Environmental effects on faecal genotyping success in mesocarnivores

Non-invasive genetic sampling can be used in research, monitoring, and conservation of wild animals to, for example, provide insights into diets, identify individuals and estimate population sizes. Non-invasive genetic sampling may be especially useful to monitor elusive species because DNA can be derived from materials such as hairs and faeces without handling individuals. However, the reliability of the results derived from this technique is dependent on the quality of DNA obtained from samples, which can deteriorate from exposure to environmental conditions and sample age. While freshness of the sample is an important factor, the combined effect of different field conditions on the genotyping success is not fully understood. To address this gap, we systematically investigated the effects of sample age and environmental conditions on genotyping success of faeces, in an experimental setting of four treatments that combined rain and temperature conditions typical of central European climates. We compared the performance of a microsatellite marker set and a SNP panel for red fox (Vulpes vulpes), as well as a microsatellite marker set for pine marten (Martes martes) from faeces resampled over 21 days. We found that genotyping success decreased significantly with sample age, however environmental treatments did not impact the success. Furthermore, the SNPs we used amplified more successfully over time than the respective microsatellites. Therefore, the use of SNPs instead of conventional microsatellites, when using faecal samples for analysis relying on correct amplifications, could be advantageous. We recommend to prioritise the collection of fresh faeces regardless of environmental conditions.