Evaluating the impact of rabbit hemorrhagic disease (RHDV2) on a feral population of naïve European rabbits ( <i>Oryctolagus cuniculus</i> )

Diseases can cause rapid declines in wildlife populations, especially in populations with no previous exposure to the disease. An acute, mostly fatal emerging lagomorph disease, rabbit hemorrhagic disease (RHD), has recently been detected in North American hares and rabbits. In February 2018, feral European Rabbits ( Oryctolagus cuniculus (Linnaeus, 1758)) were found dead on a university campus in Nanaimo, British Columbia marking the first Canadian occurrence of RHD in free-living rabbits. We used sight-resighting and rabbit count data to examine the short- and long-term impact of RHD on rabbit population size. We evaluated the medium-term impact of RHD on population size through sight-resighting surveys 6 months after the RHD outbreak started. During the initial phase of the outbreak, the population declined up to 5.75% per day and population size decreased 86% in less than 2 months. Population size remained low after the breeding season (mid-February through September) and through the following year. Population numbers began to recover within 2 years of the outbreak, and population size continued to increase through January 2025. Our results show RHDV2 can cause very high immediate mortality rates in feral rabbits and population level impacts of an outbreak can persist for years.