Rabbits In Australia Research Articles

Limits to predator regulation of rabbits in Australia: evidence from predator-removal experiments.

Predator-prey studies in semi-arid eastern Australia demonstrated that populations of rabbits (Oryctolagus cuniculus) could be regulated by predators. The functional, numerical and total responses of foxes (Vulpes vulpes) to rabbits and the numerical response of feral cats (Felis catus) to rabbits, are described. Measurement of the rabbit component of foxes' stomach contents indicates a Type III functional response. The size of the fox population in summer was dependent on the availability of rabbits over the immediately preceding rabbit breeding season but there appeared to be no density-dependent aggregation of young foxes in areas of surplus food. The total response of foxes, estimated using the short-term numerical response of dispersing foxes, was directly density-dependent for low rabbit densities and inversely density-dependent for high rabbit densities. Two states are possible with this form of total response: a state with low rabbit densities regulated by predators and a state with high rabbit densities which occurs when rabbits escape predator regulation. The boundary between regulation and non-regulation by predators was demonstrated by a predator-removal experiment. In the treated areas, predators were initially culled and rabbits increased to higher densities than in an untreated area where predators were always present. When predators were allowed back into the treated areas, rabbit populations continued to increase and did not decline to the density in the untreated area. This is the critical evidence for a two-state system. When predators were present, rabbits could be maintained at low densities which were in the density-dependent part of the total response curve for foxes. Exceptionally high rabbit recruitment, or artificially reduced predation, could result in rabbits escaping predator-regulation. Under these circumstances, rabbits could move into the inversely density-dependent region of the total response curve for foxes.

The group selection of variola minor in the Americas: An anthroponootic analogue for the myxomatosis epizootic in Australia

It is an axiom of many parasitology texts that hostparasite systems coevolve toward a state approximating commensalism. While this hypothesis has an apriori intuitive appeal there is little empirical evidence to support it. The only documented case of a parasite evolving toward avirulence is the group selection of less virulent strains of the myxoma virus in the Australian rabbit population. It is hypothesized here that group selection also accounted for the appearance of variola minor in the Americas.

Distribution of Rabbit, Oryctolagus cuniculus, Warrens in relation to Soil Type

Rabbit warrens in a semiarid environment of New South Wales were concentrated in those areas where impact penetrometer readings indicated friable soil to a depth of at least 75 cm. Isolated warrens in areas with few warrens were found in restricted patches of favourable soil. The absence of warrens from areas with shallow soil was considered to be due to high soil temperatures. The distribution of the rabbit in Australia was examined in relation to deep soil temperatures. It was suggested that the application of bituminous coating on ripped warrens may be a useful technique for the control of rabbits in the arid zone.

Myxomatosis: a Search for a Strain of Virus to Immunize a Wild Population of Rabbits, Oryctolagus Cuniculus.

FS98, a grade IV strain of myxoma virus, was found to be suitable as an immunising virus for wild rabbits in Australia and suitable for introduction as a biological control agent into a wild rabbit population with the flea Spilopsyllus cuniculi (Dale) as vector. The Nottingham attenuated strain was found not to be a suitable virus for immunising wild rabbits. Seven samples of virus taken from the field in Australia and assessed as grade V virulence in 1965 were more virulent when reassessed in 1976. Possible misclassification by chance was examined by means of randomly selected survival times from actual data and rejected as a complete explanation. Testing with a wide range of different mixtures of a cloned highly virulent and a cloned attenuated strain of virus failed to support, but did not exclude, the idea of changes in virulence grading being caused by differential survival in mixtures during storage. ADDITIONAL ABSTRACT: Strain FS98 of myxoma virus, isolated in Australia in 1967, was suitable for immunizing wild Australian rabbits by means of infected fleas, but the Nottingham attenuated strain was unsuitable. Strain FS98 was of grade IV virulence in the scale of Fenner & Marshall (1957). Changes in virulence during prolonged storage were discussed.

Domestic rabbits and wild Australian rabbits display similar variable heavy-chain haplotypes

Sera from 266 wild Australian rabbits, Oryctolagus cuniculus, and samples (17) from a smaller isolated group of feral rabbits were tested for allotypes of the variable heavy-chain subgroups a and y. Three allotypes of the a locus (a1, a2 and a3) and two allotypes of the y locus (y33,— and y33,30) were assayed. Only 3 or perhaps 4 haplotypes of a and y were detected. Significantly, the a− y haplotypes found in the wild rabbits are the same ones previously reported for the domestic rabbit. Thus, in an evolutionary context, the V H genes of the rabbit appear tightly linked with no evidence of recombination. The theoretical implications of these findings are discussed.

