Electronic data capture of the nearly 60 years of field data on northeast Kansas snake populations collected by Henry Fitch enabled review of ontogenetic changes in taillength from birth through adult size in Agkistrodon contortrix. Data from 5084 northeast Kansas Copperhead (Agkistrodon contortrix) records collected by Fitch from 1948–2003 (2287F:2797M) were examined to assess the nature of ontogenetic changes in relative tail length of sexes. We suggest that the longer relative tail length of neonate and juvenile copperheads, combined with tail color, enhances the effectiveness of caudal luring, and offer suggestions for further study.