Abstract
An overabundance of deer is well known to impact on plant communities and ecosystem processes. Impacts from deer are amplified in New Zealand because these systems evolved in the absence of mammalian herbivores. Extensive deer farming is a recent development in deer farm management whereby animals are stocked at much lower rates than conventional methods and are run in paddocks traditionally used for high country sheep and beef grazing. Such areas often contain remnants of native vegetation and it is therefore important to understand potential impacts that red deer may have on such conservation values so managers can move to mitigate these impacts.
Red deer behaviour, habitat use and diet preference were investigated on two farms (Kilmory and Haycocks Station) that were under extensive management. Vegetation and plant communities were first examined to develop an understanding of the environments on extensive deer farms. Distribution and habitat use was explored using pellet counts as an indicator of presence. Plant cuticle fragments from faecal pellet samples collected on Haycocks Station were examined to establish the diet of red deer within an extensive environment. Cafeteria trials involving four young red deer hinds compared preference between 16 plant species found on the study farms.
The vegetation on both study farms was more diverse than conventional intensive pastures and was able to be classified into one of five broad plant community groupings. The relationship between deer distribution (pellet abundance) and plant community groupings on Kilmory indicated a higher use of habitats dominated by exotic pasture grasses. However this relationship was not shown on Haycocks Station. Cuticle analysis of faecal pellets from Haycocks Station highlighted a number of plant species that were selected over and above their environmental abundance such as Festuca novae-zelandiae and Coprosma rugosa. This analysis also showed that species such as Agrostis capillaris and Anthoxanthum odoratum that were avoided relative to their environmental abundance. Cafeteria trials found that exotic forbs and grasses were most preferred and short native tussocks were least preferred.
These results highlight the complex interaction between red deer behaviour and the diverse environment found on extensive farms. The contrasting trend in deer distribution between the two study farms is thought to be driven by animal density. Results from the cuticle analysis contrasts with cafeteria trials and those found in other studies. This may be due to seasonal shifts in plant species preference and animal behaviour shown in other studies.
Successful sustainable management of conservation values within extensive deer farms is likely to be farm specific. Mitigating potential negative impacts to native plant species requires an in depth understanding of the dynamics between the diverse environment and deer behaviour. Further research is needed to fully understand the impacts of seasonal changes in deer behaviour and diet selection, as well as the mechanisms behind plant preference