Density, body size, and reproduction of feral house mice on Gough Island

Abstract

Feral house mice Mus musailus have occurred on Gough Island, South Atlantic Ocean, for about 180 years. The population was sampled during the austral spring of 1990. Estimated density on a live-trapping grid in dense cover (woody plants, ferns, grass) near the coast was 224 mice/ha. Snap-trapping at high altitude, in open moorland and bog, indicated lower densities in exposed habitats. In overall size the mice were larger than Mus musculus from other localities, and larger than specimens collected on Gough Island during 1955–56. At the time of sampling 43% of adult females were pregnant or lactating and juveniles made up 14% of the trapped sample. The mean number of 9,2 foetuses per pregnant female suggests that litter size may be larger than those recorded in other feral mouse populations. Mice collected from high altitudes were smaller, and there were no juveniles in the sample. The inference is that breeding commences later at the cooler, high elevations.