What's with the range maps?  I get this question a lot, in fact.  Visitors to oksnakes.org wonder why the range map for a particular species doesn't show the animal in their county when they know they're there.  First, let me state that I don't generate the maps.  They were all taken from the latest edition of A Field Guide To Oklahoma's Amphibians And Reptiles by Greg and Lynnette Sievert.  Here is an explanation of the maps by the authors, as it appears in their new book:

"Herpetologists have no way of finding and tracking every amphibian and reptile in Oklahoma.  The range maps we have constructed for each species in this book are based upon the combined efforts of Greg Sievert, Richard Lardie, Mark Howery, and Julianne Hoagland.  The range maps drawn for each species include only the counties in which the senior author (who is solely responsible for any errors) believes they currently exist, rather than where they could be found based on similar habitat, as in the first editions.  Many outlying counties were omitted from each of the range maps in this book either because they were based on a sight record or the museum record was from a long time ago and the senior author does not believe they exist there any more.  Therefore, the ranges of many of the amphibians and reptiles in Oklahoma appear smaller than in the first editions of the two Oklahoma herpetological field guides.  The ranges of all species are dynamic and new information is collected each year regarding the distribution of reptiles and amphibians.  As new records are collected, these should be shared with the Oklahoma Biological Survey and the scientific community.  It is likely that the placement of voucher specimens into curated museum collections will further clarify the actual ranges of Oklahoma amphibians and reptiles."