Observations on the Reproduction and Age Structure of the Fox, Vulpes vulpes L., in New South Wales

Abstract

A total of 838 foxes were collected throughout New South Wales from 1969 to 1974. In every month of the year there were some males producing sperm but there was a major peak of activity during June, July and August. The major period of female reproductive activity commenced in July and reached a peak in August. There were indications that some females ovulated during February and March although no pregnancies were recorded outside June-October. At least 30 % of vixens suffered preplacentation loss of ova or blastocysts, but an accurate estimate was impossible because of an apparently high incidence of polyovuly. Resorption accounted for the loss of 8 % of embryos from 35 pregnant females. A mean litter size of 4.0 was calculated from pregnancies; the mean number of placental scars was 3.7; three deformed embryos were found. The proportion of juvenile animals in the sample decreased from January to the beginning of the breeding season. The weight of the eye-lens was unsuitable for differentiating between yearling and adult foxes in this type of sample.