Above Picture: Hawadax Island from the air, photograph by Graeme Gale
Continuing a series on past, current and planned introduced mammal eradication projects on seabird islands around the world, Gregg Howald of Advanced Conservation Strategies and former Director of Global Affairs of the USA-based international non-profit organization Island Conservation writes of his involvement with the successful effort that removed introduced rodents from now-renamed Hawadax Island (formerly known as Rat Island) in Alaska’s Aleutian island chain.
Gregg Howald, British Columbia, Canada, photograph from Island Conservation
The Aleutian Islands archipelago – a string of islands straddling the North Pacific Ocean and Bering Sea that links North America to Asia – is renowned for its abundant and cacophonous wildlife. Over 20 breeding species of seabirds (including puffins, auklets and murres or guillemots) that line the archipelago’s rugged cliffs, endemic subspecies of land birds (such as the Aleutian Giant Song Sparrow), numerous shorebirds, plus rare Asiatic migrant birds have called this chain of islands home. An estimated 40 million seabirds alone have formed breeding colonies across the islands, depositing guano that enriches the soil and providing nutrients for the plant life, which is dominated by grasses. But it is not just birds that have found refuge in the archipelago. Its beaches heave with the bellows of sea lions and fur seals and its freshwater streams are rich with salmon. The cold and productive marine waters that course around the shores directly (and indirectly) sustain this abundance and biodiversity.
On 2670-ha Rat Island, though, something was amiss: where typically these small island chains bear an endless stream of sound, smells and textures from thriving ecosystems; here … it was quiet. Almost lifeless.
Rat Island gained its name after the introduction of Norway Rats Rattus norvegicus from a Japanese fishing vessel that ran aground in the 1780s. The island holds a unique spot in the archipelago. Archeological evidence from middens of a historic Aleut village site on the island indicates that a diversity of seabirds once thrived there but declined precipitously soon after the arrival of rats. The same story plays out on a number of the islands along the Aleutian chain. Norway Rats pillage seabird nests, eventually excluding the vast majority of birds that, every year without fail, are ready, willing and able to use the islands for breeding.
Globally, the non-native commensal rats Rattus spp. and the House Mouse Mus musculus, which have been introduced onto over 80% of the world’s islands, are two of the leading causes of island ecosystem degradation and loss of island biodiversity. Approximately 86% of all documented extinctions that have occurred on islands (including more than half of all seabird extinctions) have been caused by invasive species known to prey on eggs, chicks and even adult seabirds.
In the early 2000s, the Alaska Maritime National Wildlife Refuge (AMNWR) turned its attention to rat eradication, following a long and successful programme to eradicate introduced Arctic Foxes from the archipelago. Incredible success stories, such as the recovery of the once-presumed-extinct Aleutian Cackling Goose provided hope and promise that these restoration efforts could return the region to its historical abundance. But full restoration can only be realized if rats are also removed from the islands.
Landing on Rat Island to begin the preparations for rat eradication could only be described as unusual. Stacey Buckelew, Project Manager with the Restoration Project, noted after her first visit to Rat Island “A typical Aleutian island is teeming with wildlife, swirling with noisy, pungent birds. Not this place. It was crisscrossed with rat trails, littered with rat scat and scavenged bird bones, it even smelled wrong”. The island was eerily quiet, with the expected clamour of seabirds conspicuously absent, foretelling a slow-motion shift from guano-dependent vegetation cover toward something more akin to maritime tundra.
Field camp, Rat Island, 2007, photograph from Island Conservation
Bringing back marine birds and repairing the functional role they play in the Aleutian Island ecosystem meant ridding the island of rats. In the boreal fall [autumn] of 2008, after several years of planning, a mixed team from the AMNWR, The Nature Conservancy and Island Conservation boarded a fully loaded commercial vessel and the r.v. Tiglax in Homer, Alaska. They headed west for over 2000 km, bound for Rat Island with two helicopters following, island hopping and refuelling along the way.
