I call a lot of open country and will call to distant bears that I spot first. Almost everytime, a sow will send the cubs up the nearest tree immediately before responding to a call if she is going to come all the way in aggressively. I have had a sow send the cubs up a tree, come towards me 200-300 yards and then turn around and go back to the cubs and head out the other way.
On a slow approach I have had them bring their cubs in with them, but they act much more cautious and tentative.
So study the body, remember big in front boar, big in back sow. Watch to see if they look around or behind them, which can signal another bear is in the area. Look at the head shape. Try to be as careful as possible and if you do accidently pull the trigger on a mom with cubs, don't be afraid to notify the game department.
