Does the removal of finder's share influence the scrounging decisions of herbivores?

Abstract

Group-living animals use social information when making patch-joining/scrounging decisions. However, the extent to which they use finder's share (i.e. amount of food eaten in a patch before other individuals arrive) as a cue when making these decisions is unknown. It is likely that the removal of finder's share decreases patch attractiveness to scroungers. However, it is unclear how large a finder's share must be to reduce attractiveness, or how this varies with food availability. To answer these questions, we recorded the patch-joining decisions of dominant goats, Capra hircus, when presented with a choice between an artificial patch where finder's share had been removed by a subordinate patch holder (producer), and one where the patch holder had just started eating. We used time spent feeding by a patch holder (10, 30, 60 and 120 s) as an index of finder's share size, and tested this using three food availabilities (40 g, 100 g and 300 g). At low (40 g) and intermediate (100 g) food availabilities, scrounging goats avoided the finder's share patch once the patch holder had fed for ≥30 s (i.e. 25% and 17% of the food removed, respectively). However, at the highest food availability (300 g), these goats continued to join the finder's share patch even after the patch holder had fed for 120 s (18% removed). Ultimately, our results indicate that goats weigh up both food availability and the finder's share when making scrounging decisions. Nevertheless, finder's share removal was less important in patches with more food.