Cynomys ludovicianus June 30 1955 Montrose, Colo. NW of Cortez in area of about 12 townships. There apparently do not not grain that has poison (40-1080), tho they eat superimposing col- ored or not. Apparently the dogs can detect poison. (V. Schoffner suggests that, as in humour, certain mice can taste poison, others cannot, in a genetic ratio; & that those that can taste it might survive). Crawford Dearing both verified the decreasing effectiveness of any poison when long used. Crawford here since 1938, Dearing 1942. After 3-4 seasons, poison soon effect. A new 100-70 kill was made in Delta County on leucuum salagy lost (in this ?) year, but this unusual, 4 season unknown. Poisoning effectiveness varies with season, early effectiveness high (30-40% April-June), then poor to about July 20, then better until fall. Young come out about time Silver Bloom, said Dearing, usually May 15 to early June, all 3 forms having young about same time. Pre- side hibernation differs in length & time of year. Deermin hib- erator largest, white-tailed shortest. Dearing said leucuum little active midday, especially when dry weird, but much morning & late afternoon. We think they eat much cheatgrass & are often found when Brown occurs. Wellington, Colo. June July 2, 1955. AT 7:43 a.m. arrived at Wellington preserve. Warm, clear, calm. At no evidence of expansion of salagy to N., most like- ly direction, beyond stated leucuum. In fact, some stoked show no rise. Few seen near N. edge. In many areas green Kochia espec- ially thick & tall on edges mounds & for several inches around them, when burrow little used (same with shub), about 8-10" tall at mound, 2-3" in surrounding area. To N. of inhabited area open stand Atriplex canescens 2-3' high. Two years of high population