Giraffe’s patches (spots) 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 large blood vessel that then branches off into smaller vessels underneath the patch.
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 left image 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 corresponds directly with the heat radiation pattern on the body of the giraffe.
All images from BBC 4 documentary ‘Inside Nature’s Giants – Giraffe’.