The best cat deterrent that I presently have ismy dog. When she is in the yard, nothing dares cross the fences thatborder my neighbors' backyards. Unfortunately that isn't much of asuggestion for you...the only thing I can offer is a hutch that'scat/squirrel/raccoon/andallotherenemies safe - no chicken wire, as wassuggested, latches that cannot be opened easily, and a solid house partto the hutch where they can retreat and be safe from any predators (italso offers a bit of a reprieve from terror if they are under attack,as rabbits can easily die of fright). And whenever your bunnies areloose in the yard, be out there with them. An accident, an escape, oran attack can happen in a moment's notice...