School of Earth & Environmental Science
Lester, Joshua, Monitoring Feral Deer in the Illawarra Escarpment State Conservation Area, BEnvSci Hons, School of Earth & Environmental Science, University of Wollongong, 2016.
Since the beginning of the Anthropocene, human induced impacts have led to reduction in ecosystem functioning and a reduction in biodiversity, the like of which has not been seen for 60 million years. One of the most common impacts faced by scientists and land managers alike is the threat of ecological invasions and effects that they are able to impose on regional environments. To allow for the creation of well informed and successful management procedures, effective and reliable methods of monitoring and surveying populations of invasive species are needed.
Locally, feral deer populations are responsible for a reduction in faunal and floristic biodiversity, the destruction and clearing of large volumes of biomass, the degradation of soil quality, increased rates of soil erosion, and cost residents in excess of $500 000 a year in damage to property. Worldwide, various methods have been developed to monitor trends in deer abundance over time. From a management standpoint relative measures are often favoured as they are generally cheaper and more easily implementable. To investigate the most suitable practice for monitoring deer populations of the area, relative abundance estimates garnered from three different methodologies, camera trapping, modified distance sampling methods and faecal accumulation plots, were compared in terms of their reliability and ability to monitor changes in deer abundance over time.
No two methods provided significantly similar estimates of relative abundance at all sampled sites. At two of the three sites, data from camera traps and spotlight assisted distance sampling procedures were significantly correlated. Faecal plots and daytime visual observations were not significantly similar to any other measures of abundance. Data from faecal accumulation methods were highly variable and may not be suitable for use in scientific or management procedures. Distance Sampling of feral deer indicate that there are 0.4 deer per hectare within the IESCA, which is equivalent to approximately 1090 deer in the conservation area.
It is suggested that long term monitoring procedures focus on either camera trap based methodologies or spotlight assisted distance sampling to monitor deer populations. This information will hopefully allow for the creation and implementation of more effective monitoring and management procedures in the future. Future studies should investigate the effect of increasing periods of deployment on the reliability of estimates garnered from camera traps and faecal accumulation plots. Additionally, these methods should be tested against a population if a known size to test if garnered estimates are representative true abundance patterns.