Cross-species Analyses of Social Hierarchies
Social hierarchies are found across animal taxa. We are interested in how universal social processes within social hierarchies are, and what types of variation exist in social hierarchies. Recent projects have included examining how different species establish social hierarchies. Working with Dr Ivan Chase, Stony Brook University, we have shown that groups of mice, cichlid fish and chickens show remarkable similarity in the structural evolution of networks of social hierarchies.
Winner-Loser Effects
Mathematical models have demonstrated that winner effects (the increased probability of winning your next fight given you won your previous fight) and loser effects (the increased probability of losing your next fight given you lost your previous fight) can lead to highly linear dominance hierarchies even when individuals do not vary in intrinsic fighting ability. Experimentally, studies in many species have demonstrated winner-loser effects when animals of similar size, who have an experimentally induced differential history of winning or losing, are paired together.
Statistical Modeling of Social Dominance Interactions
We are interested in applying statistical methods to the study of aggressive social interactions. In one study, we developed methods for determining from all occurrence behavioral data when pairs of mice resolve their dominant-subordinate relationship.
Development of Social Competence
In the wild over 90% of Mus musculus females will rear their offspring in communal nests. In the laboratory, the typical method of rearing is one dam with her litter. I have shown that rearing pups in large communal nests (three dams sharing litters) leads to profound changes in the maternal and social behavior of mouse offspring as well as the distribution of oxytocin and vasopressin receptors in several brain regions.
The Meaning of Weaning
We have shown that the age at which animals are weaned has significant effects on their social development. Usually in the laboratory, mice are removed from their mothers at day 21 postnatally. We show that mothers will nurse and lick/groom their offspring beyond this period up to day 28 postnatally. During this fourth week postpartum dams will actively wean offspring by pinning and mounting them in response to pups’ nipple solicitations.
Behavioral Plasticity
Studying complex social behavior in the laboratory is challenging and requires analyses of dyadic interactions occurring over time in a physically and socially complex environment. In our laboratory we conduct long-term behavioral observations of animals housed in groups in large vivaria that mimic the burrow systems of their ancestral species Mus musculus.
Physiological Plasticity
Individuals must adapt to their current social environment. Dominant and subordinate animals each face unique challenges that require them to adjust their physiology as well as behavior. Dominant male mice increase not only their levels of aggression, but also their patrolling behavior and scent-marking.
Processing of Social Status Signals
Many species use social cues or signals to guide the expression of contextually appropriate behavior, yet little is known about how the brain processes such information. We are currently investigating this question by exposing mice to social cues and analyzing neural excitation and the expression of other receptors and neurotransmitters in the brain using various histological techniques.
Social Status Transitions
Subdominant male mice are able to rapidly respond to the emergence of power vacuums. When an alpha male is removed from a hierarchy, subdominant males rapidly (within 3 minutes) recognize that there exists a social opportunity and they aggressively exert their own dominance over all other animals in the group. These males socially ascend to become the new alpha males and are able to stay at the top of the hierarchy. This demonstrates great social competence on behalf of these males to be able to so quickly respond to a change in the social context of the group.
