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Evaluation of DNA extracted from timber rattlesnake (Cotalus horridus) cloacal and blood swabs for microsatellite genotyping


D'Amore, Aaron D.; Donlon, Kate C.; Hoffman, Andrew S.; Peterman, William E. (2022), Evaluation of DNA extracted from timber rattlesnake (Cotalus horridus) cloacal and blood swabs for microsatellite genotyping, Dryad, Dataset,


Genetic research is a key component to modern wildlife conservation, but it is contingent on the collection of reliable and high-quality genetic samples. Invasive genetic sampling techniques have potential to negatively impact individuals, which may be prohibitive when working with threatened and endangered species. Prior to sample collection, project managers must try to balance the negative impact on individuals included in the study with the demand for DNA and the difficulty of obtaining samples. Although established methods for blood and tissue collection in reptiles meet the need for high-quantity and quality DNA, they inherently require longer handling times and more skill to obtain. Thus, non-invasive DNA collection methods, such as cloacal swabs, may be preferred when animal welfare is a priority. Cloacal swabs are quicker, easier, require less training and reduce handling time. To evaluate cloacal swabbing as an alternative to collecting blood, we obtained both cloacal and blood swabs. We extracted DNA from cloacal and blood cells that were collected from 23 Timber Rattlesnakes (Crotalus horridus). We assessed DNA by purity (A260/A280), concentration, and microsatellite genotyping. Our results show high-quality DNA can be obtained from both cloacal swabs and blood samples, but quality and concentration of DNA was significantly lower from cloacal swabs. Further, degradation and contamination affects the performance of cloacal DNA when compared to blood DNA in microsatellite-based genotyping. Although we recommend collecting blood samples whenever possible to obtain the highest-quality DNA, cloacal swabs represent a viable alternative for genetic sampling when using microsatellite loci as genetic markers.


DNA and microsatellite summary data and code used for analysis.

Usage Notes

Data analyzed using R.