Factors affecting the numbers of house mice(Mus musculus)in hard beech(Nothofagus truncata)forest

Abstract

Nothofagus produces heavy crops of seed infrequently, and then house mouse (Mus musculus) populations increase greatly. In the Orongorongo Valley, near Wellington, seedfall of hard beech (Nothofagus truncata) and the numbers of house mice were measured for 22 years. Four heavy seedings were recorded and the numbers of mice were significantly correlated with the beech seedfall. Most mouse stomachs contained remains of arthropods, especially caterpillars and spiders, as well as plant material. Moths emerging from the litter of the forest floor in summer were sampled for seven years; the numbers of Tingena epimylia (Oecophoridae), whose larvae are litter-feeders, were strongly correlated with beech seedfall. The correlation between the numbers of moths and mice was slightly stronger than that between the numbers of beech seed and mice. Because the numbers of T. epimylia varied so greatly, components of the litterfall were also measured for three years. In a seeding year spent male flowers were a substantial part of the litterfall and might be responsible for the higher numbers of moths. These results indicate that factors other than quantity of seed may be important in the beech seed -mouse relationship and need to be explored further.

Annual and seasonal patterns of litter‐fall of hard beech(Nothofagus truncata)and silver beech(Nothofagus menziesil)in relation to reproduction

“…Daniel for monitoring seed-fall (Fitzgerald et al 1996), were permanently mounted 1. Litter from the traps was oven-dried at 45 °C until weight was constant.…”

“…Silver beech trees are present above 480 m and dominate the forest from 600 m to the highest point in the research area (Mt Tapokopoko) at 843 m (Campbell 1984). Annual seed-fall of hard beech has been recorded there since 1968 (Fitzgerald et al 1996), and the litter-fall of adjacent mixed podocarp-broadleaved hardwood forest has been investigated (Daniel 1975;Daniel & Adams 1984;Cowan et al 1985;Cowan & Waddington 1991).…”

“…Thus, 1995 was the heaviest seeding in 24 years. Hard beech had no "partial" seedings from 1971 to 1995; nor did it seed well in successive years (Fitzgerald et al 1996). Heavy seeding of silver beech in two successive years (1971 and 1972) was reported by Manson (1974) and Burrows & Allen (1991), but seed-fall in the second year (<3000 seeds m-2 ) was in Wardle's (1984) category of a "partial" seeding.…”

“…Wardle (1984) defined three categories of seeding effort: "full" (>4000 seeds m-2 ), "partial" (500-4000 seeds m-2 ), and "poor" (<500 seeds m-2 ). Hard beech in the Orongorongo Valley has had five "full" seedings since 1971 (Fitzgerald et al 1996). Three traps used in all years since 1971 (more traps were added later) gave the following mean seed-falls in years of "full" seeding: 6086 seeds m-2 in 1971, 7139 in 1979,4220 in 1986,5540 in 1990, and 9599 in 1995.…”

Rats dying for mice: Modelling the competitor release effect

“…Such mouse population might be released from rat competition if the latter is suddenly removed, triggering an explosion of the mouse population. Such a dramatic increase could be disastrous as mice have been shown to be active predators of invertebrates, reptiles and even birds that can be 300 times their weight (Newman 1994;Fitzgerald et al 1996;Campos & Granadeiro 1999;Ruscoe 2001;Le Roux et al 2002;Smith et al 2002;Cuthbert & Hilton 2004;Wanless et al 2007).…”