Orcas Display Never-Before-Seen Kelp Grooming Behavior

A unique population of orcas, already known for their unusual habit of wearing salmon on their heads, has been observed engaging in a behavior never before documented in marine mammals: using kelp for grooming.

Researchers at the Center for Whale Research in Friday Harbor, Washington, captured drone footage of these orcas interacting with bull kelp (Nereocystis luetkeana) in a way that suggests a grooming ritual. The orcas were seen breaking off sections of kelp and rubbing them against each other.

Michael Weiss and his team believe this is the first instance of tool manufacture by a marine mammal, the first known case of tool use benefiting two individuals simultaneously in a wild animal, and the first observation of a non-human animal manipulating a tool with its body core rather than an appendage. The findings were published on June 23 in current Biology.

“They’ll use their teeth and the movement of their heads and their bodies to break off about a two-foot-long length of that kelp’s stem, or stipe, then approach another whale and flip it onto their rostrum, or their kind of nose, and press that kelp against the side of their partner,” Weiss explained.

The orcas then maneuver their bodies to keep the kelp wedged between them, rolling it back and forth for a few seconds to as long as 15 minutes.

implications of Kelp Grooming

Deborah Giles, an orca specialist at the SeaDoc Society, who was not involved in the study, described the behavior as “super interesting,” noting that the orcas are purposefully creating the tool they intend to use.

“It might just feel good to put a salmon on your head.”

this behavior has been observed in both male and female orcas of all ages,across different social groups within the southern resident community.

Grooming in animals typically serves to reduce stress, maintain health, and strengthen social bonds. Is this the reason for the orcas’ kelp rubbing?

Els Vermeulen, a cetacean specialist at the University of Pretoria, who was not involved in the research, stated that while the study is new, this specific behavior is not entirely surprising, given the social nature of orcas.

Weiss’s team discovered that kelp rubbing is more common between related individuals and those of similar ages, which aligns with the idea that grooming is linked to strong social relationships. They also found that whales with more dead skin were more likely to engage in rubbing,suggesting a potential hygiene benefit.

“When we talk about animal behavior, there’s the function, or the fitness benefit the animal gets, and that will relate to health and wellness. But there’s also the mechanism in the brain causing them to want to do this,” Weiss said. “I think a lot of that is that it feels nice.”

Tool Use Among Marine Animals

While tool use is known in animals like chimpanzees, birds, and elephants, it is indeed less common among marine animals.Sea otters use stones to open shellfish, and dolphins use sponges on their noses to help them forage, but these are not examples of tool creation.

Orcas have also been observed creating waves to dislodge seals from ice floes, demonstrating their ability to manipulate their habitat.

Currently, the southern resident orcas are the only population known to use kelp for grooming. This may be due to the challenges of observing such behavior from boats, where smaller pieces of kelp are arduous to see.

“I’ve often observed killer whales rolling around on each other from a boat. It makes me wonder if they’ve been engaging in this behavior all of that time,” said Giles. “Drone imagery has created an chance for us to see into the lives of these animals in a way that has never been possible before.”

The southern residents are listed as an endangered population under the U.S. Endangered Species Act. With only 73 individuals remaining at the last census, the loss of these whales would mean the disappearance of unique cultural traditions and a society unlike any other.