Sailors of yesteryear believed that whales spat water through a hole in their head. With these exhalations of hot air that condenses upon contact with cold air, whales can be spotted and an initial attempt can be made to identify their species, often from quite afar. Differences in temperature and pressure… height of the air column… straight, round, V-shaped, slanted… expelled from a single or double blowhole… Time to hone our observation skills!
A blue whale can breath in just 1 to 2 seconds. With each breath, whales replace up to 90% of the air contained in their lungs (compared to 10-15% for humans). Air is expelled from their lungs at high speed (up to 720 km/h recorded by scientists in a young gray whale) through their nose, which is found on the top of their head and is called a “blowhole”. The hot (37°C) air condenses upon contact with the colder outside air and forms a cloud. In addition to the difference in temperature, since the air exhaled is compressed, the difference in pressure between the lungs and the ambient air also causes condensation or vapour. In this mass of expelled air are also water and oil droplets from the upper respiratory tracts or the top of the blowhole.
Spout characteristics vary by species as a function of their size and the structure of the blowhole: a double blowhole forming a bump on the head for baleen whales (mysticetes), and a single blowhole or orifice at the crown of the head for toothed whales (odontocetes).
A number of factors can influence the height and shape of the cloud: wind that blows the spouts or alters their shape, light conditions and the humidity of the ambient air. The height of the spout also depends on the activity of the animal. It will be more discrete when the whale is resting or minimally active, or when its dives are short and close to the surface.
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