The hazard posed to northern quolls, Dasyurus hallucatus, during aerial baiting programs for the control of dingoes was studied in a pastoral area of Western Australia. The incidence of mortality and the movements of the animals were studied by means of radiotelemetry. Minimum activity areas ranged from 5 to 1109 ha, and the longest movement recorded was 3.5 km over 7 days. All animals could have encountered baits. Mating occurred shortly before baits were laid. The animals subsequently lost condition and body weights were low at the time of baiting. No quolls died in the 2 weeks following the baiting. This suggests that northern quolls and other, theoretically less susceptible, non-target species of mammals in the pastoral areas of Western Australia are not at risk from 1080 aerial baiting programs.
The survival of Oryctolagus cuniculus was investigated at 2 sites in the southern part of Western Australia using live-trapping. Winter myxomatosis appears to have been a major factor in determining the changes in population size, through its effect on the survival of young rabbits.
Descriptions are given of 2 study sites in the south-west of Western Australia, on which rabbit numbers were monitored. Breeding seasons began in March or April, with the onset of winter rain, and rabbit numbers peaked in October-December, followed by a fall over the non-breeding period in summer. Winter epizootics of myxomatosis, which were spread by Spilopsyllus cuniculi, caused severe declines in rabbit numbers at both sites. Summer epizootics at one site before the introduction of the flea as a biological control agent, and rabbit mortality during these, was lower than in the winter epizootics.
'The reproduction of the European rabbit, Oryctolagus cuniculus (L.), at two intensive study sites in south-western Australia is compared with reproductive data from rabbits taken throughout the coastal and inland districts of the south-west region. South-western Australia has hot, arid summers and cool wet winters. Rabbit breeding in the region is characteristic of that in Mediterranean climates, with a winter breeding season which begins when pastures germinate with the initial winter rainfall (April-May) and ceases when the pastures dry out at the end of the year. Unseasonal cyclonic rain can promote pasture growth in summer, leading to limited breeding. At all times of year there were some fertile males, with fewest at the height of summer, followed by an increase before the winter breeding season. Near the coast, male fertility increased more rapidly than further inland. At our two study sites at Cape Naturaliste (on the coast) and Chidlow (55 km inland) the pattern was similar to that in the coastal district. Production of kittens was greater near the coast than further inland, because near the coast there was a high early peak in incidence of pregnancy, a second peak late in the year, and litters remained large throughout the breeding season. In the inland district, the early incidence of pregnancy was lower, there was no second peak, and litter sizes fell at the end of the year. Female reproduction at Cape Naturaliste was typical of that in the coastal district, but that at Chidlow was typical of the inland. The second peak of pregnancy at Cape Naturaliste was due to intensive breeding by subadults born earlier in the year. The differences in female reproduction and productivity between the coastal and inland districts are probably because pasture growth begins earlier and is better in the more fertile coastal areas than in the inland. That nutrition is better for rabbits in the coastal areas than in the inland is reflected in higher growth rates of kittens at Cape Naturaliste than at Chidlow. It is postulated, on the basis of the literature and the results of our studies, that the factor which determines whether rabbits will breed is the presence of growing vegetation, and that the intensity of breeding is influenced by a seasonal cycle in fertility.
The susceptibilities of mice Mus musculus, guinea-pigs Cavia porcellus and brushtail possums Trichosurus vulpecula to sodium monofluoroacetate (compound 1080) were determined at various ambient temperatures in the range 4-33�C. Toxicity was greater at both ends of the range than in the middle. In mice the LD50 at 24�C was five times that at 12.2�C; in guinea-pigs the LD50 at 17�C was twice that at 4�C; in possums the LD50 at 23.5�C was two and a half times that at 10.5�C. It is important to consider these differences when assessing the efficacy of 1080 for pest control, and potential hazards to non-target species, in situations where such temperature ranges may be commonly expected.
Eye-lens weight-age relationships were determined for rabbits from a wild population and from an enclosed population (of the same stock) in south-western Australia. Previously published curves of lens weight v. age for rabbits in eastern Australia are not entirely satisfactory models for the western Australian data. However, the differences, though obvious, are minor, and for general aging any of the published curves are adequate. For accurate aging, regional curves may have to be determined.
