The whales — mostly humpbacks, with two gray whales, two southern right whales and a northern right whale — were spotted throwing, lifting, swimming through and rubbing up against clumps of seaweed, even wrapping it around their own fins. Aerial observations were made off Australia’s east coast, but the behavior was also spotted in North America.

Given better aerial observation tools and technology such as social media, the researchers write, it’s now possible to document kelping in whales that, although social, aren’t thought to play with objects as often as other marine creatures such as dolphins. They found the behavior in four distinct humpback whale populations, with adults most likely to interact with the seaweed.

What drives the whales to fuss with the seaweed fronds?

There are several potential answers, the researchers write. The whales could be using the seaweed to treat skin bacteria with algae from the kelp. Or they might be seeking out a playful sensory experience, finding a “welcome sensation” as the kelp brushes against their tubercles — sensitive lumps that give humpbacks their bumpy appearance.

It could also be pure play, a behavior that can boost learning and help animals survive in the wild.

The researchers call for more work on whales’ kelping, especially given recent, large kelp die-offs that have endangered kelp beds in Australia, California and elsewhere.

And aside from helping direct conservation efforts, the researchers identify another reason to keep looking out for kelping whales — publicizing the practice can engage people outside of the scientific community, too, “fostering public engagement in species conservation.”