DOI: 10.5061/dryad.15dv41nv0
title: Ant behavioral maturation is mediated by a stochastic transition between two fundamental states

description: The remarkable ecological success of social insects is often attributed to
 their advanced division of labour, which is closely associated with
 temporal polyethism in which workers transition between different tasks as
 they age. Young nurses are typically found deep within the nest where they
 tend to the queen and the brood, whereas older foragers are found near the
 entrance and outside the nest. However, the individual-level maturation
 dynamics remain poorly understood because following individuals over
 relevant timescales is difficult, hence previous experimental studies used
 same-age cohort designs. To address this, we used an automated tracking
 system to follow &gt;500 individuals over &gt;100 days, and
 constructed networks of physical contacts to provide a continuous measure
 of worker social maturity. These analyses revealed that most workers
 occupied one of two steady-states, namely a low-maturity nurse state and a
 high-maturity forager state, with the remaining workers rapidly
 transitioning between these states. There was considerable variation in
 the age at transition, and, surprisingly, the transition probability
 transition was age-independent. This suggests that the transition is
 largely stochastic rather than a hard-wired age-dependent physiological
 change. Despite the variation in timing, the transition dynamics were
 highly stereotyped. Transitioning workers moved from the nurse to the
 forager state according to an S-shaped trajectory, and only began foraging
 after completing the transition. Stochastic switching, which occurs in
 many other biological systems, may provide ant colonies with robustness to
 extrinsic perturbations by allowing the colony to decouple its division of
 labour from its demography.
description: <strong>Experimental set-up</strong>
 To investigate long-term worker behavioral maturation, we
 continuously recorded three queenright Camponotus fellah colonies for
 ~100-days. The environmental conditions and nest dimensions were identical
 to those described in Mersch et al (2013). Thus, colonies were housed in a
 double-chamber setup, with a nest box (26x16cm) that was dark 24 hours a
 day, connected (via a tunnel) to a foraging arena (26x16cm) under a 12:12
 light-dark and temperature cycle. Underfloor reserves of water and dilute
 sugar solution (3g/100ml) were connected to the foraging arena via cotton
 wicks. Ten dead flies were also provided weekly in the foraging
 arena. <strong>Automated ant
 tracking</strong> The location of every worker
 within the nest and foraging boxes was determined by gluing a unique ARtag
 barcode to the thorax of each individual in the colony, and recording
 their movements using monochrome digital video cameras (4560x3048 pixels
 at 2 frames/sec) coupled to a machine-vision system (Fiala, 2005; Mersch
 et al., 2013). Physical contacts between workers were extracted based on
 the proximity and orientation of workers relative to one
 another. <strong>Worker age
 determination</strong> For several years prior to
 the experiment, and during it, newly-eclosed workers were paint-marked on
 a weekly basis. All worker ages given in the manuscript reflect the time
 elapsed since the day when the worker was painted, hence the actual age of
 a `5 day-old' ant is in the range 5 to 5+7=12 days old.  The head,
 thorax and gaster of each worker was marked with a paint code indicating
 the week of birth.<br> Codes were applied after immobilizing the
 ants by placing them in a petri dish placed on ice (dish
 temperature 2<sup>o</sup>C). Cooling typically lasted
 &lt;5 minutes, and painted ants recovered within few minutes. Each
 newly-painted ant was photographed with a hand-held digital microscope
 (MAOZUA, 5MP USB Microscope) and comments about their physical appearance
 were referenced in a table. These photographs and comments were later used
 to distinguish between ants with the same colour code (the same age) that
 lost their identification tags during the same week.
  
description: Each .txt.gz file contains a time-ordered edge-list representing
 all pairwise physical contacts between ants over a one week period. These
 files are named according to the colony identity and the week.
 The accompanying .xlsx files provide both the AprilTag number,
 and the paint-code of each individual. The Col_Ant.csv
 file contains the date of birth of each ant. The
 Experiment_description.csv file gives the start and end times for each
 week of tracking for each colony. The
 README_for_contacts.txt file contains a description of the columns in the
 contacts files.