A new study led by the University of Bristol has revealed that tropical paper wasps help out neighboring nests by babysitting when there are extra workers available. The findings suggest that when their closest kin are less in need, the wasps seek to help more distant relatives.
“These wasps can act like rich family members lending a hand to their second cousins. If there’s not much more you can do to help your immediate family, you can turn your attention to the extended family,” explained study lead author Dr. Patrick Kennedy.
Around the Panama Canal, the researchers observed 20,000 baby wasps and their caregivers to investigate the usefulness of workers in colonies of different sizes. The study showed that as the number of colony members rises, the worker bees become less useful due to a surplus of help.
“By helping more distant relatives who are more in need – those living next door with fewer carers – workers can pass on more copies of their genes overall,” said study co-author Professor Andy Radford. “We believe that similar principles of diminishing returns might explain seemingly paradoxical acts of altruism in many other social animals.”
Dr. Kennedy said the fact that these paper wasps help at other colonies is really bizarre when you consider that most wasps, ants, and bees are extremely hostile to outsiders. ‘To solve this puzzling behavior, we combined mathematical modelling with our detailed field observations.”
“We ended up being stung a lot. But it was worth it, because our results show that worker wasps can become redundant at home. A wasp on a colony with few larvae but lots of other workers becomes almost useless: the best thing to do is to babysit the larvae of other relatives.”
The evolution of “altruism” in animals had remained a mystery for many decades since the time of Charles Darwin.
“In 1964, the legendary biologist W. D. Hamilton figured out the cardinal rule of animal altruism. Lavish help on your family because they share many of your genes. Copies of your genes will triumph in the population,” said Professor Radford.
However, the behavior of tropical paper wasps baffled Hamilton back in 1964. He was surprised to notice that Polistes wasps were leaving their close family in their home nests and flying off to help the neighbors, who are less closely related.
Previously, study co-author Professor Seirian Sumner reported that over half the workers in a Panamanian population of paper wasps were helping on multiple nests. This comes as a surprise considering that wasps usually viciously attack outsiders, and suggests that something unusual is going on.
“Wasps offer amazing windows into the evolution of selflessness,” said Professor Sumner. “There is so much going on in a wasp nest: power struggles, self-sacrifice, groups battling against the odds to survive… If we want to understand how societies evolve, we should look more deeply at wasps.”
The study is published in the journal Nature Ecology and Evolution.