Male killer whales 'more likely to DIE if they are not centre of social group'

MALE killer whales are more likely to die if they are not at the centre of their social group, suggests new research.

Killer whales podGETTY

Male killer whales are large and require a social network to ensure they are adequately fed

Scientists found that the most socially isolated males were three times more likely to die in any given year than those in the “most central social positions”.

The effect was much stronger in years where food was scarce, and it didn't affect females - possibly because males are larger and need more support from the group to get enough food.

The findings come from a study of Southern Resident killer whales, a critically endangered population in the Pacific Ocean that - following a recent death - numbers just 76.

The research, published in the journal Proceedings of the Royal Society B, was conducted by scientists from Exeter Univeristy and York University, and from the Centre for Whale Research in the United States.

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On a broad scale, research like this examines the fundamental question of why social relationships and friendships have evolved

Professor Darren Croft

Study lead author Dr Samuel Ellis, of Exeter University, said: “This research highlights the importance of social bonds to male killer whales, and shows that males that are less socially connected are more likely to die when times are hard.

“Killer whales are highly cooperative, and males at the centre of a social group are likely to have better access to social information and food-sharing opportunities.“

Southern Residents were among the groups from which killer whales were taken into captivity in the 1960s and 1970s, and the researchers say that human activity is now posing much greater threats to their survival.

Ken Balcomb, of the Centre for Whale Research, said: “Salmon is the main food for these whales, and stocks have been driven down by overfishing and the blocking of spawning grounds by damming rivers.

“These factors make it all the more important to understand the drivers of survival and mortality among these whales.”

Study co-author Dr Dan Franks, of York University, said: “Our research shows the importance of considering social positions and family ties in understanding and predicting the future of endangered populations.”

Previous research has shown sociability has an effect on human life expectancy, but this is the first study to show that social position across the lifespan can predict survival in non-human animals.

Study senior author Professor Darren Croft, of the Exeter University, said: “These whales have been studied for more than 40 years and they are all recognisable by unique markings.

“By seeing which whales regularly swam together across a year and across multiple years, we started to understand a network of what in humans we would call friendships

“In terms of this research, a central social position meant whales either having many individual connections or being the connection between two or more groups.”

Professor Croft added: “On a broad scale, research like this examines the fundamental question of why social relationships and friendships have evolved.”

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