The impact of rabbits on a grazing system in eastern New South Wales.1. Ground cover and pastures

Abstract

Although there have been a number of studies that have examined the effects of rabbits on pasture, the relationship between rabbit density and pasture degradation caused by rabbits has never been quantified. An experiment was conducted at Cowra, New South Wales, from October 1984 to October 1987, to determine the impact various densities of rabbits have on pasture composition, indices of pasture biomass and ground cover. Using plots set stocked with the equivalent of 8 sheep/ha (the district average) and 4 densities of rabbits as treatments, 0,�24, 48 and 72 rabbits/ha, the consequences of rabbit grazing were investigated.Pasture composition changed with season, year and rabbit density. Cumulative effects were also evident. Rabbits severely depleted improved pastures of legumes (subterranean clover particularly), with grass cover increasing proportionate to rabbit density. In the final year of the experiment, the rabbit-free treatment had 31% legumes and 25.2% grasses, whereas the highest rabbit density treatment had 6.2% legumes and 47.4% grasses. Indices of pasture biomass were highest in the zero rabbits/ha treatment and lowest in the 72 rabbits/ha treatment. More bare soil was exposed in the highest rabbit density treatment. Once seasonal and year effects were accounted for, the relationship between rabbit density and percentage damage was positive.

Threatened inland sand vegetation in the temperate zone under different types of abiotic and biotic disturbances during a ten-year period

“…However, species diversity of the investigated area did not change and the plots showed only minor shifts in the DCA diagram. Sheep grazing reduced the num- ber of tall-growing plant species and primarily sheep-grazed plots had a lower litter cover, which is consistent with findings of Croft et al (2002), Eldridge andMyers (2001), or Hellström et al (2003). In accordance with our hypothesis 1 we assume that these sites can maintain their structure due to positively related disturbance effects, which are in particular grazing and trampling in moderate intensities.…”

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

“…Like lagomorphs elsewhere (Bailey 1923;Cooke 1974;Turkowski 1975;Chapuis 1979;Hulbert et al 1996;Croft et al 2002), rabbits from the three different Mediterranean habitats in south-western Australia also exhibited a considerable degree of flexibility in the range of food items eaten, with over 67 plant species consumed. The changes in the diet we observed, combined with behavioural modifications such as utilisation of burrow/shelter microclimate where evaporative water loss can be reduced by up to 40% (Hayward 1961), and the ability to increase the concentration of urine and decrease urine volume over the summer months (limited capacity : Hayward 1961;Cooke 1974Cooke , 1982aWood and Lee 1985), appear to enable rabbits to prosper in these Mediterranean habitats without the need to consume large amounts of truly succulent vegetation.…”

“…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

“…In a study of damage to wheat by wapiti (Cervus elaphus) in Idaho there was no significant effect on yield (Brelsford et al 1998). Grazing by European rabbits significantly reduced pasture height in an experimental Australian study (Croft 1990;Croft et al 2002). The loss in pasture height is a measure of indirect damage for co-occurring sheep and was negatively related to mean sheep liveweight.…”