Mistletoe and the brushtailed possum in silver beech forest, South Westland, New Zealand
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
The distribution of mistletoe in South Westland silver beech forest was investigated. Stand structure and densities of Peraxilla colensoi (pirita) were assessed along six altitudinal transects. Host size and forest structure were both found to be important factors influencing density and distribution of mistletoe. Generally large beech trees were favoured as mistletoe hosts. There was also significant variation in mistletoe density between forest types. In a different study the leaf area removed by possums and insects from a population of mistletoe plants was quantified over a nine month period. Insects browsed all plants, and on average consumed around 4% of each mistletoe's leaf area. The overall consumption of mistletoe leaf area by possums was around 2%, but possum browse was not evenly spread over the population. Of the forty plants sampled, seven were attacked by possums with one plant being heavily browsed. By the end of the monitoring period the leaf area retained by possum browsed plants was significantly lower than that of unbrowsed plants. If individual mistletoes continue to be selectively browsed then defoliation and death of some mistletoe plants seems a likely outcome. Possum diet was assessed by means of gut sample analysis and compared to estimates of food availability within silver beech forest. Possums utilised a wide range of food types but two or three species were dominant at any particular time of the year. Seral species such as wineberry, pohuehue, fuchsia, and lawyer were generally the most important foods. Mistletoe was not an important food item, contributing less than 1% of annual possum diet.