Figure 4. Foraging cycles.

(a) The estimated crop load of a single forager during the first two hours of an experiment. As typical for a forager, her crop load oscillates as she alternates between feeding at the food source (pink areas) and unloading in trophallaxis (gray areas) in continuous back-and-forth trips. (b) The foraging frequency of individual foragers, calculated as the inverse of cycle times (the time interval between two consecutive feeding events of a single forager), grows linearly with the empty space in the colony, $1-F$. Data points and error bars represent means and SEM of cycles. The pooled data from all three observation experiments is grouped into equally-spaced bins of colony state (n = 57,39,28,26,26, for bins 1–5, respectively, see Figure 4—figure supplement 1). A linear fit is presented in red: $y={\mathrm{0.8\hspace{0.25em}10}}^{-3}+{\mathrm{3.6\hspace{0.25em}10}}^{-3}(1-F)$, $R^2=0.98$. (c) Forager cycle durations are composed of an indoor phase (green) and an outer phase (yellow), the former accounting for most of the rising trend. The pooled data from all three observation experiments was binned and averaged as in panel b (n = 26,26,28,39,57, for bins 1–5, respectively, Figure 4—figure supplement 1). (d) Food accumulation in a perturbation experiment. Food rises to an initial plateau, and rises again to a secondary plateau after new hungry ants are introduced (black line). (e) Durations of foragers in the nest in the manipulation experiment described in panel d. Durations grow longer, drop after new hungry ants are introduced (black line), and subsequently rise again. Data points and error bars represent means and standard errors of durations of cycles grouped into time bins (n = 28,36,21,14,9,28,27,19,5, for bins 1–9, respectively). Raw data and results from a second replication of the perturbation experiment are presented in Figure 4—figure supplement 2. (f) A schematic representation of the observed negative feedback between the colony state and the foraging frequency. Source file for panels b and c is available in the Figure 4—source data 1. Source file for panels d and e is available in the Figure 4—source data 2.

Figure 4—figure supplement 1. Foraging cycle times.

Both panels relate to the pooled data from all three observation experiments. (a) Foraging frequency, calculated as the inverse of cycle times (the time interval between two consecutive feeding events of a single forager) grows linearly with $1-F$. Raw data (gray) was binned into equally-spaced bins of colony state (n = 57,39,28,26,26, for bins 1–5, respectively, in black mean $\pm$ SEM.) Linear fits to the raw data (red) and the binned data (blue, hidden behind the red) yield similar lines: $y={\mathrm{0.8\hspace{0.25em}10}}^{-3}+{\mathrm{3.6\hspace{0.25em}10}}^{-3}(1-F)$, $R^2=0.35,0.98$, respectively. (b) Forager cycle durations are composed of an indoor phase (green) and an outer phase (yellow), the former accounting for most of the rising trend. Data was binned and averaged as in panel a (n = 26,26,28,39,57, for bins 1–5, respectively).

Figure 4—figure supplement 2. Perturbation experiments.

Food accumulation, represented by the total fluorescence (top row), and durations of foragers in the nest (bottom row), as a function of time in the two experimental colonies that underwent colony state manipulation (see Methods). Solid black line represents the time of introducing new hungry ants to the system. The results of colony M2 are presented in Figure 4d–e in the main text, where a detailed explanation may be found in the caption. Note that the plots depicting durations in the nest here differ from that in Figure 4e, in that here durations are plotted by two separate groups: those of foragers which were active during the whole experiment (M1: n = 47,13,15,13,12,16,17,14 for bins 1–8, respectively; M2: n = 28,36,21,14,5,15,18,10,4, for bins 1–9, respectively) and those of foragers that began foraging after the manipulation (M1: n = 6,3,2, for bins 1–3, respectively; M2: n = 4,13,9,9,1, for bins 1–5, respectively). In Figure 4e, all were pooled together. The observation that foragers of both groups displayed similar patterns after the manipulation highlights the causality of the effect of colony state on forager behavior as opposed to time or the forager’s history.