Watch: Orcas use seaweed tools to scratch each other's backs

Telegraph

3 days ago

Killer whales have been filmed fashioning seaweed sticks to scratch each other's backs in the first evidence of tool-making by marine mammals.
Scientists spotted the behaviour in drone footage of orcas swimming in the Salish Sea, off the coast of Washington state in the US.
The orcas were seen to bite off the end of a kelp stalk, position it between themselves and a partner and roll the kelp between their bodies for prolonged periods.
Dr Michael Weiss, of the Centre for Whale Research (CWR), said: 'We were amazed when we first noticed this behaviour.'
He added: 'The more observations we had, the more we realised they weren't just finding these pieces of kelp in the environment and grabbing them, they were actually fashioning these tools or these tools from complete kelp stalks.'
Whales are known to play with seaweed and are often seen draping it over their backs or wearing it as hats in a process called 'kelping'.
But this discovery is different because the kelp is deliberately selected, torn off and manipulated by two whales working together. Researchers have called the new behaviour 'allokelping', which means 'kelping with another'. The pieces of kelp the orcas use are around two feet long.
The Salish Sea whales have been studied since the 1970s, and their habits were thought to be well known. But new drone technology has allowed researchers to observe behaviour that they believe may have been happening for decades without being seen.
'Happening all the time'
Rachel John, a Master's student studying animal behaviour at the University of Exeter, said: 'We hadn't noticed 'allokelping' before because the videos being collected from our previous aircraft weren't of high enough quality, but the footage we're getting now shows this behaviour in great detail.
'I was watching one of those really close-up videos when I saw something that looked like a brown stick between two whales that were in contact with each other. We looked back at lots of videos and realised that rubbing kelp between their bodies wasn't just a one-off thing – it was happening all the time.
'And once we saw whales breaking off pieces of kelp intentionally, it became clear that this is not just play – this is something important in the social lives of the 'southern resident' killer whales.'
Over a 12-day study period, the whales performed 'allokelping' on eight of the days and were more likely to carry out the practice on closely related whales or similarly aged partners, leading experts to suggest that it may be a form of grooming.
Bull kelp stalk is firm and flexible, like a filled garden hose, with a slippery outer surface, which experts said made an ideal grooming tool.
The team also saw some evidence that whales with more moulting or dead skin were more likely to take part in 'allokelping', suggesting that it may also serve as a hygienic function.
Important for skin health
Prof Darren Croft, of the University of Exeter and CWR's executive director, said: 'We know touch is really important. In primates – including humans – touch moderates stress and helps to build relationships.
' Killer whales often make contact with other members of their group, touching with their bodies and fins, but using kelp like this might enhance this experience. It might also be important for skin health.
'Whales and dolphins have a variety of strategies to help them slough dead skin, and this may be yet another adaptation for this purpose.
'Brown algae like bull kelp also have antibacterial and anti-inflammatory properties that may provide further benefits to the whales.'
Other killer whale pods have been spotted rubbing their bodies on smooth stone beaches, possibly to remove dead skin and parasites. However, the Salish Sea whales have not been seen doing this, suggesting that the kelp may offer an alternative solution.
The researchers said it was unclear whether the grooming behaviour was entirely unique to this population or more widespread among other whale populations and species.
The study was published in the journal Current Biology.