Interaction between marine mammal species is not uncommon. Sea lions will mingle with pods of feeding dolphins and sea lions and dolphins occasionally swim alongside whales.
But the type of playful behavior exhibited in the accompanying video -- bottlenose dolphins receiving rides atop humpback whales in Hawaiian waters -- is exceptionally rare.
As mentioned in a recent post for GrindTv, the photographs used to produce the video are the first recorded examples of these incredible events. One occurred off Maui and the other off Kauai.
The video was posted recently to the American Museum of Natural History website as part of its Science Bulletins program.
"The two species seemed to cooperate in the activity, and neither displayed signs of aggression or distress," the website explained. "Whales and dolphins in Hawaiian waters often interact, but playful social activity such as this is extremely rare between species."
The Kauai encounter featured one documented event. During the Maui encounter, scientists watched a humpback whale and bottlenose dolphin performing this ride-and-slide episode six times, with the dolphin gliding gently off the whale each time.
It remains unclear whether this is pure play or which species gets the most enjoyment from the interaction, but for marine mammal enthusiasts it's sure fun to watch.
-- Pete Thomas