Brush-tail Possums are the largest of all possums, weighing up to 4.5 kilograms. They are a nocturnal (night-time active), and arboreal (live in trees) animal that belongs to the marsupial mammal family. Their tail is semi-prehensile, without fur on the underside, enabling them to grip with their tail. On average they live about 12 years; becoming sexually mature at two years of age. Brush-tail Possums will have 1 joey at a time, who will stay in the pouch for about 6 months. They are found over most of Australia, including Tasmania.  On the mainland of Australia, possums are generally brown, black and grey. In Tasmania, some of the population are a naturally occurring golden colour due to genetic isolation. The golden colour is a result of a recessive gene that is less likely to be suppressed due to the closed gene pool in Tasmania.  Brush-tail Possums were introduced to New Zealand in the 19th century; they are now considered an agricultural and conservation pest in New Zealand. Brush-tail Possums are omnivorous; feeding mainly on leaves/foliage, fruit & berries, occasionally mice, insects, lizards and baby birds. They forage in the trees, and also on the ground.