It's against pretty much every best practice to leave life safety ropes in areas where animals or other things can damage them, at least for extended periods of time.
That being said, there are tons of squirrels where I have my ropes out and I've never had one damaged. Some ropes are more UV resistant than others. Animal damage on ropes is pretty easily seen if you check. And this is the ONLY reason I feel comfortable leaving them: I can inspect them before climbing. Can't do that if your tie in point is 50' up.
The ropes I leave out have a 7900mbs. I'm having them break tested in August. By that time, they'll have been out for almost a full year. I'm expecting to be around 7000lbs for the break strength. Rope construction is also a factor. Industrial ropes are more resistant to UV and chemicals and generally wear like iron.
Sap doesn't really weaken climbing ropes btw
This is not me officially saying to leave ropes out. Do things at your own risk