Both my rabbits are fixed (spayed/neutered).
However, anytime there's a new pet in the house (currently a guinea pig), my rabbits start spraying (marking with pee).
While it would seem like this would coincide with questions about pecking order, it also occurred when we rescued a Yorkie off the highway and held it for a few days before its owner claimed it.
Moreover, I would attribute it to territory and having to share space, as the guinea pig and the rabbits like the same hideaways, but in the case of the Yorkie, it never entered their territory.
Are there some general tricks, or things I can do to discourage this type of behavior?