They may not have raped and pillaged, but “Viking” mice conquered the outer reaches of the British Isles all the same.

Rodents living in Wales, Scotland and Ireland can trace their ancestry to Norwegian house mice, presumably stowaways on Viking ships.

Because grain-eating house mice – Mus musculus domesticus – depend on dense human populations, they serve as a reliable proxy for human settlement and migration, says Jeremy Searle, an evolutionary biologist at the University of York, UK, who led the new study.

“It’s just a completely different angle to look at and potentially add new pieces of evidence that historians and archaeologists can use,” he says.


The discovery that mice made the journey to the northern and western British Isles at the time of the Vikings isn’t much of a surprise in itself. The Orkney Islands served as a major Norwegian Viking settlement in the 11th and 12th centuries, and rodents probably sailed between Scandinavia and Scotland.

Earlier settlers

What surprised Searle’s team was the difference in mitochondrial DNA from these “Viking” mice and those recovered in other parts of Britain. When they examined the ancestry of rodents from elsewhere in the British Isles, they found a link to Bronze Age human migrations, beginning about 2300 BC.

This probably means that the Vikings were the first humans to live densely enough in Scotland and Ireland to support house mice, Searle says.

“If a place is empty of mice the first that come are the winners,” agrees François Bonhomme, an evolutionary biologist at Montpelier University, France, not involved in the study. “One boat with three mice – that’s sufficient to start a population.”

Other such human and house mice populations should prove more interesting and enlightening, Searle says. “Now that we’ve got a Viking mouse, if you like, we can actually focus on much more specific aspects of Viking history.”

For instance, mice could solve two puzzles about the settlement of Iceland. Some historians think that Iceland was home to multiple Viking settlements, each with a different home base in the Viking kingdom, a contention that mice could bolster.

Also, the Hebrides may have served as a pit stop from Norway to Iceland, where Viking men picked up women for second leg. This theory might be confirmed if DNA from Icelandic mice most closely matches that of Hebridean mice.

Journal reference: Proceedings of the Royal Society B: Biological Sciences, (DOI: 10.1098/rspb.2008.0958)

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