Summer/autumn movements, mortality rates and density of feral ferrets (Mustela furo) at a farmland site in North Canterbury, New Zealand

For two summer/autumn periods (1999, 2000), we studied the movements and survival of feral ferrets (Mustela furo L.) at a site in North Canterbury that had been previously subjected to intensive control of ferrets. Movement distances of juvenile ferrets from the place of initial to final capture were generally low (median = 1.2 km) though variable [mean = 2.5 ± 1.0(±S.E.M.), range 0.1-21.7 km]. The estimated instantaneous mortality rate of juvenile ferrets was high (mean = 0.8 per year), though imprecise (95% C.I. 0.4-1.8 yr(- 1)), as was that of adult ferrets (mean = 1.1 per year, 95% C.I. 0.3-4.5 per year). Summer/autumn home ranges of adult ferrets in North Canterbury were larger than estimates from comparable studies. The density of ferrets during May was 1.7 per km² in the first year and 2.5 per km² in the second year. This corresponded with a trend for juvenile movements to increase, and juvenile survival rates to decrease. Our results suggest that formal studies to determine whether movements and survival of juvenile ferrets are density-dependent are warranted.