Research Accomplishment Reports 2011

Distribution and Ecology of the North American River Otter (Lontra canadensis) in Kentucky

M.J. Lacki
Department of Forestry

 

Non-Technical Summary

The North American river otter (Lontra canadensis) was historically distributed throughout most major drainages in the continental United States and Canada, from the arctic in Alaska south to Texas and as far east as Florida. The largest populations of river otters in the United States existed in areas with abundant aquatic habitat including coastal marshes, the Great Lakes region, and glaciated areas of New England. Excessive trapping and a lack of proactive population management have resulted in population declines and local eradication of otters in many areas across their almost, continent-wide distribution.

In Kentucky, river otters were distributed widely until populations declined during the early 1900s due to unregulated harvest and human destruction of forested-riparian habitat. By the 1950s, the distribution of river otter populations in Kentucky was limited to the Jackson Purchase physiographic region in far western portions of the state. The Tennessee Valley Authority and the Kentucky Department of Fish and Wildlife Resources (KDFWR) conducted an experimental restocking of river otters in the Land-Between-the-Lakes (LBL) area of western Kentucky in 1982 and 1983. Results demonstrated that river otters could naturally repopulate and expand their range in the Jackson Purchase physiographic region. Encouraged by the successful release of river otters at LBL, KDFWR began a program to restore self-sustaining populations of river otters throughout suitable habitat in Kentucky. During 1991-1994, 355 river otters were released among 14 sites in central and eastern Kentucky.

Sightings and reports of nuisance river otters have subsequently increased in areas where otters were reintroduced, and the remnant population in the western portion of the state appears to have become widespread. The increased frequency of otter sightings, incidental trappings, roadkills, and complaints about nuisance river otters by landowners throughout Kentucky suggests that the statewide otter population is growing, and experimental harvests, conducted in 2004 (west Kentucky only),and again in 2006 and 2007 (statewide), have met with considerable capture success. Thus, there is an immediate need to determine the distribution and abundance of river otters throughout all watersheds in Kentucky, along with an analysis of the growth potential of populations across differing habitats and regions of the state.

This project will employ presence/absence surveys along watersheds to determine the extent to which otters are distributed across the state, develop habitat models of preferred otter habitat based on associated presence/absence data, and use necropsies of otter carcasses to assess reproductive potential of otters and to use this information to develop predictive models of population growth of river otters in Kentucky. The overall goal of this project is to assist KDFWR in determining whether a carefully regulated harvest of river otters is an appropriate management strategy for this furbearing species in the state.

2011 Project Description

Necropsies of adult female river otters were completed. Data for pregnancy rate (0.72) and average litter size (3.14) of adult females for the statewide population were used in modeling future population growth of river otters in Kentucky. Values for reproductive parameters recorded for Kentucky fell within the range of values published for populations in adjacent states. Population growth projections were evaluated using survivorship rates for Kentucky, as well as surrounding states where otter populations are recovering.

Portions of the results of this research have been published or accepted for publication in two journals. A completed Doctoral Dissertation (Erin Barding) has been submitted to the Kentucky Department of Fish and Wildlife Resources for use with management of the river otter population in Kentucky. Changes to harvesting protocols, especially in western and north-central portions of the state where otters are more abundant, are being considered based upon the finding presented in the dissertation.

2011 Impact

Projected results from population modeling of river otters suggest a wide range of growth trajectories ranging from extirpation (using West Virginia survivorship rates) to exponential growth (using Tennessee survivorship rates). Based on survivorship rates for Kentucky, which are only from populations in the Jackson Purchase physiographic region, projected growth predicts approximately 2000 river otters statewide by 2015.

We believe this estimate to be conservative based upon trapper success over the past 3 years, and we recommend a need for improved data on survivorship of river otters in Kentucky. Changes to harvesting protocols, especially in western and north-central portions of the state where otters are more abundant, are being considered by the Kentucky Department of Fish and Wildlife Resources based upon the finding presented in the completed dissertation of Erin Barding.

2011 Publications

Barding, E.E., and M.J. Lacki. 2011. Winter diet of river otters in Kentucky. Northeastern Naturalist. In press.

Dodd, L.E., E.G. Chapman, J.D. Harwood, M.J. Lacki, and L.K. Rieske. 2012. Identification of prey of Myotis septentrionalis using DNA-based techniques. Journal of Mammalogy. In press.

Dodd, L.E., M.J. Lacki, E.R. Britzke, D.A. Buehler, P.D. Keyser, J.L. Larkin, A.D. Rodewald, T.B. Wigley, P.B. Wood, and L.K. Rieske. 2011. Forest structure affects trophic linkages: how silvicultural disturbance impacts bats and their insect prey. Forest Ecology and Management. In press.

Dodd, L.E., M.J. Lacki, and L.K. Rieske. 2011. Habitat associations of Lepidoptera in the Ozark Mountains of Arkansas. Journal of the Kansas Entomological Society. In press.

Johnson, J.S., K.S. Watrous, G.J. Giumarro, T.S. Peterson, S.A. Boyden, and M.J. Lacki. 2011. Seasonal and geographic trends in acoustic detection of tree-roosting bats. Acta Chiropterologica 13: 157-168.

Barding, E.E., M.J. Lacki, and L.L. Patton. 2010. Recovery of the river otter to Kentucky. Proceedings of the Southeastern Association of Fish and Wildlife Agencies 64: 112-117.