Common ringtail possum

Common ringtail possum[1]
Conservation status
Least Concern (IUCN 3.1)[2]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Infraclass:	Marsupialia
Order:	Diprotodontia
Family:	Pseudocheiridae
Subfamily:	Pseudocheirinae
Genus:	Pseudocheirus
Species:	P. peregrinus
Binomial name
Pseudocheirus peregrinus (Boddaert, 1785)
Common ringtail possum range (except western ringtail possum (Pseudocheirus peregrinus occidentalis) range) (blue — native, red — introduced)

The common ringtail possum (Pseudocheirus peregrinus, Greek for "false hand" and Latin for "pilgrim" or "alien") is an Australian marsupial. It lives in a variety of habitats and eats a variety of leaves of both native and introduced plants, as well as flowers and fruits. These dietary factors have, over time, aided burgeoning introduced (pest) populations in New Zealand. This possum also consumes a special type of faeces that is produced during the daytime when it is resting in a nest. This behaviour is called coprophagia and is similar to that seen in rabbits.

Taxonomy

The common ringtail possum is currently classified as the only 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, such as the Western Australian Pseudocheirus peregrinus occidentalis, but the entire population may be a species complex.^[1] The arrangement as the only extant species of Pseudocheirus is:^[1]

• Pseudocheirus peregrinus pereginus, the type subspecies based on a collection made at Endeavour River
• Pseudocheirus peregrinus convolutor,
• Pseudocheirus peregrinus pulcher,
• Pseudocheirus peregrinus occidentalis, called the western ringtail possum, found in the south west of the country. Taxonomic opinion favours regarding this as a separate species, Pseudocheirus occidentalis, though the currently contradictory evidence would not allow this recommendation to be formalised.^[3]

Description

The common ringtail possum weighs between 550 and 1100 g. It has grey 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 molar teeth of the ringtail possum is similar to that of the koala and the greater glider with the four major cusps being shaped into crescentic blades.^[4]

Ecology

Range and habitat

Common ringtail possums are found along the eastern coastline of Australia, Tasmania, and the south-western corner of western Australia.^[5] They generally live in temperature and tropical environments and are rare in drier areas. Ringtail possums prefer forests of dense brush.^[5] The common ringtail possum and its relatives occupy a range of niches in a matter similar of lemurs, monkeys, squirrels, and bushbabies in similar forests on other continents.^[6]

A common ringtail possum perched on a utility pole

Diet and foraging

The common ringtail possum prefers to feed on Eucalyptus foliage and the highest densities of ringtail possums are found in areas where Eucalyptus are found.^[4] However, ringtail possums will eat foliage, flowers and fruits from other species of trees and shrubs from the lower levels of the forest.^[7] When foraging, ringtail possums prefer young leaves over old ones. One study found that young possums emerge from the pouches when the flush of plant growth and the flowering and fruiting of the tea-tree, Leptospermum.^[8] Young eucalypt foliage have a higher concentration of nitrogen and lower cell-wall concentration than older leaves and the higher concentrations of tannins make the protein less available.^[9] When feeding, the possum’s teeth cuts the leaves in very small pieces. Much like the koala and the greater glider, the common ringtail possum has a large caecum which is where the fine coarse particles that are separated.^[4] These particles are retained in the caecum for up to 70 hours.^[4] Here, massive colonies of micro-organisms attach to the tissue components and cause partial digestion of cells walls and tanned cytoplasts.^[10]

What distinguishes the system of the digestive system of the common ringtail possum from that of the koala and the greater glider, is the caecal content is taken directly back to the stomach, where they go on a second passage through the gut. Because of this, the ringtail possum gains far greater access to protein and the energy products of bacterial fermentation in its caecum.^[4] This is also done by lagomorphs like rabbits and pikas. Hard faeces are produced during the night while foraging and are not eaten, while soft faeces are produced during the day while resting have been recorded being taken directly from the cloaca.^[11]

