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Brushtail Possum Mortality and Ambient Temperatures Following Aerial Poisoning Using 1080

Clare J. Veltman and D. Neil Pinder
The Journal of Wildlife Management
Vol. 65, No. 3 (Jul., 2001), pp. 476-481
Published by: Wiley on behalf of the Wildlife Society
DOI: 10.2307/3803100
Stable URL: http://www.jstor.org/stable/3803100
Page Count: 6
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Brushtail Possum Mortality and Ambient Temperatures Following Aerial Poisoning Using 1080
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Abstract

Kill rates estimated after aerial broadcast of cereal baits containing sodium monofluoroacetate (1080) to control brushtail possum (Trichosurus vulpecula) populations in New Zealand varied from 61-100% in 48 operations between 1994 and 1999. Possum mortality was not related to size of treated area (mean 5255 ha, SD 3684 ha), toxin concentration, bait sowing rate (median 5 kg/ha), or year of operation. We tested the hypothesis that ambient temperature influenced operational outcome using temperature measurements from meteorological recording stations (local scale) and latitude (regional scale) nearest to application sites. Field temperatures ranged from 3.0-17.4 °C, and both temperature and latitude contributed significantly to a regression model for predicting possum kill rates. Highest estimated kill rates were observed during winter and at southern latitudes, consistent with previous laboratory studies of 1080 toxicity at warm and cool temperatures. Modeling showed populations that were reduced by more than 90% returned to 95% of initial density after 14.5 years, while sites with a kill rate of 70% needed only 9 years to reach 95% of initial density. During 9 years following an operation, simulated average possum densities were over 2 times greater in forests that experienced a 70% kill. Shorter intervals between control operations led to lower average densities for given kill rates in simulated populations. Therefore, we recommend that managers limit their operations to months with coldest average temperatures and consider varying treatment intervals to remedy the ecological effects of low possum mortality after some operations.

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