Deficiencies in estimating the extinction date of the thylacine with mixed certainty data

The last captive thylacine died in the Hobart Zoo in 1936 (Paddle 2000). Beyond this historical fact, the subsequent fate of the Tasmanian tiger, an iconic marsupial predator, is shrouded in controversy (Rounsevell & Smith 1982). Persecution by graziers (encouraged by government and private bounties), snaring by fur traders, habitat modification, and perhaps disease caused a population decline, such that thylacines were regarded as rare by 1910. The final confirmed wild trapping occurred in the early 1930s (Guiler 1985). However, hundreds of unverified observations have been reported in Tasmania over subsequent decades. Carlson et al. (2018) used physical evidence and uncertain sightings to analyze the record of thylacine encounters in Tasmania from 1900 to 2015. They concluded that extinction was likely by 1940 and that there was virtually no chance of persistence to the present day (1 in 112 trillion against). We argue that this conclusion is unjustifiably confident, given the circumstances of the species’ decline.