Dog urinating on other dog..HELP!!!

I have a 7 year old poodle..and ever since I got my Chocolate lab over a year and a half ago he is constantly peeing on her when shes laying down etc Im constantly bathing her and Im at the end of my rope on why its happening or how to stop it. Weve always had at least 3 dogs and this has never happened before..he's not fixed and the vet said that probably wouldnt help.does anyone know why he's doing it ( besides the obvious territorial ) and how I can stop it..I have a cairn terrier also and havent noticed that he does it to this dog. Thank you so much for all your help!!!

 

He loves her

 

A new pet in the house has resulted in the older dog feeling insecure. Thus, he feels the need to show his dominance. I assume the poodle is smaller than the lab, so when the lab lies down and appears vulnerable the poodle can't resist the opportunity. The poodle feels like he is not getting enough attention and may be feeling anxious because the new pet has upside his routine.

If your poodle is not neutered, do so. Involve both dogs in walks, games, and activities in order to strength their relationship and to reduce the feelings that there is rivalry. Keep an eye on the poodle. When he begins to urinate, interrupt him with a loud noise and take him outside. If he urinates outside, praise him and give him a treat. When you’re unable to watch him, put your dog in confinement (a crate or small room where he has never marked) or tether him to you with a leash. Don't punish your dog after the fact. He will not understand.