We had guinea pigs and dogs when I was a child. Our dogs showed no interest at all although Meg was a keen mouser. Sadly the female was attacked by a visiting dog - she was heavily pregnant and died of shock. I was totally heartbroken. The male pig suffered the same fate about a year later, another visiting dog ( JRT) . A quick shake and he was gone. I really love guinea pigs, such sweet little animals , but would obviously be much more aware now. To be honest I think Reena would be scared of them, she doesn't appear to have any prey drive at all.