With the beginning of the great voyages of discovery and colonization that set out from Europe from the 15th century onward, domestic cats crossed the Atlantic for the first time. Taken on board sailing ships to control infestations of rodents, they had ample time on the long sea passages to the Americas to produce kittens.
When they arrived at ports of call, many of these burgeoning cat families simply jumped ship, or were perhaps traded with local communities, while others accompanied pioneering settlers into the interior of the New World.
In the opposite direction, cats headed for Australia on convict ships and alongside colonists. There is a possibly apocryphal story that the first cats to reach Australia were in fact survivors of a Dutch shipwreck in the mid-17th century.