On introduction to Australia, European rabbit fleas spread myxomatosis among young wild rabbits during winter; recruitment into the adult rabbit population was strongly reduced. Nonetheless, the reasons behind the high efficacy of flea-borne myxomatosis remain poorly understood. A 17-year data set from Witchitie, a semi-arid site in South Australia, was reviewed to ask whether red foxes, specialist rabbit predators, could have enhanced mortality by preying on disease-debilitated rabbits. Advantage was taken of a natural experiment where, after initial establishment of fleas, drought greatly reduced their abundance, providing two periods for comparison, one where fleas actively spread myxoma virus, followed by another where fleas were no longer effective vectors and myxomatosis reverted to former mosquito-vectored summer outbreaks. The hypothesis that foxes contributed to the efficacy of flea-borne myxomatosis was not rejected. Instead, the study showed that when myxomatosis was being actively spread by fleas, foxes were not only abundant enough to have eaten most of the young rabbits produced each year, but fox population dynamics were also strongly associated with rabbit productivity. Related studies support the likelihood that predators significantly enhance disease-related mortality and indicate that further experimental study of an interaction between flea-borne myxomatosis and predation would be worthwhile.
Cooke, B. D. (2019). Does red fox (Vulpes vulpes) predation of young rabbits (Oryctolagus cuniculus) enhance mortality from myxomatosis vectored by European rabbit fleas (Spilopsyllus cuniculi)? Biological Control, 138. https://doi.org/10.1016/j.biocontrol.2019.104068