Targeted Research to Improve Invasive Species Management: Yellow Crazy Ant Anoplolepis gracilipes in Samoa

Abstract

*[We describe targeted research designed to inform the potential eradication of the invasive yellow crazy ant Anoplolepis gracilipes on Nu’utele island, Samoa. Within the infested area, there were few other ants larger than A. gracilipes, as well as fewer spiders & crabs, indicating that A. gracilipes is indeed a significant conservation concern. A total of 24 ant species from 15 genera were collected within pitfall traps over both sampling times; 18 species from 13 genera within the October sample & 20 species from 13 genera within the May sample. Nine ant species from 7 genera were collected within foliage beats over both sample times, with the October & May samples each having 7 species. The timing of male reproduction appears to be consistent with places elsewhere in the world, but queen reproduction was outside of the known reproductive period for this species in the region, indicating that the timing of treatment regimes used elsewhere are not appropriate for Samoa. Worker abundance & nest density were among the highest recorded in the world, being greater in May than in October. These abundance & nest density data form baselines for quantifying treatment efficacy & set sampling densities for post-treatment assessments. The number of plants & insects capable of providing a carbohydrate supply to ants were greatest where A. gracilipes was present, but it is not clear if this association is causal. Regardless, indirectly controling ant abundance by controling carbohydrate supply appears to be promising avenue for research.]