| Sugar glider[1] | |
|---|---|
 | |
| Illustration byNeville Cayley | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Infraclass: | Marsupialia |
| Order: | Diprotodontia |
| Family: | Petauridae |
| Genus: | Petaurus |
| Species: | P. breviceps |
| Binomial name | |
| Petaurus breviceps Waterhouse, 1839[3] | |
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| Range map of the formerly recognized subspecies of sugar glider:[note 1] P. b. breviceps (introduced in Tasmania) | |
| Synonyms | |
P. (Belideus) breviceps, Waterhouse 1839 | |
Thesugar glider (Petaurus breviceps) is a small,omnivorous,arboreal, andnocturnalgliding possum. The common name refers to its predilection for sugary foods such assap andnectar and its ability toglide through the air, much like aflying squirrel.[8] They have very similar habits and appearance to the flying squirrel, despite not being closely related—an example ofconvergent evolution.[9] Thescientific name,Petaurus breviceps, translates fromLatin as "short-headed rope-dancer", a reference to theircanopyacrobatics.[10]
The sugar glider is characterised by its pair of gliding membranes, known aspatagia, which extend from its forelegs to its hindlegs.[11]Gliding serves as an efficient means of reaching food and evading predators.[8] The animal is covered in soft, pale grey to light brown fur which iscountershaded, being lighter in colour on its underside.
The sugar glider, as strictly defined in a recent analysis, is only native to a small portion of southeasternAustralia, corresponding to southernQueensland and most ofNew South Wales east of theGreat Dividing Range; the extended species group, including populations which may or may not belong toP. breviceps, occupies a larger range covering much of coastal eastern and northern Australia,New Guinea, and nearby islands.[4][5] Members ofPetaurus are popularexotic pets; these pet animals are also frequently referred to as "sugar gliders", but recent research indicates, at least for American pets, that they are notP. breviceps but a closely related species, ultimately originating from a single source nearSorong inWest Papua.[12] This would possibly make them members of theKrefft's glider (P. notatus), but the taxonomy of PapuanPetaurus populations is still poorly resolved.[13]
The genusPetaurus is believed to have originated in New Guinea during the midMiocene epoch, approximately 18 to 24 million years ago. The modern AustralianPetaurus, along with New Guinean members of what were formerly consideredP. breviceps, diverged from their closest living New Guinean relatives ~9-12 mya. They probably dispersed from New Guinea to Australia between 4.8 and ~8.4 mya, with the oldestPetaurus fossils in Australia being dated to 4.46 million years.[14] This may have been possible due to sea level lowering from about 7 to 10 mya, resulting in land bridges between New Guinea and Australia.
The taxonomy of the species is complex, and is still not fully resolved. It was formerly understood to have a wide range across Australia and New Guinea, being the onlyglider to have this distribution, and to be divided into seven subspecies, with three occurring in Australia and four in New Guinea.[15] This traditional subspecific division was based on smallmorphological differences, such as colour and body size.[14] However, a 2010 genetic analysis usingmitochondrial DNA indicates that these morphologically-defined subspecies may not represent genetically unique populations.[15]
Further studies have found significant genetic variation within populations traditionally classified inP. breviceps, sufficient to warrant splitting the species into multiple. The subspeciesP. b. biacensis, fromBiak Island off of New Guinea, was reclassified as a separate species, theBiak glider (Petaurus biacensis).[note 5] In 2020, a landmark study suggested thatP. breviceps actually comprised threecryptic species: theKrefft's glider (Petaurus notatus), found throughout most of eastern Australia and introduced toTasmania, thesavanna glider (Petaurus ariel), native to northern Australia, and a more narrowly definedP. breviceps, restricted to a small section of coastal forest in southernQueensland and most ofNew South Wales. In addition, other sugar glider populations throughout this range (such as those onNew Guinea and theCape York Peninsula) may represent undescribed species or beconspecific with previously described species. This indicates that contrary to previous findings of a large range (which in fact applied toP. notatus and, to a lesser extent, toP. ariel),P. breviceps is a range-restricted species that is sensitive to ecological disasters, such as the2019-20 Australian bushfires, which significantly affected large portions of its habitat.[4][5][16]
P. breviceps andP. notatus are estimated to have diverged ~1 million years ago, and may haveoriginated from long term geographic isolation. The early-midPleistocene saw an uplifting of theGreat Dividing Range, contributing to and coinciding with aridification of the interior of Australia, including on the western side of the range.[15] This, as well as other climactic and geographic factors, may have isolated the ancestors ofP. breviceps torefugia on the eastern, coastal side of the Great Dividing Range.[4] This would be an example ofallopatric speciation.
