Correlates of group size in a cooperatively breeding cichlid fish (Neolamprologus pulcher)

Neolamprologus pulcher, a cooperatively breeding cichlid fish from Lake Tan ganyika, lives in permanent social groups comprising one breeding pair and helpers of both sexes. Variation in group size (1-14 helpers) provides an o pportunity to investigate factors that affect how many helpers remain in a group and in turn how group size affects reproductive success. This field s tudy showed that larger groups live in larger territories with more shelter Group size was more strongly correlated with territory quality than with b reeder size. Experimental enhancement of territory quality did not affect g roup size but group size decreased when territory quality was reduced. Bree ders living in a large group benefit because such individuals feed more oft en and have lower workloads and greater reproductive success. Helpers in la rger groups also fed more frequently but did not have lower workloads. This is one of the first experimental studies to examine the factors influencin g group size in cooperative breeders.