bonded rabbits mounting when outdoors

Question
Hi, I have a pair of bonded (but not from the same litter) neutered male rabbits, both about 4 years old. I brought them outside today for the first time this season to play in the grass (I have a playpen with a cover, and I sit inside it with them, and we don't use any pesticides on our lawn!). One rabbit was very interested in telescoping, exploring and nibbling grass, while the other one kept mounting him. After a few times, I noticed that when he'd mount him, he'd also bite out a little tuft of his fur. What is this behaviour, and is it anything for me to be concerned about? They both seem completely healthy otherwise.

Thank you!!

Answer
Dear Lisa,

As long as the mounting doesn't trigger a fight, it's no big deal.  The mounter probably just feels a bit excited and insecure, and is trying to exert some dominance/control over his more inquisitive pal.  Just keep an eye on them and make sure they don't start to fight, which could be a disaster.  Rabbits have a long memory and don't readily forgive. :(

I hope this helps.

Dana