Experimental predator intrusions in a cooperative breeder reveal threat-dependent task partitioning

In cooperatively breeding species, non-breeding individuals provide alloparental care and help in territory maintenance and defence. Antipredator behaviours of subordinates can enhance offspring survival, which may provide direct and indirect fitness benefits to all group members. Helping abilities and involved costs and benefits, risks and outside options (e.g. breeding independently) usually diverge between group members, which calls for status-specific differentiated behavioural responses. Such role differentiation within groups may generate task-specific division of labour, as exemplified by eusocial animals. In vertebrates, little is known about such task differentiation among group members. We show how breeders and helpers of the cooperatively breeding cichlid Neolamprologus savoryi partition predator defence depending on intruder type and the presence of dependent young. In the field, we experimentally simulated intrusions by different fish species posing a risk either specifical...