Natural Resources, School of


Date of this Version



Hamilton, J. C., Johnson, R. J., Case, R. M., and Riley, M. W., "Assessment of Squirrel-Caused Power Outages," in Vertebrate Pest Control and Management Materials: 6th Volume, ASTM STP 1055, Kathleen A. Fagerstone and Richard D. Curnow, Eds., American Society for Testing and Materials, Philadelphia, 1989, pp. 34-40.


Copyright (c) 1989 by ASTM International. Used by permission.


Squirrel-caused power outages in Lincoln and Omaha, Nebraska, were evaluated by examining company power outage reports and by consulting with power company representatives. Reports showed that squirrel-caused outages at pole-mounted transformers were most prevalent during May, June, and October (48% of total) and between 1 and 4 h after sunrise (38%), patterns that coincide with squirrel dispersal or morning activity periods. In Lincoln, 1980 and 1981, squirrels caused 177 outages per year, which was 24% of all outages and 90% of animal-caused outages. Estimated minimum annual costs were $23 364 for repairs, public relations, and lost revenue while meters were not running. In Omaha, 1985 and 1986, squirrels caused 332 outages per year, costing at least $47 144 annually. Squirrelcaused outages at substations cost an additional $400 (Lincoln) to $810 (Omaha) annually. Between 1982 and 1985, squirrel guards were installed on all 13 000 Lincoln transformers at an estimated minimum cost of $20 per guard, or $260 000 total. Records from Lincoln after all guards were installed (1986 and 1987) indicate that annual costs were reduced 78% to $5148. Life expectancy of the guards is unknown. The extent of squirrel-caused outages and associated costs may vary among cities and regions. Assessment of these outages as described here can be used for timing biological studies and as a procedural structure for making similar economic assessments in other areas.