We had three at one time a Brittany female came first, and quickly became the alpha. A year later came a Yorkie female puppy. The Britt tolerated the Yorkie but was never overly friendly toward her. A year later a Boxer female came. The Boxer and the Yorkie quickly became lifelong best friends, and played together constantly. As the Boxer grew it was amazing at how careful she was in her play with the Yorkie, despite their tug of war battles with mock growls and head shakes, she knew instinctively to not hurt her buddy. The Brittany and the Boxer was another story. They ignored each other most of the time but as the Boxer grew in size she started questioning the Britt's alpha spot. Had several fights, over the years.