Sugar gliders are distributed in the coastal forests of southeasternQueensland and most ofNew South Wales. Their distribution extends to altitudes of 2000m in the eastern ranges. In parts of its range, it may overlap withKrefft's glider (P. notatus).[5][17]
The sugar glider occurs insympatry with thesquirrel glider andyellow-bellied glider; and their coexistence is permitted throughniche partitioning where each species has different patterns of resource use.[18]
Like all arboreal, nocturnal marsupials, sugar gliders are active at night, and they shelter during the day in tree hollows lined with leafy twigs.[19]
The averagehome range of sugar gliders is 0.5 hectares (1.2 acres), and is largely related to the abundance of food sources;[20]density ranges from two to six individuals per hectare (0.8–2.4 per acre).
Native owls (Ninox sp.)[17] are their primary predators; others in their range includekookaburras,goannas,snakes, andquolls.[21]Feral cats (Felis catus) also represent a significant threat.[17][21]
The sugar glider has a squirrel-like body with a long, partially (weakly)[22]prehensile tail. The length from the nose to the tip of the tail is about 24–30 cm (9–12 in), and males and females weigh 140 and 115 grams (5 and 4 oz) respectively.[23]Heart rate range is 200–300 beats per minute, andrespiratory rate is 16–40 breaths per minute.[24] The sugar glider is asexually dimorphic species, with males typically larger than females. Sexual dimorphism has likely evolved due to increased mate competition arising through social group structure; and is more pronounced in regions of higher latitude, where mate competition is greater due to increased food availability.[25]
The fur coat on the sugar glider is thick, soft, and is usually blue-grey; although some have been known to be yellow, tan or (rarely)albino.[a] A black stripe is seen from its nose to midway on its back. Its belly, throat, and chest are cream in colour. Males have fourscent glands, located on the forehead, chest, and two paracloacal (associated with, but not part of thecloaca, which is the common opening for the intestinal, urinal and genital tracts) that are used for marking of group members and territory.[17] Scent glands on the head and chest of males appear as bald spots. Females also have a paracloacal scent gland and a scent gland in the pouch, but do not have scent glands on the chest or forehead.[17]
The sugar glider is nocturnal; its large eyes help it tosee at night and its ears swivel to help locate prey in the dark. The eyes are set far apart, allowing more precisetriangulation from launching to landing locations while gliding.[26] Sugar gliders have demonstrated trichromacy in behavioral testing with sensitivity in the ultraviolet/blue, green, and red ranges. Ultraviolet sensitivity is corroborated by genetic evidence. The physiological source of their middle wavelength sensitivity is not yet confirmed.[27]
Each foot on the sugar glider has five digits, with an opposable toe on each hind foot. These opposable toes are clawless, and bend such that they can touch all the other digits, like a humanthumb, allowing it to firmly grasp branches. The second and third digits of the hind foot are partiallysyndactylous (fused together), forming a grooming comb.[22] The fourth digit of the forefoot is sharp and elongated, aiding in extraction of insects under the bark of trees.[17]
The gliding membrane extends from the outside of the fifth digit of each forefoot to the first digit of each hind foot. When the legs are stretched out, this membrane allows the sugar glider to glide a considerable distance. The membrane is supported by well developed tibiocarpalis, humerodorsalis and tibioabdominalis muscles, and its movement is controlled by these supporting muscles in conjunction with trunk, limb and tail movement.[11]
