Observations on the reproduction and ecology of the Brush-tailed possum. Trichosurus Vulpecula Kerr (Marsupialia), in New Zealand.

Abstract

In all 366 adult possums and 139 pouch young were examined. Five samples were collected and a study of a live population was conducted. Data are presented on the relationships of weight, tibia1 ossification, and sexual maturity, which indicate that two age classes can be distinguished in the fully grown animals on the basis of epiphyseal union of the tibia. Correlations between body weight, testis length, and the presence of sperm are presented for 53 males. The reproductive condition of 209 females was examined and successive observations were made on another eight. It is considered that Trichosurus is dioestrous and monovular. Pregnancy lasts between 15 and 24 days and is sometimes followed by a post-partum ovulation. Cyclic changes in the uterus and the urogenital sinus are described. The urogenital sinus exhibits marked cornification at oestrus, similar to the vagina of eutherian mammals. Anoestrus in February is followed by increasing reproductive activity in March. By the beginning of May, 90 per cent. of the adult females are pregnant or post-partum and the offspring is carried in the pouch until August or September. Some females may produce a second offspring in October. Some observations on the movements of individuals are presented.