Why do dogs pant?
For grown-ups: the science
Dogs pant because quick breaths help heat leave through their wet mouths and tongues.
Dogs have relatively few functional sweat glands, mainly on their paw pads, so evaporation from the moist tongue, mouth, and upper airways during panting is their main cooling method. Panting increases airflow while limiting deep breathing that could disrupt normal blood carbon dioxide levels.
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Transcript
A dog runs across the grass with its tongue out. Why does it breathe so fast?
When a dog gets warm, it opens its mouth and takes quick breaths. This is called panting.
Air moves over the dog's wet tongue and mouth. Some water turns into water vapor and carries heat away.
Dogs do sweat a little through their paw pads, but panting does most of the cooling. It helps their body stay at a safe temperature.
So dogs pant to let heat leave their bodies. A cool, shady rest helps too.