My 11 yr. old female Yorkie is very protective of my 10 yr. old female Yorkie who is half her size. When Cocoa is chewing on a raw hide Rosie won't allow either of the fur-boys close. Rosie also runs to check Cocoa out if she utters a peep. Cocoa is mentally challenged and sometimes I think that Rosie knows it. I rescued Rosie after I got Cocoa but the second she walked in the house she took to protecting Cocoa.