Strauss Lab

Societies in motion

Coordination and conflict in heterogeneous groups

Societies are built from the everyday decisions of the individuals that live in them—cooperate or compete, move on or stay put, reply or ignore. Societies exist because evolution favors sociality when individuals benefit from living in groups, despite often conflicting interests among group-mates. We study social dynamics and collective decision-making in heterogeneous groups to understand how individuals and groups navigate the tension between cooperation and competition in complex societies. We seek to understand how groups of individuals with conflicting interests regulate competition, coordinate behavior, and cooperate for mutual benefit. We address this question across timescales, linking moment-to-moment decisions to social dynamics spanning generations.

Our primary study system is the Mara Hyena Project, a long-term individual-based study of spotted hyenas in the Maasai Mara National Reserve in Kenya. Our work unites the traditional observation-based tools of behavioral ecology with cutting-edge biologging technologies, computer simulations, and bioacoustics to deliver a process-based understanding of collective decision-making and social dynamics in complex groups.

Research

A spotted hyena walking across wet grass wearing a GPS tracking collar

Coordination and collective intelligence amid conflicting interests

Most studies of collective behavior assume individuals are homogeneous, but many societies exhibit collective intelligence despite differences and divergent interests among individuals. Spotted hyena groups are a striking example of this, where the same individuals might compete fiercely over resources in one moment and cooperate in dangerous fights with other predators in the next. We examine collective intelligence and group function in the face of these conflicts of interest, linking long-term social relationships to the individual decisions that produce dispersion, cohesion, and coordination at the level of the group.

A spotted hyena nosing through tall dry grass, tail raised

Animal monarchies: stability and change across lifetimes and generations

Dominance hierarchies are one of the primary ways that societies regulate conflicts of interest within the group. In spotted hyenas, as in many primates, an individual's position in the dominance hierarchy is acquired through social inheritance, where offspring rank just below their mothers. This monarchy-like process of status inheritance produces hierarchies that can remain remarkably stable across generations, punctuated occasionally by coups that can dramatically shake up the social order and reshape the fortunes of entire lineages. Drawing on more than 30 years of continuous individual-based records, we study how social inheritance, social relationships, and demographic change interact to shape hierarchy dynamics, and what these dynamics mean for the structure and evolution of animal societies.

Two spotted hyenas on a dirt track running past a refuse dump on the edge of a city

Social relationships and collective behavior under changing environments

Human activity is changing the ecological conditions many animals live in faster than evolution typically operates. Spotted hyenas occupy a wide range of environments, from protected reserves to the edges of expanding cities, which makes them well suited to studying how societies respond to rapid change. By comparing hyena populations across gradients of human disturbance, we ask which aspects of social structure, social relationships, and collective behavior adjust flexibly to new conditions, which remain fixed, and what the consequences are for individuals when the structure of their society no longer matches the environment around it.