When the female of the species is leader of the pack

Why females can lead some groups of herd mammals

source: New Scientist 14 Feb 2009 vol 201 no 2695 p16

Females are often leaders among herd mammals such as sheep, elephants and reindeer. University of Sussex's Larissa Conradt and her team used simulations from a computer model to understand why. They discovered that individuals could become leaders and move a herd either if they had a lot to gain, for example if they were hungry and wanted to go where food was more plentiful, or if they stood to lose least if the group split. Males can lose mating opportunities if a group divides. 
SP,BT