Effect of Interactions between Harvester Ants on Forager Decisions

Abstract

Harvester ant colonies adjust their foraging activity to day-to-day changes in food availability and hour-to-hour changes in environmental conditions. This collective behavior is regulated through interactions, in the form of brief antennal contacts, between outgoing foragers and returning foragers with food. Here we consider how an ant, waiting in the entrance chamber just inside the nest entrance, uses its accumulated experience of interactions to decide whether to leave the nest to forage. Using videos of field observations, we tracked the interactions and foraging decisions of ants in the entrance chamber. Outgoing foragers tended to interact with returning foragers at higher rates than ants that returned to the deeper nest and did not forage. To provide a mechanistic framework for interpreting these results, we develop a decision model in which ants make decisions based upon a noisy accumulation of individual contacts with returning foragers. The model can reproduce core trends and realistic distributions for individual ant interaction statistics, and suggests possible mechanisms by which foraging activity may be regulated at an individual ant level.

The Role of Information Acquisition and Processing in Decision‐Making by Individual within Insects Colonies

“…Therefore, the individual decision-making in social insects is a result of the individual information processing performed by insects. The information come from a set of internal and external stimuli perceived by insects, including their cognitive, genetic, metabolic and behavioural abilities, their interaction with the environment and with other insects (Withers et al, 1993;Fahrbach, 2006;LeBoeuf et al, 2013;Czaczkes et al, 2016;Davidson et al, 2016).…”

Regulation of Harvester Ant Foraging as a Closed-Loop Excitable System

“…The "Foraging" component maps λ out to λ in using a random time delay with an associated probability distribution to represent the time an ant spends outside the nest foraging. neuron-to-neuron interactions that underlie the cognitive abilities of 81 organisms [13,[23][24][25][26]. Using well-studied excitability dynamics of a weakly interacting 82 collective, we introduce feedback at multiple time-scales and explore general questions 83 concerning stability and responsiveness to a changing environment.…”

“…Because each forager searches until it finds a seed, 35 the rate of interaction serves as a noisy measurement of the current foraging 36 conditions [6, 15]. A higher rate of forager return, which reflects a greater food supply, 37increases the likelihood that available foragers will leave the nest to forage [12,13,16].…”

“…In the integrator model of [13], each available forager inside the nest collects evidence 39 from incoming foragers by integrating its recent experience of antennal contacts. When 40 the integrated stimulus passes a threshold, the available forager is likely to leave the 41 nest; in the absence of interactions the forager is likely to descend from the entrance 42 chamber to the deeper nest [12,16], protecting the colony from the inherently noisy 43 signal that results from limited and uncertain interactions [17].…”

“…Previous modeling work has elucidated how the outgoing foraging rate depends on 71 the incoming foraging rate [15], and how individuals assess interaction rate [13]. But we 72 do not know how these are combined to adjust foraging activity across minutes to 73 hours-long timescales, how the adjustments may depend on environmental conditions, or 74 how they may differ from colony to colony.…”