Cichlid-catfish mutualistic defense of young in Lake Malawi, Africa.

Bagrid catfish and cichlid parents engage in a mutualistic defense of their young from predators. Over 50% of the catfish broods observed contained cichlid young, primarily of three species: Crytocara pleurostigmoides, C. pictus and Rhamphocromis sp. Three catfish broods, monitored for over 50 days, had a survivorship rate 6 times greater during periods when cichlids were present than when cichlids were absent. During two and a half h of observations of catfish broods without cichlids, I observed 23 strikes by predators on catfish young. However, when cichlids were present no foraging attacks were observed upon the catfish, but 32 occurred against cichlids in two and a half hours of observations. When the catfish parents were experimently removed the cichlid young were consumed first then the catfish young. When cichlids were present the catfish young survived over 80% longer than those in broods without cichlids. It is concluded that the parental catfish increase the survival of their own young be allowing cichlids into the brood. Because of an asymmetry of costs between the two species, cichlid mothers are more likely to abandon these interspecific broods than are the catfish.