The ecological effects of the decline in Rabbits (Oryctolagus cuniculus L.) due to myxomatosis

Abstract

ABSTRACTThe Rabbit (Oryctolagus cuniculus) population in the British Isles increased rapidly from the 1800s to 1950 due to climatic amelioration, predator reduction and agricultural changes. It became the major vertebrate pest of agriculture, causing an estimated £50 million in damage and lost production each year. Myxomatosis reached Britain in 1954‐55 causing 99‐9% mortality in some Rabbit populations and, carried by the mosquito and flea vectors, the disease spread rapidly. The consequent decline in the Rabbit population caused dramatic changes in agriculture and the native fauna and flora. It promoted woodland regeneration and increased grassland and cereal production; herb and grass height increased, flowering was noticeable and plant successions ensued. Some small legumes and annual plants became extinct locally and much floristically rich vegetation became dominated by a few grass species or shrubs. The increased grass growth probably promoted an increase in the number of many invertebrate species as well as in the vole (Microrus agrestis). Some species of insect became reduced in number and the Large Blue Butterfly (Maculinea arion) has become extinct (1979) since the decline of the ant (Myrmica spp.) fauna necessary to rear the butterfly larvae. Breeding sites for the Sand Lizard (Lacerta ugilis), Stone Curlew (Burhinus oedicnemus) and Wheatear (Oenanrhe oenanthe) have been reduced by habitat change. Immediately after myxomatosis many predator populations suffered from a lack of Rabbit prey with consequent poor breeding success, but those able to switch to voles, and other predators which are no longer taken in Rabbit trapping, have increased in numbers, e.g. Fox (Vulpes vulpes), Polecat (Mustela putorius), Short‐eared Owl (Asio Barnmeus) and Kestrel (Falco tinnunculus). Others such as the Stoat (Mustela ermineu) and the Buzzard (Buteo buteo) declined immediately after myxomatosis through lack of prey and have recovered in nubers only slowly; the Peregrine falcon population has declined partly as a result of lack of open habitat. The breeding success of many predators was also reduced. Parasites of the Rabbit also declined; the flea (Spilopsyllus cuniculi), roundworms and tapeworms, as well as coccidiosis carried by Rabbits and particularly affecting young hares (Lepus europaeus) were all considered to be affected. Species such as the Pheasant Phasianus spp., the hare and the Roe Deer (Capreolus capreolus) increased their use of woodland habitat and/or benefited from the increased food available. Rats (Rartus nomegicus) appeared to decline following increased predation and loss of habitat.In Australia similar vegetational changes occurred in many areas after the introduction of myxomatosis and predators such as the Fox and Wedge‐tailed Eagle (Aquila audax) were reduced by control measures following increased predation on sheep. Many bird and marsupial species were reduced in number after the loss of Rabbit prey or on becoming an alternative prey item.In Britain the loss of the fur industry has been outweighed economically by the increased agricultural production and reduced control and maintenance costs following myxomatosis. Since myxomatosis appeared Rabbit numbers have increased only slowly, probably because of increased predator pressure on low density populations and the periodic recurrence of the disease. Rabbit behaviour may have changed so that burrows are not used as much as in the past, Rabbit trapping has ceased and many habitats have been lost. Rabbit numbers could still reach moderate densities but a reversal of many of the ecological effects of my xomatosis is unlikely.