Intrinsic and extrinsic factors affecting group decision-making

Abstract

To stay cohesive and benefit from group-living, members of social species must frequently make decisions together. Variation in intrinsic characteristics, such as dominance and sex, leads to conflicts of interest. But extrinsic factors, such as intergroup conflict, are also likely to affect group decisions. This thesis investigates how both factors influence group decision-making by using two complementary study systems: wild dwarf mongooses (Helogale parvula) and captive colonies of the monogamous ant Temnothorax nylanderi. Using long-term behavioural and GPS data from dwarf mongooses, Chapter 2 shows that dominants and males are most likely to lead group movements from a morning sleeping burrow, especially in the breeding season. Dominant males led more the day after an intergroup interaction in the non-breeding season, and male leadership increased in territory areas overlapping with neighbouring groups. Chapter 3 provides experimental evidence that acoustic movement signals in dwarf mongooses attract followers. Whilst group members are equally likely to respond to the movement calls of dominants and subordinates while foraging, a simulated rival group did not impact follower responses. The remaining data chapters are based on an experiment where Temnothorax nylanderi colonies were split and recombined as a host (with a nest) or an invader, to investigate how the presence of queens affects colony fusion. Chapter 4 presents the development and testing of an automated image-processing script used to generate data from the experimental photographs. Chapter 5 uses those data to show that fusion is less likely when both colonies contain a queen, and post-fusion dynamics are affected by the presence of at least one queen. For example, the presence of a queen meant colonies remained separated within the nest even after fusion, suggesting colonies may be waiting to split once again. Overall, this thesis demonstrates that both intrinsic and extrinsic factors, particularly conflict, affect group decisions.

Date of Award	5 Dec 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Andrew N Radford (Supervisor), Patrick Kennedy (Supervisor) & Innes C Cuthill (Supervisor)