Northern Prairie Wildlife Research Center
| 1969 | 1970 | 1971 | 1972 | 1973 | ||
| Drift plain | ||||||
| Twp. 1 | 3 | 3 | 9 | 8 | 10 | |
| Twp. 2 | 3 | 7 | 9 | 9 | 11 | |
| Avg. | 3 | 5 | 9 | 8.5 | 10.5 | |
| Families/km2 | 0.03 | 0.05 | 0.10 | 0.09 | 0.11 | |
| Missouri Coteau | ||||||
| Twp. 3 | 6 | 6 | 12 | 17 | 15 | |
| Twp. 4 | 3 | 4 | 5 | 14 | 17 | |
| Twp. 5 | 6 | 8 | 10 | 10 | 14 | |
| Twp. 6 | 7 | 10 | 10 | 11 | 13 | |
| Avg. | 5.5 | 7 | 9.3 | 13 | 14.8 | |
| Families/km2 | 0.06 | 0.08 | 0.10 | 0.14 | 0.16 | |