Sophie Flett of Milton Primary School asks :-
When Dalmation puppies are born why dont they have spots?
Alex Davies, a verterinarian at Massey University, responded.
First of all, what are the spots? Dark skin and dark hairs are due to the presence of melanin pigment, produced by special cells that are to be found where the spots are, but not where the skin is pink and the hairs are white. Those of us humans with white skins still have these cells, because melanin forms in our skin when it becomes tanned in the summer sunshine. It is a natural protection for delicate hides from the sun's radiation.
At a time when the puppy is an embryo only about 5 mm long (not much bigger than a match head), the cells that make melanin migrate from along the back, round the sides, to all parts of the skin in a black Labrador and only to certain places in a spotted dog. Most spotted dogs (including Telecom's famous Jack Russell terrier) are born with their spots in place. Dalmatians are therefore unusual, in that presumably the melanin is produced later on. This is a bit like other animals, especially birds, that have a very different colour when they are young. This may protect them from predators while they live hidden in an environment different from where they will be as adults.
Of course, there is nothing natural about Dalmatian spots. Most breeds of dogs have been created by humans for our own requirements. In this case, the fact that we created the 'designer coat' of the Dalmatian doesn't mean that we can explain the timing of when the spots first appear.