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Harriman Expedition Retraced



The 1899 Expedition
The 1899


Original Participants

Brief Chronology

Science Aboard the Elder
Aboard the

History of Exploration
Exploration &

Development Along Alaska's Coast
Growth Along Alaska's Coast

Alaska Native Communities


The Rat Threat in Alaska

The phenomenon known as a "rat spill" takes place when a ship carrying rats docks at, or sinks near, an island previously rat-free. The rats come ashore by way of the gangplanks and ropes tied to the dock. If the ship is sinking, the rats swim. Once a few rats reach shore, a colony is quickly established, and the bird population of the island is seriously threatened. It is little wonder that a rat spill strikes terror in the hearts of scientists and island dwellers throughout Alaska.

The Dora, mail packet

Norway rats stowed away on ships of all types and sizes. Pictured here is the mail packet, the Dora, which made routine runs from the mainland to the Aleutian Islands.
Click image for a larger view

For centuries, most islands in the Aleutian chain and in the Bering Sea had few terrestrial mammals besides humans. In the absence of predators, bird populations flourished in ideal ground nesting and feeding conditions. But in 1828, Norway rats traveling (uninvited) on Russian ships, began to infest Alaskan islands, and infestation increased steadily. In the early 1940s hundreds of U.S. military ships routinely visited the Aleutians, and the rat infestation grew ever more serious.

The natural characteristics of the Norway rat account for much of the problem. It has been an opportunistic sea traveler for centuries. It is an incredibly adaptable species, surviving and flourishing anywhere humans do. With good eyesight, keen hearing and a sharp sense of smell, these small mammals adapt quickly to the harbors and rocky coasts of the Alaskan Islands, where nesting birds, eggs, and hatchlings provide an excellent source of food. Rats are agile, curious, and amazingly prolific breeders. They are short-lived (their life expectancy is about a year), but they are productive. A single female will have up to forty nestlings in a year. They are also destructive. In the 1950s rats devastated the bird population of the Queen Charlotte Islands. Two types of auklet and two types of petrels entirely disappeared from the locale. Tufted puffins, which had numbered in the hundreds of thousands, are now rarely seen.

A Threat to the Pribilof Islands

It is not only the bird populations that suffer once rats are introduced. David Cormany, who works for the National Marine Fisheries Service on the Pribilof Islands, told film director Larry Hott in 1999 that he regards "the introduction of rats to be worse than an oil spill. A rat infestation could very well introduce diseases to the northern fur seals here, and would certainly decimate the sea bird population. The Pribilof economy is now built largely around seafood processing. And with that seafood processing we get a lot of vessel traffic which brings the threat of rats."

Rat populations are very difficult to eradicate, which means that if rats do reach the Pribilofs, they will most likely be there for good. That is why Pribilof Island officials have established a campaign to keep rats off their shores. Ships with rats cannot come within three miles of the harbor; traps and poison have been set out in St. George and St. Paul at points where the rat spill is likely to occur. Prevention seems to be the key -- in New Zealand, scientists have successfully gotten rid of rats on very small islands, but on larger ones they are simply unable to eradicate the tenacious rodents that threaten the native species.




For information on the Harriman Retraced Expedition e-mail: harriman2001@science.smith.edu

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