DO LITTLE BLUE PENGUINS SIGNAL THEIR INTENTIONS DURING AGGRESSIVE INTERACTIONS WITH STRANGERS

A model of an intruder was used to determine whether burrow-dwelling little blue penguins, Eudyptula minor, signal their intentions during aggressive interactions with strangers. When penguins were first made aware of the simulated intruder, they either gave a 'threat' call (hiss, growl or bray) or remained silent. When both members of a pair were present in a burrow, they were more likely to threaten the intruder than to remain silent; the opposite was true when one of the partners was absent. Contrary to the predictions of game theory, the choice of threat call by a lone male or pair revealed information on how likely they were to attack or peck the model when it was moved toward their burrow (lone females rarely attacked the model). Penguins that hissed were more likely to attack than penguins that growled or brayed. However, in no case did growl and bray (i.e. calls that grade into one another) differ in what they revealed about a penguin's subsequent behaviour. The results do not necessarily mean that penguins 'actively' convey information on their intentions. Instead, the ability to predict what an animal will do following its display may be the simple consequence of an escalation process, during which animals progress step by step from low-risk to high-risk behaviour. © 1991.