Pit bulls and Chihuahuas share one incredibly heartbreaking trait - they are the leading two breeds euthanized in shelters across the country. Why? I mean, they're aggressive, right? We hear all about those scary pit bull type dogs and tiny little angry chihuahuas who seem to be on the top of the list when people comment or joke about "bad" or "aggressive dogs". But how are those things related? What traits do these two groups of dogs share and why in the world does it matter?