A tiny marsupial, the only survivor of an ancient group, which lives only on nectar and pollen and hold a number of extraordinary records amongst mammals: the smallest newborns, the largest testes in proportion to body size, and the largest sperm.

Life span
1 year (never more than 2).

Statistics
Male 6.5-8.5cm long with a tail 7-10cm; female 7-9cm with a tail 7.5-10.5cm. Females about a third heavier than males.

Physical Description
A small, mouse-like marsupial with a long nose, small ears and large black eyes. They have a very long, naked pink tail which is partially prehensile. The rest of their body is covered in soft greyish brown fur with a cream belly and an orange tinge to the sides. There is a dark stripe from the nape of the neck to the base of the tail, with a faint stripe either side. Their hands and feet are very good for grasping, with opposable big toes, and rough pads rather than claws. They also have a very long tongue for collecting nectar and pollen.

Distribution
South-western Australia.

Habitat
Heathland.

Diet
Nectar and pollen.

Behaviour
Honey possums are nocturnal and solitary, clambering around bushes in search of flowers such as Banksia and dryandras. These plants have blossoms of 250-2,500 flowers and are usually concealed and near the ground in order to encourage pollination by these mammals rather than by insects or bats. Males and females both have small home ranges, with the males' being slightly larger and overlapping those of several females. Females appear to be dominant to males.

Reproduction
Breeding can take place at any time of year, with more births when nectar is widely available. Courtship is brief, and females mate with many males. This has led to a lot of competition for fertilisation, and hence the males have the largest testes proportional to their body than any mammal, weighing 4.2 per cent of their body weight. They also have the largest sperm of any mammal, measuring 0.36mm. Gestation is about 28 days, after which 2-3 (occasionally 4) young are born. When born, they are the smallest young of any mammal, weighing only 0.0005g. The young develop within the mother's pouch for about 60 days. They emerge from the pouch with fur and eyes open, weighing around 2.5g. They follow the mother, occasionally suckling or riding on her back for another week or two before dispersing. A second litter is usually born soon after the first litter leaves the pouch, as fertilised embryos can be halted in their development until the pouch is about to be vacated. Sexual maturity is reached at 6 months old, and females often start breeding before being fully grown, and can carry up to 4 litters in a year.

Conservation status
Not listed, but its small distribution is shrinking.

Voice
High-pitched squeaks.

Records
The smallest young at birth, the largest testes and the largest sperm of any mammal.

Records
The smallest young at birth, the largest testes and the largest sperm of any mammal.

History
The honey possum is the only survivor of a group of marsupials which diverged very early on from the ancestors of possums and kangaroos. It probably evolved about 20 million years ago when heathlands were more common in Australia, although the oldest fossils known are only 35,000 years old.