'Mega-masts' and the management of invasive mammals
Rats attacking a bird’s nest (rodent numbers erupt following a mast year) (Ngā Manu Images).
Many New Zealand plants periodically have very high seed production, called masts.
In beech forest masts, rodent populations erupt, followed by a build-up in stoats and increased predation on indigenous species by rodents and stoats. In a mega-mast, widespread outbreaks of rodents and their predators can drive indigenous species closer to extinction, but the cost of pest control after a mega-mast can be prohibitive.
We have shown that masting is triggered by relative summer temperatures over successive years, which enables us to use national climate data to predict where a mast will occur the following year. Planning, budgeting and pest control programmes begin in advance, particularly when a mega-mast is expected. DOC used the 2014 mega-mast forecast to support a massive boost in preemptive pest control for areas with the most vulnerable biodiversity – the ‘Battle for our Birds’ campaign. The campaign has cost about $21 million but an untargeted campaign to protect biodiversity across almost 4 million hectares of beech forest that was predicted to mast in 2014 would have cost about $68 million.