Hi XXXXXX,
Humping /mounting is a sign of dominance and even though they have been together for a while they are at the age where one is going to try to take over being the head of the pack which should be reserved for you. Sometimes this works among a pack without the human getting involved because the respect is there , but in this case the one who is humping is trying to be dominant over the other and the other may be fighting because they are in the same pen and there is no way to move away from the other or, the other also wants to be the leader.
It is usually harder to get two females to get along than it is two males as females are more strong willed. If they are not spayed it's time to do this.
What you want to do is train daily three times a day each dog alone with you. Put them on the nothing in life is free diet to further your status and respect. Pick up all toys, bones, beds, dishes , (except water dish) so there is nothing to fight over. Until you get this under control you should separate the pen situation so more damage is not done.
Here are some sites to explain what I have talked about. If you have problems handling this yourself don't hesitate to bring in a trainer to help you.
` Clicker training/positive method training
http://www.clickerlessons.com/
video http://www.clickertrainusa.com/clicker-training-videos.htm
Nothing in life is free
http://www.winnipeghumanesociety.ca/yelp_Line/dogs/nothing_free.php
NILF being the leader
http://siriusdog.com/articles/kids-dogs-bites-safety-prey.htm
dog training consultant
24 years training & behavior,pet first aide, Therapy dog eval., PA Animal Response Team
Thanks for your answer. I'm sure both dogs know who the alpha dog is (me) but I"m sure you're right about the dominance thing.
thanks for the links and advice :)
Rick