Metabolism

The re-ingestion of caecal content also serves to maintain the ringtail possum’s energy balance. Ringtail possum seem to prefer Eucalyptus andrewii over other species and feed almost exclusively on it in captivity.^[12] When consuming these plants, ringtail possums gain the much of their gross energy from reingestion.^[12] The the common ringtail possum has a daily maintenance nitrogen requirement (MNR) of 290 mg N/kg^0.75, similarly to the koala but is half the requirements of the greater glider. Still, common ringtail possums gain much of their MNR from consuming their nitrogen-rich caecal pellets. A ringtail possum would need to obtain 620 620 mg N/kg^0.75 if it did have this additional access to metabolic nitrogen.^[4] For the ringtail possum, 96% of the urea that is produced in the liver is recycled into the caecum and is then synthesised into bacterial protein from there. However, this is only useful with re-ingestion since the bacterial protein must be digested in the stomach and the amino acids in the small intestine.^[4] By recycling urea, the ringtail possum also conserves water. Instead of being released as urine, some of the water is returned to the stomach in the caecal pellets. Ringtail possums get most of their water intake from the free water in the leaves they eat which is supplemented with drinking water.^[4] Re-ingestion is thus important in water conservation and for feeding on Eucalyptus leaves which have a nitrogen content of only 1.1%.^[4] It is particularly important during late lactation which requires 1.4 g of protein to be export each day in milk to support the growth of the young.^[13]

Behaviour and life history

Common ringtail possums are mostly nocturnal and are well adapted to arboreal life. They are rarely found on the ground and use their prehensile tail extensively.^[5] They have been known to communicate with soft, high-pitched, and twittering calls.^[14]

Asleep in daytime roost. Common ringtails usually build nests. This one prefers the open air.

Nesting

Common ringtail possums live a gregarious lifestyle that is centred around the communal nests. Ringtail possums build nests called greyer in the branches of trees or in large tree hollows. A communal is made up of an adult male with one or two adult females, their dependant offspring and immature offspring of the previous year. ^[7] A group of ringtail possums may build several greyer at different heights and localities. Ringtail possums are territorial and will drive anyway any strange conspecifics from their nests. A group has a strong attachment to their site. In one experiment, a group was removed from their territory and it was not recolonised for the next two years.^[7] Ringtail possum nests tend to be more abundant in low scrub or areas regenerating after partial clearance and are less abundant in heavy timbered country with sparse under-story. ^[4] Greyers are an important element in the survival of the young after they relinquish their mother’s back. They also serve as a daytime refuge for adults.^[4]

Reproduction and growth

Common ringtail possums are marsupials, thus they carry their young in a pouch while they develop. Depending on the location in Australia, the mating season can take takes place anywhere between April and December.^[5] The majority of the young are born between May and July. The ringtail possum has an estrous cycle lasting 28 days.^[6] It is both polyestrous and polyovular. If a female prematurely loses her liter, she can return to oestrous and produce a second litter in October as a replacement if conditions are right.^[4] The average number of young in a litter is two, although four young can be reared as the female has four teats in her pouch.^[4] Usually two of the four nipples are functional at one time and pouch has a forward facing opening and.^[5] Initial growth of the common ringtail possum young is generally slow. This slow growth occurs during the period when the weight of the female is at its lowest. The slow growth rate is due to the quality of the milk being providing to the young. As with other marsupials, the common ringtail possum’s milk changes through lactation.^[15] In comparison with the milks of other marsupial species, ringtail possum milk is relatively dilute and low in lipid. During the second phase of lactation solids represent around 16% (w/w) and increases to 25% (w/w) when the young first emerges from the pouch.^[15] During this time, concentration of carbohydrates declines while concentrations of protein and lipid peak.^[15] The long lactation of the ringtail possums may provide the young the opportunity to learn skills in the communal nest and develop their ability to climb and forage in the trees.^[4]

The young both open their eyes and are able to make clear vocalisations, between 90 and 106 days after birth,.^[5] The young emerge from their mother's pouch 120–130 days after birth. However, lactation generally does not stop until 180–220 days after birth and sometimes ends as early as 145 days.^[6] Both sexes become sexually mature in the first mating season after their birth.

