You really can't get a degree in herpetology today. But you can get a good BS in biology, and go to a school where you can work in the lab of a herpetologist and eventually do your own research projects.

Schools to check out with good herpetology faculty includ
Cornell (google search cornell herpetological society)

University of California, Davis

UC Berkeley

U. Texas Austin

U. Kansas

to name just a few