Getting more aggresive

Question
My dad, step mom and I just adopted an 11 month old pure-bread male brown lab (Elvis). We have an almost 6 month old female lab (Ellie). We just got them fixed the 9th, well today is the 10th and last night they did fine, but today Elvis has been having real bad mounting behavior with my step mom, and he actually started to attack her and he got real aggresive. The doctor gave us meds for both of them, could it be that the meds are whereing off on him, or maybe he feels as if he can't feel his man hood, I really don't know, I just need answers! Please write me back!!

Savanna.

Answer
Sounds like the dog is definitely feeling better after his surgery.  I would consider keeping him crated to make sure that he rests and allows his area to heal.  

The mounting is probably more that the dog just came into the house and is trying to assert his dominance over the pack.  I don't mean dominance in a bad way.  Dogs continually test the pack dynamics to see if they can move up in the hierarchy.  With Elvis being new, he's come in and decided that he needs to test the situation to see if he can become the leader of the pack.  This is where you and your family need to really start teaching him the rules of the house and reminding him of any obedience lessons he may have learned before you got him.  Set the rules for the house and enforce them.  When he starts to hump, you tell him NO, physically get him off your step mom and redirect his attention to a toy that he likes.  I would also consider enrolling him some obedience classes.  You can't start until he's fully healed (typically 2 weeks from the surgery), but as soon as possible.  If you step mom is willing, she might be the one to handle the dog in class as it seems that he probably sees her as an easy target to become dominant over.  

In the worst case, when he's being very bad, you can put him in his crate for a time out, but don't do it in frustration or anger.  Redirect his attention off the bad behavior so that he doesn't think he's getting rewarded for acting bad, give him a treat like a marrow bone, a cookie, or maybe a stuffed kong, and get him to go into his crate for an hour to cool off.