Natural mortality of juvenile rabbits (Oryctolagus cuniculus ) in North Canterbury, New Zealand

Abstract

Rabbit-breeding stops were monitored over 35ha of improved farmland, with relatively stable rabbit numbers, in North Canterbury, New Zealand. The number of stops dug varied seasonally, with most in spring, fewest in autumn. Pasture quality appeared to have a marked influence on breeding activity and productivity of the rabbits. Of the 427 breeding stops located, litters were found in 33%. Most (97%) of these stops were lined with grass and belly fur from the doe. Most juvenile rabbit mortality occurred prior to weaning. Of the 126 litters monitored, 38% were preyed upon, 29% drowned and 20% were either preyed upon or drowned prior to emergence. Young drowned when sufficient rainfall for a particular soil type caused flooding of stops. In all, 13% of litters were weaned and left the breeding stop, with late spring-early summer being the most favourable period for survival. Predator numbers were lowest during this period. Ferrets were the most numerous predator; cats and harriers were also present. Disease was not significant. Of those rabbits that emerged, approximately 50% survived to 14 weeks of age. Less-frequent drowning during a sequence of dry years may explain an increase in rabbit number observed in previous years. This may make it possible to predict the need for control.