Recent headlines have highlighted the unusual ways that whales can behave when they come into contact with humans. Reports and videos depicting pods of orcas attacking yachts and other large boats are circulating on social media and elsewhere on the web, with attacks on the rise since 2020. Theories abound behind the behavior, with marine biologists chalking it up to varied causes including playful behavior with damaging consequences, simply the latest behavioral trend being passed among killer whale pods, or even an act of revenge triggered by past trauma.
“The orcas are doing this on purpose,” said Alfredo López Fernandez, a biologist at the University of Aveiro and co-author of the study identifying the rise in attacks. “Of course, we don’t know the origin or the motivation, but defensive behavior based on trauma, as the origin of all this, gains more strength for us every day.” López Fernandez identified the behavior as triggered by a “critical moment of agony” for White Gladis, the female orca leading the attacks. "That traumatized orca is the one that started this behavior of physical contact with the boat," he said.
Orcas aren’t the only cetaceans whose behavior is affected by human encounters.
Whales who are tagged with measuring devices often behave differently in the time immediately following their tagging. As tagging becomes increasingly common, scientists are beginning to study the extent of tagging’s effect on whale behavior.
A newly published study uses a statistical approach to solve the question of how quickly narwhals and bowhead whales can be expected to return to their normal behavior after being tagged. Scientists from the Greenland Institute of Natural Resources and the University of Copenhagen’s Department of Mathematics collaborated to use quantile regression and relative entropy to characterize the whale’s behavior over time, deeming it “normal” or “abnormal” at any given point in time. The new method allows marine scientists to more quickly identify when tagged whales have returned to their everyday behaviors, rendering the data collected by measuring devices as usable.
"This research is extremely valuable to us as marine biologists who are interested in the behaviour and well-being of whales. It provides us with a standardised approach by which to distinguish between natural behaviour and affected behaviour in whales,” said study co-author Outi Tervo.
The methods identified in the paper can also be applied to similar situations in which other animals’ behavior has been perturbed by a disturbance. And, the scientists have also learned important lessons about how to minimize the effect of tagging on whales, thanks to their models.
"Based on this study, we already know that the amount of time we spend putting the equipment on is an important factor for how much the animals are affected afterwards,” said Tervo. “Therefore, we can set up some time limits -- where we stop and set the whale free if it takes more than X number of minutes allowed.”
Sources: Marine Mammal Science; LiveScience; Ecology and Evolution; ScienceDaily
