Burying beetles that have been in contests for food and resources previously will spend more time assessing their opponent but this cautious behaviour doesn't mean they're more likely to win, say scientists.
The new study, published in Behavioural Ecology, wanted to understand whether older beetles put more effort into fights over places to breed and females, since they have less to lose.
'We predicted that the older you are the less chance you have of reproducing in the future, so since you have less to lose you may be more aggressive in contests,' says Dr Nick Royle of the University of Exeter's Centre for Ecology & Conservation, and lead researcher on the project. 'We also expected naive males with little social experience to be more aggressive as they have had no experience of the consequences.'
Instead, the researchers found that beetles with more social experience of these contests were more likely to spend time sizing up their opponent.
'Vertebrate carcasses are quite difficult to find in the wild so competition is fairly ferocious as it may be the only opportunity these animals have to breed,' Royle says.
To test their theory the team put two beetles into a box with a mouse carcass – a common breeding resource for burying beetles – and observed them until a winner was declared. The winner was the beetle who was seen on the mouse carcass for two observations in a row.
Before the contest some of the beetles were isolated, giving them less social experience, while others interacted with other males for 24 hours prior to the experiment.
'We found age doesn't affect behaviour at all. And while social experience did affect the male's behaviour, it didn't affect the outcome of the contest,' explains Royle.
While their social experiences changed the way the beetles interacted during contests, it seems this different behaviour didn't give them enough of an edge to win. The researchers found that the ultimate factor determining which beetle would triumph was their size, with the larger beetles succeeding most often.
The burying beetles get their name because in the wild once they've found a carcass, a mating pair will strip the fur, process it and bury it underground.
They use antimicrobial secretions to keep it free from bacteria and create a small crater of partially digested mouse soup, ready to feed to their larvae.
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Victoria E. Lee, Megan L. Head, Mauricio J. Carter, and Nick J. Royle. "Effects of age and experience on contest behavior in the burying beetle, Nicrophorus vespilloides." Behavioral Ecology. November 8, 2013. DOI: 10.1093/beheco/art101