In this irregular cycle, heavy seeding leads to a rapid increase in predator numbers. The predators turn to birds for food, threatening native species survival.
Beech masting is the mass fruiting of beech trees triggered by a summer warmer than the previous one. Some other plants such as rimu and tussocks also mast.
Beech is New Zealand's dominant forest type. When it masts, the abundance of seed leads to much higher rodent and stoat numbers. These introduced pests prey on our endangered birds. Our control programmes protect our native wildlife from predators.
Climate change with more variable weather may increase the chance of a temperature difference between summers and make forest masts more common.
What the predator plague cycle diagram shows:
Summer: When beech seed flowers heavily, much seed is produced.
Autumn: When seed is abundant, the rodent population increases rapidly.
Winter: Stoats feed on abundant rodents.
Spring: When the seed rots or germinates, plagues of rats turn to bird eggs and nestlings.
Summer onwards: Stoat numbers explode and they also turn to birds for food.