Invasive Deer Demonstrate Species-Specific Niche Habitat Selection in the Australian Alps

Australia's invasive deer populations continue to expand in abundance and distribution, yet there is limited information on their movement patterns and habitat preferences. This inhibits the prioritisation of areas for control and conservation protection. We tracked 20 fallow deer (Dama dama), 5 red deer (Cervus elaphus), and 14 sambar deer (Rusa unicolor) to characterise their seasonal movement and habitat preferences in alpine and sub-alpine southeastern Australia. Autocorrelated kernel density estimated annual home ranges (km² ± SE) averaged 226.9 ± 54.3 for male, and 55.1 ± 46.5 for female fallow deer, 70.2 ± 35.5 for female red deer, and 25.3 ± 4.0 for male, and 80.7 (one individual) for female sambar deer. Red and sambar deer were mainly restricted to eucalyptus forest/woodland (97% of fixes for sambar, 92% for red) and native grassland (2% of fixes for sambar; 8% for red). Fallow deer, however, were more generalist, and used comparatively less eucalypt forest/woodland (73%), spending more time in cleared areas (14%), and native grasslands (13%). Seasonal resource selection functions (RSFs) showed that, relative to eucalypt forest/woodland, fallow deer preferred cleared land for all seasons except summer, heathland for all seasons except winter, and inland aquatic areas in summer. All species tended to inhabit higher elevations in summer (average: 1517 m ASL for fallow; 1709 m ASL for red; 1463 m ASL for sambar), and lower elevations in winter (average: 1344 m ASL for fallow; 1483 m ASL for red; 1102 m ASL for sambar). Additionally, seasonal RSFs showed that red deer exhibited a preference for higher elevations within their available range in every season except winter, when they preferred lower elevations. Of concern, we found that sambar deer showed a preference for previously burnt areas in autumn (53% of fixes) and spring (89% of fixes), preferring areas with low to moderate and high-severity fire damage. Prioritising areas for control and conservation should be informed by deer movement and habitat preferences, and differences in such preferences between the three species studied herein suggest the need for tailored approaches for control to be effective in reducing their numbers and impacts on ecosystems.