The impact of rabbits on a grazing system in eastern New South Wales. 2. Sheep production

Abstract

Much research, time and money have been invested in the control of rabbits in Australia, yet the relationship between rabbit density and livestock production losses has not been quantified. We experimentally investigated the variations in sheep production parameters caused by 4 densities of rabbits, 0, 24, 48 and 72 rabbits/ha. Medium to strong wool merino wethers were run at a constant stocking rate in replicated plots with rabbits at 4� different densities. Sheep liveweight and body condition and wool production variables were measured over 3�years. Low to medium densities of rabbits were not found to reduce liveweights of wethers, whereas wethers run with the high density of rabbits were significantly lighter. The presence of rabbits reduced the body condition of sympatric sheep with the lowest body condition recorded at the high rabbit density. Mean greasy fleece weights, wool yields and clean-fleece weights were significantly different between densities of rabbits. Wethers run with the high rabbit density grew less wool than the wethers run with the other 3 densities of rabbits. The cumulative gross return per ha from wool production was highest for the medium rabbit density and lowest at high rabbit density. At the conclusion of this short-term experiment, the presence of some rabbits enhanced returns from wool production because of lower fibre diameter and comparable clean-fleece weights of fleeces grown at low and medium rabbit densities. These production characteristics might have been caused by synergistic effects on pasture growth or a sheep stocking rate that was too conservative for the prevailing seasonal conditions. At high rabbit density, competition for pasture between rabbits and sheep overrode possible synergistic and understocking effects. The economic implications of the presence of rabbits on merino sheep production are discussed.

Seasonal changes in the diet of the European rabbit (Oryctolagus cuniculus) from three different Mediterranean habitats in south-western Australia

“…Significant consumption of seed of pasture species suggests that the impact of rabbits on agricultural production (Phillips 1953;Myers and Poole 1963) and rangeland regeneration Crawley 1999a, 1999b) may be greater than previously thought. Such impacts reduce pasture biomass and promote the dominance of undesirable species, which, in turn, often result in decreased agricultural productivity (also see Croft et al 2002;Fleming et al 2002). Continued rabbit-grazing may also reduce the soil seed bank in the longer term.…”

“…Although there have been several dietary studies for O. cuniculus overseas (Williams et al 1974;Bhadresa 1977;Chapuis 1979;Rogers 1979;North et al 1994), with one exception, similar studies for this species in Australia have been restricted to the east coast. The Australian studies have been primarily concerned with either the quality of food eaten by rabbits (Stodart and Myers 1966;Myers and Bults 1977;Cooke 1979), their impact on sown pastures in eastern Australia (Myers and Poole 1963), or their dietary overlap with sympatric herbivores (Dawson and Ellis 1979;Dawson and Ellis 1994;Cooke 1998;Croft et al 2002;Fleming et al 2002), including dietary overlap with a sympatric endemic omnivore, Bettongia lesueur, in semiarid coastal Western Australia (Robley et al 2001). …”

Yield, compensation and fertility control: a model for vertebrate pests

“…For example, abundance of European rabbits was negatively related to mean sheep liveweight in Australia (Croft 1990;Fleming et al 2002). Yield of grass for silage was reduced with high rabbit densities in England (Dendy et al 2003).…”

Assessing the potential impacts of non-native small mammals in the South African pet trade

“…Economic impacts have also been reported for some non-native small mammals, e.g. the European rabbit O. cuniculus has been indicated to compete with livestock for pasture in Australia (Fleming et al 2002). In addition, species such as the eastern grey squirrel, the Norwegian rat Rattus norvegicus and the house mouse Mus musculus have been reported to cause impacts on infrastructures and crops of economic importance (Signorile and Evans 2007;Almeida et al 2013;Panti-May et al 2017).…”

“…There is a relative paucity of information on the potential impacts associated with non-native small mammals sold as pets in South Africa. Non-native small mammal pets such as the sugar glider Petaurus breviceps (Heinsohn et al 2015), the domesticated ferret Mustela putorius furo (Davison et al 1999), the European rabbit (Fleming et al 2002), the common and the black tufted-ear marmoset (Malukiewicz et al 2014;Kotait et al 2019) have been reported to cause impacts in their invaded areas. The aim of the present study was, therefore, to identify which non-native small mammal species sold as pets in South Africa have potentially high environmental and/or socio-economic impacts.…”