Busymom, I used good quality duct tape, but I check it pretty often. It is hard to make a good seal but so far my duct tape has worked.
Thanks Bonibelle,
The stuff I've tried is called the "Great Stuff" it's that foaming stuff The little tester section is doing better now, I will attach the rest and see what happens. I wonder why Marquis doesn't just put a screen over this like it does the vent? :-/ Seems like an easy fix.
Texas, maybe this won't be an issue for me, there are several neighborhood cats that occasionally come through my backyard, maybe that would be enough.