@FortheLoveofStella:
I have a rescue male, who was being used as a stud dog. He was neutered two weeks before I got him. He was aggressive towards other dogs when I first got him, but he has settled down a lot since then - although he still "has to" mark his territory.
Did he come from a puppy mill situation? That would account for the marking… because typically Basenjis are one of the few breeds that males don't mark, in fact, it is usually the females that tend to mark.
Also you should get them both DNA tested for Fanconi (for your own peace of mind)... www.basenjihealth.org
