| Summary: | 碩士 === 國立臺灣大學 === 生態學與演化生物學研究所 === 99 === Reaching consensus on moving direction is important for gregarious animals performing collective movement. As an example of collective movement, cooperative retrieval is performed by many ant species to cooperatively carry food items too large to be carried by single individuals.
When a food-retrieving group (FRG) encounters a barrier, it is necessary for the group members to reach consensus on moving direction so as to bypass the barrier. In addition, if one of the two sides of the barrier is blocked, it will be better for the FRG to choose the more passable side. This study was set to investigate how FRG members of crazy ants Paratrechina longicornis reach consensus on moving direction, and to verify whether FRGs are able to choose the more passable side to bypass the barrier. To answer these questions, a series of experiments using barrier device were conducted, and data of both individual-level as well as group-level behaviors were integrated to investigate the behavioral mechanism of FRG members to reach consensus on moving direction. The results show that in 36 of 50 cases members of FRG reached consensus when encountering a barrier. In 25 of the 36 cases where consensus was reached, some members would leave FRGs and explore either side of the barrier. After exploration some of these individuals returned to FRGs, leading the group toward the side they had explored by performing tugs. In this way, these individuals assisted the group in bypassing the barrier. Furthermore, when one of the two sides of the barrier was blocked, individuals behaved differently according to whether the side they had explored was blocked, and hence assisted FRGs in choosing the unblocked side.
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