The Effects of Red Imported Fire Ants on Northern Bobwhite and Eastern Cottontail in the Gulf Prairies and Marshes of Texas

Abstract

Northern bobwhites (Colinus virginianus) have been declining throughout their range since the 1960s. The decline in the Gulf Prairies and Marshes Ecoregion (GPM) has primarily been the result of habitat loss and fragmentation. With the population already reduced, additional causes of quail decline become important issues. In 1957, red imported fire ants (RIFA, Solenopsis invicta) began to invade the GPM. RIFA can potentially affect bobwhites by direct predation of pipping chicks, reduced survival of young chicks, and competition for food. Eastern cottontails are another important species that could be impacted by RIFA. Previous work has documented RIFA predation of altricial young born in pen-raised cottontail nests.

The Attwater Prairie Chicken National Wildlife Refuge in Colorado County, Texas received large-scale aerial treatment of RIFA with Extinguish Plus™ insecticide as a management action for the endangered Attwater’s prairie-chicken (Tympanuchus cupido attwateri). This presented me with an opportunity to evaluate the effects of RIFA treatment on: (1) bobwhite nest success and brood survival, (2) bobwhite abundance and density, (3) bobwhite movements and ranges, and (4) cottontail numbers. An additional objective was to (5) contribute reference data for bobwhite in the GPM to address this region’s lack of data. To investigate these objectives bobwhites were radio-collared and tracked, RIFA were sampled, and cottontails were surveyed in both the treated and non-treated areas.

Treatment with Extinguish Plus™ successfully reduced the abundance of RIFA in iii the treated area from 2014–2017. However, I found that flooding can negate the effectiveness of the treatment when the treated area is surrounded by adjacent non-treated areas. Bobwhite densities were 76.6% higher (P = 0.042) in the treated area compared to the non-treated area. There was no difference between bobwhite consecutive movements (P = 0.275) or seasonal ranges (P = 0.783) in the treated and non-treated area. However, there was a difference (P = <0.001) by category. Nesting season females without a brood had larger movements (P = <0.001) than nesting season females with a brood and larger movements (P = 0.002) than pre-nesting females. Cottontail numbers were higher (P = 0.003) in the non-treated than the treated area.