Madagascar is home to a unique biodiversity with a large number of endemic species, among those many lemur species, including the mouse lemurs. This diversity is also found in their retroviruses, a team led by scientists from the Leibniz Institute of Zoo and Wildlife Research (Leibniz-IZW) and the University of Stirling reports in the journal “Virus Evolution”. They analysed the mouse lemur genome and identified viruses of two classes that represent ancient infections of the mouse lemur germline. The viruses now behave similarly to lemur genes and are thus called endogenous retroviruses (ERVs).