Outbreaks of house-mice in South Australia in 1965

Abstract

There were three plagues of house-mice in South Australia in the autumn of 1965. One outbreak was confined to a small plantation of seedling pines, because planting procedures favoured the mice. Most seedlings had been ring-barked by the mice, which were heavily preyed on by foxes. Another outbreak covered about 200 square miles (518 sq km) of prime wheatlands. Fields were pocked with holes. Some had been vacated but others held high densities. Most mice were mature but non-breeding. Hawks and crows were prevalent. A small 4-yr-old wheat stack was very heavily infested. About 500 mice were caught around it in a few hours. None of the mice caught were breeding, not even the males. This is thought to be the first record of a completely non-breeding population of mice from a cereal stack. At least two factors were involved: high density and extreme shortage of food. Sick mice emerged from the stack, at the rate of 10-12 per hr, to fall to the ground and die. All were emaciated, cold to touch, extremely light in weight, heavily infested with blood-sucking mites (three species), possessed no abdominal fat, had pale livers and spleens, and had extremely low haemoplobin counts. Sick mice were quickly revived by feeding. There was no macroscopic evidence of disease, but their symptoms could have been due to an eperythrozoan infection coupled with murine hepatitis.