Bear in mind that I am in Florida & don't know what a prairie is. That said, looking at photographs in a Field Guide by Conant, your critters both look like the great plains skink, Eumeces obsoletus.

I say this because the striping on the prairies (E. septentrionalis sp) is a clean stripe or stripes, while thos on obsoletus are just suggestions of stripes, with dark edged scales...more a dotted line effect than clear striping.

Knowing exactly where they were found might help, unless they were found where the species overlap.

~~Greg~~