Non-invasive Genetic Sampling of Free-roaming Horses to Estimate Population Size, Genetic Diversity, and Consumption of Invasive Species

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Molecular tagging is a new application of molecular genetic techniques to traditional mark-recapture methodology designed to address situations where traditional methods fail. In such studies, non-invasively collected samples (such as feces, feathers, or fur) are used as a source of DNA that is then genotyped at multiple loci such that each individual animal can be uniquely identified. Thus, each individual’s DNA represents a unique tag analogous to a band or other mark used in traditional mark-recapture studies.

Wild horses

Wild horses running on the prairie. USGS photo.

There is a stated need for robust, repeatable, and transparent methods to estimate the size of free-roaming horse populations. Current population estimates are mostly based on aerial surveys, which are expensive, risky, and can be biased if protocols are not carefully followed or if a substantial proportion of the population is essentially invisible to observers. This study involves developing a new method for estimating horse population sizes based on non-invasive techniques; using genetic analysis of fecal samples (dung) and mark-recapture population estimation models. This research is in collaboration with Colorado State University and BLM.