The Desertification of Central Otago, New Zealand

The utilization of tussock grasslands in the semi-arid and sub-humid tussock grasslands of Central Otago, South Island, New Zealand, by European sheep farmers, began during the 1850s. Many of the sheep farmers and their hired shepherds migrated from the Scottish Highlands, and brought with them the management practices with which they were familiar. The extensive sheep farms or ‘runs’ were rented on government-owned land, and the graziers did not enjoy long-term security of tenure; nor did they receive compensation for any improvements which they might have undertaken during their occupancy.The combination of frequent burning of the vegetation and overgrazing soon resulted in a perceptible decrease in vegetation cover, such that land deterioration accelerated in the 1870s and 1880s when a rabbit pest irrupted. No effective action was taken to deal with the problem of land deterioration, and by the early part of the twentieth century parts of Central Otago were described as man-made desert. The tussock grassland had given way to almost bare soil interspersed with patches of Scabweed (Raoulia lutescens), and accelerated soil erosion resulted in slope-wash and gullying. Remedial action was delayed by the outbreak of the First World War, but a major Commission of Inquiry at the end of the war concluded that unsuitable forms of land tenure had contributed significantly to the desertification and land deterioration.Eventually, changes in land tenure were introduced, providing for security of tenure, entitlement to compensation for land improvements, and controls on husbandry and stocking levels.

Some Biological Characteristics of a Feral Rabbit, Oryctolagus Cuniculus (L.), Population of Wild and Domestic Origin.

Some biological characteristics of a population of rabbits on a small island off Victoria, Australia, are described. The common ectoparasites of the rabbit in Australia, Leporacarus gibbus (Pgst.), Cheyletiella parasitivorax (Megn.) and Haemadipsus ventricosus (Denny), were found on all 24 rabbits examined in detail. The occurrence of Ctenocephalides canis (Curt.), Ixodes cornuatus Roberts and I. tasmani Neum. has already been reported. Spilopsyllus cuniculi (Dale) was not found, although it had been released on an island nearby 2 years earlier.

Lack of serological evidence for venereal spirochaetosis in wild Victorian rabbits and the susceptibility of laboratory rabbits to Treponema paraluis-cuniculi.

Sera from 608 wild rabbits were examined using serological tests for syphilis as an indicator of infection with Treponema paraluis-cuniculi. Only eight sera gave positive or weakly positive results in the rapid plasma reagin (RPR) test, and none of these eight sera gave positive results in the Treponema pallidum haemagglutination assay (TPHA). Thus, it appears that wild rabbit populations in Victoria, Australia, are not naturally infected with T paraluis-cuniculi. Normal Australian laboratory rabbits however were readily infected with T paraluis-cuniculi, either by intradermal or intratesticular inoculation or by the venereal route. In the latter case, treponeme-containing lesions developed after about five months' cohabitation with infected mates. The disease was successfully transmitted from male to female and from female to male rabbits by the venereal route. In most cases infected rabbits became RPR-positive (17/19 rabbits) and in all cases TPHA-positive (19/19), indicating that serological tests for syphilis can be used to screen rabbits for this disease.

Uterine and renal renin release after ligation of the uterine arteries in the pregnant rabbit

Uteroplacental ischemia is associated with uterine renin release in pregnant nephrectomized rabbits. In the present study, uterine and renal renin release after uteroplacental ischemia were investigated in 10 Australian white rabbits at 24 to 28 days' gestation. Pentobarbital was administered, and both uterine arteries were ligated close to their origins. Blood samples were taken for plasma renin activity (PRA) determinations from the femoral artery, uterine vein, and right renal vein before ligation and at 30 and 60 minutes after ligation. Mean arterial blood pressure (MAP) was monitored throughout. In five additional pregnant rabbits renal blood flow (RBF) was measured with an electromagnetic flowmeter. The preligation uterine vein-artery PRA difference was not significant (1.9 ± 1.1 ng/ml/hr). Postligation uterine vein-artery PRA was 11.4 ± 3.2 at 30 minutes and 6.6 ± 1.9 ng/ml/hr at 90 minutes (p < 0.02). Preligation renal vein-artery PRA was 32.3 ± 10.5 ng/ml/hr (p < 0.02) and did not change significantly after ligation. MAP remained stable and RBF was unchanged after uterine artery ligation. These observations confirm the finding that the kidney is the primary source of renin in the normal pregnant rabbit and demonstrate that following acute uteroplacental ischemia there is significant uterine renin release even when the kidneys are intact.

