The greatest force behind the decline of Oryctolagus cuniculus has been two diseases that appeared in the 20th century. Myxomatosis is a South American virus, primarily spread by insect (mosquito and flea) vectors, that was intentionally introduced by a farmer in the mid 1950s in France to control the rabbit population (Angulo and Cooke 2002). An estimated 90% of European rabbits have perished due to myxomatosis since the 1950s (Virgos et al. 2005). After symptom onset, death results in an average of 13 days (Ward 2005). Rabbits with the virus are made more vulnerable to predators (Villafuerte et al. 1995). Juveniles are more susceptible to myxomatosis than adults. Myxomatosis cases peak during early summer to fall (Angulo 2004).

Rabbit Haemorrhagic Disease (RHD) is a virus that appeared in Europe in the late 1980’s, initially causing the death of 55-75% of rabbits in the Iberian peninsula (Villafuerte et al. 1995). RHD is primarily spread by direct contact. Death typically results within 24 hours of symptom onset, with a short incubation time of under 48 hours (Villafuerte et al. 1995). Adult rabbits are more susceptible to RHD than juveniles (unlike myxomatosis), and RHD is more prevalent in late winter and spring (Angulo 2004). Global warming may increase disease incidence by creating a warmer, drier climate in Spain and Portugal (Ward 2005).

Habitat loss and fragmentation are continuing causes of decline for O. cuniculus, which requires scrub-forest vegetation for food and shelter (Ward 2005). Modern intensive agriculture negatively impacts rabbits more than small scale mixed farming, which may have initially increased suitable habitat within the rabbit’s natural range (Delibes et al. 2000). High intensity livestock production contributes to habitat degradation and resource competition. Fallow farm land often returns to closed forest rather than scrub, which is not a suitable habitat (Ward 2005). Tree plantations planted in Spain and Portugal have replaced habitat for both rabbits and their predators and urbanization presents a threat as does increased fire danger in existing habitat, and climate change (Ward 2005).

Exploitation of O. cuniculus by humans has recently become a threat, especially as the populations are already declining due to other causes, so rabbits cannot sustain hunting and control measures as well as in the past. Farmers control rabbit populations directly by poisoning, trapping, and destroying warrens. They indirectly cause decline through habitat conversion and excessive pesticide and fertilizer use. Hunting presents a threat to rabbit populations, compounded by their existing decline from disease, possibly eliminating many rabbits that have acquired resistance to the diseases (Delibes et al. 2000). 70% of Spain is designated as hunting area. Hunter registration doubled between 1960 and 2005 (Angulo 2003), though the overall catch is declining, probably due to shrinking rabbit abundance (Ward 2005).

Future threats to the European rabbit may include a genetically modified version of the myxomatosis virus being developed in Australia to suppress rabbit fertility where the European rabbit has been introduced (ABC 2003). Unlicensed release of the modified virus to the native range could devastate the remaining populations (Ward 2005).