Hi mine is 2 and he is still turned out next to mares. He has known what they are for about a year but he stands very politely at his side of the fence looking at them doing "naugties and slappin ghis tummy". But he is not causing any probs yet (fingers crossed!!!).
A friends colt is just over a year (around 14 months) and is now mounting his sister (her other foal born the same time) - vet man with sharp knife coming on monday!