Rabbit ears - ears or air-conditioners?
Unlike people, rabbits do not sweat to lose body heat rather they use their unique ears and a panting action to do so.
If you look close enough at a rabbit's ear you will find large blood vessels which dilate when the rabbit is overheated. Overheating may be a result of warm weather, exercise or in some cases, disease. When air moves across the ear it cools the blood as it passes though the large vessels and returns to the body slightly cooled.