Age-dependent winner–loser effects in a mangrove rivulus fish, Kryptolebias marmoratus

Cheng Yu Li, Chun Ying Pan, Yuying Hsu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The outcomes of recent fights can provide individuals information about their relative fighting ability and affect their contest decisions (winner–loser effects). Most studies investigate the presence/absence of the effects in populations/species, but here we examine how they vary between individuals of a species in response to age-dependent growth rate. Many animals’ fighting ability is highly dependent on body size, so rapid growth makes information from previous fights unreliable. Furthermore, fast-growing individuals are often at earlier developmental stages and are relatively smaller and weaker than most other individuals but are growing larger and stronger quickly. We therefore predicted winner-loser effects to be less detectable in individuals with high than low growth rates and to decay more quickly. Fast-growing individuals should also display stronger winner than loser effects, because a victory when small indicates a strength which will grow, whereas a loss might soon become irrelevant. We tested these predictions using naïve individuals of a mangrove killifish, Kryptolebias marmoratus, in different growth stages. Measures of contest intensity revealed winner/loser effects only for slow-growth individuals. Both fast- and slow-growth fish with a winning experience won more of the subsequent non-escalated contests than those with a losing experience; in fast-growth individuals this effect disappeared in 3 days, but in slow-growth fish it did not. Fast-growth individuals also displayed winner effects but not loser effects. The fish therefore responded to their contest experiences in a way which reflected value of the information from these experiences to them, consistent with our predictions.

Original languageEnglish
Pages (from-to)1477-1488
Number of pages12
JournalAnimal Cognition
Issue number5
Publication statusPublished - 2023 Sept


  • Age
  • Fighting experiences
  • Growth rate
  • Kryptolebias marmoratus
  • Winner–loser effects

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Experimental and Cognitive Psychology


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