Summary: | This research arose from concern over declining success rates of rabbit
poisoning operations in Central Otago. It consisted of a detailed study of
behaviour in a natural population of rabbits which was subsequently poisoned.
The aim was to test the hypothesis that social behaviour and the existence of
neophobia could be contributing to control operation failures. Several other
aspects of rabbit biology in Central Otago were investigated including
population age and sex structure, growth and condition, and reproduction.
Information on rabbit behaviour was obtained from intensive observation
of a population of 50-100 rabbits over a period of two years. Activity budget
results for the period of peak emergence (late afternoon-early evening)
revealed similar patterns to those recorded previously, with some minor
differences in the classification of individual behaviours. Social
organisation varies seasonally and spatially, with a range of social
structures present at anyone time. Heterogeneity of the habitat, in
particular the patchiness of the food supply, influenced spatial and temporal
features of social organisation. Reproductive efficiency and optimal use of
resources appear to be important determinants of social structure; the concept
of economic defendability is relevant. Activity range size and shape were
extremely variable with female rabbits generally having larger ranges than
males. Some relationship between activity range size and metabolic
requirements and economic defendability was evident. Gross movement patterns
were a product of habitat heterogeneity and the limited availability of
permanent resting locations because of the unsuitability of the substrate for
burrowing.
Age structures of rabbit populations in Central Otago are characterised
by relatively few individuals greater than 24 months old; this suggests high
mortality and a rapid turnover rate. Growth and condition results reflect some
measure of environmental conditions in Central Otago. Seasonal variation in fat-related condition suggests hormonal control of fat reserves rather than
regulation by resource availability. The breeding season is sharply defined, a
product of severe and strongly seasonal environmental conditions. Annual
productivity is about 22 young per female.
Evidence is presented for the existence of neophobia in Central Otago
rabbit populations. Despite the genetic basis for this trait, environmental
factors may influence an individual's propensity to exhibit neophobia. This
may account for the considerable variation in neophobic responses among
individual rabbits.
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