The role of familiarity in grouping decisions of Trinidadian guppies

Trinidadian guppies (Poecilia reticulata) show no evidence of a familiarity preference after 15-day or 55-day cohabitation, despite strong overall conspecific grouping.

• Why it matters: Grouping can benefit fish but also impose costs, so understanding whether prior experience with groupmates shapes stay-or-leave decisions is key.
• What they did: In two guppy populations, the study tested preferences for familiar individuals after 15 days and 55 days of cohabitation using two binary-choice designs.
• The result: Familiarity did not bias grouping choices in either population, implying that context- and population-level factors may limit familiarity effects on teleost social decisions.

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