Chipmunk Wars

One of the surprise appeals of this new home was the discovery, last summer, of a population of chipmunks living in the trees on the property line and under the back deck.

They are impossibly cute and with a little patience can be trained to take nibbles from your hand. And, bonus round, they upset the cat to no end. He doesn't care about the squirrels, or birds, but the chipmunks really get him going.
About a month ago I discovered that one of these little fellows has discovered a path into the basement. For days I've been listening to him scampering around on the ceiling tiles. He's completely ignored the live traps I've placed for him. This seems to be one chipmunk who doesn't care for peanut butter.
Every other day now for weeks, I've been sticking my head up into the ceiling area, trying to determine how the little bugger is getting in. I've done dozens of laps around the house, looking for any holes. I've crawled under the rear deck. All to no avail.
Today I pried up a deck board as a last resort and discovered a potential point of entry. When the current deck was built, the old concrete stoop was left in place and just built over. That left a previously unseen spot where a bump-out for the kitchen comes over the stoop and the underside is inaccessible to humans.
I went back inside and pulled out an insulation batt and discovered a piles of nesting material, feces and chewed insulation. I think I found the point of entry. I've boarded over the joist bay.
Here's hoping.
If I had a shotgun, I'd be replacing ceiling tiles this weekend.