<tt>The following article was recently published in the online edition of
the journal Animal Behaviour:</tt><br>
<br>
<tt>Deecke, V. B., Slater, P. J. B. & Ford, J. K. B. 2005. The vocal
behaviour of mammal-eating killer whales (Orcinus orca): Communicating
with costly calls. Animal Behaviour,
doi:10.1016/j.anbehav.2004.04.014.</tt><br>
<br>
<tt>ABSTRACT<br>
The cost of vocal behaviour is usually expressed in energetic terms;
however, many animals pay additional costs arising from predators or
potential prey eavesdropping on their vocal communication. The
northeastern Pacific is home to two distinct ecotypes of killer whales
(Orcinus orca): resident killer whales feed on fish, a prey with poor
hearing abilities, whereas transient killer whales hunt marine mammals,
which have sensitive underwater hearing at the frequencies of killer
whale vocal communication. In this study, we investigated how the
superior hearing ability of their prey has shaped the vocal behaviour of
the transient ecotype. We recorded pulsed calls and the associated
behavioural context of groups of transient and resident killer whales in
British Columbia and southeastern Alaska. Transient killer whales
emitted pulsed calls significantly less frequently than residents.
Transient killer whales only exhibited significant amounts of vocal
behaviour after a marine mammal kill or when the whales where displaying
surface-active behaviour. Vocal activity of transients increased after a
successful attack on a marine mammal. Since marine mammals are able to
detect killer whale pulsed calls and respond with anti-predator
behaviour, the reduced vocal activity of transients is probably due to a
greater cost for calling in this ecotype resulting from eavesdropping by
potential prey. The increase in vocal behaviour after a successful
attack may represent food calling (informing other animals in the area
about the presence of food), but is more likely to reflect an increase
in social interactions during feeding and/or the fact that the cost for
vocal behaviour is comparatively low after a successful attack.</tt><br>
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<tt>KEYWORDS:<br>
predator-prey interaction; predator-prey coevolution; vocal activity;
vocal communication; vocal behaviour; eavesdropping; killer whale;
Orcinus orca; Northeast Pacific; hearing</tt><br>
<br>
<tt>For further information please contact Volker Deecke
<[EMAIL PROTECTED]></tt><br>
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