Depending on friends makes life easier for reef fish

A growing collection of research shows that animals with much less complex minds than humans are surprisingly connected on a social level. A new study reveals that reef fish and other types of social fish depend on friendships for their very survival. 

Study lead author Dr. Lauren Nadler is an assistant professor in the (NSU) Halmos College of Arts and Sciences at the Nova Southeastern University.

“We studied how the presence of ‘friends’ versus ‘strangers’ affected how fish responded to a predator threat,” said Dr. Nadler.

“The presence of ‘strangers’ seemed to distract fish, making them react more slowly and greatly increasing the chance that they would become lunch for a hungry predator when in the wrong social scene.”

To investigate how familiarity may influence groups of social fish, the researchers focused on schooling coral reef fish.

Dr. Nadler and her colleagues believe that their results come down to trust. The experts found that reef fish rely on alerts from their trusted friends to avoid predators. 

According to the researchers, the fish must balance the risk of being attacked with the possibility of wasting their energy in response to inaccurate information. It appears that reef fish adjust their reactions to social information based on the level of familiarity in the group.

“Trust among individuals is critical. This is true for humans as well as many other species, including fishes,” said study co-author Dr. Jacob Johansen of the University of Hawaii Manoa.

“Our research in fishes shows that when accurate information transfer breaks down, so too does the chance of survival for the individual and the group as a whole.”

The researchers found that the first fish to detect the predator exhibits the greatest amount of vigilance, and that the most useful information is shared among neighboring fish.

“Our work shows that readiness to react to a threat depends on who is around you, if you are a fish,” said Dr. Paolo Domenici. “If you are in an unfamiliar social environment, this is already something you need to pay attention to. If you are surrounded by familiar individuals, then you will be able to pay attention to any external threat more readily.”

The findings suggest that animals have evolved to associate with friends over strangers to promote survival in the wild. 

“Friendship networks matter, both for humans and for less evolved taxa like fishes,” said Dr. Mark McCormick. “The more you can rely on your friends, the easier and more fulfilling your life will be.”

The study is published in the journal Communications Biology.

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By Chrissy Sexton, Earth.com Staff Writer