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Distribution and Ecology of the North American River Otter (Lontra canadensis) in Kentucky
Department of Forestry
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.
2009 Project Description
The initial phases of the project are underway. A total of 170 river otter carcasses was obtained from across the state with the help of the Kentucky Department of Fish and Wildlife Resources through experimental harvests. Acquisition of additional carcasses is planned and targeted for watersheds where insufficient carcasses were obtained in the initial harvests. Necropsies have been performed on all carcasses, with emphasis in year one placed on analysis of stomach contents. All other organs and tissues were extracted, preserved and stored for future analysis. Stomach were removed and the contents extracted, sorted and identified to the lowest taxonomic level discernible.
Fish (86% of stomachs), crayfish (27%), and amphibians (5%) comprised the majority of the diet of otters. Among families of fishes, the Centrarchidae (66 % of stomachs with fish scales) was eaten most frequently followed by Catostomidae (21%), Cyprinidae (21%), Clupeidae (13%), Percichthyidae (6%), Esocidae (4%), Percidae (1%), and Amiidae (1%). There was no difference in composition of fish in the diet of male versus female otters, or between otters from eastern versus western Kentucky. Data for the Centrarchidae were further categorized as Group A (sunfish and crappie species) and Group B (black bass species). Results demonstrated most cetrarchids eaten were of Group A, with scales of species in Group B occurring in only 9% of stomachs with centrarchid remains. Of the remaining items found in otter stomachs, over 50 % of stomachs with crayfish remains were of species in the genus Orconectes and all amphibians remains were of species in the family Ranidae. Some evidence of consumption of snakes, turtles, and birds (mallard duck, Anas platyrhyncos) was also found in otter stomachs.
Preliminary results from the experimental harvests and the stomach content analyses suggest three principle findings.
First, river otters were harvested from all major drainages throughout Kentucky indicating the restoration effort of the mid-1990s has been successful in returning this once extirpated species back to the state.
Second, the success of the experimental harvests also suggests that a sustained annual harvest may be possible, although numbers of otters remain low in the far eastern portions of the state (Cumberland Plateau region) and data on reproductive potential and population modeling projections have yet to be completed.
Third, diet analyses demonstrated that sportfishes (black bass species, Group B) are uncommon in the diet of river otters in Kentucky. Therefore, maintaining a viable river otter population long-term is not likely to be in conflict with the sportfish industry in Kentucky, and the perceived decline in black bass in the state is not likely due to increasing otter numbers; this has been the misconception of the public in recent years (KDFWR, pers. commun.).
Dickinson, M.B, M.J. Lacki, and D.R. Cox. 2009. Fire and the endangered Indiana bat. Pp. 51-75 in Proceedings of the 3rd fire in eastern oak forests conference (Hutchinson, T.F., ed.), Northern Research Station, USDA Gen. Tech. Report, GTR-NRS-P-46.
Lacki, M.J., D.R. Cox, L.E. Dodd, and M.B. Dickinson. 2009. Response of northern bats (Myotis septentrionalis) to prescribed fires in eastern Kentucky forests. Journal of Mammalogy 90: 1165-1175.
Dzialak, M.R., K.M. Carter, M.J. Lacki, D.F. Westneat, and K. Anderson. 2009. Activity of post-fledging peregrine falcons in different rearing and habitat conditions. Southeastern Naturalist 8: 93-106.
Lacki, M.J., D.R. Cox, and M.B. Dickinson. 2009. Meta-analysis of summer roosting characteristics of two species of Myotis bats. American Midland Naturalist 161: 321-329.