A simple and effective method for obtaining mammal DNA from faeces

The use of faecal DNA, although a promising tool for the population monitoring of mammals, has not yet become a fully exploited and standard practice, mainly because low target DNA concentration, DNA degradation, and co-purification of inhibitors demand extra laboratory procedures to improve success and reliability. Here we evaluate a simple method that enables sampling of DNA in the field through the collection of the intestinal cells present on the surface of a scat using a swab. The swab is immediately placed in a vial containing a lysis buffer that preserves the DNA for its later extraction. DNA extracts of three species of herbivores (goat, fallow deer and white-tailed deer), two carnivores (Iberian lynx and domestic dog) and one omnivore species (brushtail possum) were characterised in terms of target and total DNA quantity, PCR inhibition and genotyping success. Direct comparison was carried out with duplicate samples preserved in 96% ethanol and extracted via a commonly used commercial DNA extraction kit for faecal material. Results from these comparisons show that swabbing the samples in situ not only simplifies field collection and sample handling in the laboratory, but generally optimises target DNA recovery, minimises co-purification of PCR inhibitors and provides good quality DNA for the species tested, especially for herbivores. This method is also less time-consuming and more cost-effective, thus providing a more convenient and efficient alternative for non-invasive genetic studies.