Loading the bait bucket, Rat Island, 2008, photograph from Island Conservation
With favourable weather conditions rarely experienced in the late fall, the team unloaded the ships, set up camp and initiated the aerial bait application across the entire island in September 2008, repeating the process again about a week later. Veteran helicopter pilots Peter Garden and Graeme Gale from New Zealand added an international note to the team. The normally storm-laden shoulder season did not materialize, and the operation from start to finish was completed in about a month. Rat removal was a success and as a result, all direct negative impacts from rats ceased. Ecosystem change finally had a chance to take hold.
Good flying weather! Aerial bait application, Rat Island, 2008, photograph from Island Conservation
During the two years following bait application, monitoring teams found no evidence of invasive rats but did discover and document that several bird species (including Rock Sandpiper, Pigeon Guillemot, Common Eider, Red-faced Cormorant and Grey-crowned Rosy-Finch) were successfully nesting on the island. Other birds, that were once highly susceptible to rat predation had started to return, among them Black Oystercatchers and Glaucous-winged Gulls. All produced chicks. The Aleutian Giant Song Sparrow, previously thought to have been extirpated, appeared for the first time on the island, indicating a likely return of this species. Just five years after rat eradication, Tufted Puffins recolonized and bred successfully for the first time. Six nests were found on the island, compared to none found before eradication.
A Tufted Puffin flies over the Aleutian Islands, photograph by Ilana Nimz/USFWS
Despite careful planning and mitigation efforts, some species were unexpectedly poisoned by rat eradication efforts, including Bald Eagles and Glaucous-winged Gulls. But even still, their populations too, have subsequently increased in numbers. Gull nests burgeoned from only five nests pre-eradication to 27, while the population of Bald Eagles recovered to 10 individuals. Peregrine Falcons have also continued to breed successfully.
Even the soundscape has changed – passive acoustic surveys on the island have detected activity by Leach’s and Fork-tailed Storm Petrels at suitable breeding sites (petrels were also thought to have been extirpated due to rats). These success stories and recoveries demonstrate the incredible resiliency of natural systems and their ability to “bounce back” once limiting factors are removed.
Within 11 years after rat eradication, there has been evidence of astonishingly fast recovery in parts of the island’s ecosystems. With the re-establishment of native shorebirds as the apex predators in the intertidal zone, the intertidal community has returned to an ecosystem that is more typically found on rat-free islands: fewer intertidal invertebrates and higher algal cover, thereby enhancing the habitat for a variety of other species.
The story of Rat Island is not over, at least not yet. Whereas the birds are returning, the island’s vegetation recovery could be a longer process. It might take decades for the plant cover to revert from low shrubs to the high grasses that are more typical on the Aleutian Islands. A thriving bird population, and the functional role they play by dispersing seeds and enriching the soil, is crucial to producing diverse vegetation types.
But perhaps one of the more unexpected outcomes of rat eradication on Rat Island has been the insight into the impact of island restoration beyond protecting biodiversity. Following the successful eradication, the Aleutian Unangan community successfully petitioned the U.S. Board of Geographic Names to change the name of Rat Island to its native ‘Hawadax Island’. Pronounced “how-AH-thaa”, it translates to “entry” and “welcome”. The name likely refers in part to the two dominant peaks of the island visible from the ocean and assisting with maritime navigation, but certainly is a symbolic return to pre-colonial contact.
After almost 250 years, Hawadax is no longer quiet. For the birds, it is returning as a welcoming refuge.
The eradication of invasive species from islands removes one of the many pressures birds face, and we are proud to be contributing to these globally significant programmes around the world. The Mouse-Free Marion Project is one of the most ambitious and I look forward to hearing of its ultimate success.
Selected Literature:
Stolzenburg, W. 2001. Rat Island. Predators in Paradise and the World’s Greatest Wildlife Rescue. New York: Bloomsbury. 278 pp.
Gregg Howald, Advanced Conservation Strategies, 28 February 2023
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The Mouse-Free Marion Project is a registered non-profit company (No. 2020/922433/08) in South Africa, established to eradicate the invasive albatross-killing mice on Marion Island in the Southern Ocean. The project was initiated by BirdLife South Africa and the South African Department of Forestry, Fisheries and the Environment. Upon successful completion, the project will restore the critical breeding habitat of over two million seabirds, many globally threatened, and improve the island’s resilience to a warming climate. For more information or to support the project please visit mousefreemarion.org.
