Female Masai giraffes live in distinct social communities of up to 90 other friends, and although areas used by these ‘girl gangs’ often overlap, they have very different rates of reproduction and calf survival. This means the girl gang social units may be important to giraffe evolution. These findings were published this week in the Journal of Wildlife Management by a team of scientists from Penn State University and University of Zurich as part of the largest giraffe study in the world. “We used social network analysis of hundreds of females and discovered this girl gang social organization from the giraffe’s own preference and avoidance behaviors,” said Derek Lee, associate research professor at Penn State and senior author of the study. “Gang membership was pretty tight, and even though members of different girl gangs often spent time in the same areas, members of different communities rarely interacted with each other.”