I don't think a cat or a dog could fit through the lattice; it's pretty small. That's why I suspect mice, not squirrels. I haven't seen any tears in the screen either so I suppose that's a good thing. I actually tried rat traps for a while and all I caught was a Cardinal (the bird). That made me feel really guilty - and what was a Cardinal hopping around the bottom of my shade house for anyway? - so I opted for the poison.
