| Central bearded dragon | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Iguania |
| Family: | Agamidae |
| Genus: | Pogona |
| Species: | P. vitticeps |
| Binomial name | |
| Pogona vitticeps Ahl, 1927 | |
 | |
| Native distribution | |
The central bearded dragon (Pogona vitticeps), also known as the inland bearded dragon, is a species of agamid lizard found in a wide range of arid to semiarid regions of eastern and central Australia. [2]
Pogona vitticeps was first described by German zoologist Ernst Ahl in 1926, who placed it in the genus Amphibolurus . [3] [4]
Mature bearded dragons can reach a total length of around 60 cm (24 in), or two feet, with the tail accounting for more than half of that. Some sexual dimorphism is present, as males can be distinguished from females by a wider cloacal opening, a wider tail-base, a larger and more angular head, a more developed beard (guttural throat-pouch), and the obvious possession of hemipenes. [5] Males also have more pronounced femoral pores than females (these can be seen as waxy bumps on the underside of the back legs). [6] Bearded dragons can vary widely in scale colouration, ranging from a blend of light brown, reddish-brown, red, yellow, white and orange; additionally, many interesting colour "morphs" exist today, thanks to selective breeding by hobbyists and professionals.
Somewhat like chameleons, bearded dragons are capable of inducing moderate changes in coloration based on mood. Additionally, they can slightly raise the pointed scales that run along either side of their throat, neck, head and torso by inhaling air into their lungs to maximum capacity, thus appearing larger to predators. The sharp-looking growths and protrusions are, in actuality, quite soft and delicate to the touch, but may be off-putting to predators such as birds of prey, foxes, feral dogs or dingos. When cornered or threatened, a bearded dragon will flatten its body against the ground, expand its rib cage outwards, open its mouth and expand its "beard" (guttural pouch; similar to a frilled lizard’s defense tactics, albeit on a smaller scale). The guttural pouch is what essentially earns the species its nickname of "beardie", and can darken in color when threatened or during courtship or territorial displays. Both of these characteristics appear similar to a human's beard. Males typically have a darker "beard" than females, and during mating season and courtship it will typically darken to near-black. The bearded dragon, like most agamid lizards, has strong legs which enable it to lift its body completely off the ground while it moves. This is done to reduce heat absorption from the hot ground, and facilitates airflow under the body.
A study conducted in 2014 established the existence of endogenous circadian rhythm in pigmentation changes in P. vitticeps; if exposed to sun, the dorsal skin of the lizard becomes darker, and if exposed to darkness, it becomes lighter. Under constant darkness (i.e. in the subjective night), the lizard's dorsal skin becomes the lightest. [7]
Many species of Pogona have a parietal eye (or "third eye"), a photoreceptor found on the centre of the forehead. This unique feature is responsible for thermoregulation and hormone regulation, and possibly helps the lizards make decisions based on the seasons, weather, etc. [8] A March 2020 study of the central bearded dragon found that light-dependent magnetoreception occurs when light with a wavelength under 580 nanometers enters the parietal eye. [9] [10]
 | This section needs additional citations for verification .(November 2018) |
P. vitticeps is native to semiarid woodland, arid woodland, and rocky desert areas of Central Australia, primarily the inland regions of New South Wales, Northern Territory, Queensland and South Australia. They are skilled climbers and often spend just as much time perching and basking on tree limbs, fence posts, and within bushes as they do on the ground. They often spend the mornings and early evenings sunning themselves on exposed branches or rocks, and retreat to shady areas or burrows during the hottest parts of the afternoon.
P. vitticeps are opportunistic omnivores. They live in areas where food may be hard to find, thus they are not particularly finicky eaters. Their stomachs are large enough to accommodate significant quantities of vegetation, fruits, insects, worms, and the occasional small rodent or lizard. [11] Favored insect prey includes crickets, grasshoppers, beetles, caterpillars, moths, butterflies, or any insect that can comfortably be swallowed.
