Landscape effects of deer control in alpine Australia

Abstract

In this PhD, I examined the movement and habitat preferences of the three deer species, the effectiveness of control efforts, the behavioural and genetic responses of deer to culling, and the effects of landscape scale culling on vertebrate scavengers. Movement analyses revealed that these species have larger home ranges than conspecifics in their native ranges and have differentiable habitat preferences which can be used to inform species-specific control and conservation measures. A landscape-scale aerial culling effort took place to reduce the deer population in this region between 2022 and 2024. Density estimates indicated that despite long term extensive culling efforts, the deer population within the region did not decrease. Nonetheless, I found that aerial culling operations caused decreases in daytime activity, and increases in dusk and nighttime activity, suggesting that deer can shift their diel activity patterns towards nocturnality to avoid an aerial superpredator. Post-cull, I monitored scavenger responses to the presence of large carcass loads. I found that foxes scavenged on carcasses year-round, while dingoes scavenged in warmer periods. The probability of dingo scavenging increased with increasing sambar deer carcass density. Nonetheless, neither fox or dingo scavenging on carcasses was linked to accelerated biomass loss, and biomass loss was driven by warmer temperatures. I then investigated the genetic effect of extensive culling on fallow deer and examined population connectivity, diversity and dispersal potential of populations in south-eastern Australia. Genetic analysis of deer sampled over multiple years before and during culling indicated that control did not cause appreciable changes in the diversity and population structure. This research provides critical information for prioritizing areas for control, optimising control efforts, and elucidates the effects of landscape scale aerial culling on surviving deer, and the wider ecosystem.