Ok, this is very identifiable so I have namechanged, if any of you recognise me please don't out me. Bella, yes it is me.
My wonderful, bonkers, over-active dog was staying at a friends house today whilst I work, this happens quite regularly (well, it did), she is very experienced with dogs. They also have guinea-pigs....can you guess what comes next? I can't even bring myself to write it 
Obviously I feel terrible. Friend is being fabulous, sad and upset but also realistic and reasonable. Sorry doesn't cover it, there is nothing I can say to make this ok.
The question I am hoping you can help with though is about my dog, he has always had a very high prey drive. He loves to chase small dogs, cats or anything else that moves, never aggressive but definitly focused...as he has now moved on from chasing and into catching do I assume that he will catch anything - including small dogs? Is my only option now to keep him on a lead or muzzled? Is this a behaviour that a behaviourist can help with or is it just too instinctive?
He is in no way aggressive and is simply hunting, I have no concerns about his character....just his ability to control himself around small fluffies. Oh, and to add to my concern we have a cat.
I would be grateful for any suggestions (ideally sensible ones, he is not going to eat my children and I am not going to have him PTS or rehomed - just to get that bit out of the way!)