Natural Resources, School of


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A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science Major: Natural Resource Sciences Under the Supervision of Professor Craig Allen Lincoln, Nebraska January 2011 Copyright 2011 Amy R. Williams


River otters were extirpated in Nebraska in the early 1900’s. In 1986 Nebraska Game and Parks Commission began reintroducing otters. In support of developing an otter management plan, I conducted research on two aspects of otter ecology in Nebraska. First, I examined otter use of habitats dominated by the non–native aquatic plant, Phragmites australis, in the Big Bend reach of the Platte River. Sixteen otters were trapped, radio–tagged, and tracked between 2006 and 2009. I identified 517 den/resting locations, 127 of which were unique locations. I compared den/resting site habitat use to availability to determine if otters were using Phragmites in proportion to availability. Females use unique sites in Phragmites more than expected but males do not. However, the frequency of use of Phragmites for both males and females was in proportion to availability. Phragmites provides cover for females and is likely used for resting locations when traveling with pups. Second, I used non–invasive genetic techniques to estimate river otter density in the Big Bend reach of the Platte River and the feasibility of using this technique across Nebraska. 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 scats 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. Otter populations in the central Platte River are high and not negatively impacted by the invasion of Phragmites. Results from this study will support the creation and of an otter management plan and ensure the persistence of otters in Nebraska.