Kinship reduces alloparental care in cooperative cichlids where helpers pay-to-stay.

Alloparental brood care, where individuals help raising the offspring of others, is generally believed to be favoured by high degrees of relatedness between helpers and recipients. Here we show that in cooperatively breeding cichlids, unrelated subordinate females provide more alloparental care than related ones when kinship between dominant and subordinate group members is experimentally manipulated. In addition, unrelated helpers increased alloparental care after we simulated egg cannibalism by helpers, an effect not shown by related helpers. By supporting predictions of pay-to-stay theory, these results suggest that in Neolamprologus pulcher, reciprocal commodity trading is important for the decision of subordinates to invest in care of the dominants' offspring.