Use of Historically Fishless High-Mountain Lakes and Streams By Nearctic River Otters (Lontra canadensis) in California

Abstract In California, River Otters (Lontra canadensis) are most commonly associated with food-rich lowland aquatic habitats where they forage primarily on fish and crustaceans. Their distribution in high-elevation montane regions of the state, areas in which fish and crayfish were absent historically, is largely unknown. We compiled occurrence records of River Otters in California from elevations >1100 m, and evaluated them using evidentiary standards. Based on 126 records, we report the widespread presence of River Otters in the Klamath, southern Cascades, and Sierra Nevada mountain ranges, including at elevations exceeding 3000 m. Sixty-three percent of the records met our definition as “verified”, and the remaining 37% were considered “unverified”. The distribution of observations through time and habitats in which observations were made were similar between verified and unverified records. River Otter records spanned the period from 1900 to 2010, with 50% occurring between 1991 and 2010. Ninety-thre...