Friends of a friend of mine have recently taken on a Chihuahua male puppy, they already have four other male dogs all intact.....A Bullmastiff, Dogue De Bordeaux, Staffordshire Bull Terrier and a Springer Spaniel....The Staffy, Dogue or Bullmastiff are not yet fully mature all under 18 months old..I can see only one way this will go and it will not be good for any of the dogs concerned