Defense by exploitation in Negev gerbils.

In this study, we addressed how frequently a non-traplining animal should visit food patches. More specifically, we investigate if non-traplining animals engage in a behavior called "defense by exploitation", which is characterized by an increase in visitation rates with increased intra-specific competition. We ran four tests with two gerbil species in the Negev Desert. Firstly, we measured patch use of Gerbillus pyramidum and Gerbillus andersoni allenbyi. We assumed that activity and competition would decrease through the night and that patch use would decrease with number of visits. Secondly, we measured how the number of visits to resource patches increased with the addition of individuals. Thirdly, we repeated this experiment, but instead removed individuals. Lastly, we conducted a simulation to compare these results against theoretical expectations. In the first test, we found support for defense by exploitation in G. pyramidum. The second and third test found no support. The fourth test found support for this increase visitation, but only if costs of locomotion are relatively small.