Blowhole (anatomy)

In cetology, the study of whales and other cetaceans, a blowhole is the hole (or spiracle) at the top of the head through which the animal breathes air. In baleen whales, these are in pairs. It is homologous with the nostril of other mammals, and evolved via gradual movement of the nostrils to the top of the head.^[1] The posterior placement of blowholes on cetacean heads is believed to minimize the energy used when breathing at the water's surface.^[2]