Reciprocity between endocrine state and contest behavior in the killifish, Kryptolebias marmoratus

Ryan L. Earley, Yuying Hsu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

80 Citations (Scopus)


Given the dramatic behavioral effects of winning and losing contests, and pronounced changes in stress and sex steroid hormones post-fight, it is reasonable to suppose that these hormones also dictate future behavior. We sampled water-borne cortisol, testosterone (T), and 11-ketotestosterone (KT) before and after contests in the mangrove killifish, Kryptolebias marmoratus, to determine how endogenous steroid hormone levels might predict and respond to contest dynamics or success. Pre-fight cortisol related negatively, and pre-fight T related positively to contest initiation and winning, particularly in the smaller opponent. In the pairs where a larger fish won the contest, winners with higher pre-fight T and lower pre-fight cortisol delivered more attacks to the losers. Contest duration and escalation influenced post-fight hormone concentrations primarily in losers. Escalation significantly increased post-fight cortisol, T, and KT for losers but not for winners. However, winners that attacked losers at higher rates had higher levels of post-fight cortisol. Losers also demonstrate the most consistent post-fight hormone responses, particularly to contest escalation and duration. Despite the bidirectional relationship between hormones and contest behavior, we found no overall mean differences in pre- or post-fight cortisol, T, or KT between eventual winners and losers. Thus, it is evident that the categorical states of winner and loser cannot alone reveal the complex, reciprocal associations between endocrine systems and social behavior.

Original languageEnglish
Pages (from-to)442-451
Number of pages10
JournalHormones and Behavior
Issue number3
Publication statusPublished - 2008 Mar


  • 11-ketotestosterone
  • Aggression
  • Cortisol
  • Dominance
  • Testosterone

ASJC Scopus subject areas

  • Endocrinology
  • Endocrine and Autonomic Systems
  • Behavioral Neuroscience


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