Proceedings of the First Symposium on Marsupials in New Zealand

The Model Population

The Model Population

For the purposes of this paper the model population is assumed to have a maximum rate of increase of 1.4, in which maximum adult survival is 90% and recruitment to the adult population is 1.0 per adult female. The population prior to control is assumed:

i. to be a stable population of 10 000 adult possums (1 year old and over) capable of breeding, with a sex ratio of 1:1;
ii. to be at the maximum sustainable density for the habitat;
iii. to be capable of breeding when 1 year old (and hence the adult population is 1 year old and over);
iv. to be isolated and not subject to emigration or immigration;
v. to have an annual adult survival of 74%, and an annual rate of recruitment to the adult population of 0.52 (adults recruited per adult female) which balances mortality (26%).

The figure for adult survival is taken from live-trapping studies by Crawley (1973) in the Orongorongo Valley and Jolly (1976) in Birdlings Valley. Re-working of age distributions presented by Bamford (1972) in the Taramakau Valley and Boersma (1974) in the Hokitika River catchment provide estimates of adult survival ranging from 70% to 80%.