Ecological Genetics of the Wild Rabbit in Australia. III. Comparison of the Microgeographical Distribution of Alleles in Two Different Environments

The differences in distribution of gene frequencies at three polymorphic loci (adenosine deaminase, carboxylesterase-1 and phosphogluconate dehydrogenase) were determined for rabbit populations living in two markedly different environments. One, a highland population from Snowy Plains N.S.W., has low productivity and high survival rates, and the second, a dry plains population from Urana, N.S.W., has high productivity and low survival rates. The amount of sub population differentiation at each locus was distinctive, and was different in the two environments with significant differentiation occurring for phosphogluconate dehydrogenase at both areas, for carboxylesterase-1 at Snowy Plains and for adenosine deaminase at Urana. The general significance of these results was demonstrated by determining the distribution of the variation in a third population. This population was subject to the same historical climatic events as the Urana population and showed a similar pattern of variation. Various explanations of the data are considered and a combination of chance and selection, rather than either alone, seems to offer the most satisfactory explanation. The demographic differences between the populations seemed to play no part in explaining the patterns observed.

Ecological Genetics of the Wild Rabbit in Australia. II. Protein Variation in British, French and Australian Rabbits and the Geographical Distribution of the Variation in Australia

A survey for genetic variation was carried out using 21 proteins controlled by 26 loci in rabbits from Britain, Mediterranean France and Australia. Five enzymes, adenosine deaminase, phosphogluconate dehydrogenase, carboxylesterase, carbonate dehydratase and dihydrolipoamide reductase (NAD+) were found to be polymorphic. The average heterozygosity in wild rabbits was 6%. The genetic distances separating the various populations indicated that three different stocks were present in these populations. The rabbits from Britain and mainland Australia belonged to one group, those from France to a second group and the rabbits from southern Tasmania were a distinctive third group. Highly significant differences in gene frequency were found between the various local populations studied from mainland Australia. This variation showed no clear pattern and was attributed to genetic drift due to small effective population sizes. Bottlenecks in population size occur regularly in local rabbit populations in Australia through, for example, drought, myxomatosis outbreaks or rabbit control programs.

The profession and wildlife management

Abstract Extract The idea that disease may be a potent factor in the environment of indigenous wildlife, ranking with things like habitat destruction and introduced predators and competitors in shaping the distribution and fortunes of our native species, has yet to enjoy wide currency, or even thorough and systematic examination in New Zealand. Its potential importance is recognised, however. Referring particularly to mammals, Gibb and Flux (1973 Gibb, J. A. and Flux, J. E. C. 1973. “Mammals”. In The Natural History of New Zealand, Edited by: Williams, G. R. 334–371. Wellington: A. H. & A. W. Reed. In [Google Scholar]) stated: Diseases and parasites are rarely primary causes of mortality in wild animals, even in New Zealand where the mixing of mammals from diverse continents could have upset formerly stable equilibria between pathogens and their hosts. The recent history of myxomatosis in wild rabbits in Australia shows how a pathogen can cause calamitous mortality to a new host before evolving a new equilibrium. Even so, disease among indigenous wildlife species is generally dismissed in a word or two because of lack of data.

Immunoglobulin allotypes in some Australian wild rabbit populations

Several populations of Australian wild rabbits, Oryctolagus cuniculus, were surveyed for the distributions of alleles and phenotypes at the a and b immunoglobulin loci. Three alleles were found ateach locus. Significant genetic differentiation was found between populations separated by bothlong and extremely short geographic distances. No influences of natural selection on the geographicdistributions of allotype alleles could be detected. The high levels of heterozygosity at the immunoglobulin loci are in marked contrast to the low levels found in red cell enzymes and some other blood protein loci of Australian rabbits.

Immunocytochemistry of Surface Changes in Ascaris Spermatozoa During Maturation

Substances removed from the male accessory gland in Ascaris have been shown to induce the immotile, spherical spermatozoa to become active ameboid cells. This change Indicates the advent of the sperm's competency to penetrate oocytes and therefore represents the final maturation of the spermatozoa. Although the morphological changes of these altered active spermatozoa have been well defined (1 and 2), the qualitative differences in the plasma membrane have not been followed in detail.In the present study, antibodies were prepared against both the inactive and active Ascaris spermatozoa in female Australian white rabbits by weekly intramuscular injections of washed cell populations in combination with Freund's complete adjuvant.

