Persistence in ants and its effects on cooperative transport efficiency

Ants utilize cooperative transport to move objects much heavier than themselves. Studying cooperative transport in ants can be used to improve upon artificial intelligence in swarm robots. We hypothesize that persistence, or the rate at which an ant will change direction, may be an important behavioral parameter that affects the efficacy of cooperative transport. Higher persistence should lower efficiency during cooperative transport because they will not change strategy as often, thus taking more time to return food to their colony. We developed a method for measuring persistence, as the average time it takes an individual to change strategy when her transport attempt is unsuccessful. We collected persistence data from three different ant species within the same genus, Formica, that are not highly efficient at cooperative transport. This baseline information can be used as a foundation in future comparisons to highly efficient species, such as Paratrechina logicornis. We studied multiple wild colonies of F. podzolica, F. pallidefulva, and F. obsuripes through video recordings. For each trial we pinned a cricket to a board that served as an arena. We video recorded ants as they tried to transport this cricket. Later we analyzed these videos, measuring the length of pulling bouts for each individual as well as each change in the direction of pulling. The data from each video was extracted using JWatcher and then analyzed in Excel and R. For these three species, we find significant differences between F. pallidefulva and F. obscuripes; F. obscuripes was the most persistent and F. pallidefulva was the least persistent. F. podzolica showed no significant difference between the other two species. In the future, we will compare this persistence data with other types of efficiency data from these three species, to see if in fact persistence is a good predictor of cooperative transport efficiency.