Britannica Sources used in this answer

Why do rorquals have grooves on the underside of their bodies?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Illustration showing various cetaceans, including baleen whales like the blue whale, fin whale, humpback whale, gray whale, sei whale, northern right whale, and bowhead whale, as well as toothed whales such as the sperm whale, narwhal, beluga, Baird's beaked whale, killer whale, dolphins, and porpoises. Each species is labeled with its scientific name and typical or maximum length, with a size scale in the corner for reference. — cetacean Whales (order Cetacea).

Rorquals, which are a group of baleen whales, possess distinct ventral grooves that extend from their chin and lower jaw down to their belly. These grooves are a specialized anatomical feature that allows the animal's oral cavity to expand significantly.12

This expansion is essential for gulp-feeding, a method where the whale takes in a massive volume of water containing prey. By stretching the throat and mouth area, the grooves enable the whale to engulf large quantities of food in a single mouthful before straining the water out through its baleen plates.12