Dirk has worked for the Florida Fish and Wildlife Conservation Commission, The Nature Conservancy, the Department of Defense, The Orianne Society, and a number of environmental consulting firms. Most of his career has been devoted to population monitoring of reptiles and amphibians native to longleaf pine ecosystems - including the eastern indigo snake, gopher tortoise, striped newt and flatwoods salamander.

Since 1996, Dirk has conducted annual mark-recapture studies and distributional surveys of eastern indigo snakes throughout southern Georgia and has partnered with numerous researchers on conservation-based, ecological studies of this magnificent snake. Recently, he has assisted the U.S. Fish and Wildlife Service with authorship of the Eastern Indigo Snake Recovery Plan Revision and is a member of the Eastern Indigo Snake Reintroduction Committee.

Dirk has also conducted status surveys for imperiled invertebrates. He has authored over 100 technical/popular articles and his photos appear in a number of publications including Amphibians and Reptiles of Georgia (2008, University of Georgia Press). His popular articles have appeared in Wildlife Conservation, Alabama Wildlife, South Carolina Wildlife, Illinois Audubon, Georgia Backroads, and the Savannah Morning News.