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According to the RSPCA, there are only two species of rats living in the UK - brown rats and black rats.

Department of Agriculture has added black rats to the growing list of mammals that have been infected by H5N1 bird flu.

Outbreaks there are associated with agriculture, deforestation, the black rat -- and fleas.

Soon after their arrival, the bones suggest, brown rats began to rapidly outcompete black rats in coastal cities, eventually eating their smaller relatives out of house and home.

One probable reason they dominated, researchers suggest, is that they ate food black rats would otherwise have consumed – which may have reduced reproduction among black rats.