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Proceedings of the First Symposium on Marsupials in New Zealand

General Discussion

page 233

General Discussion

WODZICKI. What do you call temporary sterilisation?

SPURR. Temporary sterilisation is preventing the breeding of a female for one year only i.e. in subsequent years she can join the breeding population again.

CLOUT. You have not taken any account of immigration in your model. Immigration could have a major impact. Certainly I found in my studies of possums that dispersal of animals into an area that had been poisoned could raise the population level quite rapidly after control. So you present a rather simplified view.

SPURR. Yes, typically the situation will be that you have both immigration and emigration. Only if the poisoned area was sufficiently large or sufficiently isolated would you have a situation where such movements were less important.

CLOUT. It would have to be very isolated since possums can move vast distances during the dispersal phase.

KEBER. If the animals have an average life-span of say 4 years and you permanently sterilise them, then you still have them doing potential damage for several years. In my particular area of exotic forest this could mean the difference between a crop harvested or not.

SPURR. Yes, I said killing gives the only immediate relief from damage. The purpose of the whole paper was to see if there was any advantage in searching for a chemo-sterilant.

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