Coordination of personal preference and behavior with colony needs in seed harvester ants.
Ioulia Bespalova, Ioulia Bespalova , Jennifer Fewell
Arizona State University; Arizona State University ; Arizona State University
In social insect foraging, a subset of individuals make decisions about food collection that affect the whole group. As such, coordination is necessary between group needs and a forager’s personal choices. Seed choice in harvester ants is an under-explored example of this kind of decentralized decision-making. Colonies prefer some kinds of seeds to others and often have a few favorites that make up most of their intake. However, foragers individually make decisions upon encountering a seed. On top of this, seed nutrients are often obscured by a shell, and novel seeds necessitate a period of learning. This leads to the question; How is forager behavior and personal preference coordinated with colony needs? To answer this, I provided field colonies of Pogonomyrmex californicus with novel seeds of different quality, and found that colonies not only consistently preferred the higher calorie seed, but became more biased over days. This was largely driven by foragers changing their preference toward the more popular type of seed. However, there was still much individual variation in preference, with some continuing to collect both seeds equally or shifting their preference in a contrary direction. Foragers even vary in preference when choosing between seeds of similar quality. I also provided lab colonies with different quality seeds to see how colonies learn and inform foragers. The acceptance or rejection of seeds was observed, concurrently with the forager behavior and preferences. Lab colony preference matched that of field colonies, with extreme bias against the low calorie seed type by foragers, but intermittent attempts at processing in the nest. The interactions between foragers and processed seeds, other workers, and brood will be discussed. Harvester ant foraging is another example of how sophisticated group behavior arises out of individual who are just doing their best, relying on local cues and limited knowledge based on a narrow range of experiences.