Estimating River Otter Density Using Non-invasive Genetic Techniques

This project began in September of 2009 to compliment two ongoing otter projects. Since river otters were reintroduced to Nebraska in 1986 little research has been conducted on their ecology or the status of the populations throughout the state. In 2006 Sam Wilson of the Nebraska Game and Parks Commission and Coop Unit graduate student, began a study to examine river otter home range and habitat use in the Big Bend Reach of the Platte River, a biologically unique landscape. Graduate student Amy Williams joined the project in 2008 to study the effects of Phragmites australis, an invasive plant species, on otter den use. In 2009 she added this genetic study to estimate otter density. Density was estimated using DNA from scat and mark recapture methods. Otter scat was collected along 29 kilometers of the Platte River during two independent sampling sessions in fall of 2009. DNA was extracted from the scat samples and genotyped at 10 microsatellite loci. Unique individuals were identified for both sampling sessions, noting recaptures between sessions. River otter density was 0.99-1.13 otters/kilometer. The density is higher than previously reported for otters in North America. The complexity of the central Platte River, the prevalence of sand pits, and the fact that this population has been unexploited since its initial reintroduction, likely accounts for the relatively high density.

This project not only provided valuable insight into the status of a reintroduced otter population, but also demonstrated the relative ease and efficiency with which this method can be utilized to estimate otter density throughout Nebraska's rivers. This project was completed in January 2011 and the Nebraska Game and Parks Commission plans to utilize these techniques in the future to obtain a state-wide population estimate to evaluate the success of the reintroduction.

Goals

This project used DNA from river otter scat to estimate otter density in the Big Bend Reach of the Platte River and evaluated the feasibility of using the technique to estimate otter population densities throughout Nebraska.

Current Status

This project is complete with results compiled into a master's thesis. This project not only provided valuable insight into the status of a reintroduced otter population, but also demonstrated the relative ease and efficiency with which this method can be utilized to estimate otter density throughout Nebraska's rivers.

This project was completed in January 2011 and the Nebraska Game and Parks Commission plans to utilize these techniques in the future to obtain a state-wide population estimate to evaluate the success of the reintroduction.