The way my pen is set up only one side is in full sun and is deep loamy soil, the other side is gravel, shaded most of the day by the house, and has a pond on that side, so there is a general area where they lay eggs, so I look for a spot the looks disturbed then start digging with my fingers, most of the time it is just where one of them burrowed in the night before. I mostly just get lucky in finding them I guess. Plus I know its close when I see females walking around in the afternoon.
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Jeff Benfer
gartersnakemorph.com