![Sample our Environment & Agriculture journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5934/TOC-Subject-Sample-2021-Environment-Agriculture.jpg"})
Abstract
Mice (Mus musculus) in New Zealand's Nothofagus forests reach peak densities after mast seeding, but the role of beech mast and winter breeding in these fluctuations is uncertain. In the Orongorongo Valley, near Wellington, seedfall was measured and mice were trapped quarterly in mixed hard beech (N. truncata) and podocarp/hardwood forest (100–250 m a.s.l.) from 1971 to 1993, and in silver beech (N. menziesii) forest at higher altitude (580–786 m a.s.l.) from 1973 to 1978. Density (indexed by the percentage of traps catching mice, adjusted for linearity; ± SE) reached peaks of 6.2 ± 1.0–13.8 ± 1.6 after masting in 1971, 1979, 1986, and 1990, but also without mast in 1975, 1977, 1982, and 1983. Females bred in spring and summer. In the lower‐altitude population, most breeding in mast years preceded autumn seedfall, and almost no mice bred in winter. The density index peaked in the following spring when the population comprised overwintered mice. Apparent recruitment between winter and spring is probably caused by increased trappability. Few mice bred in the summer after masting. The causes of pre‐masting population increase and post‐mast suppression of breeding need to be investigated further. Density indices in silver beech increased from near zero in autumn to peaks of 10.1 ± 2.3 and 15.9 ± 2.9 in spring following partial masting and winter breeding in 1974 and 1976. This study, together with others in beech forests in the South Island of New Zealand, shows that different populations vary in the extent of winter breeding in mast years. In some, a large proportion of the mice breed in winter of mast years, but in others few mice breed. Winter breeding in mast years is therefore not necessary to generate peak populations.
