Rangitoto and Motutapu March 2011 project update

The once distant dream of seeing a pest free Rangitoto and Motutapu is almost within our grasp after some dedicated hard graft from the pest eradication team.

Ever since the very successful bait drop over the 2009 winter, a range of DOC staff and contractors have maintained a large network of traps, spent nights searching the islands with spot lights, and led specially trained dogs across every part of both Rangitoto and Motutapu trying to sniff out any remaining pests. With all this effort, no pests have been detected on the islands since late last year.

Tui and bellbird

As we get close to two years since the aerial bait drops were undertaken (winter 2011) and given that pests are no longer being detected, we should soon be able to declare Rangitoto and Motutapu islands pest free.

Success so far

There have already been some great signs of success on the islands. Kakariki and bellbirds are being seen and heard all over both islands after being completely absent a few years ago. Tui numbers have soared and a number of other small bird species have quickly increased in number. The dawn chorus is improving all the time!

As we get more confident that the islands are pest free, our thoughts are turning to which birds and lizards could be brought back to the island. Things like saddleback, kiwi, takahe and tuatara could all be possible over the next few years.

Kakariki/red-crowned parakeet

Update on pest control work

Rats and mice

There has been no confirmed sightings of rats or mice since June 2009. Four specially trained rodent detection dogs and their handlers have recently completed a search of both Rangitoto and Motutapu and found no sign of rodents.

There has been an extensive network of over 1000 traps over both islands that have not caught a single rat or mouse since the trapping began shortly after the aerial bait drops were undertaken in winter 2009.

Rabbits

Intensive searching with spotlights and hunting for rabbits with indicator dogs has been underway since July 2009. Just two rabbits have been trapped since then and no evidence of a remnant breeding population has been observed. The last rabbit caught was in March 2010 and there have been no sightings since.

DOC Ranger setting a stoat/hedgehog trap

Stoats

An island wide network of over 1000 traps was set in August 2009 to target stoats and hedgehogs. Fortnightly checks of the trap network initially yielded no captures, but a stoat was caught in June 2010.

This was a complete surprise and interestingly, DNA analysis suggests that the stoat may have come from the mainland rather than being a survivor from the bait drop.

Prior to the operation it was assumed that Rangitoto was out of swimming distance for stoats, but it seems that may not be the case. While this is not ideal, it simply means we will need to maintain a greater number of traps to ensure any stoat which makes it to the islands is caught.

Hedgehogs

Hedgehogs were an unknown quantity at the beginning of this project. We were not sure how much effort would be required to eradicate them, but it has turned out to be a lot!

The same trap network targeting stoats has also been used to control hedgehogs. They are also being targeted with indicator dogs. To date 287 hedgehogs including juveniles have been trapped, located by spotlighting or by dogs. Hedgehogs are now the one species being actively targeted by the team on the islands. The last capture was an adult in December 2010.

Cats

Rangitoto and Motutapu islands

There has been no confirmed sightings of cats since September 2009 on the islands.

However, our regular discussions with boaties have uncovered the fact that a surprising number of people take their cats with them on their boats. Our monitoring network will need to cater for the possibility that someone could somehow lose their cats onto the island.

Where to from here?

Specialised detection dogs will search both islands over March and April 2011 to check for any last surviving pests. If they find nothing, we will gradually reduce the trap network down to the level that will be required to be kept in place to monitor for any new invaders.

Planning will also get underway for bringing those rare birds back onto the islands, hopefully in the 2011 winter, bringing the ambitious and exciting programme to create an accessible, iconic nature sanctuary on Rangitoto and Motutapu islands - right on Auckland's front door step - into the next phase.