Researchers from Oregon State University have captured drone footage of gray whales foraging in the waters off the coast of Oregon.
The whales’ acrobatic movements include forward and side-swimming, the use of 'bubble blasts' and headstands – a head-down position where the whale pushes its mouth into the ocean floor.
The observations, which were made using drone footage captured over seven years, offer new insights into the remarkable feeding methods employed by gray whales, says Clara Bird, a researcher from the university's Marine Mammal Institute.
Bird found that the probability of whales using these acrobatic feeding behaviours changes with age, most notably that younger, smaller whales are more apt at using forward-swimming behaviours while foraging; while older, larger whales are more likely to headstand.
“Our findings suggest that this headstanding behaviour requires strength and coordination," Bird says. "For example, we often see whales sculling much like synchronised swimmers do while they are headstanding. It is likely this behaviour is learned by the whales as they mature.
“We have footage of whale calves trying to copy this behaviour and they’re not able to do it successfully.”
The study shows that whales alter their foraging tactics depending on the habitat and depth of the water they are in. For instance, they are more likely to use headstanding when they are on a reef, because mysid shrimp, their primary prey, often aggregate on reefs with kelp, Bird explains.
The findings were published in two new papers authored by Bird and co-authored by Associate Professor Leigh Torres, who leads the GEMM Lab at Hatfield Marine Science Center in Newport.
Torres says that studying to gray whales over the past 10 years has been an amazing journey. "They are underwater acrobats, doing tight turns, upside-down swimming and headstands.
“We have now connected these behaviours with the habitat, size and age of the whale, which allows us to understand much more about why they go where they go and do what they do. This will help us protect them in the long run.”
Find out more about the work: Growing into it: evidence of an ontogenetic shift in grey whale use of foraging tactics
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