The spinner dolphins that inhabit nearshore areas of the Hawaiian Islands are friendly and curious, and they put on a fun show- jumping, flipping, and spinning out of the water and through the air. But there’s a lot more to these adorable creatures than their acrobatics.
Most people are familiar with bottlenose dolphins and their sleek gray bodies, so it may come as a surprise when they see a spinner dolphin for the first time. I was shocked to see how much smaller they were than their bottlenose relatives! Spinner dolphins average about 6 feet in length. Their coloring is quite different, as well. Spinners are dark gray on their dorsal (back) side, white on their ventral (belly) side, and have a lighter gray coloring along their sides almost like a racing stripe.
Spinner dolphins are nocturnal. They rest during the day in the safety of their pod and swim to deeper waters as the sun goes down to hunt for marine life that are beginning to rise from the depths at nightfall. The dolphins “sleep” by shutting off parts of their brain, so they get rest but are still conscious and able to surface for air. If they slept like humans do, spinners would essentially forget to come up for a breath and drown. Switching back and forth between brain hemispheres is a pretty cool solution to that problem! Staying close together while they rest serves as good defense against predators, and you’re likely to see mothers and their calves toward the middle of the group. Check out this mama and baby swimming side-by-side in the bottom of the frame:
Spinners are incredibly social and are one of the best examples of animals that play. The dolphins communicate with each other through touch and movements, whistles through their bubble trail, and echolocation, which is like sonar. The Hawaiian spinners have been seen bowriding in the wake of boats, and of course they leap and spin as they surf the waves together. The coolest way spinners have been observed playing is by creating toys out of objects they come across and tossing them to each other like a game of catch. This could be a piece of seaweed, an unfortunate fish, or a plastic bag that made its way into the sea.
And the biggest mystery of all… Why do they spin?! Scientists can’t tie it to one single reason, but have several theories. The dolphins spin to rid themselves of parasites and remoras that may be along for the ride. The dolphins spin to communicate with each other; the splashing of leaping and slapping of spinners landing back in the water generate quite a bit of sound. The dolphins may spin to help regulate their body temperature. But it would appear that the dolphins spin because it’s fun and they can, and that may just be good enough a reason itself.
I was lucky to experience a large pod of spinner dolphins cruise by the western coast of Oahu while I was out snorkeling recently. Enjoy a video of the Hawaiian spinners relaxing in the shallow coastal waters on my Instagram ♥