Research Accomplishment Reports 2010

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.

2010 Project Description

Data bases on distribution of river otters in Kentucky were accumulated using sign surveys at bridge crossings, and damage reports and harvest data provided by the Kentucky Department of Fish and Wildlife Resources (KDFWR). The pooled information indicated that river otters exist in all 12 major watersheds in Kentucky. Otter presence was highest in the Jackson Purchase physiographic region in west Kentucky and in the reintroduction zone in central Kentucky. Otters were most scarce in the Cumberland Plateau and mountain regions of eastern Kentucky. The number of otters harvested was highest in 2006-07, but has since leveled off in subsequent harvests. Several predictive models of otter population growth are being evaluated for their applicability to the Kentucky otter population and results of those analyses are pending.

2010 Impact

Results of survey efforts suggest that river otters have been successfully reintroduced into Kentucky. The remnant population in the far western end of the state appears to be linked to the increasing number of otters in the central reintroduction zone, with the lowest populations of otters in eastern Kentucky; the latter likely a function of lower habitat quality in mountain regions and greater distances to source populations in the Jackson Purchase and the central reintroduction zone.

Results suggest that otters should be able to be harvested on an annual basis, although refinement of harvest schedules is needed to ensure that populations are not overharvested and pushed to far below carrying capacity. The development of a predictive model for the state of Kentucky is intended to address this concern. The success of this reintroduction program adds to the biodiversity of Kentucky, the economy of the state through added opportunities and income for trappers, and to the health of aquatic ecosystems in forested environments. A more comprehensive understanding of the role that otters play in these ecosystems needs further study.

2010 Publications

Dickinson, M.B., J.C. Norris, A.S. Bova, R.L. Kremens, V. Young, and M. J. Lacki. 2010. Effects of wildland fire smoke on a tree-roosting bat: integrating a plume model, field measurements, and mammalian-dose response relationships. Canadian Journal of Forest Research 40: 2187-2203.

Kroll, A.J., M.J. Lacki, and E.B. Arnett. 2010. Managing snags for birds and bats on forested landscapes in the Pacific Northwest, USA. Western Journal of Applied Forestry. (In press).

Barding, E.E., M.J. Lacki, and L.L. Patton. 2010. Recovery of the river otter (Lontra canadensis) to Kentucky. Proceedings of the Southeastern Association of Fish and Wildlife Agencies 64: in press.

Lacki, M.J., M.D. Baker, and J.S. Johnson. 2010. Geographic variation in roost-site selection of long-legged myotis in the Pacific Northwest. Journal of Wildlife Management 74: 1218-1228.