David completed an MSc on the ecology of the Diamond Python at the University of Sydney in 1986. In 1987 he joined the Australian Antarctic Division in Hobart as a vertebrate ecologist and began ecological research on the Southern Elephant Seal at Macquarie Island, and Heard Island. He spent two winters and eight summers on Antarctic and sub-Antarctic research expeditions. He completed a PhD on the foraging ecology of the southern elephant seal from Heard Island at the University of Tasmania in 1996. While at the Antarctic Division he conducted ecological research on Southern Elephant Seals, Leopard Seals, penguins, cormorants, and plastic marine pollution. 

In 1999 he moved to Christmas Island to work first as natural resource manager then Manager of Christmas Island National Park with the intention of researching some of the island’s sea birds. However, the emergence of the invasive yellow crazy ant as a serious threat to the island’s ecosystem diverted his attention to researching methods of controlling this pest species, for which the team won a Banksia Award. In 2003 he moved to Canberra and worked in strategic policy areas of protected area management and indigenous land management for the then Department of the Environment and Heritage. 

In June 2008 he joined Taronga as a research biologist of marine mammals. His research interests include foraging ecology, population dynamics, diving physiology, energetics and conservation biology of marine vertebrates.