Reproduction in a population of European wild rabbits occupying parkland habitat in East Anglia showed an annual seasonality in terms of numbers of emergent young, male testes size and an index of female oestrous status. Weather conditions showed marked variation over the four-year study period with significantly higher minimum ground temperatures and hours of daily sunshine, and less snowfall recorded during the second two years. Parailel shifts in reproductive seasonality were found with male testes size peaking in January and February as opposed to May and April, first female oestrus recorded one month earlier (January compared to February), and young emerging over an average of 5.5 instead of 4.5 months each year and their first appearance above ground advanced by two months from April to February. Mean annual productivity increased from 7.2 and 6.1 emergent young per female, to 10.1 and 9.1 over the four years, while the number of adults present in the population at the start of the breeding season increased from 22 to 45, with females always outnumbering males. The usefulness is demonstrated of a noninvasive index of vulva appearance, and morphometric measures of testes to determine female oestrous status and estimates of male testicular weight in wild populations.

The reported changes in reproduction are probably mediated through the influence of climatic variables on the quality or quantity of food available to the rabbits. These data demonstrate the possible effects of predicted global warming on productivity in the rabbit and highlight the major influence of climate on reproductive seasonality in this important pest species.