Patch Shape Emergent Properties Figure 8. Directionality towards the inside, where 1 means pointed towards the inside of the patch, and -1 means pointed towards the outside. A: Overall effects for different edge behaviors and edge shapes. Bars are grouped by behavior to edge, and within each group, bars show animals’ behaviors to the edge: straight, in and out. The main differences are in the type of avoidance behavior, not in edge shapes. B: For the Out shape only, To-inside vs. width of edge shape. Each color represents different edge behaviors. With all behaviors, directionality changes very close to the tips of the edge shapes. doi:10.1371/journal.pone.0021886.g008 An alternate hypothesis, suggested by my model, is that herbivore behaviour at edge shapes is governed just by their response just to edges, not to edge shapes. First we need to determine their response to edges. Since the herbivores, that normally live in the forest, do graze on the grass in the open areas, this suggests that they are attracted to the edges. Then my model predicts that if they are attracted to edges, they would concentrate at convexities, not concavities. Thus we would expect that seed dispersal of the woody colonizers, and thus their density, would be greater at convexities. Since my model’s predictions are the opposite of Hardt and Forman’s [4] results, this rejects the hypothesis that only edge response is important, and supports Hardt and Forman’s [4] hypothesis that the herbivores actually recognize and respond to edge shapes. In this way, even though my model only addresses one mechanism of edge shape response (edge effects), one can use it sometimes to test for edge shape recognition. Another aspect of predictions is the scale of the edge shapes. The units used in this model are biologically relevant and thus useful for predictions in other systems. In this model, ‘‘steps’’ do not represent physical steps of animals - rather, they represent decision points [21]. At each step the animal chooses the next spot to go to and travels towards it; the straight section from one decision point to another represents an animal walking in oriented Figure 7. Directionality towards the tip of edge shapes, where 1 means pointed towards the tip of the shape along the edge, and -1 means pointed towards the base. A: Overall effects for different edge behaviors and edge shapes. Bars are grouped by behavior to edge, and within each group, bars show animals’ behaviors to the edge: straight, in and out. There is no overall directionality except that when animals are attracted to edges, they orient towards the tips of In shapes. B: For the In shape only, To-tip vs. width of edge shape. Each color represents different edge behaviors. With attraction, animals orient more towards the tip the closer they are to the tip. C: For the Out shape only, To-tip vs. width of edge shape. With all behaviors, animals orient more towards the tip right at the tip of edge shapes. doi:10.1371/journal.pone.0021886.g007 concave into the forest. Hardt and Forman [4] hypothesized that this happened because herbivores that typically live in the forests go into the grassy areas to feed, but that for protection, the herbivores would concentrate in the grassy areas where the edge intrudes into the forest – and thus disperse seeds of the woody colonizers into the grassland areas close to the concave edges. Thus their hypothesis is that herbivores specifically recognize and respond to edge shapes. PLoS ONE | www.plosone.org 6 July 2011 | Volume 6 | Issue 7 | e21886