| Summary: | Forty-seven mountain and silky cuscuses, and coppery ringtails were radio-tagged at Mt. Stolle, Papua New Guinea, from June 1995 to July 1998, and 15 of these were closely monitored. A total of 4,922 trees of ≥10 cm diameter were measured and identified from 5 randomly chosen hectares. About 70% of the trees were <20 cm in diameter, and <15 m high. Trees of the families Lauraceae, Myrtaceae, and Guttiferae represented >45% of the sample. Bootstrap averages of numbers of trees and species per hectare were 978 and 119 respectively. Daytime searches required significantly more effort to find animals, and provided significantly fewer captured animals per unit effort, than nighttime searches. However, chances of capturing animals once detected were higher during daytime. Drug doses of 9–17 mg Kg−1 immobilized animals within 1 minute, effects lasted 19 minutes, and recovery took an additional 28 minutes. Data for 10 species of Phalangerids and Pseudocheirids from 3 museum collections, and from measurements taken directly from the radio-tagged animals, were used to investigate the degree and nature of sexual dimorphism. Correlates of dimorphism were evaluated in two of the monitored species by analyzing behavioral and ecological data, including behavior budgets for three broad categories (eating, sitting, and walking), time between feeding bouts, home range size, absolute and relative distance traveled per hour, and five denning hole characteristics (type, visibility, height, dbh and height of tree). Sexual dimorphism in which males are larger than females exists in New Guinean medium-sized arboreal marsupial species, but not as commonly as previously reported. Seasonal weight fluctuations in correlation with reproductive status were observed in mountain cuscus females only. Lastly, animals had selective diets and ate mostly superabundant (>10 trees/hectare) species; also, overlap in the diet between the sexes did not differ from random chance, and females had more diverse diets than males. Dens were numerous, but very few were used more than 5 times. Home ranges overlapped very little in animals of the same sex, but little to extensively between sexes. Behavioral data suggest a facultative polygynous mating system in mountain cuscus and coppery ringtail.
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