For many, the image of dolphins evokes playful leaps and acrobatic twirls. However, a recent study suggests these aquatic games may be more than just frolic and fun. Researchers from the University of Bristol have found that young male bottlenose dolphins who actively engage in social play with each other — which often involves role-playing in which they pretend to be either male or female adults — are more likely to father offspring later in life.

Dolphin play date

This study provides new insight into why animals engage in social play, a behavior that has puzzled scientists for over a century. It doesn’t, in a strictly Darwinian sense, make sense for animals to play unless play itself has some adaptive value.

One hypothesis to explain play in animals is physical training. It may allow immature individuals to ‘practice’ skills, like pouncing, that they will need as adults. A study of bear cubs found that cubs that played more had better survival rates. Similarly, cheetah cubs that spent more time pretending to stalk their family also did more stalking of prey.

Now, this study shows that playing can help dolphins sire more offspring by practicing the equivalent of cetacean dating.

Male dolphins are known to form lifelong bonds that aid them in finding mates. The study revealed that these bonds start forming early, with young dolphins practicing mating behaviors with other juveniles years before they reach sexual maturity. The researchers analyzed 30 years of data. The study tracked young males aged four to fourteen, using genetic paternity tests to determine the number of offspring each dolphin sired.

Juveniles in Australia’s Shark Bay take turns pretending to be adult males and females, even mimicking the clicking noises, or “pops,” that adults use to attract mates. This early training appears crucial for their future reproductive success.

“Play behavior is widespread in humans and other animals, but the reasons that animals play together have long remained a mystery,” said Dr Stephanie King, associate professor from the University of Bristol’s School of Biological Sciences.

“This study provides compelling support for the idea that animals in the wild play together to practice behaviors that will be important for them as adults, and that if they practice enough, they will be more successful as adults.”

From playtime to parenthood

Male dolphins belong to complex social structures, which include large, stable alliances and smaller, less stable groups. These smaller groups often team up to mate which involves tactics like stealing females from other alliances or defending against outsiders. In general, dolphin mating is not pretty. Gangs of male bottlenose dolphins often isolate a single female from a pod and essentially rape her, sometimes for weeks. However, dolphin mating is as complex as it is brutal and these new findings serve as a fascinating window into the intimate lives of the marine mammals.

“We found that juvenile play involves immature versions of adult reproductive behaviors that are crucial for males to access and mate with estrous (sexually receptive) females, and the time spent doing these play behaviors predicts how many offspring males eventually sire as adults,” said Dr. Katy Holmes, who completed this work as part of her doctoral research at the University of Western Australia.

“Our work is exciting because historically it has been notoriously difficult to link play behavior to reproductive success, in this case the number of sired offspring, in wild animals.”

The findings appeared in the journal Proceedings of the National Academy of Sciences.