Doc working hard to contain pest incursions

STOATS can swim for several kilometres and it seems seas could be getting easier to cross, as pests reach predatorfree islands.

The Department of Conservation (Doc) reported earlier this week pests had been found on two islands which had been mainly predatorfree.

Chalky Island, in southwest Fiordland, had been free of stoats since 1999. It is a haven for several threatened and endangered species including saddleback/tieke, little spotted kiwi, Te Kakahu skink and kakapo.

Stoat footprints were discovered during a Doc field trip late last month and subsequently found in several locations across the island.

On Resolution Island, also in southwest Fiordland, two rats were found in traps in late July during a standard stoat trap check.

While the island has mice and very few stoats and deer, it is free of possums, and until now was one of New Zealand’s largest islands without rats.

Rats were also found on Ulva Island, near Oban in Stewart Island. It was previously predatorfree.

Doc Te Anau biodiversity team leader Tim Raemaekers said there did not appear to be any common factor in the incursions.

‘‘Ultimately, these incursions occurring at the same time is probably a matter of coincidence,’’ he said

‘‘Heavy forest fruiting years can lead to a boom in pests, and this can often mean hungry animals searching for new pastures. But we’re not seeing unusually high rat and stoat numbers in Fiordland just now.

‘‘Last summer was a warm one with aboveaverage sea temperatures and often calm seas. It may be that it’s getting easier to swim across stretches of sea to reach these islands.

‘‘Both rats and stoats are surprisingly good swimmers — stoats can swim several kilometres when they really want to. When it comes to rats, it’s always possible that they hopped off a boat.

Doc was taking the incursions seriously and was working hard on a response to contain and eradicate the pests.

‘‘It’s a difficult job but Doc is a world leader in eradications of these species. These incursions are our top priority and we’re doing all we can to get on top of them.

‘‘We already have trap networks in place on these islands and the smaller islands that surround them, to try and prevent any potential incursions.’’

Traps on islands neighbouring Chalky Island had caught several stoats in the past.

‘‘It seems that this particular stoat [caught on Chalky Island] was cautious about entering traps, and got through,’’ Mr Raemaekers said.

‘‘We are currently addressing this by trying some other trap designs.

‘‘On Resolution Island, we have intensive rat trap grids around common boat mooring sites.’’