By the early 1900’s, unregulated trapping, water pollution, and other degradations of aquatic and riparian habitats had caused otter populations to decline throughout most of their historic range (Nilsson 1980; Toweill and Tabor 1982; Melquist and Dronkert 1987). Improvements in water quality and furbearer management strategies, including implementation of reintroduction projects, have enabled the reestablishment of otter populations to various aquatic habitats in portions of their former range. Reintroduction projects have been especially useful in restoring otter populations to riverine habitats in interior regions.

Methods for determining relative abundance of North American river otters include track counts in the snow (Reid et al. 1987; St-Georges et al. 1995), radioactive isotopes (Knaus et al. 1983; Testa et al. 1994), catch/unit effort (Chilelli et al. 1996), and scent-station surveys (Humphrey and Zinn 1982). Density estimates of river otters range from 1 otter/1.25-3.60 km of coastline in Alaska (Testa et al. 1994) to 1 otter/3.9 km of waterway in Idaho (Melquist and Hornocker 1983).

Stable