Humpback whales are incredibly intelligent creatures, so it’s perhaps no surprise that they’re also savvy hunters. As Cosmos magazine reports, humpbacks off the northeastern coast of Vancouver Island have been seen tricking fish into swimming directly into their open mouths.
These cetaceans usually lunge toward their prey, and since they're about the size of a school bus, this is generally a pretty sound method. However, researchers spotted two humpback whales testing out a totally new tactic in 2011. Instead of chasing after fish, the crafty cetaceans were seen holding still while looking up towards the sky with half of their heads poking above the water. When they open their jaws, the dark recesses inside their mouths can easily be mistaken for a safe harbor, where fish might seek refuge from predatory seabirds. The cetaceans also use their pectoral fins to draw water towards them, and once the Pacific herring have been lured inside, they snap their powerful jaws shut. On average, they keep their mouths open for 18 to 90 seconds.
“The whale is providing a shadow or shelter,” Christie McMillan, executive director of the Marine Education and Research Society, tells The Vancouver Sun. “It’s like a Venus flytrap, a sit-and-wait idea. It’s not working so well for the herring, but it’s working for the whales.”
This trap-feeding technique was described for the first time by researchers from the society in a recent issue of Marine Mammal Science. Even more remarkably, the behavior seems to be spreading, which means the whales might be learning from each other. Only two humpbacks were spotted using the technique in 2011, but 16 were seen trap-feeding in 2015.
“Based on the rapid diffusion of the behavior and the characteristics of the prey consumed using this technique, trap-feeding appears to be an energetically efﬁcient method of foraging on juvenile herring that is culturally transmitted between humpback whales," the researchers write in their paper.
The behavior hasn’t yet spread among humpbacks beyond British Columbia, as far as researchers can tell. However, Bryde’s whales in the Gulf of Thailand have exhibited similar feeding behaviors, according to The Vancouver Sun.