Whales can be very stealthy, despite their size, when they have to catch fish to feed. This was discovered by a team of researchers led by David Cade, author of the study published in Proceedings of the National Academy of Sciences.
The researchers at Stanford ensure that whales know how to use stealth and deception, an apparently paradoxical feat, to catch fish during their “sinking” actions. The sinking is a predatory technique used by whales when they throw themselves underwater to catch as many fish as possible in the middle of a shoal, opening their mouths as much as possible and then filtering the excess water and swallowing only the animals.
Initially the scientists, as Cade himself states in the article presenting the study, wanted to understand why the fish, grouped in large schools, could not escape when this huge animal was approaching, so big that it was really very difficult not to see it.
By also conducting laboratory experiments that simulated the escape reaction of anchovies to a virtual whale and using the behaviour of real whales near the bay of Monterey, California, monitored by tags mounted on their bodies, the researchers came to the conclusion that the whale manages to avoid triggering the escape response of the fish with a precise timing when it opens its mouth in the middle of the shoal.
They manage to make up for their lack of speed and manoeuvrability, being quite large animals, opening their mouths only at the right time and sneaking relatively close to their prey. “This made sense when we realized that the fish have evolved to avoid being eaten by small predators for at least 100 million years, but feeding with lunges is a relatively new feeding strategy, in evolutionary terms”, reports Cade himself.