Localized resources enable noninvasive genetic monitoring of small populations of mountain ungulates

Abstract Small populations of mountain ungulates pose monitoring and conservation challenges for wildlife managers, with population dynamics and genetic status often unknown. Mineral licks are an important aspect of mountain ungulate ecology that offer wildlife managers an opportunity to efficiently monitor population status in remote and rugged areas. From 2019 to 2022 we conducted noninvasive fecal DNA sampling of bighorn sheep in the Teton Range, Wyoming, USA, focusing on mineral licks during summer to evaluate abundance, apparent survival, and genetic status. Agency staff and volunteers visited sites at approximately 2‐week intervals, with 5 sampling occasions from 2019–2021, 6 in 2022, and opportunistic collections annually. We used 9 microsatellite loci to identify individuals; unique individuals were genotyped at 16 loci to evaluate genetic diversity, structure, and gene flow between 2 Teton Range demes and with 2 nearby populations from which we collected samples. We found the northern and southern demes within the Teton Range are linked by movement and gene flow in both directions. Ten individuals genetically assigned to the northern deme were detected in the south and 6 assigned to the southern deme were detected in the north. Successful interbreeding and close relatives were also detected between the 2 demes. Genetic diversity was moderate in the Teton demes (H e = 0.60–0.62), which showed weak genetic structure ( F ST = 0.07) and were more strongly differentiated from neighboring populations ( F ST min–max = 0.10–0.16). We estimated abundance using Huggins closed‐capture models and attained total abundance estimates ranging from 118 (95% CI = 103–155) to 132 (95% CI = 122–148) adults >1 year old, with coefficients of variation <10% each year after 2019. We used Cormack‐Jolly‐Seber models to estimate sex‐ and deme‐specific apparent annual survival rates, which ranged from 0.72 (95% CI = 0.48–0.88) to 0.92 (95% CI = 0.61–0.99). Samples collected at sites distant from our core sites or from subsequently captured animals suggested nearly all bighorn sheep in the Teton Range were available for detection at our sites. Noninvasive fecal DNA sampling focused on mineral licks can be an effective approach for agencies to monitor small mountain ungulate populations in inaccessible areas of the Rocky Mountains.