Rat numbers rocket in Rimutaka forest

20:17, Jul 28 2014

Rat numbers have exploded in Rimutaka Forest Park, threatening native wildlife, local conservationists say.

With seven others, David Ogilvie monitors and maintains 76 traps around Orongorongo Valley, home to small numbers of the rare harrier, pipit and brown kiwi.

While annual catches usually fluctuate around 50 rodents, more than four times that number have been killed this year, even with several months remaining.

While more rats trapped the better, the higher kills indicate the rodent population has shot up. Numbers have soared nationwide after what is known as a "mast", in which beech trees produce a higher than normal amount of seeds, causing population explosions in rats and stoats.

"The theory is when the food runs out, [the pests] start eating the birds - and if seeds start running out about this time, they'll get the baby birds and the eggs," Ogilvie said.

But Department of Conservation monitoring has concluded masting has not been a major problem in the Rimutaka and Tararua forests.

DOC launched a $9 million supplementary trapping and toxin campaign this month targeting pests, but apart from one Taranaki forest, all the Battle for our Birds action was in the South Island.

Ian Armitage, president of the volunteer Rimutaka Forest Park Trust, said: "The masting in the hard beech forests in Wellington might not be as strong as the South Island.

"There do appear to be more rats. It is a concern, but we can do no more than maintain our current trapping effort."


The Dominion Post