Bearded dragons do not vocalize, except to hiss softly when threatened. Instead, they communicate through colour displays, posture, and physical gestures, such as arm waving and head bobbing. Bearded dragons are not social animals, but will sometimes gather in groups, especially in popular feeding or basking areas. At these times, a distinct hierarchy will emerge: the highest-ranking animals will take the best – usually the highest or sunniest – basking spots, and all other individuals arrange themselves lower down. [12] If a low-ranking animal tries to challenge one of the dominant dragons, the dominant animal will demonstrate its superiority by bobbing its head and inflating its beard, at which point the challenger may signal submission by waving one of its arms in a slow or fast circle. If the low-ranking dragon does not submit, it will return the head bob, and a standoff or fight may ensue.
The head bob gestures are: [13]
The male will only wave to show submission to a dominant male, whereas the female will wave, followed by a slow head bob, to show she is ready to mate. Gravid females will often refuse the advances of a male by chasing him and lying on his back.
When under direct attack, the central bearded dragon opens its mouth to display its yellow membranes and extend its beard. [14] It darkens the colour of its skin and flattens its body, and will hiss and make small jumps towards the attacker. Bearded dragons are not known to attack humans. [5]
Adult male bearded dragons can bite more forcefully than adult females and this difference is associated with greater head dimensions. [15]
Bearded dragons have been shown to be able to learn from watching the behaviour of conspecifics. An experiment demonstrated that after one individual was trained to open a door to reach a food item, most other bearded dragons watching this action were able to perform it as well. [16]
The age of sexual maturity has not been measured, although it is estimated to be about one or two years. [2] Body size and growth rates are more important than age when determining sexual maturity in bearded dragons. [5] Males will become very aggressive towards each other and will assert their dominance by inflating their beards and through fast head bobbing. Breeding typically occurs in the early spring. Females will lay a clutch of 11–30 oblong-shaped eggs in a shallow nest dug in the sand. After being laid, the eggs are buried and are left unattended. The eggs will hatch approximately 60 to 80 days later, depending on the incubation temperature. In captivity, they can be incubated in a styrofoam fish box, but without a male lizard, the female's eggs will not be fertile. However, a female bearded dragon can retain sperm, and thus produce fertile eggs even after being separated from a male.
Courtship involves the male "head bobbing" to display dominance. If the female displays submissive behaviour, the male will use his mouth to grab the back of the female's head and the male will also wrap his front legs around the female's upper torso to keep her from moving. Copulation and insemination are quick. The gestation period averages about a month and a half.
A 2015 study showed that high-temperature incubation of eggs transforms genetically male individuals into functional females. [17] Normally their sex is determined genetically. Males have ZZ sex chromosomes, females ZW. However, when their eggs are incubated at temperatures above 32 °C (90 °F) some genetic males are born female. These females are fertile, sometimes producing more eggs than the ZW females. [18] As juveniles, the sex reversed ZZ females resemble ZZ males with respect to relative tail length and boldness. [19] However, as adults sex-reversed ZZ females lack the larger head and greater bite force of ZZ males and more closely resemble ZW females. [15]
Several of the Pogona genus are bred in captivity as pets; the two most popular are this species and the Rankin's dragon (Pogona henrylawsoni). [20] [21] The majority of captive-bred bearded dragons today are thought to have originated from stock illegally exported from Australia during the 1970s. [22] Australia has since prohibited the importation and exportation of its native species, thus guaranteeing any bearded dragons found today outside of Australia have been captive-bred, hand-raised and socialized with human interaction from a very young age. The anti-exportation policies in Australia also ensures that bearded dragons (and indeed all Australian species found abroad) are not forcibly taken or poached from the wild and shipped around the globe via the black market—as is the case with Madagascar's rare and sensitive chameleons, geckos and frogs, for example.
However, captive bearded dragons worldwide are threatened by Agamid adenovirus, an HIV-like virus that compromises the immune system of the animal, and leads to death from other diseases. Still, the majority of the infections are subclinical. Subclinically-infected animals show no symptoms, but are active carriers of the disease and will thus infect other bearded dragons. As with nearly all reptiles and amphibians, captive bearded dragons are commonly susceptible to metabolic bone disease (MBD) if not provided with adequate calcium in the diet, a condition similar to human osteoporosis. Numerous supplements are available for sale to dust insect prey or plant matter with before each feeding. Additionally, they may be at-risk of constipation or digestive impactions from inadvertently ingesting decorative sand, gravel or even insects that are inappropriately sized for them to consume. [23]
When the female is ready to lay eggs, she will generally stop eating, and spend most of her time trying to dig.
