Constantly grazed land had a average of 1 colony/730 m2 while ungrazed land averaged 4 colonies/730 m2 and there was a significant difference in the frequency of harvester ant colonies between the 2 grazing regimes, P = 0.003, single tailed t-test. Since soil type also varies across the estate the number of colonies by soil type was also tested. Forest-Pinleno association is found on the west side of the estate while Eba very gravelly loam predominates the eastern portion of the estate. There was no significant difference in harvester ant colony density between these 2 soil types, P = 0.12, single tailed t-test. This suggests that soil composition, and secondarily plant species diversity, are not a major contributor to harvester ant colony frequencies on the estate in the semi-arid southwest, but rather the frequency of grazing (constantly grazed versus ungrazed land) is the more important determinant of harvester ant colony frequency in and around the estate.
|Frequency of harvester ant nest colonies.|
|Soil map of the Painted Pony Resort.|