In order to make lunge-feeding work, you have to have a really big mouth to capture enough water in one gulp. But in order to have a big mouth, you need a big body. And in order to keep that big body running, you need to get a lot of food. And in the very act of getting that food–diving deep, lunging open-mouthed, and then pushing a school-bus-sized volume of water forwards–requires a lot of energy on its own.
This type of feeding might explain the size of whales.
If the scientists are right, they may have discovered one of the big ironies in evolution. Lunge-feeding may have allowed whales to become the biggest animals ever to roam the planet. But this was not an open-ended invitation.r. Once whales got large enough, lunge feeding itself became so costly it prevented them from getting any bigger.