A house mouse (Mus musculus) population eruption in response to rimu (Dacrydium cupressinum) seedfall in southern New Zealand

We document an increase in house mouse (Mus musculus) abundance in a year (2002) when there was light beech (Nothofagus species) seedfall but very heavy rimu (Dacrydium cupressinum) seedfall in Waitutu Forest, southern New Zealand. On our nine study grids, mouse numbers in November were highly correlated with rimu seedfall. Feeding trials with wild-caught captive mice showed that mice typically opened the rimu nut and ate the seed (endosperm and embryo) leaving the husk.

Decline in capture rate of stoats at high mouse densities in New Zealand Nothofagus forests

We present two statistical models documenting variations in density indices of stoats and of mice in New Zealand southern beech (Nothofagus spp.) forests. They confirm previous, simpler correlations showing that the summer capture rate of stoats increases with spring mouse density index up to about 20–25 mouse captures per 100 trap-nights (C/100TN). However, at much higher mouse densities (60–80 C/100TN), observed in the Grebe and Borland Valleys in southern Fiordland in 1979/80 and again in 1999/2000, fewer stoats were caught than expected.