Linda I. HollÃn, Tim Clutton-Brock, Marta B. Manser (2008): Ontogenetic
changes in alarm-call production and usage in meerkats ( Suricata
suricatta ): adaptations or constraints? Behav. Ecol. Sociobiol. 62(5),
821-829.
Abstract: In many species, individuals suffer major mortality in their
first year because of predation. Behaviours that facilitate successful
escape are therefore under strong selection, but anti-predator skills
often emerge gradually during an individualâs early development. Using
long-term data and acoustic recordings of alarm calls collected during
natural predator encounters, we aimed to elucidate two largely unsolved
issues in anti-predator ontogeny: (1) whether incorrect predator
assignment is adaptively age-appropriate, given that vulnerability often
changes during development, or whether age-related differences reflect
true mistakes made by immature individuals; and (2) the extent to which
the development of adult-like competence in alarm-call production and
usage is simply a function of maturational processes or dependent upon
experience. We found that young meerkats (Suricata suricatta) were less
likely to give alarm calls than adults, but alarmed more in response to
non-threatening species compared to adults. However, stimuli that pose a
greater threat to young than adults did not elicit more calling from
young; this argues against age-related changes in vulnerability as the
sole explanation for developmental changes in calling. Young in small
groups, who were more likely to watch out for predators, alarmed more than
less vigilant young in larger groups. Moreover, despite similarities in
acoustic structure between alarm call types, calls appeared in the
repertoire at different rates, and those that were associated with
frequently encountered predators were produced relatively early on. These
results indicate that experience is a more plausible explanation for such
developmental trajectories than maturation.
URL: http://www.springerlink.com/content/u5l71rx534263270/
For reprints please contact Linda I. HollÃn (Email:
James A. Nicholls (2008): Site specificity in advertisement calls and
responses to playbacks of local and foreign call variants in satin
bowerbirds, Ptilonorhynchus violaceus. Behav. Ecol. Sociobiol. 62(5),
831-841.
Abstract: Avian vocalisations often show patterns of geographic variation.
Previous work on the satin bowerbird has shown that although spatial
variation in this speciesâ advertisement calls is strongly associated with
habitat structure, some variation is apparent within habitat types.
Seventeen populations located throughout the speciesâ distribution were
used to examine whether spatial call variation could be influenced by
other processes such as random drift or the presence of fine-scale vocal
traditions; if this were the case, differing call variants would be
expected at geographically discrete sampling sites both within and among
habitat types. There were population-specific call variants at each of the
sites sampled, with different variants apparent even within habitat types.
At most sites, individuals gave only a single variant of advertisement
call, and the call variant at one site, sampled after a 5-year interval,
appears to have been relatively stable. Playback experiments were
conducted at three populations to examine whether local call variants
invoked a greater response than several non-local variants differing in
their degree of similarity to the local variant. Birds responded strongly
to local call variants but not to either of two foreign variants, one of
which was similar to their local variant and one of which was very
different. A pattern of geographic variation across populations, the fact
that local and non-local variants evoke different responses and
circumstantial evidence indicating that individuals can learn new calls
all suggest that factors affecting song learning and the ability of males
to establish and defend a bower site may have contributed to the
establishment of geographically variable vocal cultures in this species.
URL: http://www.springerlink.com/content/y847jmj73w318273/
For reprints please contact James A. Nicholls (Email:
Kind regards
Sonja Amoser
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