Behavior in heat

Question
madison,
we have 2 golden full breeds. One male and one female. Our female is about 14 months old and in heat and our 18 month old male is trying. The problem is that he seems to be very agressive when it comes to caging time. When we are not around we cage our dogs seperately. He is showing his teeth and would definitely bite if given the chance. We do not know why. I am thinking it has to do with protection of the female or something. What do you think?

Answer
yes he is just being protective about his mate. he would die for her when she is in heat. she should return back to normal when she has stopped here heat cycle. he just wants to protect her, and he cant if he is in a cage where he id locked from her.  -Madison