Use of nest trees by the mountain brushtail possum (Trichosurus caninus) (phalangeridae:marsupialia). I. Number of occupied trees and frequency of tree use

The use of trees with hollows by 10 adult male and six adult female mountain brushtail possums (Trichosurus caninus) at a 35-ha site in central Victoria, south-eastern Australia, is described. Radio-tracking was used to identify which trees were being used as den sites by animals during an 18-month period between September 1990 and March 1992. Analyses of our data showed that, although 113 different trees were used by the 16 animals, most were occupied infrequently. The total number of trees used by a given animal ranged from five to 23. However, the majority of individuals spent most of their time denning in 1-3 trees. Of the 113 den trees, 70 were found to have been used by only one animal, 54 trees were used exclusively by males, and 28 trees by females only. Twelve trees were used extensively (on >40 occasions) but only one was used extensively by both sexes. Most of the T. caninus radio-tracked typically used two or more nest trees per week, indicating that animals moved frequently between den sites. Some animals used up to six different trees per week. Some possible reasons for this behaviour in T. caninus are discussed.