Northward Extension of the Kangaroo Rat in Washington

Abstract

For many years kangaroo rats, Dipodomys ordi , have been blocked in their northward dispersal in Washington by the Columbia and Snake rivers. It was 100 years ago that Baird reported kangaroo rats in the Northwest. At the present time they are common over the sagebrush plains of eastern Oregon, occurring all along the south bank of the Columbia from The Dalles eastward for 140 miles to the Snake River (Bailey, N. Amer. Fauna 55: 235,1936). In southeastern Washington they have been observed in western Walla Walla County only as far north as the Snake, and have been reported along the south bank of the river from its mouth for about 5 miles upstream. Kangaroo rats also occur in considerable numbers on Blalock Island in the Columbia River. This large island is several miles southwest of Paterson, Benton County, Washington. The northern limits of the range of D. o. columbianus have been given by Miller and Kellogg (U.S. Nat. Mus. Bull. 205: 403, 1955), Setzer (Univ. Kans. Publ., Mus., Nat. Hist, 1: 544, 1949) and Dalquest ( ibid ., 2: 300, 1948). Kangaroo rats now occur north of the Snake River in the triangle formed by the Snake and Columbia. I first observed signs of Dipodomys there in April of 1956, along the road leading east of Pasco to Levey. There were many burrows in the sandy soil along the right of way. The last of the dens were about 6 mi. ENE Pasco. On April 28 specimens were obtained a few miles north of the Snake River east-northeast of Pasco. Twenty live traps were set on a small isolated sand dune about ¼ mile north of the highway; 6 Dipodomys ordi and 9 Perognathus parvus were captured. The surrounding country was rolling plains covered with a fairly …