Attention male blog followers can you explain why you have to mark your territory?

I wonder why it is that men become territorial after a break up? I see this happen all of the time where they can’t accept that any other man is touching what at one point they considered to be theirs. Women are more territorial during the relationship. I have hear more than one of my friends say “Keep your hands off my man!”, But it’s AFTER a relationship ends when men become overly terratorial of their exes. It’s like when a dog pisses on a specific fire hydrant to mark their spot.  I haven’t quite figured out why this is but maybe my male bloggers can shed some light?