Impact of Solenopsis invicta on small mammal habitat utilization and abundance

Abstract

Habitat use by small mammals at a prairie site in central Texas was examined on a 1.44 ha grid from which red imported fire ants (Solenopsis invictal were removed, and on an adjacent control grid containing natural densities of fire ants during a 22-month markrecapture study (February 1991-November 1992). Relative abundances of S. invicta and small mammals were correlated along an 83-km transect representing a gradient of S. invicta densities in eastern Texas during June (1990) and July (1991). Sigmodon hispidus was the most abundant small mammal at the prairie site, with Baiomvs tavlori. Peromvscus maniculatus. and Reithrodontomys montanus also present. Habitat use by S. hispidus. as indicated by mean distances moved between captures and mean home range sizes, was not significantly different (P > 0.05) on fire ant removal and control grids. P. maniculatus moved significantly (P <0.01) further between captures on the removal than on the control grid. Data on the other species were insufficient to permit these calculations. On the control grid, S. hispidus were captured often in areas of relatively high fire ant activity and did not preferentially locate nests in areas of relatively low fire ant activity, whereas B. tavlori and P. maniculatus were captured most frequently in areas of relatively low fire ant activity. Six species of small mammals (S. hispidus. B. tavlori. Rattus rattus. Peromvscus spp., Reithrodontomys spp., and Microtus pinetoriuml were captured along the transect. Abundance of S. hispidus was not correlated significantly (P > 0.05) with the number of S. invicta mounds, whereas total abundance of the other species, grouped together, was significantly (P < 0.001) negatively correlated with number of mounds.