The Demography of a Rabbit Population in an Arid Region of New South Wales Australia

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Abstract
A study was made from 1970-1974 of a rabbit population occupying an area of small sand dunes beside tree-encircled ephemeral swamps in the arid zone west of the Darling River, New South Wales. This particular site was an area where rabbits survived during droughts. The commencement of each breeding season followed rainfall sufficient to initiate plant growth, and was not related to month of year. The length of the breeding season varied from 4-14 mo. and was related to a soil moisture index. Seasonal peaks in numbers of rabbits were associated with birth of young. The adult population did not increase more than 2-fold above the initial level of about 3 rabbits/4 ha. Subpopulations inhabited particular warren groups. The productivity of the subpopulations was related to the depth of the warrens, to the type of soil in which they were dug, and to their particular location. There was very little immigration into or emigration out of the study area. Growth rate of weaned rabbits of less than 750 g body weight was about 10 g/day. Young rabbits over 750 g had a growth rate of about 8 g/day. Mortality of rabbits under 9 mo. of age was never less than 88% and in one year reached 99.75%. Predation was the principle factor involved. Fox predation in nestlings accounted for between 26 and 75% of the mortality in a particular season''s cohort, and was more severe in dry years than in wet years. Myxomatosis epizootics occurred only in wet seasons and killed between 7 and 15% of the season''s cohort. Rabbit populations remained relatively stable in some sandy areas where rabbits survive droughts, unlike in other areas of the arid region where violent population fluctuations often occur. Density dependent predation may be responsible.