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IV

Ivon Vassileva

McGill University
Who should I follow today? Experience shapes shoaling behaviour in Trinidadian guppies

I. Vassileva, S.M. Reader

Many animals form groups, as there are multiple benefits to group living such as protection from predation and access to social information. However, there are also costs associated with grouping, including increased competition with conspecifics. The Trinidadian guppy Poecilia reticulata is a social fish species, that is often seen to shoal (group) with conspecifics, but with variation in grouping tendencies between wild populations. In general, guppies, like many fish, prefer larger groups. However, under low predation, smaller group sizes are seen, likely the result of intraspecific competition. We examined flexibility in shoaling tendencies in female guppies by attempting to experimentally shape shoaling preferences by training. Fish were trained over 20 trials with food to either join large (6 fish) or small (2 fish) shoals, followed by a preference test. Before training, subjects preferred the large shoal. Experimental training had a significant effect on this prior preference, with fish trained to the small shoal increasing their preference for a smaller shoal. Thus we find that guppy shoaling tendencies are flexible, can adjust rapidly to recent experience, and that fish can be trained to selectively approach and shoal with shoals of different sizes, even without changes in predation or competition. Our method of shaping grouping phenotype can be used to further test adaptive hypotheses of fish grouping behaviour. Key words: fish, grouping, social behavior