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 33 surveys). During these surveys we identify latrine sites, monitor scat deposition as an index of population size, and evaluate seasonal changes in latrine use. In 2017, we surveyed 15 km of river in spring and 10 km in fall. In spring, latrine densities (1.9 per km) and fecal deposition (3.9 per site) were comparable to previous years (average for 2001 – 2016: 1.7 ± 0.6 latrines per km [± 95% confidence intervals], and 4.3 ± 1.4 feces per site). Fall values were lower than the long-term average with latrine density estimated at 0.4 per km (long-term average 0.6 ± 0.3) and fecal deposition of 4.0 feces per site (long-term average 2.4 ± 1.0). These values translated into a density of 0.50 otters per km of stream or a total of 7 otters in spring and 0.21 otters per km of stream or a total of 2 otters in fall for the surveyed section. As in previous years, we found no relation between stream flow and otter density in either spring or fall. Nonetheless, because climate predictions suggest that drought conditions will persist in the Rocky Mountain Region, otter monitoring should continue in the future.