While I only have cats, I see a similar thing happen here. The youngest (male) is incessantly playful and is always up for some playtime, whereas the two older girls only occasionally play.
It's sometimes hard to figure out if a girl is fleeing from him, or playing with him. We observed for a long time, and found that we often interrupted genuine play time because we thought the playing was getting too rough.
It's relatively easy to see when a cat is genuinely distressed. Some cats gets fearful, others get aggressive (well beyond playfulness). Specifically look out for:
- Long drawn out meows
- High pitched fierce meows (think of the sound you hear when two cats are fighting outside - often used in TV and movies)
- Arched back, raised hairs
- Trying to find higher ground where the chaser cannot reach.
If your cat doesn't look like it's either ready to attack (with anger) or fearing for its life, you can usually consider it playing.
Our youngest was a bit oblivious as to whether the others were interested in play time or not. As they were still getting to know each other, we helped "save" their relationship by making sue that he didn't ruin his relationship with the girls.
There was a pattern of escalation here. Whenever he took it too far, he would subsequently encounter:
- Yelling his name and telling him to stop.
- Loudly clapping my hands
- Physically separating them by putting the offender in a different location.
We used the spray bottle for most other things but didn't use it in this case, because we wanted to avoid hitting the girls. The negative feedback needed to be clearly directed at him.
Interestingly, distracting him would often reveal if it was playing or fighting/harassing. If the girl made a hasty retreat when he was looking at us because we called his name, she clearly wasn't enjoying herself. If she stared at us as much as he did, then we had apparently interrupted genuine play time.
While the feedback you give your dog is likely different from the feedback I gave my cat, the same principle applies:
- If you think it's bordering on harassment, interrupt the interaction and see if the alleged victim escapes.
- Tell the attacker off for taking it too far (but allow him to resume normal play if he's able to)
- Repeated offenses get punished more severely.
- Eventually, the offender will be put in timeout.
- As you get better at distinguishing between playing and harassing, try to avoid interrupting playing. If you're consistent (and correct) about your negative feedback, your dog will understand the line between playing and harassing better.