[dmurray]

300-ish man-hours from (probably) untrained volunteers, seems OK for an exhaustive census like this. I'd expect mark-and-recapture to be more expensive, just because it's tough to get people skilled in catching and tagging squirrels. Maybe you can get grad students to do it.

If they couldn't get enough volunteers, the natural next step would seem to be counting a sample of the 350 plots rather than all of them.