A morph with underdeveloped dorsal scales is popular as a terrarium pet under the name of "leatherback bearded dragon". [24]
Lizard is the common name used for all squamate reptiles other than snakes, encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The grouping is paraphyletic as some lizards are more closely related to snakes than they are to other lizards. Lizards range in size from chameleons and geckos a few centimeters long to the 3-meter-long Komodo dragon.
Agamidae is a family of over 550 species of iguanian lizards indigenous to Africa, Asia, Australia, and a few in Southern Europe. Many species are commonly called dragons or dragon lizards.
The mulga dragon is a species of agamid lizard found in Western Australia. The species is up to 250 mm long, the length from snout to vent is 95 mm, with a long, slender tail that ends abruptly. The patterning over the legs and body is grey and brownish streaks. This provides an excellent camouflage on mulga trees, its usual habitat, it is also found beneath mulga leaf litter. Diporiphora amphiboluroides generally remains motionless and unobserved, this allows it to operate as an ambush predator and elude animals that would prey on it.
Pogona is a genus of reptiles containing eight lizard species, which are often known by the common name bearded dragons. The name "bearded dragon" refers to the underside of the throat of the lizard, which can turn black and become inflated for a number of reasons, most often as a result of stress, if they feel threatened, or are trying to entice a mate. They are a semiarboreal species, spending significant amounts of time on branches, in bushes, and near human habitation. Pogona species bask on rocks and exposed branches in the mornings and afternoons and sleep at night, making them a diurnal species. Their diet consists primarily of vegetation and some insects. They are found throughout much of Australia and inhabit environments such as deserts, and shrublands.
The eastern bearded dragon, also known as common bearded dragon or simply bearded lizard, is an agamid lizard found in wooded parts of Australia. It is one of a group of species known commonly as bearded dragons. Other common names for this species include Jew lizard and frilly lizard, the latter being a confusion between this and another dragon, the frill-necked lizard. This species was originally described in 1829 by Georges Cuvier, who named it Amphibolurus barbatus.
The Australian water dragon, which includes the eastern water dragon and the Gippsland water dragon subspecies, is an arboreal agamid species native to eastern Australia from Victoria northwards to Queensland. There may be a small introduced population on the south-east coast of South Australia. The Gippsland Water Dragon is generally the more southern of the two subspecies and the more cold adapted and heat sensitive. Visually distinguishing the Gippsland Water Dragon from the Eastern Water Dragon is relatively easy, as long as their skin is reasonably clean and not stained from the water, as identification of the two subspecies depends largely on observable differences in colours and patterns.
Physignathus cocincinus is a species of agamid lizard native to southern China and mainland Southeast Asia. It is commonly known as the Chinese water dragon, Indochinese water dragon, Asian water dragon, Thai water dragon, or green water dragon.
Rankin's dragon is a species of Australian agamid lizard. It may also be called the pygmy bearded dragon and the black-soiled bearded dragon.
Pogona minor is a species of agamid lizard from a group commonly known as bearded dragons, and is found on the southwest coast and interior of Western Australia. This taxonomic name includes the widespread type known as western bearded dragon, Pogona minor minor which is widespread across West Australia between the Pilbara and the south coast, and the subspecies, Pogona minor minima is confined to the Wallabi Group of islands. There is another subspecies, Pogona minor mitchelli which lives in tropical woodlands of the Kimberley area of Western Australia.
Agamid adenovirus, also called Bearded dragon adenovirus 1, is a type of virus in the Adenoviridae family. The virus is widespread in captive populations of Pogona vitticeps, known commonly as the central bearded dragon, in the United States. Other countries with confirmed cases are Australia, Japan, Germany, The Netherlands, Belgium, the UK, and El Salvador. It is often discovered in association with other infections, and causes increased juvenile mortality and adult deaths.
