Over 150 years ago Japanese ships were designed, by order of the Emperor, to swamp if they ventured into large following seas and traders were banned from going abroad. About this time, a wrecked Japanese ship was noted on the shores of the recently discovered and relatively unexplored island in the Aleutians. The early Russian visitors to the island noted that, unlike other Aleutian Islands, this one was infested with rats. The island became known as Rat Island. Later, other islands in the chain became infested by norway rats during these wooden ship days.
Rats can colonize an island quickly because of abundant food such as nesting seabirds, absence of other mammal predators or competitors. Norway rats are especially adept at preying on upon a wide range of wildlife, especially along coasts and wetlands. Besides eggs, chicks and nesting seabirds, rats also eat leaves, stems, berries, insects, spiders and fish. Rat populations are able to survive on islands after the seabird migration because they can utilize a wide variety of foods.
A new wave of invasion of rats to the Aleutians came during WWII in ships and cargo of both American and Japanese troops. No one knows exactly when rats first came ashore to the outposts, but over seven large islands that had been rat-free before the war became infested during their occupation.