Orcas use kelp as tools for social massages

In a rare and detailed study, researchers have documented a unique behavior among Southern Resident killer whales in the North Pacific, involving the deliberate use of kelp for social and possibly health-related purposes. Over the course of 12 observation days between April and July 2024, scientists recorded 30 distinct episodes where orcas appeared to engage in what has been termed "allokelping". This involved the animals biting off tube-shaped pieces of seaweed and rubbing them on each other’s bodies.

Drone footage reveals coordinated kelp massages among orcas

This newly documented behavior is now being interpreted as a form of physical bonding and tool use-something not commonly recorded in marine mammal species. The findings provide evidence that killer whales use seaweed as tools to interact socially and possibly maintain skin health. The study was published in the peer-reviewed journal „Current Biology”.

Researchers from the Center for Whale Research in Washington State and the University of Exeter used drone technology to observe orcas from above, capturing high-resolution footage that revealed never-before-seen interactions among the whales. According to lead author Dr Michael Weiss, drone coverage frequently revealed pairs of whales involved in kelp massages.

“When we fly a drone over a group of these orcas, we almost always spot at least one pair engaged in this activity,” said Dr Weiss. The behavior involves one whale retrieving a strip of kelp, often biting it off carefully, and placing it on the back or side of another whale. The orcas then use their bodies to rub the kelp between each other, moving in synchronized and deliberate ways.

The footage documented not only the rubbing but also the selection and handling of the kelp, suggesting a clear, planned use of the seaweed. “Let’s call it a kelp massage,” said Professor Darren Croft from the University of Exeter. “They’re not just playing with the kelp-they’re applying it to each other with intent.”

Possible skin health benefits observed in whales with peeling skin

During the study period, researchers noticed a pattern: whales showing signs of peeling or flaky skin were more likely to participate in the kelp massages. This observation led scientists to consider that the behavior might serve more than a social function-it may also contribute to skin maintenance or parasite removal.

This theory draws parallels to what is known as “allogrooming” in primates. In monkeys and apes, individuals often groom one another by picking through fur to remove dirt or parasites. The orcas’ version of this, now referred to as "allokelping", may serve a similar role in promoting hygiene, comfort, or healing in marine environments where conventional grooming isn't possible.

Such tactile interaction is considered crucial for building and maintaining relationships among highly social animals. Professor Croft emphasized the significance of touch in animal societies, explaining that the consistent and cooperative nature of these interactions highlights the complexity of killer whale culture.

Tool use suggests advanced social behavior in orcas

One of the most striking implications of the study is that it points to tool use in killer whales. The act of modifying a piece of kelp-selecting it, shaping it, and then using it for a specific social and possibly health-related purpose-meets the criteria for what scientists define as tool use in animals.

This finding places orcas among a small group of non-human animals, including some birds and primates, that use tools to interact with their environment. “It’s incredibly exciting,” Dr Weiss commented. “This is the first time we’ve seen marine mammals manufacturing objects and using them in this way.”

The Southern Resident killer whale population is already well known for its social complexity. Previous studies have documented the critical roles played by matriarchs, including grandmothers, in guiding and supporting younger generations. Long-term observation has also revealed that females often make significant sacrifices to assist their sons, even at their own expense.

Decades of study reveal a unique culture among Southern Residents

The study builds upon over 50 years of dedicated research on the Southern Resident population, initiated by marine biologist Dr Ken Balcomb. His early work focused on identifying threats to the orcas’ survival, especially the impact of marine park captures during the 20th century.

Thanks to this sustained research effort, the Southern Residents gained official protected status. Over the years, scientists have uncovered detailed insights into their dietary habits, communication patterns, social networks, and now-tool use.

The recent findings underscore the unique cultural traits of this population and strengthen arguments for more focused conservation efforts. The Southern Residents are critically endangered, with their numbers currently below 75 individuals. Every new discovery about their behavior enhances the case for protecting their habitats and food sources, particularly Chinook salmon.

Key takeaways from the study include:

1. 30 kelp massage events recorded over 12 days of observation.

2. Tool use identified through deliberate handling and application of kelp.

3. Social bonding and potential skin health benefits suspected.

4. Observed only in the Southern Resident population so far.

5. Drone footage provided unprecedented insight into underwater interactions.

The use of seaweed in a social context reveals yet another layer of sophistication in orca societies. As new technologies such as drone imaging continue to advance, researchers expect more discoveries that will reshape our understanding of marine mammal intelligence and culture.

Quelle: BBC