Population Survey for River Otters in the Rocky Mountain National Park

Ben-David, Merav

We conducted bi-annual population surveys of river otters (Lontra canadensis) in Rocky Mountain National Park (RMNP) since spring 2001 (total of 41 surveys). During these surveys we identify latrine sites, monitor scat deposition as an index of population size, and evaluate seasonal changes in latrine use. No surveys were conducted in 2020 due to COVID. In 2022, we surveyed 9.5 km of river in spring and fall. Surveys were limited to the northern part of the Kawuneeche Valley because the downstream areas were closed due to damage from the 2020 fires. In spring, latrine density (1.05 per km) was the lowest we measured since 2001 but fecal deposition (3.1 per site) was comparable to previous years (average for 2001 – 2021: 1.8 ± 0.4 latrines per km [± 95% confidence intervals], and 4.3 ± 1.2 feces per site). In fall latrine density (0.95 per km) and fecal deposition (1.6 per site) were similar to those observed in previous years (long-term average 0.6 ± 0.2 and 2.5 ± 0.8, respectively). These values translated into a density of 0.30 otters per km of stream or a total of 3 otters in spring, and 0.24 otters per km of stream or a total of 2 otters in fall for the surveyed section. Because climate predictions suggest that drought conditions will persist in the Rocky Mountain Region, otter monitoring should continue in the future.