Great Mercury Island is now considered catless and ratless - and DOC ranger Peter Cawson wants to keep it that way.

Following a winter campaign, he wants boaties visiting the island over the summer months to be extra vigilant about taking additional passengers on board.

Ahuahu - Great Mercury Island is now without cats and rats.

'With the busy Christmas period it would be easy to overlook checking gear for pests,” says Peter. 'The island residents and regular visitors still pose the greatest risk to re-introducing pests.”

Mice have never been detected on the island, but may be present in very low numbers.

'They are also the most likely ‘stowaway' in gear and on boats,” he adds. 'If we look for something as small as an ant, then we should also find the bigger things.”

Day visitors are welcome on Ahuahu - Great Mercury Island, but are advised to comply with the instructions on signs and requests from the island's residents and staff when visiting.

The best way to stop pests getting onto the island is to stop them getting onto boats, prior to departure.

Four DOC staff and the new farm hand have been checking and re-baiting traps around the island this week, ahead of the busy festive season.

'On the mainland we plan to have people at boat ramps, Game Fishing Club events and information at numerous sites for the busy period,” says Peter.

The biosecurity incursion training in October was also positive with a number of DOC and GMI staff now aware and capable of initiating a response should any pest get detected. Some 300 traps, 100 tracking tunnels and 150 bait stations are on the island.

Rats and cats are not the only unwelcome guests on the island; ants, rainbow skinks, weeds, hedgehogs, stoats and rabbits would also be devastating.

The $1.5 million pest eradication programme is already showing results, says Peter.

'There seems to be more bird activity,” he adds. 'We have found kaka, tui, morepork and pukeko nests on our travels.

'Two years ago we looked around the island and found several active seabird burrows and one grey-faced petrel chick.

'Last week, with our monitoring team, we had a pair of French researchers looking at a number of headlands and islets who found over fifty active burrows and over 30 seabird chicks.

'This included six little blue penguins, 24 grey-faced petrels and a single fluttering shearwater. The fluttering shearwater is about the size of a thrush and would have been dinner for any rat or cat.”

In January they will do a count of Kaka, kereru, bellbirds, tui, kakariki and kingfisher.

'We have set out a load of artificial covers for geckos around the island and plan to re-visit them in February or March to find out what is there,” says Peter.

'We'll repeat that in five years to see if there has been an increase. Interestingly many of the skinks seemed to have changed their behaviour since the eradication.

'The shore skinks on the beaches seem to be in the open more. Whereas the copper skinks are less obvious under dead wood which is probably a result of the length of the grass providing shelter and the lack of predators.”

The stock were barged off the island before two aerial drops of rat poison knocked back the rat population. This was followed by the cat eradication programme.

No rats have been detected on Great Mercury since late July. Cat detection dogs and handlers were on the island for ten days until last week and found no sign of any felines.

Removing the predators will enhance the presence of lizards and seabirds and also assist in the conservation of threatened and at risk plants on the island.

However, students from Mercury Bay Area School assisted with a weed survey of the noxious moth-plant at the planting on the Southern end of Long Beach and in the forestry.

'The unfortunate news is they found a lot of the plant and also numerous seed pods that have opened this year, adds Peter. 'The moth-plant has spread well onto the forestry adjacent to the planting.”

Large numbers of milk-tree seedlings were also noted, which are all but extinct on the mainland due to rats.