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Advisor(s)
Abstract(s)
Animal conflicts are influenced by social experience such that a previous winning experience increases the
probability of winning the next agonistic interaction, whereas a previous losing experience has the opposite
effect. Since androgens respond to social interactions, increasing in winners and decreasing in losers, we
hypothesized that socially induced transient changes in androgen levels could be a causal mediator of
winner/loser effects. To test this hypothesis, we staged fights between dyads of size-matched males of the
Mozambique tilapia (Oreochromis mossambicus). After the first contest, winners were treated with the antiandrogen
cyproterone acetate and losers were supplemented with 11-ketotestosterone. Two hours after the
end of the first fight, two contests were staged simultaneously between the winner of the first fight and a
naive male and between the loser of first fight and another naive male. The majority (88%) of control
winners also won the second interaction, whereas the majority of control losers (87%) lost their
second fight, thus confirming the presence of winner/loser effects in this species. As predicted, the success
of anti-androgen-treated winners in the second fight decreased significantly to chance levels (44%), but the
success of androgenized losers (19%) did not show a significant increase. In summary, the treatment with
anti-androgen blocks the winner effect, whereas androgen administration fails to reverse the loser effect,
suggesting an involvement of androgens on the winner but not on the loser effect.
Description
Keywords
Social experience Winner effect Androgens Testosterone Aggression
Citation
Proceedings of the Royal Society B: Biological Sciences, 276, 2249-2256