Possum (Trichosurus vulpecula) densities and impacts on Fuchsia (Fuchsia excorticata) in south Westland, New Zealand

To assess the effect of possum browse on plant growth, an index of the amount of foliage on about 50 trees of Fuchsia excorticata and the number of trees that died or were completely defoliated was measured at five sites in South Westland over 5 years. This index was compared to possum density indices taken at each site each year. At one site, possums were reduced from a high density about 6 months before the final measurement. The degree of defoliation of fuchsia was significantly related to the density of possums at each site. Possums defoliate and kill fuchsia within two years once the catch-rate index of their density exceeds about 25%. However, this impact can be halted and quickly reversed by reducing possum density.