Does the presence of an odd individual affect group choice?

作者：Quattrini Fausto G; Bshary Redouan; Roche Dominique G^*

来源：Behavioral Ecology, 2018, 29(4): 855-861.

DOI：10.1093/beheco/ary062

• Caesionidae
• coral reef fish
• Pomacentridae
• predation
• oddity effect
• shoal

Group formation (shoaling) with conspecifics is common in fishes and provides several antipredator benefits, such as improved food and predator detection. However, coral reef fishes often form mixed-species shoals, which can generate costs for some group members. For example, individuals that stand out from a group are more likely to be targeted by predators according to the oddity effect. Consequently, the presence of an odd fish might reduce the risk of predation to other group members. Alternatively, an odd individual might attract predators and increase predation risk for the group as a whole. We examined three co-occurring species of coral reef fishes using 2-choice tests to investigate: 1) whether individuals chose to associate with conspecifics over heterospecifics (i.e. the oddity effect); and 2) whether individuals associate with or avoid shoals containing an odd individual under conditions of low-and high-predation pressure. One species actively avoided associating with heterospecifics, consistent with the oddity effect. In contrast, 2 species exhibited no preference for heterospecifics versus conspecifics, perhaps due to less pronounced phenotypic differences between species pairs resulting in a lower relative risk of being odd. None of the 3 species showed either active avoidance or preference for shoals containing an odd individual, irrespective of predation pressure. In instances where the oddity effect is apparent (one species in our study), lower individual predation risk from associating with an odd fish might be negated by greater predation risk to the group as a whole.

• 出版日期2018-8