All known "distinct lineages in the black rat's family tree [originate] from a different part of Asia," according to Science Daily, but this wildly successful species hardly stayed close to its ancestral home. Scientists estimate that black rat migration began some 20,000 years ago, with the rodents reaching the Middle East first, then quickly spreading into the regions of modern day Europe. Rats would not reach Australia or the Americas until thousands of years later when they hitched rides on sailing ships during the Age of Exploration, soon spreading out all across these new habitats as well.
Today, black rats can be found all over every continent on earth except for Antarctica. They are able to thrive in crowded cities, in suburbs, on farmland, and in forests, being highly adaptable. This adaptability comes largely because, according to the Australian Museum, "it eats just about anything." Black rats can cause major problems due to their tendency to spread disease (often via parasites they carry), to damage crops and infrastructure, and to out-compete local, indigenous species. That said, today black rats are so common in so many places that their presence is expected, not endemic, and their damage was largely done in centuries past. In some remote places, however, they remain a serious problem. "Few vertebrates are more problematic to island biota and human livelihoods than R. rattus," according to BioOne Complete.
