How many feral pigs in Australia? An update

The abundance of feral pigs in Australia has been estimated previously and been a topic of some debate. This study aims to update a previous estimate of abundance (13.5 million, 95%CI: 3.5 million to 23.5 million) of feral pigs in Australia. Abundance estimates for the 1970s, 1980s, 1990s, 2000s and 2010s were collated from published literature. Mean abundances in the middle decades were estimated using the ratio method. The average abundance of feral pigs varied from 4.4 million (95%CI: 2.4 million to 6.3 million) in the 1980s, to 3.0 million (95%CI: 2.3 million to 3.7 million) in the 1990s, to 3.2 million (95%CI: 2.4 million to 4.0 million) in the 2000s. Mean density across all 142 studies was 1.03 pigs km-2. The average abundance of feral pigs in Australia during the 1980s to 2000s was much lower and more precise than estimated previously, so scientists and managers should update their use of abundance estimates. Density estimates are above, and below, estimates of threshold host densities for infectious exotic disease establishment.