He has claimed that spot as his now. He knows that that spot is his, and anyone who comes near is on his turf and he will protect it. My dog Kiki does that. When my mom comes to wake me up in the morning(yes, she still gets me up and I'm 24. Kind of sad eh?), Kiki(he sleeps on my bed), will start growling, his ears go back. He's fine when my dad comes in since he knows my dad is pack leader,