Meeting Abstract

P1.160  Tuesday, Jan. 4  Winner and loser effects in stalk-eyed flies (Diopsidae) EGGE, A.R.; SWALLOW, J.G.*; Univ. of South Dakota; Univ. of South Dakota jswallow@usd.edu

Winner and loser effects, in which the outcome of previous aggressive encounters influences the behavioral approach to and outcomes of future conflicts, have been documented in many taxa. They are prevalent in species that interact frequently because modulation of these potentially costly social interactions may influence Darwinian fitness. Stalk-eyed flies of the dimorphic species Teleopsis dalmanni engage in frequent fights over food resources, as well as over access to harems of females, with larger males prevailing when size disparities exist. However, whether and how prior experience influences fighting decisions and outcomes remains unexplored. To test for winner and loser effects in stalk-eyed flies, we reared flies in isolation until sexual maturity, then paired them first in size mismatched dyads to establish winning and losing experiences. After their first contest, the flies were paired with size matched individuals and allowed to interact. We determined whether an initial winning or losing experience significantly altered outcome probabilities in the second, size-matched encounter. Although initial winning experience did not significantly affect the second interaction, providing no evidence for a winner effect, initial losing experience did. Initial losers were significantly more likely to lose a subsequent interaction, providing evidence for a loser effect in stalk-eyed flies. Smaller males also experienced an increased probability of losing their second interaction, regardless of prior winning or losing experience, an effect that was not seen in large males. Our data suggest that the loser effects we observed, which were more pronounced in small males, could result from the energetic costs of fighting that they were less able to absorb than large males.