Widespread characterisation of orca whale interactions with yachts as “attacks” is “heavily loaded and highly contestable”, according to an article in The London Review of Books.
Over the past three years, a number of yachts have been sunk in encounters with the whales in an area now known as “Orca Alley” near the Straits of Gibraltar and off the Iberian peninsula.
As London Review of Books contributing editor Francis Gooding writes, at least 11 individual whales in a small population of around 40 have been identified as participants.
Orcas are “thought to indulge in behavioural fads, which can spread through groups quickly before petering out,” he writes.
“The most famous of these involved three pods in Puget Sound that in 1987 spent a few weeks carrying dead salmon around on their heads; in 2005, groups in the same area seemed to experience a less benign craze for tormenting and sometimes killing harbour porpoises, a species they do not eat,” Gooding states.
Human pressures on the environment, such as the longline fisheries for tuna, have been cited as one reason by a working group which studied Iberian orca behaviour.
However, Gooding recalls a period in history where orcas and humans hunted together. From the 1820s, pods of orcas near Twofold Bay in New South Wales assisted the men of the Eden whaling station in killing of baleen whales.
“Specialised focus, communicative teamwork and great adaptability means that – also like human beings – orcas can have a hugely disruptive effect on ecosystems when they choose to turn their attention to a new source of food,”he writes.
He cites Hal Whitehead and Luke Rendell, authors of The Cultural Lives of Whales and Dolphins, who documented how a small group of orcas near the coastal kelp forests of the Aleutian Islands started hunting sea otters in the 1990s.
Having almost eliminated the otters from a large area of the Aleutian coast, the kelp-eating sea urchins, which had been controlled by the otters, then “mowed down” the kelp forests, and left a barren seascape.
“Orcas may have had impacts on the ocean not dissimilar to the ways early humans affected terrestrial ecosystems, and as far as ecologically destructive overkilling goes, it is even possible that the deep history of the orca as a hunter contains a parallel with the rapacity of human behaviour,” Gooding writes.
“The appearance of orcas around ten million years ago correlates with the sudden and mysterious disappearance of more than half the known species of cetaceans, seals and sirenians (dugongs and manatees) from the fossil record,” he writes.
“As with the widespread extirpation of terrestrial megafauna from areas colonised by humans during the Pleistocene, one hypothesis is that orcas, as they expanded into new marine ecosystems, hunted many existing sea mammals to extinction,” he says.
Read the full article in The London Review of Books here
