The Long Journey Home for Campbell Island Teal: Recent Sightings of Teal Ducklings and Nests on Subantarctic Campbell Island Are Evidence of the Success of an Internationally Significant Conservation Effort Involving the World's Most Ambitious Rat-Eradication Program, a Captive Breeding Strategy, and Pioneering Work in Disease Screening and Monitoring Procedures to Protect the Re-Established Population
Shepherd, Ingrid, Ecos
Campbell Island lies approximately 700 km off the southern tip of the New Zealand mainland--an isolated subantarctic island that, until recently, was one of the most rat-infested wilderness areas on earth.
For more than 50 years, the Campbell Island Teal had been presumed extinct. Then, in 1977, a New Zealand Wildlife Service ranger discovered one of the ducks on Dent Island, a rocky outcrop off Campbell Island.
In 1984 and again in 1990 a small number of teal were brought back to the Pukaha Mt Bruce National Wildlife Centre captive breeding facility near Wellington, on New Zealand's mainland, in the hope of bolstering bird numbers, estimated at the time at less than 25 breeding pairs.
However, almost nothing was known about the ecology or breeding habits of the teal. By 1993, not a single duckling had been born in captivity. With numbers on Dent Island also perilously low, the flight less Campbell Island Teal was teetering on the edge of genuine extinction.
Rats, rats and more rats
The near-extinction of the Campbell Island Teal was largely due to rat predation. It is thought that rats first came to the island with sealers in the early 1800s. Unlike other mammals introduced later--such as cats and cattle--the rats prospered, at the expense of the native birds. They competed against the birds for food, ate their eggs and chicks and destroyed nests. This resulted in local extinctions of all the native terrestrial birds as well as several invertebrate species, and the decimation of seabird populations.
By 2001, the concentration of rats on Campbell Island fluctuated from 50 000 to 200 000, depending on the season. Prospects for eradication were dim. Not only was the island remote and rugged, its consistently inclement weather and size--about the same area as Macquarie Island--posed further challenges.
Fortunately, New Zealand's Department of Conservation had already successfully eradicated rats and mice from several other large islands in the late 1980s and the 1990s. These included Mana Island and Kapiti Island near Wellington, Fiordland's Breaksea Island and two islands just south of mainland New Zealand--Ulva Island and Whenua Hou (Codfish) Island.
However, the sheer size of Campbell Island (five times larger than islands previously targeted for rat eradication) meant that traditional bait-laying methods were prohibitively expensive. So the department developed a method based on half the usual amount of bait, which still amounted to 120 tonnes. The operation, which cost New Zealand $2.2 million, was conducted in 2001 in the middle of the subantarctic winter and involved a team of 19 people and four helicopters.
Subsequent monitoring that year and again in 2003 failed to detect any live rats, and the island was officially pronounced rat-free.
Model for eradication on remote islands
'The Campbell Island project pushed the known limits of rat eradications and required a lot of faith from both the project team and the department managers and politicians who supported it,' says Pete McClelland, the Department of Conservation's Program Manager. 'To succeed, it required innovation, dedication, skill and an element of good fortune with the weather. Some would say luck but I like the saying "Luck is when opportunity meets good planning!"
'Campbell Island has shown people that large-scale eradications on remote islands are possible, and it has got many countries considering what can actually be done.'
Campbell Island remains the largest island in the world to have been the subject of a rodent eradication program '... but fingers crossed we will soon be overtaken!' says McClelland, suggesting that Australia's Macquarie Island (11 785 ha) could be the next target.
The rat eradication program has also led to the return and repopulation of invertebrates and bird species long absent from the island. …