Context. Recovery of Australian rabbit populations from the impact of rabbit haemorrhagic disease virus (RHDV) contrasts with more prolonged suppression of wild rabbits in Europe, and has been widely discussed in the scientific community, but not yet documented in formal scientific literature. The underlying causes of recovery remain unclear, but resistance to RHDV infection has been reported in laboratory studies of wild-caught rabbits.
Aims. We document numerical changes in two South Australian wild rabbit populations that were initially suppressed by RHDV, and examine serological data to evaluate several alternative hypotheses for the cause of recovery.
Methods. Rabbit numbers were assessed from spotlight transect counts and dung mass transects between 1991 and 2011, and age and RHDV antibody sero-prevalence were estimated from rabbits shot in late summer.
Key results. Rabbit numbers were heavily suppressed by RHDV between 1995 and 2002, then increased 5- to 10-fold between 2003 and 2010. During the period of increase, annual RHDV infection rates remained stable or increased slightly, average age of rabbits remained stable and annual rainfall was below average.
Conclusions. Rabbit populations recovered but neither avoidance of RHDV infection, gradual accumulation of long-lived RHD-immune rabbits, nor high pasture productivity were contributing factors. This leaves increased annual survival from RHDV infection as the most likely cause of recovery.
Implications. Previously documented evidence of resistance to RHDV infection may be of little consequence to post-RHD recovery in rabbit numbers, unless the factors that influence the probability of infection also shape the course of infection and affect survival of infected rabbits.
