Critters in attic
There is good information at http://pcwd.info/wp-content/uploads/2016/12/1994TreeSquirrels.pdf
Dealing with the problem now rather than waiting is important. Soon it will be breeding season, and there may be baby squirrels to deal with as well, and even if you eliminate the adults, you might trap babies inside. Trapped babies can be hard to find, may starve to death, and cause an odor problem. The key (mentioned in the document above) is to determine how they are getting in, and making a one-way excluder so they can leave, but not get back in.