Food vs. safety: The question for recruiters of the ant Temnothorax rugatulus
John Yohan Cho, John Yohan Cho , Stephen C. Pratt
School of Life Sciences, Arizona State University, Tempe, U.S.A.; School of Life Sciences, Arizona State University, Tempe, U.S.A. ; School of Life Sciences, Arizona State University, Tempe, U.S.A.
Animals often face a tradeoff between obtaining food and protecting themselves from predators or other risks that accompany foraging. In eusocial insects, this tradeoff requires adaptive allocation of workers to foraging vs. protective tasks, often mediated by recruitment communication. We investigated this process in the ant Temnothorax rugatulus, by varying the relative importance of foraging vs. nest-site selection and observing whether and how colonies changed their investment in these tasks. Specifically, we manipulated their hunger state and the condition of their nest (i.e., their shelter from potential predators). We exposed colonies to all combinations of high/low starvation and destroyed/half-destroyed nest. For each combination, we then simultaneously offered each colony a rich sucrose feeder and a high-quality new nest. We measured colony response in three ways. Exploration: the number of ants outside the current nest; Visitation: visits to the food and visits to the new nest; Recruitment: how many times or how persistently the visitors tried to bring nestmates to the targets they visited. We predict that all three response variables will be higher when hunger state or nest need is high. If the ants face a food-predation risk tradeoff, we further predict that colonies will balance worker allocation to foraging and nest-site selection. In particular, colonies that face high hunger will allocate less effort to foraging when they also face high nest need, compared to when they have low nest need. Likewise, colonies that face high nest need will allocate less effort to nest-site selection when they also face high hunger, compared to when they face low hunger. Preliminary analysis indicates a stronger response to each feeder when need for it is high, as expected, but the predictions regarding tradeoffs remain to be evaluated. The results will shed light on whether and how colonies use recruitment communication to balance investment in critical tasks.