Knowledge for a sustainable world

Steven Belmain, Ruth Leavett

NRI's rodent expert, Steven Belmain, is a co-author of a research paper recently published in BMC Genetics1. The paper describes the surprising discovery of a rat species normally found in Japan and the Far East, Rattus tanezumi, is also found in southern Africa.

The Rattus genus contains some of the most invasive and adaptive mammal species known, particularly the black rat, Rattus rattus, and the Norway rat, Rattus norvegicus, both of which have spread around the world from their original Asian origins by hitching a ride on human transport. Dr Belmain led a team of field researchers in South Africa to trap rats in rural and urban communities as part of a research project to assess dangerous diseases carried by rats. As thousands of rats are caught during such studies, specialist tests used to screen DNA to confirm species identities are usually only employed to assess a small number of specimens. By accident, some specimens of what were assumed to be Rattus rattus were put forward for genetic testing. The results indicated the rats were a species that was only known to be found in Japan and parts of China and Southeast Asia. The paper highlights that current assumptions made about invasive rat species are not always correct, and it is likely that many different Rattus species have been spread around the world through international trade and shipping. Although rat species may look similar and behave in similar ways to the human eye, important physiological differences can exist. For example, researchers have shown that two very physically similar rat species react to the disease Bubonic Plague in different ways: one is very good at vectoring bubonic plague, whilst the other species is not.

  1. Bastos, Armanda D., Nair, Deenadayalan, Taylor, Peter J., Brettschneider, Helene, Kirsten, Frikkie, Mostert, Elmarie, von Maltitz, Emil, Lamb, Jennifer M., van Hooft, Pim, Belmain, Steven R., Contrafatto, Giancarlo, Downs, Sarah and Chimimba, Christian T. (2011) Genetic monitoring detects an overlooked cryptic species and reveals the diversity and distribution of three invasive Rattus congeners in South Africa. BMC Genetics, 12 (26).