It’s sort of like a day spa. But with more whales. And a whole lot more water.
Along Australia’s Gold Coast, for the first time ever, humpback whales have been video-recorded showing a behavior that is strangely satisfying to watch: it involves them exfoliating underwater by scrubbing their backs and sides clean on the sandy bottom of the bay.
Newly-released footage from whale-mounted cameras shows them rolling about almost blissfully, to and fro, on the ocean floor like some sort of whale wellness camp.
In the shallower waters of Queensland’s Gold Coast Bay—a well-known resting spot along a whale migration route, an inquiry was conducted into the underwater behavior of this charismatic whale species.
Humpbacks were fitted with suction cup CATS (Customized Animal Tracking Solutions) tags that record light, pressure, temperature, and GPS data, as well as high-definition video footage; these were used to observe the behavior of whales “rolling” on the sandy substrate below.
“On all occasions of sand rolling, the whales were observed on video to be slowly moving forward with their head first into the sand followed by rolling to one side or a full roll,” said Griffith University’s Dr. Olaf Meynecke, who led the study.
Humpback whales live in all oceans across the world. Most observations of these and other cetaceans are derived from surface behavior, where they exhibit complex interactions and feeding strategies. Previous tagging endeavors have also tended to focus on their breeding and feeding grounds, with very few looking into their resting and socializing areas or migratory corridors.
So, making their southernly annual migration from tropical breeding grounds to cooler feeding grounds in the Antarctic, the humpbacks revealed some of their less oft-seen behaviors during the journey.
In this particular study, Meynecke, alongside researchers from the Whales and Climate Research Program and the Coastal and Marine Research Centre, focused on one known humpback rest stop, Gold Coast Bay, and they delved deeper into their activities beneath the waves.
On three occations, the team deployed CATS suction cup tags—respectively on August 31, 2021; October 6, 2021; and September 26, 2022—and in each instance, within minutes, the camera recorded the behavior of the whale rolling on the coarse bottom of the bay at depths of up to 49 meters. It captured other whales doing the same, indicating the action was not an effort to remove the tag itself but one that multiple whales were engaged in.
Ultimately, the behavior was attributed to improvements in the whales’ wellbeing, enhancing molting—skin cleanliness—as well as some form of socialization. The tags were set to automatically release within approximately four hours of being deployed.
Full Body Scrubs on Seafloor: A Health Boon For Humpbacks?
There appear to be health benefits to the whales’ scrubbing their backs clean on the seabed. In tropical and subtropical waters, ectoparasites such as barnacles attach to whales in the early stages of their lives, and whales need to remove these frequently to avoid excessive growths that lead to drag and energy loss.Bio-fouling is a common problem for humpbacks and other large cetaceans. Lice and parasites commonly plague the animals’ rostrums, flippers, ventral pleats, as well as wounds. While actions like breeching can help, this cannot completely remove the growths.
“We believe that the whales exfoliate using the sand to assist with molting and removal of ectoparasites such as barnacle and specifically select areas suitable for this behavior,” Meynecke said. “Humpback whales host diverse communities of skin bacteria that can pose a threat for open wounds if bacteria grow in large numbers.”
Data and footage collected from the CATS tags revealed full and side roll performances on an area of the seafloor lined with fine sand or rubble. During each roll, cameras showed dead skin floating off as well as juvenile silver trevally picking it directly off the whale’s body.
Spa Day on the Sea Bottom: A Humpback Social Pastime?
Besides the obvious benefits of cleanliness for the mammal, the apparent social aspect of the behavior was also observed. Male humpbacks demonstrated both courtship behavior, interacting with mother and calf pairs, and competition, shoving other males roughly about, in between rolling frolics in the sand.“During the different deployments, the sand rolling was observed in the context of socializing,“ Meynecke said. ”The behavior was either following courtship, competition, or other forms of socializing.”
The researchers said there is still much more to learn about this charismatic ocean giant, and they advocate further study to see if this rolling behavior consistently repeats.
Meanwhile, new technologies continually offer novel possibilities for future exploration—possibilities such as obtaining 360-degree underwater video footage, or even recording the singing of the humpback males that frequent the Gold Coast Bay.
