DOC readies for rat and stoat invastion

The Department of Conservation is preparing to deal with a widespread increase in rat and stoat populations next year after an unusually heavy flowering in North and South Island beech forests this summer.

On some years favourable climatic conditions see beech trees produce far larger than normal quantities of flowers and seeds, an event known as a “beech mast.”
The abundance of food on the forest floor leads to a surge in the numbers of rats and mice and consequently stoats which prey on vulnerable populations of endangered birds and native bats.

It is predicted that beech forests in some areas could produce up to 18,000 seeds per square metre – providing abundant food for rats and causing some stoat populations next year to increase by up to five times their usual number.
DOC scientist Graeme Elliott says the scale of this year’s beech mast is a one-in-ten year event and poses a significant threat for some of our most at risk species.
“During a particularly severe beech mast back in 1999-2000, we lost entire populations of yellowheads (mohua) in some areas. It’s devastating to have 90-100 percent losses in birds that just have no chance against such high numbers of rats and stoats.
“In areas where we actively control pests, we can maintain populations of endangered native species. Sadly, in areas without pest control, vulnerable populations will decline.” he says.

Most at risk are juvenile kiwi, bats and hole-nesting birds such as yellowheads (mohua) and orange-fronted parakeets (käkäriki). Stoats climb up into nests to eat the eggs and the adult bird keeping them warm. Many of this year’s newly hatched blue ducklings (whio) may also be killed by stoats.
DOC’s Operation Ark – which works to protect the most vulnerable species from possums, rats and stoats in the South Island – is already looking at its control programmes to manage the predator wave expected next year.

Project coordinator, Richard Suggate, says staff identified the beech mast early and are looking to organize trapping and bait programmes to best counter large rat and stoat threats in critical locations.

“We are doing all we can to make sure we’ve got the best programmes in place in the right areas so we can protect the most vulnerable populations.”

For more information about Operation Ark, go to www.doc.govt.nz.