19 March 2012

Boasting little penguins build their reputations

NEW ZEALAND - Take that, loser! By showing off after they win a fight, male little penguins make it less likely that other males will challenge them, a study by University of Waikato scientists has found.

The study, published in Animal Behaviour, used an innovative method to look at the effect of 'triumph displays' on nearby little penguins - 'social eavesdroppers' - at Flea Bay in New Zealand.

The researchers edited audio recordings of fights among two sets of little penguins (who don't live at the colony) into two 'fights', each ending with a triumph call. First, they played the recordings to penguins nesting in their burrows through speakers set up 5 metres away. Then, 5 minutes after the 'fight' was over, they played either the winner's triumph call or a call from the loser from speakers set up 2.5 metres away from a burrow - making the burrow's inhabitants think the winner or the loser was coming closer.

Cleverly, the nesting penguins' stress levels were measured by using an infrared egg, temporarily switched for their real egg, that monitored the penguins' heart rate.

Both male and female penguins were stressed (had increased heart rates) while listening to the fights, with females similarly stressed regardless of whether a winner or loser approached their burrows. Males, however, were more stressed if a winner, rather than a loser, approached their burrows, and were also less likely to challenge an approaching winner by calling. Females stayed silent no matter whether the winner or loser approached.

The findings suggest that by advertising their victories, i.e. boasting, male penguins may establish a ‘reputation’ for winning fights within the colony, potentially reducing the likelihood of being challenged in the future.

Animal Behaviour citation
Triumph displays inform eavesdropping little blue penguins of new dominance asymmetries, Solveig C. Mouterdea, David M. Duganzichb, Laura E. Mollesc, Shireen Helpsd, Francis Helpsd, Joseph R. Waas, Animal Behaviour, Volume 83, Issue 3, March 2012, pp.605–611

Sources
How to say 'in your face' like a penguin by Jane J. Lee, 9 March 2012, ScienceNOW
Why little penguins 'show off' (photo gallery), 8 March 2012, BBC Nature News

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