple contexts,
before one can be sure that the entire repertoire is cataloged.
Data on sharing of whistles among social companions are somewhat
conflicting. Most studies suggest that infants only occasionally copy their
mother, who is their primary social partner during the first few years of life
(Sayigh et al. 1990, 1995; Reiss and McCowan 1993; McCowan and Reiss
1995b). Yet other studies show sharing of whistles among other types of
companions (Connor and Smolker 1995; McCowan et al. 1998) and even
apparent imitation of a trainer’s whistle (Tyack 1997). Currently, it is
unclear who serves as the primary tutor and why.
Three males in a coalition increased the similarity of their whistles as the
tenure of their coalition lengthened (Fig. 4.2; Smolker 1993; Smolker and
Pepper 1999). Given the information on the potential size of repertoires
and the extent of shared calls, it is unclear whether males socially modified
existing whistles to increase similarity, acquired novel whistle types, or
increased their use of a particular whistle already in their repertoire.
Because of the possibility that convergence results from changing use rather
than the generation of novel whistles, Smolker and Pepper (1999) did not
demonstrate vocal learning in the sense outlined by Janik and Slater (1997)
(e.g., acquisition of novel calls or modulation of call frequency characteristics). However, it seems quite likely that the whistle type these males
used depended on their social affiliation, which meets the criterion for
vocal learning that we use. The contribution of by-product distinctiveness
to variation among individuals in these shared whistles should be studied.
Dolphins have been trained operantly to match a whistle of a particular
contour presented as a stimulus (Richards et al. 1984; Reiss and McCowan
1993). This requires vocal flexibility and auditory–vocal feedback to achieve
matching. Such work demonstrates remarkable intrinsic cognitive and vocal
abilities, but does not tell us much about the context, function, or extent of
vocal flexibility in nature.
The work on dialects in dolphins has produced conflicting results. One
study found evidence of geographic variation at both the microgeographic
162
J.W. Boughman and C.F. Moss