A new insight into one of the biggest questions in science – why some animals, including humans, work together to maintain a common good – has been gained by Sheffield University scientists.
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 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.
Birds have to work together to build and maintain it and as a result all colony members benefit.
Researchers wanted to find out how the birds worked on their homes while keeping freeloaders at bay - and whether they co-operated because they were all relatives.
Dr Rene van Dijk 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.
“This co-operation is similar to how human families may decide to accept a lodger into their home. If the lodger isn’t related to the family, he or she may pay rent but otherwise they will not care too much about the upkeep of the house.
“However, if the lodger is a known family member, then you would expect them to maintain the house which he or she may stay in for a longer period and possibly inherit. It may seem like a small difference, but it tips the balance.”