Population estimation methods, home range and habitat use for wild red deer (Cervus elaphus) at Cressbrook Dam, south-eastern Queensland

Abstract

Red deer (Cervus elaphus) have been in Australia for over 150 years. The first documented release in Queensland was on Cressbrook Station in 1873. Following further releases they have spread through the Brisbane, Mary, and Burnett River Valleys to have an estimated population of 15,000 animals. Red deer were a protected species for many years in Queensland, but in 2009 were declared a Class 3 pest animal. The Invasive Animals Cooperative Research Centre National Feral Deer Management Workshop in 2005 reported there was a lack of credible, scientific knowledge about deer in Australia. This project addressed the following research questions relating to wild red deer in south-eastern Queensland: • What is the optimal method for estimating abundance? • What is their annual and seasonal home range? • Do red deer exhibit habitat preferences and what factors affect those preferences? Estimating Abundance: Walked line transect distance sampling, aerial line transect distance sampling, vehicle based spotlight counts and faecal pellet counts were used to estimate or obtain indices of abundance of wild red deer at Cressbrook Dam. For each method the labour input, costs and precision were estimated. Spotlighting performed best overall when comparing labour and costs with precision, but had a number of limitations. Walked line transects gave estimates of adequate and repeatable precision but the method was expensive for both labour and equipment. Aerial survey estimates were quick, relatively cost-effective and comparable to walked line transect estimates, but not as precise as other methods. Faecal pellet counts were expensive in terms of labour, but were very precise. Choosing a method for counting deer will be site and circumstance specific, and some recommendations are provided to assist land managers choose a method. The density of wild red deer at the study site was very high - estimated to be between 26 and 30 deer/km2. Home Range: Wild red deer were fitted with GPS collars to provide location information every 90 minutes. Data were obtained from 22 collared deer – 11 male (4 young adult, 7 mature adult) and 11 female (1 young adult, 10 mature adult). Annual home range was estimated using the 95% Local Convex Hull method to be approximately 359 ha for hinds and 1,323 ha for stags. The data indicate that the size of seasonal home range may be linked to seasonal conditions. Stags at our study site showed no elevated activity in summer compared to European reports. The home ranges at our study site were very large considering the high deer densities encountered. Habitat Use: Habitat preferences of GPS collared deer were explored by computing the resource selection ratios. The available and used resources for individual animals were compared at the home range level for various habitat components. The large data set (over 117,000 deer locations) allowed in-depth examination of possible factors that might affect habitat use. I examined foliage projective cover, aspect and slope to explore deer habitat preferences during the winter, summer and rut for day vs. night. Hinds showed a preference for using heavier cover in the day compared to night regardless of season, whereas stags only showed this preference in winter. Hinds showed a preference for southerly facing aspects in all seasons. Stags showed southerly and easterly preferences in winter and easterly preferences in summer. Hinds generally selected gentle to medium slopes, while stags chose moderate to steep slopes. Given the spread of deer generally in Australia most land managers will likely work towards population maintenance or reduction. Estimating deer abundance will be critical in monitoring progress towards set targets. If population reduction of wild red deer is desirable the best strategy may be to reduce the number of hinds. The home range data suggest that hinds have smaller home ranges than stags. Habitat preferences observed indicate that night time is the best time to target deer in less heavily vegetated environments where they are more visible.