Chemical cues, 3-D structure, and social experience in contests between similarly sized juvenile black Midas cichlids, Amphilophus sp. ‘short’

Abstract

Juvenile Midas cichlids are not territorial or remarkably aggressive under natural conditions but become extremely aggressive when placed in small aquaria. The potential effects of prior experience with 3-D structure, recent social interaction, and chemical cues on determining the outcome of contests between juvenile Midas cichlids were tested under laboratory conditions. Fish with a clay pot in their pre-test tanks defeated opponents without such prior experience when test tanks contained an identical pot. Experience in a small group of conspecifics had no significant effect on contest outcome, although fish that held lower size ranks tended to lose contests. Conspecific chemical cues did not affect the outcome of contests. Thus, although juvenile Midas cichlids are not typically aggressive they are sufficiently plastic not only to behave aggressively under certain conditions, but to adjust aggressive behavior according to prior experience with environmental structure as do some animals that are naturally territorial.