The number of black-tailed jackrabbits (Lepus californicus melanotis) seems to increase during periods of drought in western Kansas (Wooster 1935, Bronson 1957). The authors (Bronson and Tiemeier, in press) have shown that much of an apparent population increase of this species may be caused by a concentrating of the population in response to reductions in the amount of natural food and/or daytime resting habitat. A comprehensive study of jackrabbit biology conducted immediately before and after the termination of a five-year drought (1952-56) yielded data on the amount of crop damage in relation to these population movements. Jackrabbit numbers and the resulting crop damage reached such proportions in some areas during the drought that many southwestern Kansas counties offered bounty payments. That jackrabbits are capable of doing heavy crop damage when feeding in large numbers is attested by the jackrabbit: cow feeding equivalent of 60:1 calculated by Vorhies and Taylor (1933). The data were collected on or near a study area located approximately six miles southeast of Lakin, Kearny County, Kansas across an ecotone of sandhill pasture and river valley cropland. Population studies (Bronson and Tiemeier, op. cit.) indicated that population densities were high on the study area from July 1956 through May of 1957 and low between May and November of 1957. The high densities resulted from jackrabbits migrating into the study area from the extensive sand-hill region south of the Arkansas River valley. When drought and overgrazing depleted the natural food supply in the sand-hills, jackrabbits concentrated along the edge of the hills. Heavy precipitation in the spring of 1957 caused a dispersion of these concentrations throughout the former range and consequently densities on the study area became much lower. When natural food was not available in the hills, the majority of the animals on the study area utilized the cover along the edge of the hills as a daytime resting area and nightly moved north into the river valley croplands to feed on wheat, grain sorghum, or alfalfa fields. Nocturnal feeding densities of 14 per acre were recorded on winter wheat fields located adjacent to the hills in the winter of 1956-57.