Rodent Eradication on
Pitcairn & Henderson Islands
D KinchinSmith
Background
Important note:
This is a holding page only, posted here as this site hosts Island Restoration News – which covers work by RSPB and partners to restore both Gough and Henderson islands. A dedicated site will be established should the go-ahead be given by Pitcairn Island to commence full-scale planning for eradication operations on Pitcairn and Henderson islands.
The Pitcairn group of islands comprises Pitcairn, Henderson, Ducie and Oeno and lies in the South Pacific Ocean approximately 5,300 km northeast of New Zealand and 6,600 km west of South America. Pitcairn is the only inhabited island in the group with around 40 residents. Henderson Island is a raised coral atoll circled by up to 15-metre-high cliffs and, at 4,300 ha, is by far the largest island in the group. Oeno and Ducie are small sand and coral atolls with a maximum elevation of 5 and 4.6 metres respectively.
Together, the Pitcairn Islands hold over 95 species found nowhere else on Earth, host a designated World Heritage Site - Henderson Island - and look after the world’s third largest fully protected marine reserve. Between them, the four islands support at least 18 breeding seabird species and hold more than 95% of the global population of Murphy’s Petrel Pterodroma ultima and the Endangered and near-endemic Henderson Petrel Pterodroma atrata, as well as significant populations of Kermadec Petrel Pterodroma neglecta and Phoenix Petrel Pterodroma alba.
The Pacific Rat Rattus exulans was introduced across the island group during the era of Polynesian exploration. After settlement on Henderson Island at least five bird species – Henderson Archaic Pigeon, Henderson Ground Dove, Henderson Ducula Pigeon, Henderson Sandpiper and Pacific Swallow – went extinct. In addition, six of the 22 land snail species were also wiped out.
Thanks to the eradication of Pacific Rats in the late 1990s, Oeno and Ducie are now rodent-free and support vast populations of seabirds including approximately 95% of the global population of Murphy’s Petrel and around 500,000 pairs of other petrel species including Henderson and Phoenix Petrels - one of the fastest declining Pterodroma species. But both islands are incredibly vulnerable to sea-level rise from climate change. Henderson and Pitcairn have much higher elevations and greater land areas, but they are still impacted by invasive non-native Pacific Rats following unsuccessful attempts to eradicate this invasive predator in the 1990s (Pitcairn) and in 2011 (Henderson). The rats continue to cause much reduced breeding success for seabirds including complete breeding failure in some cases. Henderson’s other unique wildlife is under threat, too. Many of the more than 70 vascular plant species present on Henderson are endemic, half the remaining snail species are endemic as are 20% of the 180 described insect species and all four of the remaining terrestrial bird species. We believe it is time to try again to eradicate rats from both Pitcairn and Henderson.
Above: Pitcairn Island is rugged and rocky compared to flat-as-a-pancake Henderson Island (below)
Eradication operations
There have been previous attempts to eradicate rodents from Pitcairn and Henderson which were not successful (including, in 2011, by the RSPB). In the years since these eradication attempts much work has been done to understand the causes of failure, to learn as many lessons as possible from those experiences, and to consider what might need to be done differently in any subsequent attempt.
Rodent eradications on inhabited islands are becoming increasingly common and have now succeeded with much larger populations than Pitcairn’s. Whilst Henderson will still be the largest tropical island where Pacific Rat eradication is attempted, larger and larger islands are being cleared all the time, giving us increased confidence in trying again.
Should we proceed, the plan will be to use helicopters and highly experienced pilots to spread cereal bait pellets containing a rodenticide across the islands. The timing of eradication operations for tropical islands is tricky as alternative rodent food can be plentiful year-round, so this will need to be considered carefully.
Next steps
No eradication operations will proceed without the informed consent of the Pitcairn community and Pitcairn Island Council. Currently, RSPB is consulting with every community member and together we are exploring what it would take for eradication to be successful. Alongside this, we are also gathering information relevant to eradication planning from both Pitcairn and Henderson islands. This work is supported by the UK Government’s Darwin fund and will continue throughout 2024. Permission to move to full operational planning will be sought at the end of the community consultation process.
Programme Objectives
The overriding restoration objectives would be to return Pitcairn and Henderson’s ecosystems to ones which are free of introduced predators. In so doing, we would:
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support the Pitcairn community to protect these special islands and their unique wildlife;
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fulfil the RSPB’s long-standing commitment to return to Henderson Island, restoring habitat and breeding grounds for Henderson’s four endemic terrestrial bird species, Henderson Rail Zapornia atra, Henderson Fruit Dove Ptilinopus insularis, Henderson Reed-Warbler Acrocephalus taiti, Henderson Lorikeet Vini stepheni, Gadfly petrel species, particularly Henderson Petrel, Herald Petrel Pterodroma heraldica, Kermadec Petrel, Phoenix Petrel and Murphy’s Petrel, several other breeding seabird species and the island’s numerous endemic invertebrates and native and endemic flora;
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remove the key threat to the World Heritage values of Henderson Island, namely ‘rat predation and competition and its effects on avifauna, invertebrates, and the wider ecological processes of the island’, thereby preventing Henderson Island being formally placed on the official ‘World Heritage Site in Danger’ list.