each of these two calls were not congruent with dendrograms for association. The pattern does not seem to be particularly strong for repertoire
variation either because Bigg et al. (1990) found no significant relationship
between association patterns and repertoire variation. Thus, the call-sharing
hypothesis is not strongly supported, but neither is it refuted. More data are
needed. In any case, congruence between association and call repertoire
or structure is insufficient to prove vocal learning because association can
allow for both genetic and cultural exchange.
Even though the pattern of shared calls within pods (Ford and Fisher
1983; Ford 1989, 1991; Strager 1995) and the stable social structure are consistent with a learning hypothesis, high levels of relatedness within pods also
argue for a strong genetic component. A significant correlation was found
between acoustic similarity and genetic distance (Barrett-Lennard unpublished). We cannot yet determine whether this pattern results from cultural
or genetic inheritance or a combination of the two modes. Genetically
encoded calls would serve their presumed function quite well, indicating
kinship and social affiliation simultaneously. Several authors presume that
insufficient genetic variation exists to produce complex call repertoires
and thus argue that pod-specific calls are unlikely to have a genetic basis.
In marked contrast to this view, studies cited earlier (Jones and Ransome
1993; Scherrer and Wilkinson 1993) have shown that calls with heritable
acoustic components can effectively serve as signatures, especially when the
relevant information is kinship. Determining the contributions of learning
and genetics to the pattern of pod-specific calls in O. orca requires experimental tests and additional genetic data. Analysis of both nuclear DNA and
mtDNA is ongoing (Barrett-Lennard unpublished), and the results can be
correlated with information on the degree of distinctiveness and overlap
of calls to determine how well genetic similarity predicts call similarity for
individuals and the potential role for learning. A critical test of vocal learning must control for relatedness.
3.2.3. Primates—Pygmy Marmoset Contact Calls
Pygmy marmosets (Cebuella pygmaea) are small primates that live in family
groups composed of a breeding pair, their offspring, and an occasional unrelated adult (Soini 1993). Offspring care is communal (Kinzey 1997a),
and this cooperative care may improve offspring survival although it is not
essential (Rothe et al. 1993). Cebuella inhabit mature forests in the upper
Amazon region that are seasonally flooded (Soini 1993), and they feed
heavily on gum and insects. Groups defend small, exclusive territories
centered around a primary feeding tree, but change their home ranges in
response to food abundance (Soini 1993).
Pygmy marmosets give two types of trilled contact calls, termed the
closed mouth trill (Fig. 4.8A) and the J-call. Closed mouth trills are used
when animals are in close range or within visual contact, whereas J-calls are
given when animals are some distance apart or unable to see one another.
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J.W. Boughman and C.F. Moss
variation either because Bigg et al. (1990) found no significant relationship
between association patterns and repertoire variation. Thus, the call-sharing
hypothesis is not strongly supported, but neither is it refuted. More data are
needed. In any case, congruence between association and call repertoire
or structure is insufficient to prove vocal learning because association can
allow for both genetic and cultural exchange.
Even though the pattern of shared calls within pods (Ford and Fisher
1983; Ford 1989, 1991; Strager 1995) and the stable social structure are consistent with a learning hypothesis, high levels of relatedness within pods also
argue for a strong genetic component. A significant correlation was found
between acoustic similarity and genetic distance (Barrett-Lennard unpublished). We cannot yet determine whether this pattern results from cultural
or genetic inheritance or a combination of the two modes. Genetically
encoded calls would serve their presumed function quite well, indicating
kinship and social affiliation simultaneously. Several authors presume that
insufficient genetic variation exists to produce complex call repertoires
and thus argue that pod-specific calls are unlikely to have a genetic basis.
In marked contrast to this view, studies cited earlier (Jones and Ransome
1993; Scherrer and Wilkinson 1993) have shown that calls with heritable
acoustic components can effectively serve as signatures, especially when the
relevant information is kinship. Determining the contributions of learning
and genetics to the pattern of pod-specific calls in O. orca requires experimental tests and additional genetic data. Analysis of both nuclear DNA and
mtDNA is ongoing (Barrett-Lennard unpublished), and the results can be
correlated with information on the degree of distinctiveness and overlap
of calls to determine how well genetic similarity predicts call similarity for
individuals and the potential role for learning. A critical test of vocal learning must control for relatedness.
3.2.3. Primates—Pygmy Marmoset Contact Calls
Pygmy marmosets (Cebuella pygmaea) are small primates that live in family
groups composed of a breeding pair, their offspring, and an occasional unrelated adult (Soini 1993). Offspring care is communal (Kinzey 1997a),
and this cooperative care may improve offspring survival although it is not
essential (Rothe et al. 1993). Cebuella inhabit mature forests in the upper
Amazon region that are seasonally flooded (Soini 1993), and they feed
heavily on gum and insects. Groups defend small, exclusive territories
centered around a primary feeding tree, but change their home ranges in
response to food abundance (Soini 1993).
Pygmy marmosets give two types of trilled contact calls, termed the
closed mouth trill (Fig. 4.8A) and the J-call. Closed mouth trills are used
when animals are in close range or within visual contact, whereas J-calls are
given when animals are some distance apart or unable to see one another.
180
J.W. Boughman and C.F. Moss