the individual who locates the food if it occurs in high abundance in the patch. Group hunting allows predators to take down larger prey, as well as prey that can outrun the predator but can be caught by an ambush. For example, lionesses (Panthera leo) hunt cooperatively for large prey such as zebra (Equus burchelli) and wildebeest (Connochaetes taurinus), with each lioness adopting particular positions in a formation. The presence of many predators also causes panic in groups of prey, often causing them to flee in different directions making it easier for the predators to single out a target. Foraging in a group also has some anti-predator benefits. Being part of a group dilutes an individual's risk of being attacked, as the more group members there are, the lower the probability that that individual will be the victim. Grouping may swamp the predator's capacity to capture prey - for example, hawks are unable to capture more than one yellow-eyed junco per attack. Large groups also cause predator confusion as it makes it difficult for prey to focus on one target. Groups of animals may engage in communal defences, such as mobbing, for further protection. Disadvantages Dilution of predation risk only occurs if groups of animals are not more prone to attack than individuals. Often large groups are more conspicuous to predators so grouping may increase the risk of attack. Blue acara cichlid fish (Aequidens pulcher) choose shoals of guppies (Poecilia reticulate) to attack based on how visually conspicuous they are, preferring shoals that are larger or exhibit more movement. Foraging in groups requires sharing so may also lead to greater competition for food. Effect of group size Larger groups may have a greater overall vigilance than small groups due to the ‘many eyes’ hypothesis: more eyes scanning for predators means that the proportion of time that at least one individual is vigilant (collective vigilance) is higher. This improved vigilance may allow an individual to decrease the time it allocates to vigilance without any increase in its personal risk of being attacked - particularly as large groups already have a diluted predation risk. Lower individual levels of vigilance with increasing group size has been observed in many bird, mammal and fish species. Individual ostriches (Struthio camelus) and greater rheas (Rhea americana) in large groups both spend less time with their head up than individuals in small groups, however collective vigilance increases