My chihuhua does the normal tail wag when we say we are going for a walk. But if we say lets go the the park he lets out these ungodly screams and will keep it up until he sees his first squirrel. He simply cannot contain himself if he thinks he will see squirrels.
My parents’ chihuahuas (chihuahui?) are the same with squirrels, rabbits and big dogs behind fences on their walks. Don’t know what they’d do with them if they caught them. 