Environmental conditions are generally assumed to be of crucial importance for the evolution of cooperative breeding. Subordinate individuals staying in the territory of dominants decide about dispersal and cooperative effort in dependence of the quality of the home territory and of alternative locations. However, there is currently little evidence from cooperatively breeding vertebrates that large-scale ecological patterns determine group structure and cooperative behavior of group members. Here we measured biotic and abiotic factors of potential importance for behavioral decisions of group members in eight populations of the cooperatively breeding cichlid Neolamprologus pulcher, which is distributed across a wide range of habitats in Lake Tanganyika. Our data show that habitat quality, substrate complexity and predation risk all differ substantially between the surveyed populations. This correlates with highly significant differences between populations in group size and composition, and with marked divergence in the type and quantity of cooperative behaviors exhibited by group members. Group size related to habitat type, with habitats demanding more help yielding larger groups. The demand for protection and help seem to largely determine group composition and cooperative behavior, which is in accordance with the “pay to stay” hypothesis postulating that subordinate individuals pay as much as needed to evade being evicted from the territory, if alternative options are scarce or unfavorable. This is confirmed by laboratory experiments showing that breeders more readily accept subordinates if the demand for help is high.