Numlock Sunday: Sarah Gilman on The Rat Spill

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By Walt Hickey

Welcome to the Numlock Sunday edition. Each week, I'll sit down with an author or a writer behind one of the stories covered in a previous weekday edition for a casual conversation about what they wrote.

This week, I spoke to Sarah Gilman who, a few weeks ago, wrote one of my favorite stories of the whole year, The Rat Spill, for Hakai Magazine. Here's what I wrote about it:

Rats are terrible for the wildlife native to islands, which typically have not evolved any defenses to the rodents and are slaughtered wholesale by the rats. Every year 200,000 seabirds nest on Saint Paul Island in the Alaska Maritime National Wildlife Refuge, and another 2 million nest on Saint George Island about 75 miles away. Alaska and authorities take strenuous and expensive efforts to eradicate the rats to keep the birds safe. Their track record speaks for itself: since 1600, 40 to 60 percent of all recorded bird and reptile extinctions are attributable to rats, and the loss of those species wipes out entire ecosystems. Only a dozen of the bigger islands in the AMNWR have rat infestations, explaining why 40 million seabirds go there annually. Rats are gnarly, killing more than they need to eat and reproducing quickly. Alaska has absurd fines, up to $200,000, for ships that dare come to shore with rats onboard.

This story is wonderful, and between today and next Sunday I’m running the two-part interview I did with Gilman. This week, we talked about what rats do that makes them so destructive and just what it takes to keep them out. It also includes a mild diversion into the history of these two islands — the Pribilof Islands — that was fascinating to me.

Sarah can be found at Hakai Magazine and is on Twitter, and the story is here.

This interview has been condensed and edited.


Walt Hickey: What got you interested in covering the relationship between rats and native birds?

Sarah Gilman: One of the editors at Hakai, Adrienne Mason, saw a presentation on biosecurity by Gregg Howald, who an expert at Island Conservation. That is this big nonprofit that's been a pioneer in basically protecting islands and island-endemic species from invasive species that are introduced by people, like rats. Gregg had mentioned the Pribilof Islands and Adrienne knew that I had spent a bunch of time out in the Pribilofs, so she reached out to me to see if I would be interested in writing the story. I was out there in 2017 as a volunteer for the U.S. Fish and Wildlife Service. My job was basically to go out to these cliffs around St. Paul Island and count seabirds. Every three years they do a full population census of all of their monitoring plots on the island, and they've been watching since at least the ’80s if not longer.

I had a fair amount of experience with the island, and Hakai didn't have an expense budget for the story, so they thought I would be a good person to reach out to since I had been there and they couldn't send someone as it's quite expensive to travel there because it's in the middle of the Bering Sea, the airport's tiny and it's very foggy there, so there's no guarantee that your flight will even make it in. Often, people will wait for weeks either out in Anchorage or stuck on-island waiting to leave. It turns out to be quite hard to get to and to leave as I recently discovered on a trip to St. George, the other big island in the Pribilofs.

I liked the sound of the story because the phrase “rat spill” just so captured my imagination. I was very intrigued by that idea — it's very counterintuitive. The idea that a rat can spill, or rats could be something that could pour out of something and be a force that ruins or heavily damages the place by just being themselves.


With an oil spill, eventually oil sinks and goes away, but rats breed indefinitely.

I began poking around to see what was going on in this world of biosecurity. While I was on St. Paul, one of the Fish and Wildlife people I was working with showed me these big yellow barrels that they have around the harbor, just trash cans with holes in them that are basically their primary rat defense. I was aware they had this longstanding program to try to intercept rodents that might come in from the harbor, from any ships that came in from a place that has rats like Seattle or Dutch Harbor down in the Aleutian Islands.

The Pribilofs are one of the few places on the planet that have a permanent human population and don’t have rats. For there to be a port, a harbor that's actively receiving boats from places with rat infestations, that doesn't have rats? That's a really impressive thing. Part of the reason they have been rat-free is because of the efforts of the tribes out there and of the U.S. Fish and Wildlife Service working with the tribes.

How does something get rat free? Well, first they never had rats. Rats are not native to everywhere.

Goode, George Brown (1887)

The Pribilofs only have a couple native land mammals. On St. Paul there is an endemic shrew and a blue morph of Arctic foxes. St. George also has an endemic lemming. Those are the only land mammals that belong in the ecological state on the Pribilof islands. There are introduced reindeer that were put there as a food source. That's a very long story, but it was to feed the Unangan people who are kidnapped and put out on those islands by the Russians to supply the fur trade. I know this is so complicated, maybe irrelevant —

I don't care. This is fascinating.


