Giraffe - The Facts
Giraffe patches and body heat control
Giraffe's patches are first and foremost for camouflage. But underneath each patch lies a very sophisticated system of blood vessels. Around each patch there is a quite a large blood vessel that then branches off into smaller vessels underneath the patch (see below).
A giraffe can send blood through these small branches into the middle of the patch in order to release heat through this system. Each patch acts as a thermal window to release body heat.
The figure on the left below shows the patches of a giraffe and the one on the right shows the intensity of heat radiation. You can see that the patch pattern correspondes directly with the heat radiation patter on the body of the giraffe.
The larger the neck of a giraffe, the greater the surface area for giving off this heat. The overall surface area of the long and thin body of a giraffe also increases dramatically with a larger neck. Evolution of a body shape that stays cool under the African sun could well be one of the reasons for the giraffe's extraordinary neck.
For more information and as reference for this information, please see Inside Nature's Giants, Series 1, Episode 4: The Giraffe (Channel 4, UK)