Pasture plant biomass increase following introduction of European rabbit fleas, Spilopsyllus cuniculi, into Australia to facilitate myxomatosis transmission.

• Introduction of European rabbit fleas changed myxomatosis epidemiology in Australia. • By promoting winter epizootics, young rabbits were killed before pasture was damaged. • A 21-year record of pasture cover suggests pasture biomass was increased substantially. Long-term benefits of introducing European rabbit fleas to Australia as vectors of myxomatosis have not been evaluated. To address this deficit, data on pasture plant biomass from a 21-year study in semi-arid South Australia was reviewed. A plant biomass index was derived from photographed quadrats on the site. Spring pasture biomass over a seven-year period before fleas were introduced was compared with pasture production over 14 years following their introduction after correcting for differences in rainfall. Plant biomass on the quadrats in spring (October) doubled after arrival of fleas presumably because high mortality of young rabbits reduced grazing pressure during the plant growing season; little dry plant material was carried over from previous years contrary to model outputs using the 'Aussie GRASS' program. Substantial benefits accrued from releasing rabbit fleas, especially in areas of Mediterranean-like climate in Western Australia, south-eastern South Australia and western Victoria where rabbit fleas changed the timing of myxomatosis outbreaks. Plant biomass saved from rabbits helped to maintain sheep production which was at an all-time high when fleas were released. Extra food may also have enabled native mammals such as swamp wallabies to expand their distribution soon after fleas became established. [ABSTRACT FROM AUTHOR]