National Wildlife Refuge System
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Rhino Auklet
A rhinoceros auklet peeks out of its burrow at night.
Credit: N. Konyukho, USFWS

The Case of the Missing Auklets

The hoary marmots have to go. So say biologists at Alaska Maritime National Wildlife Refuge about the prairie dog cousins suspected of out-competing native seabirds for nesting habitat on tiny Sud Island in the Barren Islands. Pending an environmental assessment this winter, biologists hope to rid the island of the non-native pests, much as they have purged other islands of non-native foxes and rats that threatened native species.

"If we choose to do nothing about invasives, we're choosing against natural biodiversity," says Steve Ebbert, invasive species coordinator. The refuge, which is made up of 2,500 volcanic islands, stretches more than 1,000 miles into the Pacific Ocean spanning much of the mainland Alaska coast.

Arctic and red foxes introduced to the islands by fur trappers drove the Aleutian cackling goose almost to extinction before the U.S. Fish and Wildlife Service intervened in 1970. The goose population now numbers about 30,000, up from a low of about 600. Accidental introductions of Norway rats have occurred on many islands; on one, an infestation caused by a Japanese shipwreck more than 200 years ago decimated local birds until the Alaska Maritime Refuge teamed with Island Conservation and The Nature Conservancy and conducted a $2.5 million rat eradication effort this year. It is too soon to say that Rat Island is definitively rat-free, however, there are signs that several species of birds, including geese, ptarmigan, black oystercatchers and peregrine falcons are starting to nest again.

Marmots were stocked on Sud Island in 1939, possibly as a food source for weather observers and lookouts stationed there during World War II. Biologists suspect the marmots upset the island's ecology by invading and disturbing the nesting burrows of Rhinoceros auklets; medium-sized puffin-like seabirds. More than 500 burrows and 1,000 rhino auklets were counted by refuge biologists visiting the island in 1975; none were found in 1990. Recently, however, biologists have found signs that some small pockets of auklets may be holding out against their island's invaders.

This summer, intrigued by reports of nearby auklet sightings, Ebbert headed to Sud Island with Gulf of Alaska Unit biologist Leslie Slater. Could a colony of auklets have returned to the island after an absence of 20 years, they wondered. If so, where were the birds' burrows? And how had they escaped the marmots?

Ebbert and Slater discovered some nesting burrows on the edge of a cliff, not on vegetated slopes that the auklets usually prefer. No one was home— not a surprise. In daylight seabirds are busy feeding; they don't return to the nest until night. But whose nest was it? Storm petrels, puffins and ancient murrelets, among other seabirds, also nest in burrows.

Ebbert and Slater first tried a physical examination. Says Ebbert, "I had to hang onto my partner's legs while she leaned over and stuck her hands as far as she could into the burrows to get some clue what using them." No luck.

Next they tried a motion-activated camera, placed near the burrow entrances. Something tripped the shutter six times during the night. When Ebbert and Slater had the film developed soon after their return from the field, the subject was plainly visible in two of the six exposures: a rhino auklet.

"This is good news," says Ebbert. "Sometimes, an invasive species will totally eliminate native species from an island and keep them off, as foxes did with Aleutian geese. But often a few holdouts will hang on in remote, inaccessible places. I think that's the case with the rhino auklet," says Ebbert. "The only reason they're nesting where they are is so the marmots can't get them." Ebbert is hopeful the seabirds will return in greater number. "Once we remove marmots from the island, maybe we'll start to see auklets nesting in other areas," says Ebbert.

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