Complex social structures, featuring both friendships and rivalries, makes evolutionary sense for animals that live a slower-paced life, according to a new study.
When researchers at the University of Exeter looked at the relationships between lifespan, reproductive patterns and social dynamics among different species, they found a correlation between long-living species and the formation of strong and weak social bonds.
The research — published Tuesday in the journal Trends in Ecology and Evolution — showed the formation and maintenance of complex social structures has a positive effect on survival.
In other words, animals that form friends and enemies tend to live longer. However, researchers found the benefits of complex social relations appear to only be useful to species that live a slower-paced life.
For fast-lived species — animals that invest a lot of metabolic energy and evolutionary capital in reproduction — complex social structures aren't particularly helpful.
"Slow-living species can afford to invest in social relationships, as they live long enough to enjoy the pay-offs," study co-author Dave Hodgson said in a press release.
"There is strong evidence that strong social bonds are beneficial for survival in slow-living species, including humans. We suggest there is a 'positive feedback' — certain social behaviors lead to a longer life, and longer lifespan promotes the development of social bonds," said Hodgson, a professor of ecology and conservation at Exeter.
Fast-living animals include shrews and crickets, while mongoose, badgers, hyenas and humans are examples of slow-living species.
Commonly, scientists used animal size as the primary proxy for estimating pace of life. Bigger animals tend to life much longer than smaller animals. But the pace of life can differ for two similarly sized species.
"If we want to understand more about social relationships and lifespan, we need to think about the relationship between the two," said lead author Matthew Silk.
"More research is needed to explore the social structures of wild animals. This could help us understand the links between social bonds, survival and reproduction," said Silk, a postdoctoral research fellow at Exeter's Center for Ecology and Conservation.
The two authors suggest a closer examination of the diversity of social relationships among different groups of animals can help researchers better understand the influence of social bonds on lifespan.
More than a proof of causation between social structures and lifespan, the newly published paper is a call-to-research of sorts, the researchers said.
"Our proposal, that strong and weak social bonds will be more prevalent in slower-living animals, is theoretical," Hodgson said. "We know a lot about animal lifespans, but we know too little about the social structures of many types of animal."