Lifespan in the wild is up to 9 years; is typically up to 12 years in captivity,[10] and the maximum reported lifespan is 17.8 years.[28]
The sugar glider is one of a number ofvolplane (gliding) possums in Australia. It glides with the fore- and hind-limbs extended at right angles to the body, with feet flexed upwards.[26] The animal launches itself from a tree, spreading its limbs to expose the gliding membranes. This creates anaerofoil enabling it to glide 50 metres (55 yards) or more.[29] For every 1.82 m (6 ft 0 in) travelled horizontally when gliding, it falls 1 m (3 ft 3 in).[26] Steering is controlled by moving limbs and adjusting the tension of the gliding membrane; for example, to turn left, the left forearm is lowered below the right.[26]
This form ofarboreal locomotion is typically used to travel from tree to tree; the species rarely descends to the ground. Gliding provides three dimensional avoidance of arboreal predators, and minimal contact with ground dwelling predators; as well as possible benefits in decreasing time and energy consumption[30] spent foraging for nutrient poor foods that are irregularly distributed.[31] Young carried in the pouch of females are protected from landing forces by theseptum that separates them within the pouch.[26]
Sugar gliders can tolerate ambient air temperatures of up to 40 °C (104 °F) through behavioural strategies such as licking their coat and exposing the wet area, as well as drinking small quantities of water.[17]In cold weather, sugar gliders will huddle together to avoid heat loss, and will entertorpor to conserve energy.[32] Huddling as an energy conserving mechanism is not as efficient as torpor.[32] Before entering torpor, a sugar glider will reduce activity and body temperature normally in order to lower energy expenditure and avoid torpor.[33][34] With energetic constraints, the sugar glider will enter into daily torpor for 2–23 hours while in rest phase.[32] Torpor differs fromhibernation in that torpor is usually a short-term daily cycle. Entering torpor saves energy for the animal by allowing its body temperature to fall to a minimum of 10.4 °C (50.7 °F)[32] to 19.6 °C (67.3 °F).[35] When food is scarce, as in winter, heat production is lowered in order to reduce energy expenditure.[36] With low energy and heat production, it is important for the sugar glider to peak its body mass by fat content in the autumn (May/June) in order to survive the following cold season. In the wild, sugar gliders enter into daily torpor more often than sugar gliders in captivity.[34][35] The use of torpor is most frequent during winter, likely in response to low ambient temperature, rainfall, and seasonal fluctuation in food sources.[32]
Sugar gliders are seasonally adaptive omnivores with a wide variety of foods in their diet, and mainly forage in the lower layers of the forest canopy.[18][37] Sugar gliders may obtain up to half their daily water intake through drinking rainwater, with the remainder obtained through water held in its food.[30] In summer they are primarilyinsectivorous, and in the winter when insects (and otherarthropods) are scarce, they are mostlyexudativorous (feeding onacacia gum,eucalyptussap,manna,[b]honeydew orlerp).[41] Sugar gliders have an enlargedcaecum to assist in digestion ofcomplex carbohydrates obtained from gum and sap.[42]
To obtain sap or gum from plants, sugar gliders will strip the bark off trees or open bore holes with their teeth to access stored liquid.[37] Little time is spentforaging for insects, as it is an energetically expensive process, and sugar gliders will wait until insects fly into their habitat, or stop to feed on flowers.[37]Gliders consume approximately 11 g of dry food matter per day.[30] This equates to roughly 8% and 9.5% of body weight for males and females, respectively.
