title: Indirect effects of red imported fire ants on Attwater's prairie-chicken brood survival.
abstract: The invasive red imported fire ant (Solenopsis invicta) has negatively affected a host of taxonomic groups throughout its acquired North American range. Many studies have hypothesized indirect trophic impacts, but few documented those impacts. We evaluated invertebrate abundance as a factor limiting juvenile survival of the endangered Attwater's prairie-chicken (Tympanuchus cupido attwateri), and whether fire ants reduce invertebrate numbers and biomass. From 2009-2013, we monitored survival of Attwater's prairie-chicken broods (n= 63) with radio telemetry during the first 2 weeks post-hatch and collected daily invertebrate samples at brood sites. Broods located in areas with the highest median invertebrate count (338 invertebrates/25 sweeps) had a survival probability of 0.83 at 2 weeks post-hatch compared to 0.07 for broods located in areas with the lowest median invertebrate count (18 invertebrates/25 sweeps). During 2011-2012, we evaluated the reduction of fire ants on invertebrate numbers and biomass by aerially treating areas with Extinguish Plus™ in an impact-reference study design. Treated fields had 27% more individual invertebrates and 26% higher invertebrate biomass than reference fields. Our results clearly document that invertebrate abundance affects Attwater's prairie-chicken brood survival and that fire ants may indirectly contribute to low brood survival by suppressing invertebrate abundance. We posit that within the fire ant's acquired North American range, fire ants are likely contributing to declines of other insectivorous species. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
authors.affiliation: Attwater Prairie Chicken National Wildlife Refuge PO Box 519 Eagle Lake TX 77434 USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Morrow
authors.affiliation: Attwater Prairie Chicken National Wildlife Refuge PO Box 519 Eagle Lake TX 77434 USA.
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Chester
authors.affiliation: US Fish and Wildlife Service 500 Gold Avenue SW, Room 4005 Albuquerque NM 87102 USA.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Lehnen
authors.affiliation: Texas A&M AgriLife Extension Service Department of Entomology Texas A&M University, Minnie Belle Heep, Room 412 College Station TX 77843 USA.
authors.forename: Bastiaan M
authors.initials: BM
authors.lastname: Drees
authors.affiliation: Society of Tympanuchus Cupido Pinnatus, Ltd. Ada MN 56510 USA.
authors.forename: John E
authors.initials: JE
authors.lastname: Toepfer
keywords: Attwater's; Tympanuchus cupido attwateri; brood survival; fire ants; indirect effects; invertebrates; prairie‐chicken