Food preferences of the little fire ant (Wasmannia auropunctata) in Hawaiʻi

Wasmannia auropunctata, one of the world’s 100 worst invasive alien species, poses significant ecological and economic threats. This study accessed its dietary preferences across protein-lipid-, carbohydrate-, and lipid-rich foods using two complementary approaches: a Visitation Frequency Assay (VFA), where we recorded ant visitation to each food over time; and a Foraging Duration Assay (FDA), where ant activity was video-recorded and analyzed using Noldus EthoVision software to generate heat maps and quantify cumulative duration spent foraging. VFA data were analyzed using a generalized linear mixed model with likelihood ratio tests, while FDA data employed a linear mixed model with Type III Wald chi-square tests; both included Tukey-adjusted pairwise comparisons. Results showed that within protein-lipid-rich foods, cooked beef and sunflower seeds were most preferred. In contrast, the least visited foods were tuna, boiled tofu, defatted peanut butter, and cockroach. Within carbohydrate-rich foods, honey was the most attractive, whereas orange juice and strawberry jam were least preferred. Among lipid-rich foods, peanut butter oil was most preferred, whereas olive, soybean, and coconut oil attracted similar number of ants. The final comparison across categories revealed that cooked beef ranked highest in preference, followed by sunflower seeds, honey, and peanut butter oil. Overall, more ants were actively feeding protein-lipid-rich foods as compared to lipid- and carbohydrate-based options. The findings can inform the design of more effective baiting and surveillance strategies for managing the little fire ant populations effectively.