Moose spawn question

How do wildlife spawns, moose in particular, work? I know there are specific spawn points but is there a set list of spawns that is made when you start a run or does the spawns rotate? Meaning if a moose isn't at a given spawn point now, will it be later?

I have been from Mountain Town to Mystery Lake, then all the way to Forsaken Airfield and have yet to find a moose. I even cheated and looked up the moose spawns in FA (shame on me). currently on my most successful run but really getting tired of this carry limit.

Are moose just that rare or have I just been unlucky?