They areopportunistic feeders and can becarnivorous, preying mostly on lizards and small birds. They eat many other foods when available, such as nectar, acacia seeds, bird eggs, pollen, fungi and native fruits.[43][44] Pollen can make up a large portion of their diet, therefore sugar gliders are likely to be importantpollinators ofBanksia species.[45]
Like mostmarsupials, female sugar gliders have twoovaries and twouteri; they arepolyestrous, meaning they can go intoheat several times a year.[20] The female has amarsupium (pouch) in the middle of her abdomen to carry offspring.[22] The pouch opens anteriorly, and two lateral pockets extend posteriorly when young are present. Four nipples are usually present in the pouch, although reports of individuals with two nipples have been recorded.[17] Male sugar gliders have two pairs ofbulbourethral glands[46] and abifurcated penis to correspond with the two uteri of females.[47]
The age of sexual maturity in sugar gliders varies slightly between the males and females. Males reach maturity at 4 to 12 months of age, while females require from 8 to 12 months. In the wild, sugar gliders breed once or twice a year depending on the climate and habitat conditions, while they can breed multiple times a year in captivity as a result of consistent living conditions and proper diet.[22]
A sugar glider female gives birth to one (19%) or two (81%) babies (joeys) per litter.[20] The gestation period is 15 to 17 days, after which the tiny joey 0.2 g (0.0071 oz) will crawl into a mother's pouch for further development. They are born largely undeveloped and furless, with only thesense of smell being developed. The mother has a scent gland in the external marsupium to attract the sightless joeys from the uterus.[48] Joeys have a continuous arch of cartilage in theirshoulder girdle which disappears soon after birth; this supports the forelimbs, assisting the climb into the pouch.[49] Young are completely contained in the pouch for 60 days after birth, whereinmammae provide nourishment during the remainder of development.[48] Eyes first open around 80 days after birth, and young will leave the nest around 110 days after birth.[17] By the time young areweaned, thethermoregulatory system is developed, and in conjunction with a large body size and thicker fur, they are able to regulate their own body temperature.[50]
Breeding is seasonal in southeast Australia, with young only born in winter and spring (June to November).[20] Unlike animals that move along the ground, the sugar glider and other gliding species produce fewer, but heavier, offspring per litter. This allows female sugar gliders to retain the ability to glide when pregnant.[51]
Sugar gliders are highly social animals. They live in family groups orcolonies consisting of up to seven adults, plus the current season's young. Up to four age classes may exist within each group, although some sugar gliders are solitary, not belonging to a group.[20] They engage insocial grooming, which in addition to improving hygiene and health, helps bond the colony and establish group identity.
Within social communities, there are two codominant males who suppress subordinate males, but show no aggression towards each other. These co-dominant pairs are more related to each other than to subordinates within the group; and share food, nests, mates, and responsibility for scent marking of community members and territories.[52]
Territory and members of the group are marked with saliva and a scent produced by separate glands on the forehead and chest of male gliders. Intruders who lack the appropriate scent marking are expelled violently.[8] Rank is established through scent marking; and fighting does not occur within groups, but does occur when communities come into contact with each other.[17] Within the colony, no fighting typically takes place beyond threatening behaviour.[53] Each colony defends a territory of about 1 hectare (2.5 acres) where eucalyptus trees provide astaple food source.[citation needed]
Sugar gliders are one of the few species ofmammals that exhibitmale parental care.[54] The oldest codominant male in a social community shows a high level of parental care, as he is the probable father of any offspring due to his social status.This paternal care evolved in sugar gliders as young are more likely to survive whenparental investment is provided by both parents.[54] In the sugar glider, biparental care allows one adult to huddle with the young and preventhypothermia while the other parent is out foraging, as young sugar gliders aren't able tothermoregulate until they are 100 days old (3.5 months).[54]
