I think I'd rather have anything up there than squirrels. It took me a year to get rid of the little b&#%rds. Finally, I ended up putting heavy 1" welded wire over all openings PLUS 6 inches past the edges of the openings. They could not get out. They got really thirsty. One day I loosened a section and two came out as I watched (I thought there was one). Closed it back up and thought that was it... But there was another up there. I put a live trap up there with a bowl of water in it. Took another 2 days for it to be trapped. They chewed sheet rock, peed and poo'd in the insulation, chewed some rafters, even some electrical lines. Why they didn't make a mess of the junk stored up there, God only knows. I tried the moth balls, Ammonia, trap, closed up the openings a few times and they just chewed around them (which is why I put so much extra wire on that last time). Even tried a rat trap. One thing I never tried, and never will, is poison. I don't want them dying up there!