Are my dogs playing or fighting?

Question
We just rescued our third dog (7 month old male St. Bernard, Capone). He joins our 3 year old male (Mugsy) and 10 year old female (Daisy).

We thought it would be a good idea to get Capone since our Daisy is becoming less mobile. In addition, we thought it would help lessen the blow to Mugsy when Daisy passes.

All three dogs get along perfectly in the house. However, when Mugsy and Capone are outside in the backyard, they seem to be nipping at each others ears, neck, and lips. No growling or yelping is going on, just back and forth nipping and chasing each other. Sometimes one or the other will fall on the ground showing their belly and the other will continue nipping. Also, the nipping seems to sometimes be hard. Is this normal play? Or are they fighting?  What the signs I should be looking for to tell if they are playing/fighting too rough? At what point should I break it up?

Thanks for advice.
RC

Answer
Hi Reeny,

They are playing.  You will definitely know they are fighting because you would certainly see snarling teeth, loud yelping and growling.    Just let them be, they are having fun and playing like dogs do.  If you are worried that the playing could escalate, just a stern STOP IT should work but I wouldn't do that unless you hear sounds from them.  As a safety measure, you could always keep a bowl of water handy.  That is the best and safest way (for you) to break up a fight.  It breaks the dogs up long enough for you to grab one of them.