Before joining UTRGV, he was an Associate Professor of Environmental Science at Post University, Waterbury CT, where he also was involved in establishing its Environmental Theories & Applications Program. Additionally, Dr. Dirrigl has over 25 years of experience serving as a professional environmental scientist in industry for environmental permitting with civil engineering firms, federal/state/municipal government agencies, and non-profit organizations. His areas of expertise include, Environmental Biology (Biomonitoring, Rare Species Biology), Environmental Permitting (Ecological Impact Assessment, Wetland Evaluation, Mitigation BMPs), Environmental Anthropology (Human Impacts and Natural Resource Conservation), and Comparative Vertebrate (Osteology-Taphonomy, Bone Biology).