Dear colleagues, We would like to draw your attention to the following paper, recently published in Behavioral Ecology and Sociobiology: Riesch, Rüdiger and Deecke, Volker B. 2011. Whistle communication in mammal-eating killer whales (Orcinus orca): further evidence for acoustic divergence between ecotypes. Behavioral Ecology and Sociobiology 65:1377–1387, doi:10.1007/s00265-011-1148-8 ABSTRACT Public signaling plays an important role in territorial and sexual displays in animals; however, in certain situations, it is advantageous to keep signaling private to prevent eavesdropping by unintended receivers. In the northeastern Pacific, two populations of killer whales (Orcinus orca), fish-eating “resident” killer whales and mammal-eating “transient” killer whales, share the same habitat. Previous studies have shown that residents use whistles as private signals during close-range communication, where they probably serve to coordinate behavioral interactions. Here, we investigated the whistling behavior of mammal-eating killer whales, and, based on divergent social structures and social behaviors between residents and transients, we predicted to find differences in both whistle usage and whistle parameters. Our results show that, like resident killer whales, transients produce both variable and stereotyped whistles. However, clear differences in whistle parameters between ecotypes show that the whistle repertoire of mammal-eating killer whales is clearly distinct from and less complex than that of fish-eating killer whales. Furthermore, mammal-eating killer whales only produce whistles during “milling after kill” and “surface-active” behaviors, but are almost completely silent during all other activities. Nonetheless, whistles of transient killer whales may still serve a role similar to that of resident killer whales. Mammal-eating killer whales seem to be under strong selection to keep their communication private from potential prey (whose hearing ranges overlap with that of killer whales), and they appear to accomplish this mainly by restricting vocal activity rather than by changes in whistle parameters. KEYWORDS: Acoustic crypsis, communication networks, eavesdropping, feeding ecology, predation, private signals, public signals, social networks Please contact the first author Rüdiger Riesch <rwriesch@ncsu.edu<mailto:rwriesch@ncsu.edu>> with any questions about this research. Best regards Volker ------------------------------------------------ Dr. Volker Deecke Sea Mammal Research Unit Scottish Oceans Institute University of St. Andrews St. Andrews, Fife, KY16 8LB Scotland UK Phone +44.1334.463459 Fax +44.1334.463443 ------------------------------------------------ The University of St Andrews is a charity registered in Scotland: No SC013532