Sociable weavers show everybody needs good neighbours: Study

Scientists at the University of Sheffield have found out a new insight into one of the biggest questions in science - why some animals, including humans, work together to maintain a common good.

Sociable weavers, a highly social and co-operative breeding bird from the savannahs of southern Africa, build the

largest nests of any bird, housing colonies of up to several hundred birds that can often weigh tonnes and last for

decades. The massive nests consist of individual nest chambers which are used throughout the year for breeding and roosting and are embedded within a communal thatch.

The question that researchers from the University of Sheffield's Department of Animal and Plant Sciences addressed is how sociable weavers work together to successfully build and maintain this public good, while keeping freeloaders at bay.

Dr Rene van Dijk, from the Sheffield research team led by Professor Ben Hatchwell, said: "Our study shows that

relatedness between colony members is low, on average, but co-operation over thatch-building is kin-directed due to the positioning of relatives within nests. Sociable weavers do not contribute to thatch building equally, but those that do contribute to it are more closely related to their neighbours within the colony than are non-builders."

The study not only demonstrates that the influence of kin selection may stretch beyond that of nuclear and extended family groups thus promoting co-operation in large social groups, but it is also the first study to show that kin selection may promote the communal construction and maintenance of an animal-built physical structure. Such structures include nests, mounds and burrows.

The mechanism for the maintenance of cooperative behaviour in sociable weavers revealed by this study is unlikely to operate at such a global scale, but within smaller communities the idea of kin-directed cooperative behaviour is likely to be widespread and relevant across many other species.