An anthropologist in England investigated personality in chimpanzees (Pan troglodytes), looking at which behavioral traits were exhibited consistently in individuals, which traits correlated with one another, and how personality differed between males and females.

 With the help of several students, she observed the behavior of 75 chimpanzees from 3 different zoos over the course of three years. They recorded information about each chimp’s behavior, who they stayed in close proximity to, and who they groomed. They found that many behaviors were exhibited consistently over time by the individuals who performed them. They also found that certain behavioral traits were significantly correlated with one another, suggesting the presence of personality groups. For instance, frequency of approaching others in a friendly manner and frequency of play and affinitive behaviors (e.g. hugs and kisses) were strongly correlated. The five personality groups she identified were “sociability”, “positive affect”, “equitability”, “anxiety”, and “activity”. Finally, she found that males were more positive, equitable, anxious, and active than females though the two sexes didn’t differ in their level of sociability.  Continue reading →

In the current issue of the journal Animal Behavior, researchers from Indiana describe their work investigating the stability of social niches (patterns of sociability and attractiveness to others) in Brown-headed cowbirds (Molothrus ater) across experimental disturbances in group composition. 

The experimenters split groups of birds being housed together into two smaller groups and then put the group back together after three days. This procedure was run once with a group of adult birds and once with a group of juvenile birds. Throughout the length of the experiment, researchers regularly observed the groups and documented all instances in which an individual closely approached another in a non-threatening manner.   Continue reading →

Researchers from Italy and the United States investigated the effect of a parasite (Polistes dominulus) on the behavior and morphology of eusocial paper wasps (Xenos vesparum).

By collecting aggregated wasps before, during, and after typical hibernation periods and investigating their parasite load, they found that infected wasps formed hibernation aggregations before uninfected wasps and stayed in these aggregations further into the post-hibernation period. After dissecting both uninfected and infected female wasps, they also found that infected wasps were smaller and more asymmetrical, had undeveloped ovaries, and had lower fat stores than uninfected wasps. Essentially, these parasites steal nutrients from their hosts and induce them to become extra gregarious in order to promote their own reproduction. Now that’s a social circle I don’t want to be part of!

Citation: In Press: Beani, L., Dallai, R., Mercati, D., Cappa F., Giusti, F, and Manfredini, F. When a parasite breaks all the rules of a colony: morphology and fate of wasps infected by a strepsipteran endoparasite, Animal Behavior (2011).