Roford Cynomys ludovicianus August 5, 1955 (CPR, Weld Co., Colo.) 50' of line transect in invaded NW area, starting about 40' W. of stake at 30W 2N. August 8, 1955 at SE end colony, no activity when 7:138 about Aug. 5, but now repair (today) to E. of OW, 28 S. mark (set 2 still traps there). Bottom soaking wet, 1" water standing, burrows there flooded (rain last night & prev. 2 days). In burrow where Cott- alias seen a few days ago, mound repaired today. Looked in 30' burial area; no snakes seen. Two gnu. Sprestyto saw burrow select visit. At NW end colony digging at burrow r 2 in PC, 4 especially active between then & fence. Completed 100' transect starting 40' W of 30W 2N, ending long. 240° 81' from 30W 4N. Marked with applier at 0, 59 100'. This area invaded May - June & still occupied. 5. end transect long. 346° 41yds. from fingerprint with @5 tooth in top; 1" pipe 1' tall at S. end line (2' S. of start). August 9, 1955 Made overlay maps showing new & old burrow sites of dogs seen. In area of 5. invasion near center, but never used to peripheral area, 4 more made since lost mapping there. This invasion reaches to edge of a flat area where Dalasla abundant & tall (1½'). Perhaps tall weeds prevent invasion; they are tallest soon after time of yr. when expansion occurs (June). Dalasla may also have resulted withdrawal of dogs from area N. of 18W to 26W. Several skulls & parts picked up near mounds. These apparently thrown out when burrows opened up (some Sylphogus have too). No eagle casts atop hill to NW colony, nor any eagles seen thus since winter. One marsh hawk seen over colony today. Divided area into 10 census 4-scale areas on map. Night concentration in Zone III & IV. These are