The effect of group size manipulations on the foraging behavior of black-tailed prairie dogs

Individuals foraging in large groups are thought to benefitbecause they are better able to detect and avoid predators.As a consequence, individuals in groups can adopt more risky,but rewarding, foraging behaviors without exposing themselvesto excessive danger. I experimentally manipulated the size ofblack-tailed prairie dog (Cynomys ludovicianus) groups to determineif individuals in large groups do forage in a more risky manner.I found that prairie dogs foraged more alertly and in less riskylocations (nearer to burrows, nearer to the center of the group,and in shorter vegetation) when group size was reduced. Effectsof group-size reductions were reversed when removed individualswere replaced, and persisted for at least three weeks in experimentswhere group size was permanently reduced. My results provideevidence that the relationships between group size and bothalertness and risk-place foraging are causal.