Experiment 4) Effect of Recruitment and the Pheromone Trail on the Movement of Food Items

Experiment 4) Effect of recruitment and the pheromone trail on the movement of food items:
Modelling the random build-up of ants at a food source

This part of the experiment aims to estimate the time required for a certain number of ants to find a food item by chance, without any form of recruitment. We placed a 15X15mm food item 2 meters from a Pheidoleoxyops nest and waited until an ant found the item. Every ant that found the item was immediately removed, and the time at which the ant had found the item, measured from the moment the item was presented, and the order of the ant (whether it was the first ant to discover the food, the second ant, and so on) was noted. This continued until 10 ants were captured or 25 minutes had elapsed from the beginning of the trial. If 25 minutes elapsed without 10 ants being captured, the remaining positions were given a value of 25 minutes. This will have the effect of underestimating the time required for 10 ants to reach the food item. Thus, the results represent a conservative estimate (erring on the side of more rapid discovery).

Using this data, we built a linear mixed-effect model which attempts to predict the time an ant was captured at by the discovery order of the ant. This model had an intercept of 141.8 and a slope of 92.4 seconds per ant which discovers the item (See figure below). The average number of ants required to begin moving the item and to move it 5cm was 2.2 and 6.6 ants, respectively. Using the model of random ant build-up, we can interpolate how many seconds would be required for those two events to happen without any recruitment. This interpolation provides the figures 345.2 and 747.3 seconds for first movement of the item and movement of the item 5cm, respectivly (see figure below).