There was an excellent point about what dog-breed or breeds your vet is familiar with. Many breeds and mixes of various breeds pack up better than GSDs do.
I think that you can make multiple females work, even with GSDs, if you have the right personality for that. I think you have to be a strong, fearless, and fair leader with plenty of energy to exercise the dogs, and committment to training. And everyone thinks they know dogs are dogs and not people, even people with foo foo dogs that they put tu tus on and let eat off of their fork think that they understand the dog is a dog and they are treating it like a dog, and more important, interpreting the dog's behaviors and body language with respect to their being a dog. But if you want two female GSDs, then you really have to be clear on this point. GSD bitches are fast, strong, merciless when fighting, don't know quit, they can show amazing patience, and they are very intelligent. In short, they can wait until the timing is right to go to town on the other female. People have literally come home to blood baths where one bitch was dead and the other bitch needed to be euthanized.
If a bitch does fight with the other, and a human gets bitten breaking them up, you have to be able to accept that this is the fault of the humans involved, not the dogs, and you cannot hold it against the dogs for chomping down on human flesh during such an situation.
Unfortunately, as often as not, people get two females, they start fighting, and the people are totally unequiped to manage them. They are unwilling or unable to crate/rotate; or they have kids, and it is dangerous to always have the possibility fo the dog fight, sometimes after witnessing the power and aggression their bitch is capable of, the owners may feel ill-equiped to manage the dog. And often this sums up to one or both females being rehomed or worse. I think the advice on this thread, for he most part, is given with the understanding that IF these bitches do decide to fight, they will be in a very precarious position.
Jenna, RN CGC & Babs, CD RA CGC HIC
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