I suggest geese. They won’t pee on anything but if they get an intruder, will peck the thief almost to death.
Peck? I wish. Our geese don’t peck. The little fuckers bite. They latch on. They don’t let go. They pound you with their wings.
Maybe we should eat them.
Maybe not, but the ones I’ve seen poop on everything.
Short answer: the skylights had been made impregnable by the past regime; we made them totally pregnable. 
Jumping down from the skylight onto a pipe above the office wasn’t so impossible. Jumping back up? Michael Jordan would’ve needed a trampoline. The thieves had to spend considerable time stacking stuff up to climb on.
Well, the fire inspector didn’t seem to care. Maybe it was because the iron gates only locked from the outside. So if you’re inside the building, there’s no way to lock them - unless of course, you broke in, in which case there’s no way to unlock them.
Worked fine for us. 
Ooops, the above drivel contains an inaccuracy. The gate in the front of the building locked from the outside, but the one in the rear locked from the inside (and, IIRC twenty years later) was supposed to be kept unlocked whenever the building was occupied, by order of the fire marshal.
Hope that clears that up. 
Years ago I read about a jewelry store in Arizona that was robbed multiple times, even though the premises were protected by attack dogs after hours. Apparently, experienced, motivated burglars can easily nullify the threat of dogs via chemical or mechanical means. So, they changed tactics and got rid of the dogs. Instead, they placed a few tarantula spiders in the window displays at night and posted a sign saying, “Premises Protected By Spiders, Enter at Own Risk. They claimed never to have been burgled from then on.
I would take it a step further at your garage, in case your burglars are sophisticated and realize tarantulas are not typically lethal and therefore pose no real threat. Post a sign on the door saying, “Premises Protected by Tarantulas and Rattle Snakes; Welcome!; Valuables are in the Back.” Don’t even bother to lock the door. If any intruder (s) think it’s a bluff and enter, have the old spill-the-contents-of-the-bucket-on-the-head trick engaged to trip when they push open the door. With a couple of live tarantulas, a rubber snake (don’t use a live rattlesnake, or you could face charges), and a throw-net fall on their head, and the sound effect of a rattlesnake’s rattle blaring from inside, you will be alerted to the presence of the tangled intruders by the sound of their high-pitched screams. You may have to cleanse the floor of human excrement the next morning.
What you want is a game camera. The even make infrared cameras, so you don’t spook the “game” with a flash.