The common ringtail possum (Pseudocheirus peregrinus, Greek for "false hand" and Latin for "pilgrim" or "alien") is an Australian marsupial.
The possum lives in a variety of habitats and eats a variety of leaves of both native and introduced plants, as well as flowers, fruits and sap. It also consumes caecotropes, which are material fermented in the caecum and expelled during the daytime when it is resting in a nest. This behaviour is called caecotrophy and is similar to that seen in rabbits.
The possum carries its young in a pouch, where it develops for 120–130 days before leaving. They are affected by land clearing, which destroys their habitat. The red fox is an introduced invasive species and predator that negatively impacts the possum.
Taxonomy
The common ringtail possum is currently classified as one of the two living species in the genus Pseudocheirus; the species of Pseudochirulus and other ringtail genera were formerly also classified in Pseudocheirus. Several subspecies have been described:
Description
The common ringtail possum weighs between and is approximately long when grown (excluding the tail, which is roughly the same length again). It has grey or black fur with white patches behind the eyes and usually a cream-coloured belly. It has a long prehensile tail which normally displays a distinctive white tip over 25% of its length. The back feet are syndactyl, which helps it to climb. The ringtail possum's molars have sharp and pointed cusps.
Distribution and habitat
The common ringtail possum ranges on the east coast of Australia, as well as Tasmania and a part of southwestern Australia. They generally live in temperate and tropical environments and are rare in drier environments. Ringtail possums prefer forests of dense brush, particularly eucalyptus forests. It is less prolific and less widespread than the common brushtail possum.
thumb|left|A common ringtail possum carrying young.
Behaviour
The common ringtail possum is nocturnal and well adapted to arboreal life. It relies on its prehensile tail and sometimes will descend to the ground.
thumb|Asleep in daytime roost. Common ringtails usually build nests. This one prefers the open air.
Diet and foraging
The common ringtail possum feeds on a wide variety of plants in the family Myrtaceae including the foliage, flowers and fruits from shrubs and lower canopy. Some populations are also known to feed on the leaves of cypress pine (Callitris), wattles (Acacia spp.) and plant gum or resins.
When foraging, ringtail possums prefer young leaves over old ones. One study found the emergence of young possums from their pouches corresponds to the flowering and fruiting of the tea-tree, Leptospermum and the peak of fresh plant growth. When feeding, the possum's molars slice through the leaves, slitting them into pieces. The possum's gastrointestinal tract sends the fine particles to the caecum and the coarse ones to the colon.
What distinguishes the digestive system of the common ringtail possum from that of the koala and the greater glider is the caecal contents are expelled as caecotropes, reingested and passed into the stomach. Because of this, the ringtail possum is able to gain more protein.
Metabolism
thumb|Common ringtail possum in Brisbane, Queensland.
The re-ingestion of caecotropes also serves to maintain the ringtail possum's energy balance. Ringtail possums gain much of their gross energy from reingestion. The common ringtail possum has a daily maintenance nitrogen requirement (MNR) of 290 mg N/kg<sup>0.75</sup>. Common ringtail possums gain much of their MNR from consuming their nitrogen-rich caecotropes. They would have to gain 620 mg N/kg<sup>0.75</sup> otherwise. It has been found that at higher temperatures, the common ringtail possum consumes less food due to a limited ability to metabolize toxins found in their diet. Because 55% of their water intake comes from the leaves and foliage they consume, their metabolic rate must remain low and stable while facing water loss. In response to this challenge, common ringtail possums can control their body temperature and conserve water by using facultative hyperthermia to temporarily raise their internal body temperature, ranging from . Ringtail possums build nests from tree branches and use tree hollows. A communal nest is made up of an adult female and an adult male, their dependant offspring and immature offspring of the previous year. During the second phase of lactation, more solid foods are eaten, especially when the young first emerges from the pouch.