Effects of a past contest on the future winning probability in a hyper‐aggressive fruit fly

• Published in: Ethology Vol. 129; no. 8; pp. 380 - 389
• Main Authors: Amino, Kai, Matsuo, Takashi
• Format: Journal Article
• Language: English
• Published: Hamburg Blackwell Publishing Ltd 01.08.2023
• Subjects: assessment strategy; Body size; contest duration; Design of experiments; Drosophila prolongata; Experimental design; Fighting; Fruit flies; Fruits; male–male competition; Statistical analysis; winner–loser effect
• ISSN: 0179-1613; 1439-0310
• DOI: 10.1111/eth.13375

In various animal taxa, prior experience of contests influences the consequences of subsequent contests. A well‐known example is the winner and loser effects, in which winners have a higher winning probability, whereas losers become more likely to lose in the subsequent contests. Previous studies have suggested that the intensity of past contests also affects the future winning probability in two ways: modulating the extent of the winner–loser effect or decreasing the winning probability of both winners and losers. However, the number of studies that investigated the effect of both the contest outcome and intensity has been limited. Here, we analyzed the effect of past fighting experience in a hyper‐aggressive fruit fly Drosophila prolongata to ask (1) whether the winner–loser effect exists in this species and (2) how the contest intensity influences the subsequent winning probability. To disentangle the multiple factors affecting the winning probability, we employed the experimental design involving both body size manipulation and the comparison of different intervals between the two contests. The results did not support the existence of the winner–loser effect: both winners and losers of the first contest showed decreased winning probability in the second contest. With a short interval (2 h), contest intensity negatively influenced the winning probability in winners, though the significance level of its effect was marginally above the statistical threshold. In contrast, contest intensity had no effect in losers. Notably, contest intensity positively correlated with the winning probability after the longer interval (1 d) in both winners and losers, suggesting that it reflects the intrinsic fighting potential of individuals. The possible mechanisms underlying the observed results were discussed. Our study illustrates the transient influence of past contests other than the winner–loser effect. We found no evidence of the winner–loser effect in a hyper‐aggressive fruit fly D. prolongata. Instead, both winners and losers decreased the subsequent winning probability, indicating that the past contest itself has a negative impact on the future contest.