Integrating behavioral observations with stable isotopic data to clarify ant trophic ecology

Invasive species can drastically alter ecological processes by restructuring communities and disrupting trophic interactions. The Argentine ant (Linepithema humile), one of the world’s most widespread invasive ants, displaces native arthropods and monopolizes resources, yet the mechanisms driving its foraging behavior remain poorly understood. This study examines how prey traits—specifically body size, mobility, and cuticle sclerotization—influence whether Argentine ants act as a predator or scavenger. We hypothesize that Argentine ants function primarily as facultative scavengers, preferring carrion as prey size increases because it reduces the risk of worker injury and energetic costs. This behavioral flexibility likely reflects a cost-benefit tradeoff in foraging strategy, where ants prioritize carrion when it minimizes risk and effort. Two field-based experiments will be conducted in Rose Canyon Open Space Park (San Diego, California). In the first, fifty cages will be deployed per replicate across ten replicates, half containing live prey and half containing carrion representing seven arthropod species varying in size and sclerotization. Prey mass loss, survival, and Argentine ant recruitment will be quantified, and camera traps will record continuous 12-hour footage on a subset of cages to assess ant abundance, feeding behavior, and recruitment dynamics. The second experiment will isolate the effect of prey body size on predation by comparing Argentine ant interactions with crickets of varying sizes. Together, these experiments will clarify when Argentine ants act as predators versus scavengers, providing insight into how this invasive species alters community structure, resource flow, and nutrient cycling within invaded ecosystems.