Assessment of an Approximate Lethal Dose Technique for Determining the Relative Susceptibility of Non-Target Species to 1080-Toxin

Abstract

The susceptibility of eight species of dasyurid marsupials and five species of murid rodents from the pastoral areas of Western Australia to the toxin sodium monofluoroacetate (Compound 1080) was assessed. Both LD*5O tests and an increasing dose procedure to determine the approximate lethal dose (ALD) were used. The results ranged from a low ALD of 1.6 mg kg-1 for an island population of Pseudomys hermannsburgensis to a high of 20 mg kg-1 for a mainland population of Notomys mitchelli. Intraspecific and regional variation in sensitivity was evident: three populations of P. hermannsburgensis showed widely different ALDS, and high ALDS were found in the Millstream area relative to elsewhere in the pastoral regions. Where both ALD and LD*5O were available, the dose response curve was steep; all LDSOS were less than a factor of 1.5 above the ALD. LD*5O values and ALDS were significantly correlated for selected dasyurids and murids, using published data. A computer simulation based on sampling a standard number of animals from 10 theoretical populations differing only in their LD~O confirmed that ALD and LD*5O gave similar rankings of sensitivity, although high variance on the LD~O reduced the strength of the correlation. Actual dosing data from eight populations of Rattus fuscipes were also analysed; both LD*5O and ALD gave similar rankings of population sensitivity. Subject to assumptions about the variability of sensitivity within a population, the ALD offers an alternative to LD~O testing that requires fewer animals, and need not cause more than one death per population tested.