Our oldest cat, Orla, has always been an alpha queen. She insists on getting fed first, claims a dominant position in the bed at night (right between my wife and I, in the middle of the bed), and had clearly established her position over the two cats we rescued after rescuing her.
However, we had an unexpected rescue last New Year's eve, as I found a stray who needed medical attention. She was so friendly that we wound up getting suckered in to keeping her (I wasn't a very hard sell!), and now we have 4 cats.
The newest, Lily, is extremely friendly, outgoing, and... assertive. In fact, she clearly is demonstrating some alpha behavior.
While she doesn't show any food aggressiveness, she does claim an even more dominant position in the bed (on the pillow at the head of the bed, between my wife and I), and she engages in dominance play with the two other, non-dominant cats.
She also consistently challenges the oldest cat, chasing her, swatting at her when she gets too close to her, etc..
Our oldest is not handling this well. She's become noticeably jumpy in general, and has reverted to hissing any time the male, our third cat (Miles), gets near her (this was common behavior for the first year after we introduced him, but it eventually tapered off). Even worse, Miles now shows signs of dominance behavior directed at Orla (but not at Lily). If Orla jumps up onto the bed, and Miles is on the bed already, he'll frequently lunge at her, and take a swat with his paw. Orla will generally react by hissing, and leaping back off the bed.
All of this seems to have started a few months after we brought Lily in, so my assumption is that it is due to a dominance challenge. Orla seems to be generally less confident around the other cats than she had been, and it is disruptive at times (particularly when we are awakened in the middle of the night by hissing cats charging across our bed).
Is there anything I can do to help bring peace between our 4 cats?