River Otter Distribution and Abundance in Nebraska
GoalsThe goal of this research is to provide state furbearer managers with a more complete picture of North American river otter (Lontra canadensis) distribution in the state of Nebraska so that they may be better equipped to make management decisions regarding the conservation status and harvest potential of this species in the state. River otters were extirpated in Nebraska by the early 1900s, and reintroduction efforts in the 1980s have been successful. Recently completed work documented the density of river otters in the Central Platte River, and their habitat use, but was of limited geographic extent. This current project specifically aims to determine current distribution of river otters in Nebraska and to identify patterns of otter occupancy.
Two field seasons were dedicated to surveying more than 1,600km of Nebraska’s rivers for otter sign. Sign was documented on the Niobrara, Elkhorn, Platte, Loup, and Cedar rivers. Two techniques were used to estimate otter distribution and occurrence patterns throughout Nebraska.
- Presence–absence data from sign surveys and data on environmental characteristics throughout the study area were used in occupancy models to estimate the likelihood of otter occupancy across the state’s larger rivers. This method suggested that the central and eastern Niobrara, Elkhorn, Platte, eastern Republican, and southern reaches of the Loup River system were most likely to be occupied.
- Presence–only data were provided by the Nebraska Game and Parks Commission, which came from more than 35 years of incidental harvest reports from fur trappers and confirmed reports from around the state. These data were used in maximum entropy models to examine patterns in otter distributions. The areas identified as being most suitable for otters using this technique were on the Platte River, one section each of the western and eastern Niobrara, the southern reaches of the Loup River system, the northern Elkhorn River, and a small section of the Big Nemaha River near the Missouri convergence.