Dynamics of sparse rabbits (Oryctolagus cuniculus), Orongorongo Valley, New Zealand

Abstract

The dynamics of a sparse population of rabbits on 100 ha of flats beside the Orongorongo River were studied for 21 years. Distribution of rabbit sign and plant cover were measured annually over the whole study area. The rabbits on 40 ha were counted monthly and live‐trapped for 10 years. The abundance of predators (cats and stoats) was monitored by the frequency of sightings, and their diet from scats. Rabbits had no warrens, but hid in the scrub by day and bred in stops. The amount of rabbit sign was correlated with their numbers and food supply. Floods reduced plant cover but opened new ground for palatable herbs. Without floods, shrubs replaced herbs and rabbits decreased. Adult male rabbits were in good condition and long lived. Adult females were in poor condition, produced rather few young, and did not live as long as males. Many young died in the nest or were killed by cats soon after they emerged. Cats also killed adult rabbits. Population regulation probably involved both extrinsic and intrinsic factors: predators and food shortage reduced the number of juveniles to a level at which territoriality imposed effective control.