sample therefore revealing the individual they came from. Just like in a paternity test, cotton swaps are used to take a smear, which is put into a plastic tube and sent to the laboratory. However, compared with blood or tissue samples, the DNA in faecal samples is only represented by a few cells, making it a very difficult procedure. "In addition to this there is also still the problem that a high number of proteins, bacteria and enzymes in the faeces disturb the analysis," reports Dr. Marion Hoehn, who is an expert in conservation genetics of vertebrates. "We have to extract the DNA and copy it several times in order to make it visible, which is prone to errors. The process therefore has to be repeated several times to obtain the true genotype."
Thus, the researchers were thrilled that they were able to more than double the success rate compared to earlier procedures. Their new method brings further crucial progress with it: it combines modern genetics with the classical approach to population studies using Mark Release Recapture (MRR). In traditional MMR, animals are captured, marked, and released, and eventually recaptured. During the recapture events researchers note whether the animal had already been marked or not. After several recapture periods it is possible to mathematically calculate just how many animals are present, based on the ratio of marked to unmarked individuals. For the cryptic otter this method is not feasible. In our novel approach, not the animal itself is captured but its "genetic fingerprint", which is derived from the faecal sample. For the accuracy of the population estimates it is important that faeces are collected every day from the same location within the same time intervals. The relocation rates should be as similar as possible, so as not to falsify the results with coincidental findings. The costs of this technique amounted to approximately 30 Euros per faecal sample. "That is still the more favourable option compared to hav
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