[MARMAM] New paper on North Atlantic killer whales
Dear colleagues, The following paper has recently appeared in the journal Aquatic Biology: Deecke, V. B., Nykänen, M., Foote, A. D. Janik, V. M. 2011. Vocal behaviour and feeding ecology of killer whales (Orcinus orca) around Shetland, UK. Aquatic Biology, 13, 79–88. ABSTRACT: Killer whales Orcinus orca are sighted regularly off Shetland, UK, but little is known about their numbers, diet and population identity. We aimed to relate vocal behaviour to diet of killer whales around Shetland in order to investigate population structure and differences in feeding strategies. Fieldwork was conducted in the summers of 2008 and 2009. We located killer whales through a sightings network and shore-based scans and collected photo-ID data, behavioural information, feeding data and acoustic recordings from a small boat. The majority of encounters (n = 14) were of small groups (1 to 15 individuals) travelling close to shore and feeding on marine mammals. Two encounters were with large groups (20+ individuals) feeding on herring Clupea harengus farther offshore. Seal-hunting groups vocalised rarely, producing pulsed calls, echolocation clicks and whistles almost exclusively when surface-active or milling after a kill. Herring-eating groups were largely silent during one encounter, but very vocal during the other. Analysis of pulsed calls identified 6 stereotyped call types for seal-hunting groups and 7 for herring-eating groups. No call types were shared between both kinds of groups. The vocal behaviour of seal-hunting groups showed striking parallels to that of Pacific marine mammal specialists and presumably evolved to decrease detection by acoustically sensitive prey. One call type produced by Shetland herring-eating killer whales matched a vocalisation that a previous study had described from Iceland and identified as a possible herding call that may function to concentrate herring during feeding. These findings point to behavioural and dietary specialisation among Shetland killer whales, which should be taken into account when making management decisions affecting these animals. KEYWORDS: Dietary specialisation, Vocal behaviour, Feeding ecology, Killer whale, North Atlantic Please contact me v...@st-andrews.ac.ukmailto:v...@st-andrews.ac.uk with any questions about this research. All the best 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 ___ MARMAM mailing list MARMAM@lists.uvic.ca https://lists.uvic.ca/mailman/listinfo/marmam
[MARMAM] New paper on whistle communication in killer whales
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 rwrie...@ncsu.edumailto:rwrie...@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 ___ MARMAM mailing list MARMAM@lists.uvic.ca https://lists.uvic.ca/mailman/listinfo/marmam
