My cats can get through some very small gaps, and if you get a badger, there is no stopping them, they will push there way through anything, wild boar I am told are the worst, I really felt sorry for the guy who got them in his garden, lucky not seen any around here.
But I like watching the hedgehog waddle though the garden, and really don't want to stop it.
Goats and sheep are a problem, the height sheep can jump surprised me, watching them walking along the top of garden walls, and the goats of Llandudno have become a real problem since Colvid, they just would wander around the Great Orm, but with Colvid they came into the empty streets of the town, and it seems will eat anything, and are protected.
So what you do depends on why you want to block the holes, think it unlikely you will stop squirrels, there is a film over the hedge which shows what happens when you try to stop wild life, thank god I don't live in the USA.