Scientific research on Australian wild deer - Diet of wild deer in South Australia
With Neale Finch
For the last few editions of Australian deer I have been discussing scientific research into wild deer in Australia. So far I have outlined the few projects that were conducted prior to 2000 and have started updating readers with more recent work since. I have attempted to focus on projects that have involved the Australian Deer Association where possible. In keeping with this theme I will summarise some recent work carried out in South Australia examining the diet of wild deer using DNA analysis to identify plants in rumen content samples.
Whilst deer were first introduced in 1861 into the south east of South Australia it is only since the 1980s that wild populations have expanded in distribution and density. Historically fallow deer were the only species present in this location and only in restricted areas. Today fallow remain the most common wild deer species however red deer and sambar are now also encountered by landholders and managers. Reports of herds up to 50 or more deer on agricultural lands along with uncertainty around possible environmental impacts lead to understandable concern for many people. Today all wild deer in South Australia are declared pests under the Natural Resources Management Act 2004. Government agencies along with NRM boards and private landowners are tasked with managing declared pests which includes research projects such as that reported here.
The diet of wild deer in South Australia project was a collaboration between staff and students from the University of Adelaide, the Adelaide and Mount Lofty Ranges Natural Resources and Management (NRM) Board and Primary Industries and Regions South Australia (PIRSA). Throughout 2017 members of the South East and Adelaide ADA branch collected samples from harvested deer for analysis as did some SSAA branches, landowners and professional contractors. In total over 200 rumen samples, taken from red (Cervus elaphus), fallow (Dama dama) and sambar deer (Cervus unicolor) were supplied for analysis. Samples consisted of two teaspoons of rumen content, taken as soon as practical from deer carcasses and then frozen at the first opportunity. All labelled samples were then forwarded on to the University of Adelaide for analysis.
Along with herd density and distribution, knowledge of the diet of wild deer is central to many management goals. In their native ranges diet studies can assist conservation and sustainable utilisation efforts whereas in colonised environments they can assist identify possible impacts. Whilst the diets of some wild deer species have been investigated in other Australian states this was the first time it had been attempted in South Australia. This study was also the first time DNA analysis has been used to investigate the diet of any wild deer species in this country. Standard methods for diet analysis can involve direct field observations of plants eaten, identifying large plant particles from the rumen (macrohistological) or identifying plant cells from stomach or faecal samples (microhistological).This study was able to identify a broad range of plant taxa eaten by wild deer using DNA metabarcoding and Next Generation Sequencing.
DNA extraction and analysis was performed by honours student and long-time ADA member Ellen Freeman. The laboratory methods used were complex to say the least. To provide some context of just how advanced DNA sequencing is over 13 500 000 DNA sequences were read from the samples to verify the various plant species in the samples. Of the plant taxa and samples analysed a wide variety of species were identified including naturalised, native, agricultural and weed species.
The results of the project are preliminary at this stage and established such things as the minimum amount of samples required to capture the full dietary range from a particular species in a specific area (at least 36 samples in case you were wondering). More work is anticipated in the future as the results were sufficient to establish DNA metabarcoding, using Next Generation Sequencing, as a comprehensive and accurate method of determining the diet of wild deer.
Some readers might cringe at the involvement of deer hunters with any research seeking to establish negative impacts of wild deer in Australia. However the reality is deer are now declared pests in most Australian states. Research projects of this nature will continue and responsible deer hunters and hunting organisations should be involved. Recreational hunters can be an important component of wildlife management. Participating in research programs such as the one reported here goes a long way to establishing respect, trust and confidence of landowners, NRM boards and government agencies.