I too think it's Yorkie "communication". I have never seen an animal that tries so hard to talk .... expecially one who rarely barks like Toto! She usually tries to speak in a tiny little voice and we have learned what she wants. If we don't immediately respond to her little voice, she has a low bark and if that doesn't work, she uses her
big voice!
She does it if we are not "on time" with her meals, her after dinner treat, if she has a pee pee spot or a poop on her pad [she refuses to use a soiled pad], if she wants to play, if she is cold and sometimes she just wants someone to sit down and snuggle her!
We were puzzled too when she first began to do this and things are sooooo much better since we began to understand her. Good luck!
