Wild weather puts dent in Arthur's Pass mouse plague

Wednesday, 25 December 2019

This supplied video outlines DOC's efforts to measure the long-term effects of 1080 in New Zealand. It claims bird numbers have doubled in one West Coast valley. (Video first published in January 2019)

Wild weather in the mountains of Canterbury has wiped away a mouse plague forecast to be the worst for half a decade.

Since the start of November, more than 1860 millimetres of rain has fallen in Arthur's Pass, according to Environment Canterbury's monitoring. Over the same time period in 2018, just 2.5mm fell.

A combination of a beech mast (or higher than usual seed production) in the forest and a tussock mast above the tree line saw rodent numbers explode as they bred over winter and had the Department of Conservation (DOC) predicting the worst mouse plague for five years in Arthur's Pass. About half of the beech forests in the country made extra seeds earlier this year.

DOC senior ranger Chris Stewart, who is based in Arthur's Pass, said a full-blown mouse plague 'hasn't eventuated', thought to be because of the prolonged rain in the area since November.

* Arthur's Pass overtaken by 'biggest mice plague in five years'**

'The residents at Arthur's Pass village trap mice to protect their houses and buildings but haven't had to do as much control work as was expected.'

Stewart described a mast as a 'food bonanza' for mice and rats. In November the dropped beech seeds began to germinate, removing the rodents main food source and turning their attention towards native birds and lizards – until the wet weather struck.

Arthur's Pass Alpine Motel co-owner Fiona Neale said there had been high mouse numbers in the region but after the rain they were 'as good as gone'.

She said on the Devil's Punchbowl track she had previously seen 50-plus mice but now she did not see any at all.

Canterbury University professor of biological sciences Dave Kelly said the mice had previously been so visible at Arthur's Pass and other forests because they were running out of food and starting to starve anyway, so were out in the day.

Mice in other beech forests that had a mast would likely be visible as they were 'taking every kind of risk' to find food because they were starving to death.

He said the bad news was the stoats had started coming out of their nests at the start of December, with some litters of up to 10 being produced to take advantage of the good conditions. Typically litters would be two or three.

Kelly said he heard a trapping group in Cragieburn had caught 19 stoats in a month. In normal years, they would catch 20 or 30 a year.

There were also more rats around Arthur's Pass and in the high country than there were 20 years ago, which Kelly attributed to global warming and more beech masts seeing them move to higher altitudes.

Stewart said there was a large scale predator control programme in Arthur's Pass and the surrounding area, trying to protect populations of vulnerable birds such as orange-fronted kakāriki/parakeet, pīwauwau/rock wren, whio/blue duck, grey duck, roroa/kiwi, kākā, kea and mohua/yellowhead.

The efforts included aerial 1080 drops and trapping networks.

'Rat and stoat plagues pose a serious risk to our native birds, bats and other wildlife,' Stewart said.

Kākāriki karaka/orange-fronted parakeet are among the endangered species found Arthur's Pass. (File photo)

Whio/blue ducks are among the rare birds found in Arthur's Pass. (File photo)

Mice were visible all over the Devils Punchbowl walking track in Arthur's Pass, but have since disappeared after a wet couple of months.

The pīwauwau/rock wren is one of the native birds at risk from predators in Arthur's Pass. (File photo)

A mouse takes refuge in a discarded tramping boot in a council skip at Arthur's Pass. (File photo)

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