Paper wasps punish rivals with poker faces
Wasps with a mismatch between fighting ability and facial patterns are treated more aggressively by other wasps.
When we think of wasps, honesty isn’t usually the first word to that springs to mind. Yet new evidence from a study at The University of Michigan suggests that aggressive and feisty as they may be, the often-misunderstood wasp holds Scout’s honour in high regard – especially when it comes to fighting.
“Why don’t animals cheat by signalling that they are strong when they are actually weak?” asks Elizabeth Tibbets, evolutionary biologist and lead author of the study. “In paper wasps, we found that inaccurate signalling produces a cascade of costly social and physiological effects.” In other words, it’s actually in a wasp’s best interest to be honest.
Paper wasps sport a variety of facial patterns that act as cues about their fighting prowess. Wasps with more black blotches on the yellow centre of their face tend to win more fights than wasps with more regular patterns, which helps other wasps judge whether it’s worth their while to pick a fight and avoid more dominant rivals.
In order to test how these facial patterns affect social interactions, the researchers collected wasps from rival nests and pitted them against each other. One wasp in each fight, dubbed “the bluffer”, was painted with patterns that suggested they were much better fighters than they actually were.
After tallying the points scored for the number of mounts, bites, grapples, and stings throughout the fight, the team found that those with a “dishonest” face were treated much more aggressively and were harassed for longer afterwards than those with an “honest” face.
Honesty is the best policy
This signalling mismatch has consequences beyond just getting a bruising in the ring. After fighting, the “bluffer” wasps experienced a drop in their levels of juvenile hormones (JH), chemicals associated with dominance, aggression and fertility in wasps, whereas the victors experienced a spike in JH.
“One of the interesting things about the paper is that it shows that cheating influences the physiology of cheaters and individuals who interact with the cheaters,” says Tibbets. “That was a surprise.”
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This system of hormone reward/punishment could have long-term impacts on a wasp’s social rank and reproduction within her individual lifetime, and could build up over the course of evolutionary time to help maintain honest communication within paper wasp communities as a whole.