The Cook Islands nature reserve Suwarrow, is located 930km north of Rarotonga.
The uninhabited atoll is rich in seabirds, turtles, crabs sharks and many other native plants and animals. For six months of the year, two National Environment Service Rangers oversee the protection of the nature reserve, providing customs and biosecurity services to yachts seeking harbour in the lagoon.
The vast ocean surrounding our islands is typically a barrier to the introduction of invasive species, but this is readily breached by boats which can provide a pathway for rats, feral cats, a multitude of insects like the yellow crazy and little fire Ant, weeds and even pest bird species like mynahs. Keeping these non-native competitors and predators off Suwarrow is critical to the protection of the seabird population and other biodiversity there..
Suwarrow is a seabird haven. Fourteen species occur there, including many thousands of breeding sooty terns (tara), frigatebirds (kotaa) and red-tailed tropicbirds (Tavake). The migratory and threatened bristle-thighed curlew (teue), also visits over winters on the atoll, before returning to its arctic breeding grounds in the northern hemisphere spring/summer.
The significance of these seabird populations has not gone unnoticed and Suwarrow is among the top oneper cent of sites globally for the conservation of birds and is a designated internationally an Important Bird Area.
But even this relatively pristine natural wilderness has not escaped the effects of our voyaging past, rats and specifically kiore, were introduced to the atoll potentially hundreds (if not thousands) of years ago. The spread of kiore has been closely linked to the earliest migrations of Pacific people. However, by 2013 only a small number of Suwarrow’s many motu were infested with kiore and to prevent their spread, Te Ipukarea Society, together with the National Environment Service and BirdLife International, mounted an operation to eradicate them.
The six-week campaign successfully baited the four infested motu, but subsequent checks by the rangers revealed only partial success as kiore had survived on Motu Tou. Motu Anchorage was now rat-free and the birds, insects and plants could return to a natural balance the threat of rats to the atoll still remained.
A review of the probable causes for the eradication failure indicated coconut crab as the probable cause. This voracious omnivore has a taste for the rat bait and essentially ate it before all rats could access it.
The crabs’ metabolic system meant the bait had no effect (as for all crabs), and they merely processed it as little more than a free lunch. Lessons learned, Te Ipukarea Society together with BirdLife and the National Environment Service have developed a new strategy that will satisfy the hungry crustaceans, ensuring sufficient bait is available for all rats on the island.
The team of six from all three partners will leave Rarotonga on May 12 to complete the project, which is expected to take a month. While it will be a further year before it’s known if the operation has been successful and Suwarrow is finally free of rats, the team is looking forward to the rare privilege of staying on the island and making a contribution to safeguarding this wilderness for generations to come.
The team will also, take advantage of stopovers on Palmerston, Pukapuka and Nassau to conduct seabird surveys and complete the last of the islands’ school composting and climate change training sessions, which have been conducted across the Cook Islands.
The expedition is expected to last about one month.