Rat and mouse numbers concern

A science  adviser to Zero Invasive Predators (ZIP) says mice and rats are running around West Coast forests in broad daylight, a sign that something is wrong, and has called for more 1080 poison.

"Anyone who knows the New Zealand forest can see something is wrong at the moment, and more 1080 is required," Associate Prof James Russell, from the University of Auckland, said.

Prof Russell, a scientific adviser to Zero Invasive Predators (ZIP) and Predator Free New Zealand said in just one week around Kahurangi National Park this month he saw dozens of mice and rats, and stoats chasing mice and rats in daylight hours.

"Our native birds and reptiles stand no chance in the face of such elevated predator numbers."

With the mast seeding event over, the pests were beginning to starve, he said.

"They are so desperate for food they are coming out in the day and turning their attention back to native birds and reptiles, just as those native species begin their critical breeding cycles."

Landcare Research ecology research Dr Adrian Monks said rat and mice numbers were still increasing, but they had almost peaked.

Work carried out in Fiordland had measured some of the highest rat densities recorded anywhere on the New Zealand mainland at about 12 per hectare.

"The primary cue for triggering a mast event is a warm summer in the previous year. This year [2019] was an extremely large mast event [extremely high densities of seeds] triggered by an extremely warm January and February in 2018.

"The evidence suggests that mast years are increasing in frequency, especially at high elevation. This has been attributed to climate change."

Over the longer term, the outcomes of a warming climate for seeding patterns were likely to be more complicated.

Masting depletes nutrients and so beech trees generally cannot produce large seed crops in consecutive years.

"One scenario is that seeding will become more frequent, but because of nutrient limitation, the crops will be smaller.

"Hence beech seed crops will become more evenly distributed across years, rather than really big years and really small years like the current situation.

"Another scenario is that trees could produce large crops every second year."


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