The tolerances to sodium fluoroacetate (1080) were estimated for Dasyurus geoffroii (LD*50, ca. 7.5 mg 1080 kg-1), D. hallucatus (ca. 7.5 mg kg-1), Antechinus flavipes (ca. 11.0 mg kg-1) and Phascogale calura (ca. 17.5 mg kg-1) from Western Australia and comparisons were made with D. viverrinus (ca. 1.5 mg kg-1) and A. flavipes (ca. 3.5 mg kg-1) from south-eastern Australia. The species from Western Australia have had evolutionary exposure to naturally occurring fluoroacetate and were more tolerant to the toxin than dasyurids from south-eastern Australia, Presumably, they have acquired this tolerance through feeding on prey which had fed on plants containing fluoroacetate.
Regressions of handling time on prey weight were determined for the dasyurids Srninthopsis hirtipes, S. ooldea and Ningaui spp. preying on grasshoppers and cockroaches in the laboratory. In all cases, a simple linear regression fitted the relationships better than logarithmic models. The slopes of the regression lines were steeper for grasshopper prey than for cockroach prey in all species, and for each prey type the slopes for the predators were ranked in order of predator weight. Capture efficiency, defined as the proportion of successful attacks, did not vary significantly between predator species and prey types, and all predators showed declining capture efficiencies with increasing prey size. Niche separation in these dasyurids does not appear to be based on different optimal prey sizes for each species.
Amphibian and reptile species that have been tested in Australia are generally more tolerant to 1080 poison than are most other animals. The most common signs of poisoning amongst both groups of animals are a lack of movement or convulsions. Visible signs of poisoning first appeared from 13 h to almost 7 days after dosing. Deaths followed from 15 h to almost 22 days after dosing. It is unlikely that amphibians and reptiles face any direct poisoning risk from pest-poisoning campaigns involving 1080, given their high tolerance and the enormous amounts of poisoned bait that would have to be eaten. Some individuals, however, could be detrimentally affected through ingesting sublethal quantities of 1080.
Spilopsyllus cuniculi, a vector of myxomatosis, was introduced by various methods at several sites in the south-west of Western Australia in May 1969 for the biological control of rabbits. It spread rapidly and within 14 months all rabbits collected within about 5 km of one of the release sites were infested with fleas. Further introductions of the flea during the past decade have resulted in a wide distribution for it throughout the south-west of the state. Flea numbers fluctuate seasonally and are highest in reproductively active female rabbits in winter and spring. Since the introductions of the flea, the timing of epizootics of myxomatosis has changed and their effect on rabbit populations has increased.
Radio-telemetry was used to determine the use by rabbits, Oryctolagus cuniculus, of different types of daytime locations at three localities in south-western Australia. The frequency of use of different types of daytime locations was clearly associated with the structure of the native vegetation. Where the understorey was dense, use of resting locations in the scrub was high. Where the understorey was sparse, rabbits sheltered principally in warrens in cleared areas. When rabbits shelter predominantly in large patches of native scrub, warren ripping and fumigation may be of very limited value as control techniques.
An enzyme linked immunosorbent assay was developed to detect antibody to myxoma virus in serum of rabbits. In ten laboratory rabbits vaccinated with attenuated myxoma virus, antibody levels were seen to increase for four weeks, after which they declined. Antibody levels in a large number of wild rabbits collected at Cape Naturaliste area, Western Australia, in 1974 were high, following an outbreak of myxomatosis. When serum samples from the same population were tested in 1978, levels of antibody were low. Using gel filtration chromatography, the main anti-myxoma virus antibody activity seemed to be in the IgG fraction, although IgM and IgA were also present.
The population fluctuations and reproductive biology of rabbits, Oryctolagus cuniculus (L.), were studied in a coastal pastoral area in the north-west of Western Australia between 1974 and 1981. Numbers were highest in late 1975-early 1976 and declined during a period of below-average rainfall in 1976-79, but were still found in all landforms. The breeding season was more regular than that of rabbits in other pastoral areas, and appeared to be a response to winter rains which were relatively predictable in timing, if not amount. Successful summer breeding also followed heavy summer rain. There appears to be no opportunity for cost-effective control of rabbits in the area by techniques currently available, as even when numbers are low the rabbits are widespread.