Communication in sugar gliders is achieved through vocalisations, visual signals and complex chemical odours.[17] Chemical odours account for a large part of communication in sugar gliders, similar to many other nocturnal animals. Odours may be used to mark territory, convey health status of an individual, and mark rank of community members. Gliders produce a number of vocalisations including barking and hissing.[55]
Under the prior taxonomy, the sugar glider was not consideredendangered, and its conservation rank was "Least Concern (LC)" on theIUCN Red List.[2] However, with newer taxonomic studies indicating that it has a small and restricted range, it is now thought to be far more sensitive to potential threats. For example, the species' native range was hit hard by the2019-20 Australian bushfires, which occurred just a few months prior to the publishing of the study indicating the true extent of its range. Sugar gliders use tree hollows, making them especially sensitive to intense fires.[56] However, despite the loss of natural habitat in Australia over the last 200 years, it is adaptable and capable of living in small patches of remnant bush, particularly if it does not have to cross large expanses of cleared land to reach them. Sugar gliders may persist in areas that have undergone mild-moderate selective logging, as long as three to five hollow bearing trees are retained perhectare.[57] Although not currently threatened by habitat loss, the ability of sugar gliders to forage and avoid predators successfully may be decreased in areas of highlight pollution.[58]
Conservation in Australia is enacted at the federal, state and local levels, where sugar gliders are protected as a native species. The central conservation law in Australia is theEnvironment Protection and Biodiversity Conservation Act 1999 (EPBC Act).[59] TheNational Parks and Wildlife Act 1974 is an example of conservation law in the state ofSouth Australia, where it is legal to keep (only) one sugar glider without a permit, provided it was acquired legally from a source with a permit. A permit is required to obtain or possess more than one glider, or if one wants to sell or give away any glider in their possession. It is illegal to capture or sell wild sugar gliders without a permit.[60]
In captivity, the sugar glider can suffer fromcalcium deficiencies if not fed an adequate diet. A lack of calcium in the diet causes the body to leach calcium from the bones, with the hind legs first to show noticeable dysfunction.[61] Calcium tophosphorus ratios should be 2:1 to preventhypocalcemia, sometimes known as hind leg paralysis (HLP).[62] Their diet should be 50% insects (gut-loaded) or other sources of protein, 25% fruit and 25% vegetables.[63] Some of the more recognised diets are Bourbon's Modified Leadbeaters (BML),[64] High Protein Wombaroo (HPW)[65] and various calcium rich diets with Leadbeaters Mixture (LBM).[66] Iron storage disease (hemochromatosis) is another dietary problem that has been reported in captive gliders and can lead to fatal complications if not diagnosed and treated early.[67]
A large amount of attention andenvironmental enrichment may be required for the highly social species, especially for those kept as individuals. Inadequate social interaction can lead to depression andbehavioural disorders such as loss of appetite, irritability and self-mutilation.[68]
In several countries, the sugar glider (or what was formerly considered to be the sugar glider) is popular as anexotic pet, and is sometimes referred to as apocket pet. In Australia, there is opposition to keeping native animals as pets from Australia's largestwildlife rehabilitation organisation (WIRES),[69] and concerns fromAustralian wildlife conservation organisations regarding animal welfare risks including neglect, cruelty and abandonment.[70]
In Australia, sugar gliders can be kept in Victoria, South Australia, and the Northern Territory. However, they are not allowed to be kept as pets inWestern Australia,New South Wales,the Australian Capital Territory,Queensland orTasmania.[71][72]
DNA analysis indicates that "the USA (sugar) glider population originates fromWest Papua, Indonesia with no illegal harvesting from other native areas such as Papua New Guinea or Australia".[12] Given that the West Papuan gliders have been tentatively classified asKrefft's gliders (albeit to be changed in the future),[13] this indicates that at least the captive gliders kept in the United States are Krefft's gliders, not sugar gliders.
(n) manna (hardened sugary exudation of various trees) : Synset (semantic) relations,direct hypernym (n) sap (a watery solution of sugars, salts, and minerals that circulates through the vascular system of a plant)
mannan. 4. The dried exudate of certain plants
Sugar gliders eat manna in the wild. Manna is a crusty sugar left from where sap flowed from a wound in a tree trunk or branch.