Serodiagnosis of nosematosis by immunofluorescence using cell-culture-grown organisms.

This simple procedure for the detection of serum antibodies to Nosema cuniculi in rabbits and other host species incorporates indirect immunofluorescence and uses as antigen N. cuniculi isolated from urine and cultured in a human fibroblast-like cell line derived from foetal tongue. Examination of rabbit sera from 8 institutions indicated that no institution was free from Nosema infection. The prevalence of infection in 4 separate Australian rabbit colonies varied from 25 to 75%.

Ecological genetics of the wild rabbit in Australia. I. Geographical distribution and biochemical characterization of phosphogluconate dehydrogenase variants.

Three electrophoretically distinguishable phQsphogluconate dehydrogenase (EC 1.1.1.44) isoenzyme patterns, probably resulting from the expression of two alleles at one locus, were found in natural populations of rabbits in Eastern Australia. The homopolymers and heteropolymer were isolated and characterized kinetically. The three proteins were found to be indistinguishable with respect to Km for 6-phospho-D-gluconate and NADP+ (both in the presence and absence of magnesium), energies of activation, specific activities in liver, pH profiles and thermal stabilities. The rare allele was not found near the major initial release site of the rabbit in Australia and may have arisen in Australia.

Establishment and seasonal variation in abundance of the European rabbit flea, Spilopsyllus cuniculi (Dale), on wild rabbits in Australia

SYNOPSISObservations on the establishment, and seasonal variations in the number, of the European rabbit flea, Spilopsyllus cuniculi (Dale), on wild rabbits in Australia.

Determination of Age of Wild Rabbits in Australia

Determination of Age of Wild Rabbits in Australia

FLOPSY, MOPSY, COTTONTAIL AND MYXOMATOSIS

Once upon a time, before spring was silent, the rabbits of South America had a benign virus disease called infectious myxomatosis, which was transmitted by an arthropod. When the virus was injected intradermally a tumorous lesion was provoked, rich in myxomatous cells with much glairy intracellular fluid. The rabbits recovered from the bite. Once upon a time, the mongoose was introduced into Hawaii, to devour the rats that had been introduced into the islands by Captain Cook. Both rats and mongooses now thrive in the Paradise of the Pacific. A similar experiment was performed in Australia, where the herbivorous rabbit eats the antipodean vegetation as fast as it grows. The myxomatosis virus was introduced, to destroy the lush Australian rabbit. Now both rabbit and myxomatosis virus flourish in Australia. It had already been known that European rabbits infected with myxomatosis virus curled up their cottontails and died of the infection

A Cottontail Rabbit Lens-Growth Curve from Southern Wisconsin

A lens-growth curve, with confidence limits, was established from 188 known-age, pen-reared cottontail rabbits (Sylvilagus floridanus) between 2 and 297 days old. Excessive variation in lens weights for any given age-class made it unlikely that year classes, other than young-of-the-year from adults, could be separated. Pen-reared cottontails from southern Wisconsin had heavier lenses and heavier body weights than those from central Illinois, at least up to 150 days old. After death, lens-weight loss due to decomposition increased with temperature. Greatest weight loss occurred during alternate freezing and thawing. At least 12 days were needed to dry lenses in a gravity convection oven. This paper reports on lens weights of 188 known-age cottontails between 2 and 297 days old that were born and raised in pens, and lens weights of 69 animals between 9 months and 4% years old that were born in the wild and held in pens after being captured at an age of between 4 and 8 months. A few animals were raised in 1961, but the majority were raised in 1962 and 1963. Since animals were reared primarily for use in experiments involving the transfer of calcium 45 from females to offspring, the lens weights were incidental to the main study. For this reason, animals of exactly known age were not available over 297 days old. Since Lord (1959) first reported using the lens for age determination, lens-growth curves have been developed for many species. Curves from which an age prediction with confidence limits could be obtained, however, have been few. Dudzinski and Mykytowycz (1961) presented a growth curve with confidence limits for rabbits (Oryctolagus cuniculus) in Australia, as did Bauer et al. (1964) for the fur seal (Callorhinus ursinus). Confidence limits were put on the Australian rabbit and fur seal lens curves after making models linear and eliminating heterogeneity of array variance. For advice throughout the course of this study, I am indebted to R. A. McCabe, J. J. Hickey, and L. B. Keith. Statistical advice and aid in calculating regression equations were provided by D. B. Siniff.