Kevin brought me back from the dead for these questions. Hello! Here we go
I never worried about wildlife on my coasters, even on Pine Mine where I probably should have. The deer could have trampled it anytime, but there really wasn't anything I could do to prevent that since it was not my property (college campus). For my other coasters in my backyard, occasionally a squirrel would check it out but at least to my knowledge none would climb on.
Regardeless of tall or short or whatever, I always anchor rods in the ground. You can check out Pine Mine and The Finisher for examples. I usually use either reds (specifically red so I could find them after) or greys if the soil is soft enough. So for depth I guess between 3.5 and 7 inches. I either pushed them in with my fingers or pounded them in with a hammer. Pretty fun. And let me tell you those supports were freaking rock solid. It's great.
My outdoor coasters in my backyard and also I guess Pine Mine were built in just a few weeks, maybe a month or so. Throughout the time it was up there just needs to be some maintenance and upkeep of track shape and maybe some relaying of tubing. Being outside will cause the tube to be softer in the summer due to temperature, so that will affect the speed and lubrication you may be using.
I'll do my best to actually come back and check again soon for a reply, and would be glad to take any more questions you have!
First time back here in years and I think it went well,
~Joel