fruits of a native conifer the Rimu tree.
The kakapo only breeds successfully when the Rimu tree fruits. If there are less than 10% fruiting tips on the trees the Kakapo cannot breed successfully that year. Each bumper fruiting year then encourages a population burst in rats feeding on the fruit and also on the chicks of the Kakapo. New Zealand birds had no natural mammalian predators prior to human settlement so the Kakapo and all of New Zealand's wildlife has evolved defenceless to the introduced rats, stoats and feral cats. There are 125 Kakapos left, the numbers are up from 18 in the 1970's, and there is a very successful and extensive breeding program managed by the New Zealand Department of Conservation.