A food habits study by scat analysis was conducted in the Thompson lakes region of Lincoln County, Montana, to help evaluate the economic status of the otter. Otter latrines were located by walking the shore lines of lakes and streams; 96 were discovered on fallen trees, beaver houses and the shore. Otter scats were easily distinguished by size, shape, and odor. A total of 2209 were collected between April, 1952, and May, 1953. Approximate date of deposit was determined foe 1374 which were assigned to winter, spring, summer and fall. These constituted the basis for this study. The limited use of electric shocking, gill net sets and fishing were employed in an attempt to obtain the relative abundance of fishes in the various waters. An indication of fur bearer abundance was afforded by "sign". Scats were analyzed in a dry state. Each was broken apart in a culture dish with dissecting needle and tweezer. The complete scat was searched for identifiable remains of items in the diet. These were identified by comparisons with reference collections. Hair identifications were restricted to fur bearers (otter, beaver, muskrat, mink); feathers to Anatidae and greys. All scats and reference collections are at Montana State College. Data are expressed at percent occurrence by seasons which was calculated by dividing the number of scats for a season into the number of occurrences of an item. Data for two separated areas (Thompson and Gary) are compared. For the entire year and for both areas fish remains were identified most frequently, appearing in 1280 (93.2%) of the scats. Invertebrates were recorded for 566 (41.2%), amphibians 253 (18.4%), mammals 84 (6.1%), birds 71 (5.2%) and reptiles 5 (0.4%). Considering all scats, sunfish occurred in 58.2%, sucker 33.3%, sculpin 21.0%, and trout 18.5%. This same order of importance was established for the Thompson area. Gary's Lake was: trout 52.0%, sucker 42.9%, sculpin 31.0% and shiner 25.0%. Dragon fly nymphs, aquatic beetles and fresh water shrimp appeared in scats consistently but seldom made up an appreciable percent of the scat. It was most common to find 1-5 of these in a dropping. Frogs were found to be a prominent part of the diet and were found throughout all seasons. Muskrat occurred in 4.4% of total scats but was present in 18.7% of the collection at Gary's lake and predominant during spring and summer. The highest incidence was in June, occurring in 14 scats. Beaver appeared in 10 or 0.7% of all scats with 8 occurring at Gary's and 2 for the Thompson. The data suggest availability to be important in determining the food habits of the otter. Tapeworm proglottids, Ligula intestinalis, were found in scats from both areas.
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