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Proceedings of the First Symposium on Marsupials in New Zealand

Spotlight Counts

page 178

Spotlight Counts

Spotlight counting is a relatively untried technique. My analysis is based on counts of possums by the M.A.F. rabbit research section, during routine counts of rabbits. In the Waikari district in Canterbury, two 27 km transects were laid out in different areas. Two men on trail bikes with helmet-mounted spotlights, each covered a transect on three or four successive fine nights, starting at dusk and finishing three to four hours later.

During a 10 month period a total of eight samples was obtained from the two areas. The 95% confidence limits of each sample averaged ± 69% of the mean, while the confidence limits of the total samples in each area were ± 27 and ± 34 percent respectively. In other words the counts did not vary much from one sample to the next, but, from night to night there was often significant variation.

Because this technique is relatively appealing to use, is not labour intensive, and because large areas can be covered, it has a high potential use in pastoral areas. While the variation between nightly counts could be reduced by increasing the number of counts and increasing the transect length, more research is required to identify the factors which influence possum activity.