Ivan Gamble, of Balclutha Primary School, asks :-

How do giraffes get their patches and why are there three types of girrafe?

Jean Arnott and Alex Davies, of Massey University's School of Veterinary Science, responded.

How interesting that you should link these two questions.

The current model proposes skin colour in all animals (including giraffes) is controlled by two chemicals found just under the skin. One chemical stimulates production of melanin and the other prevents its production. These chemicals diffuse over time to produce patterns that can be described by mathematical equations. Animal patterns, from the stripes of tigers to cheetah dots, can be described by adjusting numbers in the model's basic equations and altering the starting distribution of chemicals.

The shape and size of the animal also has a big influence over the shapes that result and this brings us to the three types of giraffe. Each has a different geometric shape. The smallest is the Reticulated. The Masai is bigger while the Rothschild is stockier. So the same basic giraffe coat pattern applied to the three giraffe shapes gives three types of pattern. It is a bit like draping mesh over different objects. The mesh would get stretched different ways depending on the shape of the object.