Suchergebnisse

The palatability and efficacy of 2.5% zinc phosphide (ZP) wheat bait that had been in dry storage for about 3.5 years was tested against house mice in canola crops in the central wheatbelt region of Western Australia. Before baiting, mouse numbers in these crops were around 90 mice ha-1. Mouse numbers were reduced by 89% in the crop where the stored bait was applied at 1 kg ha-1 by aerial broadcast. The palatability of the stored bait was also determined in additional crops by comparing the amount taken with that of `fresh' ZP wheat bait. Bait (200 g) was offered in two different types of bait station: (1) in 45-cm lengths of 50-mm-diameter plastic agricultural drainage pipe, and (2) on 40-cm-diameter plastic saucers. Regardless of station type, mice often consumed significantly more of the stored product than the `fresh' bait, particularly on Day 1. This was attributed to the stored product lacking the typical, strong ZP odour that was initially present in the fresh bait. Mouse numbers on the bait station grids (1.28 ha each) were reduced by approximately 65% after 4 days of baiting. The shelf-life and palatability of ZP wheat bait seem to be relatively unaffected by prolonged storage. If any decrease in palatability occurs, then this seems to be transient and did not reduce the overall effectiveness of the stored bait.

Virally vectored immunocontraception (VVIC) has been studied and promoted as an alternative to lethal methods for vertebrate pest control in Australia and New Zealand. Virally vectored immunocontraception offers a potentially humane and species-specific control method with potential for a good benefit–cost outcome, but its applicability for broad-scale management remains unknown. We present case studies for the house mouse, European rabbit, red fox and common brushtail possum and describe the current status of research into the use of VVIC as a broad-scale pest-management tool. All case studies indicated that there are significant problems with delivery and efficacy. The current state of development suggests that VVIC is not presently a viable alternative for the management of these vertebrate pests, and it is highly unlikely that this will change in the foreseeable future. An absence of benefit–cost data also hinders decision-making, and until benefit–cost data become available it will not be clear if there are short- or long-term benefits resulting from the use of VVIC for broad-scale pest management.

The epidemiology of myxomatosis was investigated in 12 populations of wild
European rabbits at Wellstead in southern Western Australia, which were part
of a larger study of the effects of imposing different levels of female
sterility on rabbit population dynamics. Using serology, the aims were firstly
to monitor the epidemic pattern of myxomatosis on the study sites between 1993
and 1996, and then to determine whether imposed sterility had any influence on
the prevalence of myxomatosis. Two patterns of epidemics were observed during
the study. The predominant pattern was a spring–summer outbreak that
left approximately 90% of rabbits seropositive for myxoma virus
antibodies. The second pattern was a slowly spreading epidemic that lasted
from autumn until the following spring. This second type of epidemic may be
important in the persistence of myxoma virus. Imposed levels of female
sterility as high as 80% for three years had no significant effect on
the proportion of animals seropositive for myxoma virus antibodies.

The acceptability of three types of non-toxic predator baits to a variety of indigenous non-target species was determined in the laboratory. The bait-types tested were: Dried Meat Bait (DMB), Probait and two sizes of FoxOffTM baits (30 g and 60 g). The potential poisoning risk, if the baits had been toxic, was calculated for each species from their consumption of non-toxic bait and their sensitivity to 1080. Three species consistently sampled baits; Dasyurus geoffroii, Trichosurus vulpecula and Rattus fuscipes. Where species have had exposure to fluoroacetate-bearing vegetation, their consumption of bait and their level of tolerance to 1080 was such that only 2 of 15, 4 of 15, and 3 of 6 species were considered to be potentially at some risk from toxic DMBs, Probait, and FoxOffTM baits, respectively. In contrast, and mainly because of their lower tolerance to 1080, the theoretical risk for those species without evolutionary exposure to fluoroacetate-bearing vegetation was such that 6 of 12, 8 of 12, and 8 of 9 species theoretically face a high or moderate risk from 3-mg DMBs, Probait, and FoxOffTM baits, respectively. We emphasise, however, that theoretical risk does not necessarily equate to a practical risk, and these results are best used to determine which non-target species should be monitored at the population level during predator-control operations. Factors affecting the potential risk to non-target indigenous animals, and some cautions when extrapolating data from laboratory-based studies to the field situation, are discussed.