Love hormone makes fish bond better, McMaster study shows

Mac researchers found that the hormone oxytocin is linked to social stability in fish.
McMaster researcher Adam Reddon studied what happened when fish had increased levels of a hormone. (Supplied)

What do your neighbour, your dog and an African cichlid fish all have in common?

According to new research from Hamilton’s McMaster University, they all pick up on social cues thanks to the same hormone.

The study showed oxytocin — a naturally occurring hormone that helps humans bond with one another and makes us more sensitive to social interactions — has a similar effect on certain species of fish.

When researchers increased the levels of isotocin — the fish version of oxytocin —  the fish began to pay more attention to social cues and reacted to them more often.

"It made them pay more attention to social interactions," Adam Reddon, lead researcher and a graduate student at McMaster University, explained.

When a dominant fish challenged a more subordinate one, the subordinate fish would display its belly — signaling that he was giving up — more often after the increased levels of isotocin, Reddon said.

Since oxytocin plays a role in forming bonds and relationships in humans, it’s sometimes dubbed the "love drug," but Reddon said that’s an oversimplification.

"Rather than a love drug, per se, it’s sort of a social spotlight," he said.

"It’s a naturally occurring hormone in all animals — fish, birds, mammals — and it doesn’t differ that much between species."

Reddon and his team have been looking at a unique type of cichlid fish, only found in Lake Tanganyika in Africa. They live in permanent family groups where a single, dominant pair does all the breeding, while the rest form a hierarchy and help protect the group.

"It’s like a little wolf pack," Reddon said. "They’re such a remarkably social fish."

Next in the research, Reddon said they plan to block production of the hormone to observe the effects of too little isotocin.

"You could expect that it would sort of create chaos in their social structure," he said.

"If suddenly a little guy doesn’t realize his rank and starts recklessly challenging higher-ups, it could break down their structure."