Behavioral pattern of pill bugs revealed in virtually infinite multiple T-maze

Abstract

A behavior called turn alternation has been studied extensively in terrestrial isopods. This behavior is seen when they alternate their path choice on successive trials of the T-maze test. We made the multiple T-maze device which consists of two turntables with a T-maze mounted on each and examined the behavior of 36 pill bugs (Armadillidium vulgare) that each completed 130 successive T-maze trials. As a result, in addition to turn alternation, turn repetition (turning in the same direction on two successive turns) appeared at a rate of 20%. In the turn sequences, we observed segments consisting of successive turn alternations and defined the number of turn alternations in a segment as the length of it. Cumulative frequency distribution of segment lengths obeyed power law with exponent of 1.76. This result suggests that pill bugs in the multiple T-maze device behaved as Levy walkers which forage in an environment, where resources are unpredictably distributed.