It is really fascinating. The people who live out there, there are people who have inhabited the Aleutian islands for 10,000 years but they were moved out to the Pribilofs — which were uninhabited — by the Russians in the 1700s to basically be slaves in the fur trade, and then sort of assimilated into Russian culture.

Russian Orthodox Church procession, Saint George, Pribilof Islands, 1907

They have Russian Orthodox churches out there and there's services — I went to one when I was out there in 2017 — in Unangam Tunuu, which is their native language, and Russian and also English. It's just a really fascinating amalgam of cultures that grew up there over time. The U.S. took over that operation when they bought Alaska, but it wasn't until 1966 or so that Unangan people actually were recognized with real rights as citizens. The fur trade didn't stop until 1983. So that is some history about the Pribilof Islands, how folks ended up out there.

They're naturally without rats, and then partly through this long effort that Fish and Wildlife Service and the tribes had mounted since the ’90s, had maintained this status. There was one rat that had been seen on St. Paul Island and it was leading the Pribilofs on this intense chase. So I stumbled on this great way to tell this story in real time.


The track record for rats really speaks for itself here. You wrote since 1600, 40 percent to 60 percent of all recorded bird and reptile extinctions are attributable to rats.

Isn't that nuts? And to be fair to rats are a lot like us in a lot of ways. They are extremely versatile, omnivorous, very smart, very social, and very adaptable to different environments. They tend to be able to do really well in a lot of different places that they end up in. And they also thrive alongside people. Wherever we've gone, often they've followed. Then as they go, they end up in these places and they completely alter their environments.

They may have even played a role in the fall of civilization on Easter Island by making it a less hospitable place to live and provide food for the people who lived there. They just eat everything.

As one scientist explained it to me, they're essentially opportunists in the sense that if the food source is abundant, they will eat only the richest of what's most available. If you see a grizzly bear walking along a river that's strewn with salmon carcasses, the grizzly bear won't just pick up one and eat all of it. It'll just eat all the brain casings, the richest, fattiest parts of these dead salmon.

Rats will do the same thing. If there are billions of birds on an island, as there often are on these outer islands in the ocean, rats will just kill a bunch and then eat the good parts, and they'll save the rest for later and maybe not get to it at all. On Kiska Island in the western Aleutian Islands off of the coast of Alaska, there are millions of auklets — so many millions that they black out the sky when they fly.

And there's a rat infestation there from, they believe, military activity during World War II. Scientists who have gone out there to look at the effect of this rat population on this massive auklet colony have found rat caches in the rocks of up to 148 dead adult birds. They can be really devastating for island birds in particular that nest in crevices or on the ground.

Seabirds tend to pick these far out places like steep cliffs or offshore islands that don't have mammalian predators because they'll lay an egg and then they have to leave it for long stretches of time to go out and feed, and also they sit on it for long periods of time and are kind of defenseless, especially if they're on the ground. If they can pick a place and it's like a fortress for them, then they can protect their young. But when a rat arrives in a place like that, all of those defenses are meaningless. That's true for lots of other islands species as well. They often are naive to predators. They don't have defenses that they've evolved against them. If rats show up on an island, they can devastate birds or reptile species.

Another case in Alaska actually that's really interesting is foxes. So the Russians, when they first got out there, killed off all the sea otters, which were a primary thing for the fur trade along with seals. They started introducing Arctic foxes to all of these Aleutian Islands that had no mammalian predators. That devastated seabird populations before anybody was really paying attention. One of the things the Alaska Maritime National Wildlife Refuge, which is the refuge in my story, has done over the past is have people on staff who are basically employed to eradicate foxes from islands where they had been introduced by the Russians and later by the Americans to harvest for basically fur farming on these islands. I think they cleared something like 40 islands over time and they've seen big recoveries in seabirds in those places afterward.

This interview will continue next week, when we’ll talk about the morality of invasive species, how Alaska is serious about stopping rats, and more. You should really check out this story here.


If you have anything you’d like to see in this Sunday special, shoot me an email. Comment below! Thanks for reading, and thanks so much for supporting Numlock.

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Send links to me on Twitter at @WaltHickey or email me with numbers, tips, or feedback at walt@numlock.news