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Alaska Fish & Wildlife News
May 2005

Combating Invasive Rats in Alaska

By Riley Woodford
caption follows
A norway rat. True citizens of the world, Norway rats are not from Norway, but northern Asia, and were spread world-wide through shipping and trade.

Joe Meehan was fighting rats at home before it became part of his job.

“I caught 45 rats in two weeks from under my house in Adak, using snap traps,” Meehan said. “After that I started poisoning them, but the things started crawling up into the walls and dying. So I went back to trapping them.”

Meehan worked as a wildlife biologist for six years in Adak, one of the many islands in the Aleutians infested by rodents during World War II military activity. Now based in Anchorage, he’s working to develop an invasive rodent management plan for Alaska. Meehan works for the Alaska Department of Fish and Game, and he’s particularly interested in protecting the Walrus Islands State Game Sanctuary.

“The plan will address how we can prevent them from being introduced or spread in the state, and how we can control or eradicate them,” he said. “They aren’t in Walrus Islands now, but we want to be sure if a few ever did get there we could respond before they reproduce and trash the islands.”

Meehan’s work is part of a growing effort to fight invasive rats in Alaska. Alaska’s climate and relatively isolated location have made the state somewhat less susceptible to the rat infestations that plague many parts of the world, but state and federal biologists are concerned about the potential spread of rodents, in particular the Norway rat.

As people spread across the globe, rodents took advantage of human transport, trade and colonization and tagged along. Rats and mice are responsible for billions of dollars of damage worldwide each year. They eat vast quantities of crops, food and livestock feed and contaminate far more stored food than they consume.

Rats’ ever-growing, self-sharpening teeth chew through communication and electrical lines, and rats gnaw through soft concrete and aluminum siding, damaging buildings and structures. They also spread a variety of diseases to humans, livestock and wildlife.

Rats’ profound impact on bird populations is well documented, and in the 1950s, invasive Norway rats devastated bird populations in the Queen Charlotte Islands just south of Ketchikan. But wildlife biologists in Alaska are concerned about more than birds – they’re worried about the rodents’ ability to restructure entire ecosystems.

“I’ve seen the damage rats can do all over the world,” said biologist Peter Dunlevy. “Birds can be greatly impacted, but the primary issue is large scale ecosystem-level problems.”

Rats are omnivorous. They eat eggs and birds, and they compete with native wildlife for seeds, plants and insects. Rats eat the seed bank and sprouting young plants, altering the entire vegetative community structure. Dunlevy said that’s already happened in Hawaii.

“They are affecting the whole ecosystem from the bottom up,” Dunlevy said. “You still affect birds when you change vegetative communities – a seed-eating bird is affected by seed-eating rats, even if they’re not munching on your eggs or your babies. Insects are the second biggest category of food for rats, and that impacts insect-eating birds.”

Dunlevy works for the Alaska Maritime National Wildlife Refuge, and was hired to design and implement a rat eradication program for the Aleutians. He came to Alaska three years ago after working on rat and other invasive species management programs in Hawaii and Guam.

About 17 large refuge islands in the Alaska Maritime National Wildlife Refuge have invasive rat populations from activities in World War II. Rats are established in some parts of Alaska: Ketchikan, Juneau, Fairbanks, Sitka, Nome and Kodiak, but Anchorage appears to be rat free, and the Anchorage port is the only major world port to be considered rat free.

Meehan said rat eradication programs are in their infancy in Alaska, but New Zealand has been dealing with rat infestations for years and has eradicated rats on some islands. Last year Dunlevy brought some of the best “ratters” from New Zealand to Alaska to contribute their expertise.

At this stage, Dunlevy, Meehan and others combating invasive rodents are assessing the risk of accidental introduction, surveying the extent of the invasion, evaluating potential eradication programs and establishing priorities.

“We’re laying the groundwork, and testing methods that have been used elsewhere and that need to be fine-tuned for local conditions,” Dunlevy said. “We’re surveying areas to find precisely where rats are and what they’re doing - what they’re feeding on and what effects they’re causing.”

Protecting the rat-free and wildlife-rich Pribiloff Islands is one priority. A rat introduction-prevention program is already in place there, with mechanisms to intercept stowaway rats. Rats are present on Kiska Island, and biologists are closely monitoring a large and productive auklet colony on the north side of island to gauge the impact.

“I’ve seen this colony and it’s amazing, just swarms of birds,” Meehan said.

Addressing the illegal importation and release of rats is another priority.

“We’ve had several incidents where it appears people have released pet rats,” said Meehan. “Pet rats are illegal, unless they are albino white rats. Some rats that have seen – in Anchorage, Kenai and near Wasilla – appear to be pets that were released or escaped.
If those get established, there’s a real wildlife concern. Plus these are near communities, and there’s whole other set of people-related concerns.”

Meehan is optimistic about rat eradication in Alaska, especially in urban areas.

“We have the potential to turn this around,” he said. “I can imagine we could eradicate rats from most communities where they exist at some point in the future.”

Riley Woodford is a writer with the Alaska Department of Fish and Game, Division of Wildlife Conservation. For more on Alaska’s wildlife, see http://www.wildlifenews.alaska.gov


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