The northern river otter (Lontra canadensis) is a semi-aquatic carnivore whose range extends throughout most of the United States and Canada. The northern river otter experienced a severe range contraction post-European settlement, but due to widespread management has in recent decades begun to recover much of its former range and habitat. We translocated 27 river otters from Utah and Idaho to the Provo River, Utah from November 2009 through January 2012 in a reintroduction effort to restore the northern river otter to its native range. Of these 27 otters, 6 died as a result of effects related to the translocation. We used linear regression and model selection to determine what factors had the most influence on the immediate mortality of translocated otters. We found that body mass was the most important factor, followed by sex. Indeed, otters at the high end of the body mass spectrum were 4 times more likely to survive a translocation than otters at the low end of body mass. Along with the reintroduction project, we determined the food habits of the northern river otter in the Provo River watershed. We located and monitored otter latrine sites from February 2010 through February 2012, collecting scats on a monthly basis. We identified prey items in otter scat and recorded data as the frequency of prey items per total number of scats, presented as a percentage. Fish was the primary class of prey taken by otters (96.5%), followed by crustaceans (16.9%). Otter diet varied among seasons for nearly all classes (G = 127.8, d. f. = 24, P < 0.001) and families (G = 132.94, d. f. = 18, P < 0.001) of prey. We conclude that otters are potentially selecting prey in the main channel according to their abundance and in inverse proportion to their swimming ability. However, with multiple habitat types that vary in species richness and diversity, it was difficult to determine which prey items otters are selecting for without direct behavioral data on location of foraging. We examined the diet of the northern river otter at the regional and continental scale. We examined 100 publications and 106 prey lists in order to determine the food habits of the northern river otter among ecoregions and seasons. Fish was found to occur in otter diet more often than any other class of prey, followed by malacostracans. At the family level, Astacoidea contributed more to otter diet than any other family of prey. Multiple classes and families varied by ecoregion and/or by season. Crayfish, while not the primary component of otter prey throughout North America, was found to be the primary component when readily available. Furthermore, we developed a model of river otter prey selection which includes factors that may have an impact on the availability of prey to otters. Otter prey selection is likely due to a variety of factors, including the habitat, detectability, catchability, and palatability of prey.
College and Department
Life Sciences; Plant and Wildlife Sciences
BYU ScholarsArchive Citation
Day, Casey Craig, "Translocation Mortality and Local, Regional, and Continental Diet of the Northern River Otter (Lontra canadensis)" (2012). All Theses and Dissertations. 3749.
river otter, Lontra canadensis, translocation, reintroduction, diet, food habits