Communication and foraging ecology of ants

Ants coordinate group tasks such as nest defense and foraging with their nestmates. My thesis unravels signals and cues underlying these tasks. In part 1, I investigate how ants coordinate defense. I characterized pheromonal and vibratory alarm signals of carpenter ants, Camponotus modoc, using gas chromatography-mass spectrometry, laser Doppler vibrometry, and video recordings. In bioassays, I then tested the ants' responses to synthetic alarm pheromone and playback of vibratory signals. In response to playback of vibratory signals, ants ran rapidly, or froze, but did not approach the vibratory signals. Exposed to alarm pheromone, ants frequently visited the pheromone source. However, concurrently exposed to both alarm pheromone and vibratory signals, ants visited the pheromone source less often but spent more time 'frozen'. The ants' modulated responses to bi-modal signals seem adaptative to avoid predation by avian predators. In part 2, I investigate how ants locate and assess food sources, and whether acquired knowledge about the ants' nutrient preferences can be applied to curb populations of invasive pest ants. I demonstrate that food sources rich in carbohydrates or proteins prompt long-distance attraction of C. modoc worker ants, and that attraction of ants to plant inflorescences is mediated by specific, rather than shared, floral odorants. I show that C. modoc workers deposit (2S,4R,5S)-2,4-dimethyl-5-hexanolide as their trail pheromone to guide nestmates to food sources. I further show that workers of European fire ants, Myrmica rubra, and C. modoc discern between mono-, di- and tri-saccharides, and between essential amino acids (EAAs) and non-essential amino acids. In a field experiment, colonies of C. modoc and M. rubra preferentially consumed EAAs and sucrose, respectively, with no sustained shift in preferred macro-nutrient over the course of the foraging season. Importantly, the presence of a less preferred macro-nutrient in the nutrient bait did not diminish the bait's 'appeal' to foraging ants in diverse ant taxa. In a further field experiment in a public park infested with M. rubra, I show that treatment colonies provided with a lethal liquid bait (4.55% sucrose; 1% EAA; 1% boric acid) significantly declined, whereas control colonies provided with the corresponding non-lethal bait did not.