Hiking Trails Increase Abundance of Harvester Ant¹Nests at Clear Creek, Arizona

Anthropomorphic changes to the environment can sometimes unintentionally benefit ants (Hymenoptera: Formicidae) when habitats are made favorable for nesting. We examined the effects of a hiking trail on nest abundance of Pogonomyrmex barbatus (Smith) and Novomessor cockerelli (André) harvester ants at Clear Creek, AZ. Nest abundance for both species was compared along paired transects on-and off-trail. P. barbatus was twice as abundant on-trail while N. cockerelli showed a similar directional trend, but the differences were not significant. To test potential mechanisms driving the increase on-trails, soil and habitat differences were compared. Soil compaction was two times greater and canopy cover was five times less on-versus off-trails. For P. barbatus, which nests in soil, we compared on-and off-nest soils, both on-and off-trail. Soil 5 m away from ant nests was twice as compacted whether on-or off-trail. Reduction of canopy cover and compaction of soils might create beneficial nesting conditions for the two species of ant, leading to greater abundance near the hiking trail. Increase of stinging insects near recreational trails might pose health risks, especially in remote areas distant from medical treatment. We discuss management considerations and potential ecological consequences of increased abundance of ants along trails.