Is because I have five chihuahuas two males and three females the little ones are 6 months old, but I dont want the little male to get pregnant my female chihuahuas. The other male has been taken care, I havent take the little one because I think he is to small.
6-9 months depending on the dog.
Mine is 8 1/2 months and having her first heat.
I understand the worry about the size and the procedure, if he's over 5 lbs, I'd go ahead and have him fixed. If he's under 5 lbs, I'd talk to my vet about the risks associated as well as his experiences with such a tiny dog and go from there.