The article:
Humpback whales are marine mammals known for their exceptional intelligence, sophisticated social structure, and intricate communication methods. A new study provides fresh evidence by documenting how humpback whales use kelp stems as tools to groom each other’s fur, engaging in behavior akin to “you scratch my back, I’ll scratch yours.”
According to reports from Reuters and other media outlets on June 24th, researchers used drones to observe a group of humpback whales in the Salish Sea, located in the Pacific between Washington State and British Columbia, Canada. They found that these whales utilize kelp – also known as seaweed – to groom each other’s backs, a behavior now termed as “allokelkelping,” making it one of the few known instances of marine mammals using tools.
This mutual cleaning behavior using kelp is quite common among the resident humpback whale population in the southern waters of the Salish Sea, with researchers documenting around 30 such instances within eight days.
Humpback whales locate a type of kelp known as bull kelp, which can be either attached to the seabed or floating on the water’s surface. They bite off the end of the stem, place it between themselves and another whale, and wrap the kelp around their bodies. Observations show that the whales use their teeth to cut the ribbon-like kelp, a material that is both strong and flexible like a garden hose. They then place the kelp between their bodies and rub against each other for several minutes, cleaning each other.
Researchers speculate that this behavior aids in promoting skin health and strengthening social bonds. Other humpback whale groups have been observed rubbing their bodies on smooth boulders, possibly to remove dead skin.
“Most examples of animals using tools are related to solving ecological problems, such as obtaining food. For instance, chimpanzees use sticks to catch termites. What makes this discovery remarkable is that the tool – kelp – is not used for obtaining food but rather for enhancing social interaction,” said marine biologist Darren Croft from the University of Exeter, a co-author of the study published this week in the journal Current Biology.
“This tool-using behavior driven by social motivation is extremely rare among non-human animals, previously observed only in a few primate species, often in captive environments,” added Croft, who is also the director of the Whale Research Center, a scientific institution in Washington State studying humpback whale populations since the 1970s.
Researchers documented this behavior in humpback whales of all ages and genders, suggesting that it could play a vital role in their social lives.
There are other examples of marine mammals using tools. Sea otters use stones and other hard objects to crack open shells and eat the meat inside. Some dolphins use sponges to protect their noses and stir up the seabed while foraging. Researchers note that humpback whales take it a step further by modifying objects, using kelp as tools.
“While this is not the first recorded instance of whales or marine mammals using tools, to our knowledge, it is the first case of whales manufacturing and utilizing tools. Whales not only find suitable lengths of kelp in the environment but also actively modify larger, intact kelp stems to create the fragments they use for back scratching,” said Rachel John, a graduate researcher at the University of Exeter who studies humpback whale behavior and a co-author of the study.
This behavior has only been observed in humpback whale populations.
“We found that individuals with more obvious skin shedding were more likely to engage in ‘conspecific manipulation,’ indicating that this behavior may have a skincare function. Brown algae like kelp are known to have antibacterial properties, so using kelp for rubbing may help improve skin health,” Croft explained.
“Furthermore, we believe this behavior may play a role in maintaining social bonds. Physical contact is crucial for social cohesion in many species, including humans. Just as we might hug a long-lost friend, this ‘opposites attract’ behavior could also help strengthen social relationships among whales,” Croft added.
Kelp grows in cold and nutrient-rich coastal and intertidal waters, flourishing near the North American west coast, where the habitats of these humpback whales are also located.