It varies from dog to dog. The majority of bitches go into their first heat cycle between 6 and 12 months of age, but I have known some to come into heat at 5 months and one at 18 months. I've heard that it tends to occur earlier for small dogs and later for large ones, but I've seen a Chihuahua go into heat at 12 months and a Bernese Mountain Dog mix at 7 months, so I'm not if I believe that...

Otto answered on 2/21/13. Helpful? / 0