That's my new catch phrase when discussing what to do when your puppy rolls over onto his back. Most humans interpret that as rub my belly. That it isn't true in every situation.

It can mean a number of things. That’s why context and looking at the dog’s overall body language is important. What is the rest of his body doing? His ears? His tail? His eyes? His lips?

Is his body loose and relaxed? Is it tight? Does he nudge your hand in an effort to get you to touch him? Is he staring at you or are his eyes soft and blinky? What does he do when you stop?

Belly up can be interpreted as I mean you no harm or to pacify you if you appear angry as well as indicating fear. Offering an unprotected belly is similar to showing your empty hands in the air. You are vulnerable. Nothing hidden. 

Belly up with trusted family members is different from belly up with an unfamiliar person.

That’s why when I walk into a home and a dog offers up the belly, my hands go up. I stop touching the dog and wait to see what he does. Most of the time, the dog gets right up and interacts with me. Sometimes, he will walk away.

Message received.

This is why, even with the dog’s family members, pat the dog slowly and calmly for a count of 3 then stop. Assess. What happens next? 
Does the dog nudge for more? Curl up and go to sleep? Get up and walk away?

It doesn’t have to be complicated. Give your dog the opportunity to walk away or continue to hang with you. He will let you know if he wants to be petted or not if you listen.