Exclusion cylinders were used to assess vegetation loss due to feeding activity of the Oregon ground squirrel, Spermophilus beldingi oregonus Three hardware cloth cylinders were placed within a four-acre (1.62 hectare (ha)) squirrel colony for 44 days. Sample pairs included vegetation within a cylinder and a comparable area of vegetation near the cylinder—each clipped at ground level. Green and dry weights were taken of each sample to estimate hay production. The average dry weight difference between the excluded area and the grazed area was estimated to be 1790 lb/acre (2005.9 kg/ha). Visual observations and a Lincoln Index estimated the squirrel colony population at 123 squirrels (adults and young) per acre (303.9 per ha). Visual observation and trapping resulted in no other animal significantly contributing to the assessed damage. This study indicated that exclusion cylinders are an effective means for assessing vegetation loss due to ground squirrel feeding activity.