Population dynamics of chital deer (Axis axis) in northern Queensland: effects of drought and culling

Context: Chital deer (Axis axis) are long established in the northern Queensland dry tropics, and at high densities are considered pests by cattle graziers. Cost-effective management is difficult for widespread, fluctuating populations of vertebrate pests such as these deer. Historically, control of chital deer has been limited to recreational and some commercial ground-shooting and trapping. Concerns over chital deer impacts were heightened during drought in 2015 and funding became available for aerial culling.Aim: This study set out to determine (1) distribution and abundance, (2) seasonal reproductive output, (3) potential and actual rates of increase and their determinants, and (4) efficient management strategies for chital deer in the northern Queensland dry tropics.Methods: In 2014, ~13 000 km2 of the main distribution was surveyed by helicopter. Multiple vehicle ground surveys per year monitored chital deer density on two properties during 2013–2022. Seasonal shot samples of deer on both properties assessed reproductive output during 2014–2016. Aerial surveys during 2016–2020 determined chital deer densities on seven properties, prior to aerial culling on four properties. Finally, the maximum rate of increase of chital deer was calculated from life-history data.Key results: Regionally, chital deer are patchily distributed and so are best monitored locally where densities can be >50 deer km−2. Vehicle ground surveys recorded an ~80% decline in chital deer populations on two properties over 7–10 months during drought in early 2015, with a similar rate being recorded by aerial survey at a third site. There was little recruitment during the drought, but the decline was seemingly driven by adult mortality. Aerial shooting further reduced populations by 39–88% to