Status

Common ringtail possum populations severely declined during the 1950s. However, populations seem to have recovered in current times.^[5] Because they are almost exclusively arboreal, common ringtail possums have loss a lot of habitat due to deforestation in Australia. Ringtail possums are vulnerable to being struck by cars, or hunted by cats and dogs in suburban areas.^[5] This species do not adversely affect humans. Ringtail possums do not nest within homes or human structures and as such are not considered pests.^[5]

References

1. ^ ^{a b c} Groves, C. (2005). Wilson, D. E., & Reeder, D. M, eds. ed. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 51. OCLC 62265494. ISBN 0-801-88221-4. http://www.bucknell.edu/msw3. 
2. ^ Winter, J., Menkhorst, P., Lunney, D. & van Weenen, J. (2008). Pseudocheirus peregrinus. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 28 December 2008. Database entry includes justification for why this species is of least concern
3. ^ "Pseudocheirus occidentalis — Western Ringtail Possum". Species Profile and Threats Database. Department of Sustainability, Environment, Water, Population and Communities. http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=25911. Retrieved 3 November 2010. 
4. ^ ^{a b c d e f g h i j k l m n} H Tyndale-Biscoe. 2005. Life of Marsupials. pp. 243–47. CSIRO Publishing.
5. ^ ^{a b c d e f g h i} Pseudocheirus peregrinus Animal diversity
6. ^ ^{a b c} Barnett, J.L, A., R. R.A. How. 1984. "The Population Biology of Pseudocheirus peregrinus". pp. 261–268 in A. Ian Hume, ed. Possums and Gliders. New South Wales: Surrey Beatty & Sons Pty Limited.
7. ^ ^{a b c} Thomson, JA. Owen WH. (1964). "A Field Study of the Australian Ringtail Possum Pseudocheirus peregrinus (Marsupialia: Phalangeridae)". Ecological Monographs 34 (1): 27–52. doi:10.2307/1948462. JSTOR 1948462. 
8. ^ How, R.A. Barnett, J.L, Bradley AJ, Humphreys WF. (1984) "The population biology of Pseudocheirus peregrinus in a Leptospermum laevigatum thicket", In: Possums and gliders (edited by Andrew Smith and Ian Hume) pp. 261–68. Australian Mammal Society.
9. ^ Cork SJ, Pahl. (1984) "The possible influence of nutritional factors on diet and habitat selection by the ringtail possum (Pseudocheirus peregrinus)". In: Possums and gliders (edited by Andrew Smith and Ian Hume) pp. 269–76. Australian Mammal Society.
10. ^ TP Obrien, A Lomdahl and G Sanson (1986). "Preliminary Microscopic Investigations of the Digesta Derived From Foliage of Eucalyptus-Ovata (Labill) in the Digestive-Tract of the Common Ringtail Possum, Pseudocheirus peregrinus (Marsupialia)". Australian Journal of Zoology 34 (2): 157–176. doi:10.1071/ZO9860157. 
11. ^ Chilcott M J. (1984) "Coprophagy in the common ringtail possum, Pseudocheirus peregrinus (Marsupialia: Petuaridae)". Australian Mammalogy 7:107–110.
12. ^ ^{a b} Chilcott MJ, Hume ID (1984). "Nitrogen and Urea Metabolism and Nitrogen, Requirements of the Common Ringtail Possum, Pseudocheirus peregrinus, Fed Eucalyptus andrewii Foliage". Aust. J. Zool 32 (5): 615–22. doi:10.1071/ZO9840615. 
13. ^ Munks, SA; Green, B (1997). "Milk consumption and growth in a marsupial arboreal folivore, the common ringtail possum". Physiological zoology 70 (6): 691–700. JSTOR 10.1086/515871. PMID 9361143. 
14. ^ Lee, Anthony, A. 1984. "The Evolution of Strategies for Survival and Reproduction in Possums and Gliders". pp. 17–19 in A. Ian Hume, ed. Possums and Gliders. New South Wales: Surrey Beatty & Sons Pty Limited.
15. ^ ^{a b c} SA Munks, B Green, K Newgrain and M Messer (1991). "Milk-Composition in the Common Ringtail Possum, Pseudocheirus peregrinus (Petauridae, Marsupialia)". Australian Journal of Zoology 39 (4): 403–416. doi:10.1071/ZO9910403.