Odour tracking by young convict cichlids and a mechanism for alloparental brood amalgamation

Alloparental care can be maladaptive if foster parents invest in unrelated young. Alternatively, adopted young may benefit foster parents if the presence of adopted young reduces predation on genetically related young. Convict cichlids, Amatitlania siquia, form monogamous pair bonds and provide biparental care for their eggs and free-swimming young for up to 6 weeks. Alloparental care is widespread in this species. Parents accrue fitness benefits from adopting unrelated young (1) by dilution of predation risk for their own young and (2) by selectively adopting relatively small young to be the preferred targets of brood predators. The mechanisms by which unrelated young enter foster care are poorly understood. Here, we examined whether displaced young use chemical cues to orient to parental protection and whether they discriminate between odour cues of their biological parents versus those of unrelated parental-phase adults. Young convict cichlids were more attracted to the odour of their parents and to the odour of a maternal female that was not their biological mother (allomaternal) than they were to a blank water control, and they showed no overall preference between the odour of their biological mother and the odour of an unrelated maternal female of aged-matched young. Small young were biased towards biological maternal cues whereas large young were biased towards allomaternal cues. Taken together, these results indicate that displaced young can rely solely on chemical cues to seek out caregiving adults and do not express preference on the basis of biological relatedness. Alloparenting in fishes, altricial birds and other systems with self-feeding young is driven in part by generic attraction of young to any parental conspecific. •Seventy-eight per cent of broods defended by convict cichlids include unrelated young.•Displaced young use chemical cues to orient back to parental protection.•Young orient to any maternal cue, regardless of genetic relatedness.•Small young favour maternal cues while older young are biased to allomaternal cues.•This orientation behaviour is a mechanism leading to alloparental care.