Group Coordination and Decision-Making during Foraging in Meerkats (Suricata suricatta)

Abstract

Some animal species live in stable social groups and scientists have long wondered how such groups are organized in space and how these groups maintain cohesion and make decisions. Group living animals need to trade-off the costs and benefits of close proximity to many conspecifics. Benefits can be increased, and costs reduced by preferentially choosing specific locations within a group, or by preferentially associating with specific group members. In many species, vocal communication also plays a key role in mitigating the compromises between individuals which lead to shared consensus decisions. Some animals using vocal communication to stay in contact, change their call rate depending on their location within the group and can thereby influence the movement of other group members. In this thesis, I addressed questions on group coordination and decision-making in wild meerkats (Suricata suricatta), small mongooses with a strict dominance hierarchy and a heterogeneous group composition, e.g. members varying in their needs and preferences. Meerkats live in an arid environment fluctuating in prey availability, which can influence group coordination and decision-making. Most previous research focused on decisions preceding changes in group activity. Little work has focused on coordination when ‘on the move’, on decision-making under time constraints, and on the effect of harsh environmental conditions on group coordination and decision-making. Here I used data from natural observations and an experiment, to shed light on the spatial organisation of foraging meerkat groups, their cohesion mechanism and the limits thereof under challenging environmental conditions, as well as their decisions to stop foraging and to return to their sleeping burrow. My results suggest that the cost or benefits associated with specific spatial locations are small, at least during the afternoon, as meerkats showed no preference for specific locations within the group. Individuals of the same litter and different dominance status were less likely to be within close proximity of each other, suggesting that competition might play an important role for the spatial organization of a group. During foraging, meerkats emit contact calls depending on their location within the group and follow ‘vocal hotspots’, areas with many calls. When conditions deteriorate, as during a drought, individuals vocalized independent of their spatial location within the group. The increase of the number of group splits during the drought suggests that the call pattern used for coordination is not maintained on a global level and that the cohesion mechanism of meerkats is disrupted. Data from natural observations indicate that the decision of meerkat groups to stop foraging and to return to the burrow is shared between group members. Both the decision to return and the speed of the group at the return seem to depend on the urgency, as decisions were less shared and groups moved faster, when meerkats were far from their burrow and sunset was imminent. My thesis presents different aspects of group coordination and shows that group coordination and decision-making in meerkats is affected by environmental constraints. Whereas all meerkats seem to contribute to coordination and decision-making processes, the amount of sharing seems to be strongly affected by time constraints. In addition, while meerkats seem to be able to flexible adjust their coordination mechanisms to changes in the environment, coordination breaks down under extreme conditions. These observations indicate the importance of changes in the environment on group coordination and likely the evolution of sociality.