Combat and communication in the Everglades pygmy sunfish

Changes in population density and resource patterning affect the aggressive behaviour of pygmy sunfish (Elassoma everglaidei) in many ways. Increases in density significantly reduced the proportion of fights directly over clumped prey, the likelihood of initiators winning contests or acquiring clumped prey, and the length of contests. Increases in prey dispersion also reduce the proportion of resource fights in low-and high-density populations, the greater tendency for subordinates to initiate fights directly over resources, the likelihood of initiators acquiring a contested prey item in lowdensity populations, and the length of contests. Such increases, however, increase the likelihood of initiators winning contests at moderate competitive levels, and increase the effectiveness of rapid sequential communication in populations that abandon territoriality. In addition, some of these findings, such as the inverse relationship between contest length and both prey dispersion and rank differential, are consistent with predictions of cost-benefit models of fighting behaviour, namely, that escalated contests become more likely as asymmetries in fighting ability decrease and asymmetries in resource valuation simultaneously increase.