Linda I. Hollén, 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 individual’s 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. Hollén (Email: [EMAIL PROTECTED]) 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 species’ advertisement calls is strongly associated with habitat structure, some variation is apparent within habitat types. Seventeen populations located throughout the species’ 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: [EMAIL PROTECTED]) Kind regards Sonja Amoser
