POPULATION-DENSITY AND MOVEMENT DATA FOR PREDICTING MATING SYSTEMS OFARBOREAL MARSUPIALS

A model, based on the number of encounters between male and female arb oreal marsupials, was used to predict the rate of polygyny (the propor tion of males fathering offspring with more than one female). The mode l predicted that the rate of polygyny would increase to an asymptote a s population density increased. This result formalises previous sugges tions that mating systems of arboreal marsupials may change with popul ation density. Data on movements derived from radio telemetry and trap -recapture methods were used to predict the rate of polygyny in a popu lation of the mountain brushtail possum (Trichosurus caninus) at Camba rville, Victoria, southeastern Australia. The model predicted that 26% of males that successfully raised offspring in 1995 would be polygyno us. In 1995, blood samples were taken from 13 offspring to determine p aternity by DNA profiling. The model predicted that it is unlikely (P = 0.006) that the 13 offspring would be fathered by 13 different males if T. caninus mated polygynously. Thus, the model may be used to cons truct hypotheses about the mating system of arboreal marsupials that m ay be tested with subsequent genetic analysis. (C) 1998 Elsevier Scien ce B.V. All rights reserved.