 |
 |
By Antonia Gorog
Geographic Range
Tarsipes rostratus, the only species in the family Tarsipedidae, is found in the southwestern coastal district of Western Australia from south of Geraldton through Perth and Albany to Esperance.
Biogeographic Regions:
australian 
(native ).
Habitat
The distribution of Tarsipes rostratus is restricted to the sandplain heathlands, shrublands, and open low woodlands with heath understory that patchily surround Australia's arid center. The biology of this animal is linked to the distribution and flowering patterns of nectar producing flowers, and flowering plant species-richness is directly related to numbers of Tarsipes individuals.
These animals are found in the following types of habitat:
tropical ; terrestrial .
Terrestrial Biomes:
desert or dune ; chaparral ; forest .
Physical Description
The honey possum is greyish-brown with yellow to white underparts. A dark dorsal stripe reaches the base of its tail. Two lighter outer stripes do not extend as far as the midstripe. The limbs are pale rufous, the feet white, and the head pale brown. The fur is short and coarse, the tail long and almost naked with a prehensile tip. This species is sexually dimorphic, with females the larger of the two sexes. Head and body length range from 70 to 85mm. Tail length is 88 to 100mm. A male of head and body length 78mm weighed 13 grams and a female of 81mm weighed 17 grams.
Some key physical features:
endothermic ; bilateral symmetry .
Reproduction
Courtship and contact are short in Tarsipes. The male follows a female entering estrous. The female only lets the male mount her long enough to mate after she has entered estrous. Tarsipes is thought to be promiscuous. The sperm of these possums are the longest of any mammal recorded and their testes relatively the largest. It has been proposed that this is a result of gamete selection.
Mating systems:
polygynandrous (promiscuous) .
Young honey possums have been recorded from the wild for every month of the year except December. There are three birth peaks per year, the first synchronous and the others less so. The first peak is January to February; the second and third occur at three month intervals, as three months is the length of time needed to wean a litter. Embryonic diapause, a system in which a blastocyst resulting from a post-partum mating remains dormant until young present in the pouch are weaned, allows the second litter of possums to be born soon after the first leaves the pouch. This arrangement of reproductive events places birthing seasons during times when food sources are abundant (fall, spring, and early summer). The lack of births in December corresponds to midsummer, a time when few plant species flower.
Newborn young, weighing 2 to six milligrams, are the smallest at birth of all mammals. The young remain in the marsupium for eight weeks and emerge at 2.5 grams with open eyes and the stripes characteristic of the genus. Initially they remain in the nest, which is often a deserted bird nest, while the mother forages. After a week they are able to walk steadily and they follow their mother on her forays. At eleven weeks they are fully weaned. Males and females are fully mature at six months of age.
Key reproductive features:
gonochoric/gonochoristic/dioecious (sexes separate); sexual .
Behavior
As nocturnal mammals, honey possums rely primarily on their sense of smell. A limited number of visual signals and high-pitched squeaks have also been recorded for these animals.
Tarsipes has three activity peaks; 0600 to 0800, 1700 to 1900, and 2330 to 0130. During the nocturnal peak these possums are primarily involved in foraging, during which they maneuver quickly and nimbly through vegetation, using their tails for stability, and often congregate on the same flower or plant to feed. Individuals group together to maintain heat and may enter torpor in cold weather.
Honey possums have non-overlapping home ranges of about 2.5 acres, but females with young in their pouches have smaller, exclusive home ranges of 120 square yards. In captivity females are dominant to males and are particularly aggressive to male strangers.
Key behaviors:
scansorial; motile .
Food Habits
'Honey' possum is a misnomer for this tiny marsupial. Tarsipes feeds on pollen, nectar, and insects. It explores flowers thoroughly with its long snout in search of its prefered foods, which include pollen and nectar from Banksia, bottlebrushes, hakeas, dandras, Ti, and eucalypt.
Tarsipes is uniquely adapted among marsupials to obtain food from flowers. With a snout approximately two-thirds the length of the rest of its head and a brush-tipped tongue that extends 25 millimeters beyond its nose, the honey possum can forage for food deep in flowers. Its slender long incisors and flanges on its upper and lower lips form a channel through which the tongue is retracted; during this process nectar and pollen are scraped from the tongue by ridges on the hard palate. Tarsipes moves short distances in search of flowers and, because of its small size, can feed on blossoms at the ends of thin branches. It often hangs upside down by its tail when it feeds, using its forelimbs to manipulate flowers.
Primary Diet:
herbivore (nectarivore ).
Animal Foods:
insects.
Plant Foods:
nectar; pollen.
Economic Importance for Humans: Positive
Tarsipes rostratus is a pollinator for many species of plants in the family Proteaceae. The natural history of these plants appears to be intricately linked to that of the honey possum.
Conservation Status
The honey possum is rare but not considered endangered. However, the restriction of its habitat to the wetter areas of a generally dry continent makes the threat of habitat destruction in the forms of burning and urbanization very serious. In addition, feral cats prey upon Tarsipes.
Other Comments
There is no fossil record of this species from earlier than 35,000 years ago. It is hypothesized to have evolved when Australia had many heathlands with high flower diversity, about 20mya.
Contributors
Antonia Gorog (author), University of Michigan.
