Dolphins with more close friends age more slowly

Dolphins with more close friends age more slowly

By Hasmik Kirakosyan edited by Tanya Lewis

Watching dolphins play can evoke wonder and admiration. While these delightful bonds may seem fleeting, a subset of dolphins form complex alliances based on strong, lifelong friendships. And these bonds may slow aging, a recent study suggests.

To explore that association, researchers drew on more than four decades of behavioral observations of a well-studied group of Indo-Pacific bottlenose dolphins in Shark Bay, Australia. The new research showed that social relationships influenced the pace of biological aging in the dolphins.

The Shark Bay bottlenose dolphins form lifelong relationships that form some of the most intricate social structures in the animal world. Among these dolphins, males with close social bonds spend much of their time together, often traveling, foraging, mating and resting in the same groups.

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Within the Shark Bay population, the researchers focused on 38 male dolphins with precisely known chronological ages. The team collected skin samples from the dolphins to measure DNA methylation patterns—biochemical modifications that determine which genes are activated—in order to estimate their biological ages. These patterns were analyzed by multiple epigenetic clocks, the gold-standard tool for estimating biological age. The main clock that was used in the study was a version that the team calibrated specifically for the Shark Bay dolphin population to measure regular changes in chemical markers on DNA that accumulate over the course of a lifetime.

“Aging is a complex process that includes DNA damage [such as] double-strand DNA breaks—it’s not just the mitochondria working faster or being exhausted or suddenly having a lot of mutations,” says the study’s lead author Livia Gerber.

Then a postdoctoral fellow at the University of New South Wales in Sydney, Gerber and her team found that dolphins with stronger long-term social partnerships were biologically younger than their more solitary counterparts, as measured by epigenetic markers.

Social isolation can expose animals to prolonged stress. And ongoing exposure to the stress hormone cortisol negatively affects health in many animals, including humans. Social animals such as dolphins thrive in a social context, Gerber says. If they lack that social network, “that puts a lot of stress on their bodies, which makes them age faster,” she says.

In contrast, evidence shows that positive social interactions in dolphins and other animals are associated with the release of oxytocin, a hormone associated with social bonding and well-being.

“This research suggests that, across mammals, social bonds may buffer against stress and reduce aging rates,” says Ashley Barratclough, a conservation medicine veterinarian at National Marine Mammal Foundation in California, who was not involved in the study.

It’s noteworthy that the quality of relationships, rather than simply social group size, affected the Shark Bay dolphins’ epigenetic aging. The type of social interaction also matters because large social groups could, paradoxically, have a negative effect on dolphins’ aging, Barratclough says. “Improving our understanding of these mechanisms could help with the conservation of these species,” she adds.

The research suggests that the quality of dolphins’ relationships has a direct bearing on their aging process. Like humans, the cetaceans thrive when they feel cherished and have a sense of belonging.

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