The honey possum is mainly
nocturnal, but will come out to feed during daylight in cooler weather. Generally though, it spends the days asleep in a shelter of convenience: a rock cranny, a tree cavity, or an abandoned
bird nest. In comparison to other marsupials of a similar size,
T. rostratus has a high body temperature and
metabolic rate that is termed
euthermic. They are able to reduce their body temperature when exposed to cooler temperatures or experience a lack of food as they lack
fat reserves; adverse condition induces one of two states of
torpor in the species: the first is a shallow and brief period, similar to some
dasyurids, where the body temperature is above , and the second is a deeper state like
burramyids that lasts for multiple days and reduces their temperature to less than .
Tarsipes rostratus is a
keystone species in the ecology of the coastal sands of Southwest Australia, which house complex assemblages of plants known as
kwongan. Their feeding activity involves visits to many individual plants; their head often carries a small pollen load that can be conveyed more effectively than the birds that visit the same flowers. The favoured species
Banksia attenuata appears to be obliged to this animal as a pollination vector, and both species have evolved to suit their
mutualistic interactions. Study of the amount of nectar and pollen has concluded that a nine-gram individual requires around of nectar and of pollen each day to maintain an energetic balance. This amount of pollen provides sufficient nitrogen for the species high activity metabolism, and the additional nitrogen requirements of females during
lactation is available in the pollen of
Banksia species. The ingestion of excess water when feeding at wet flowers, a frequent circumstance in the high rainfall regions of its range, is compensated by its kidneys, which can process up to two times the animal's body weight in water which is subsequently eliminated. Pollen grains are digested over the course of six hours, extracting almost all the nutrients they contain. The species is able to
climb with the assistance of its long prehensile tail and an opposable first toe at the long hindfoot that is able to grip like a monkey's paw. The bristle-like papillae at the upper surface of the tongue increase in length toward the tip, and this is used to gather the pollen and nectar by rapidly wiping it into the inflorescence. Both its front and back feet are adept at grasping, enabling it to climb trees with ease, as well as traverse the
undergrowth at speed. Radio-tracking has shown that males particularly are quite mobile, moving distances of up to in a night and use areas averaging . Some evidence indicates even greater distances; pollen found on an individual in a study area was from a banksia not found within of the collection site. Most of the time, honey possums stick to separate
territories of about outside of the breeding season. They live in small groups of no more than 10, which results in them engaging in
combat with one another only rarely. During the
breeding season, females move into smaller areas with their young, which they will defend fiercely, especially from any males.
Reproduction Breeding depends on the availability of nectar and can occur at any time of the year. Females are
promiscuous, mating with a large number of males and may simultaneously carry embryos from different progenitors. Competition has led to the males having very large
testicles relatively; at a relative mass of 4.2-4.6% to body weight it is amongst the largest known for a mammal. Their sperm is the largest in the mammal world, measuring 365 micrometres with a tail/flagellum length of 360
micrometres, also cited as the longest known. The development of
blastocysts corresponds to day length, induced by a shorter
photoperiod, but other reproductive processes are prompted by other factor, probably food availability.
Gestation lasts for 28 days, with two to four young being produced. At birth, they are the smallest of any mammal, weighing . Nurturing and development within the
pouch lasts for about 60 days, after which they emerge covered in fur and with open eyes, weighing some . As soon as they emerge, they are often left in a sheltered area (such as a hollow in a tree) while the mother searches for food for herself, but within days, they learn to grab hold of the mother's back and travel with her. Eventually, their weight soon becomes too much, and they
stop nursing at around 11 weeks, and start to make their own homes shortly thereafter. As is common in marsupials, a second litter is often born when the pouch is vacated by the first, with fertilised embryos being
stopped from developing.
Ecology The effect of
wildfire frequency on the population was evaluated in a study over a twenty three-year period, giving indications of resilience of the species to the first fire in the area and a subsequent burn six years later. The effect of increased frequency and intensity of fire, due to
global warming and
prescribed burns can adversely affect the suitability of the local habitat. The species is susceptible to the impact of
Phytophthora cinnamomi, a soil-borne fungal-like species that is associated with
forest dieback in the eucalypt forests and banksia woodlands of the region. The flowers of the nine plant species most favoured by
T. rostratus provide food throughout the year, and five of these are vulnerable to the withering condition caused by
P. cinnamomi pathogen. == Relation to humans ==