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

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Pople, A. R., Amos, M. and Brennan, M. (2023) Population dynamics of chital deer (Axis axis) in northern Queensland: effects of drought and culling. Wildlife Research, 50 (9). pp. 728-745.

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Article Link: https://doi.org/10.1071/WR22130

Publisher URL: https://www.publish.csiro.au/paper/WR22130

Abstract

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 <3 deer km−2 on four properties. Where there was no continuing control, culled populations recovered to pre-cull densities or higher after 2.4 years. One unculled property recovered to its pre-drought density after 6 years. Rates of recovery were at or higher than the maximum annual rate of increase for chital deer estimated here as 26–41%.Conclusions: Drought has a lasting effect on this chital deer population, because of the resulting large population decline and the modest rate of any recovery in the absence of culling. Culling can reduce populations to low density, but the removal rate needs to be sustained to suppress future growth.Implications: Drought provides a strategic opportunity to further reduce chital deer populations for enduring control. Large reductions are feasible given the clumped dispersion of populations within properties and in the region.

Item Type:Article
Corporate Creators:Department of Agriculture and Fisheries, Queensland
Business groups:Biosecurity Queensland
Keywords:aerial shooting, aerial survey, axis deer, numerical response, pest management, population dispersion, rainfall, rate of increase, reproduction, strategic control, ungulate.
Subjects:Science > Invasive Species > Animals > Animal control and ecology
Science > Invasive Species > Animals > Impact assessment
Agriculture > Agriculture (General) > Conservation of natural resources
Animal culture > Deer
Agriculture > By region or country > Australia > Queensland
Live Archive:15 Aug 2023 01:31
Last Modified:29 Jan 2024 04:41

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