The jacky dragon is a type of lizard native to south-eastern Australia. Other common names include blood-sucker, stonewalker, and tree dragon. It was one of the first Australian reptiles to be named by Europeans, originally described by English zoologist George Shaw in Surgeon-General John White's Journal of a Voyage to New South Wales, published in London in 1790. The lizard is well-known for its bright yellow mouth and well-developed vertebral crest, as well as the temperature-dependent sex determination of its offspring.
Iguana is a genus of herbivorous lizards that are native to tropical areas of Mexico, Central America, South America, and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena. Three species are placed in the genus: the green iguana, which is widespread throughout its range and a popular pet, the marine iguana and the Lesser Antillean iguana, which is native to the Lesser Antilles. Genetic analysis indicates that the green iguana may comprise a complex of multiple species, some of which have been recently described, but the Reptile Database considers all of these as subspecies of the green iguana.
Ctenophorus maculosus, commonly known as the Lake Eyre dragon or salt-lake ground-dragon, is a species of agamid lizard endemic to South Australia. C. maculosus mainly inhabits the edges of salt lakes in South Australia, from which its common names are derived. It survives in this harsh habitat through adaptive mechanisms to tolerate high temperatures and lack of free water. The female C. maculosus possesses unique male rejection techniques which are currently the focus of further research.
The central netted dragon or central netted ground dragon is a species of agamid lizard occurring in a wide range of arid to semiarid regions of Australia. It is widespread across the continent, commonly found in open, sandy, desert habitats. It is a popular pet and can often be found in zoos.
Ctenophorus pictus, commonly known as the painted ground-dragon or painted dragon, is a species of lizard from the family Agamidae. It is endemic to the drier areas of southern and central Australia.
Sex reversal is a biological process whereby the pathway directed towards the already determined-sex fate is flipped towards the opposite sex, creating a discordance between the primary sex fate and the sex phenotype expressed. The process of sex reversal occurs during embryonic development or before gonad differentiation. In GSD species, sex reversal means that the sexual phenotype is discordant with the genetic/chromosomal sex. In TSD species, sex reversal means that the temperature/conditions that usually trigger the differentiation towards one sexual phenotype are producing the opposite sexual phenotype.
Jennifer Ann Marshall Graves is an Australian geneticist. She is Distinguished Professor within the La Trobe Institute for Molecular Science, La Trobe University, Australia and Professor Emeritus of the Australian National University.
Ctenophorus mckenziei, more commonly known as the dwarf-bicycle dragon, is a species of endemic Australian lizard within the family Agamidae and genus Ctenophorus. Originally identified as the agamid Amphibolurus mckenziei, the lizard had been identified within the regions of Western Australia and South Australia in which it occupied the shrubbery and woodland areas as its habitat. It was subsequently transferred to the genus Ctenophorus along with other Agamid species in which it shared similar morphology and characteristics. The name mckenziei is in reference to Norman Leslie Mckenzie, who was a zoologist and discovered the existence of the lizard. Listed on the IUCN red list page, threats to its population numbers are evaluated as least concern; however, their numbers are threatened by habitat loss, climate change, and feral predators.
Ctenophorus parviceps, commonly known as the Gnaraloo heath dragon or northwestern heath dragon is a species of agamid lizard occurring in pale coastal sands and shell grit with open heaths and beach spinifex, between the North West Cape and Carnarvon, Western Australia and on Bernier Island. The Gnaraloo heath dragon is a lizard that can be found along the coast of Western Australia between Exmouth Gulf and Shark Bay, and is also known as the northwestern heath dragon. It is native to Australia and usually inhabits sandy coastal dunes. The species' longevity is 3–50 years and its population density is extremely low. The Gnaraloo heath dragon is a member of the Agamidae family, which contains 15 genera. The lizard is under the Ctenophorus genus which has up to 33 species. This genus shows the most morphological and ecological diversity out of the three large agamid genera. 83% of the lizards in this genus lack a crest, while 17% possess crests. They are smaller than most agamids but do have relatively large heads. The Gnaraloo heath dragon can be differentiated from related species by a series of spines on the tail's base, a pale-grey brown broad vertebral band along its back, and hour-glass bars extending upwards to meet the pale vertebral band. It is usually 45mm in terms of length, measuring from snout to vent.
The evolution of sex-determining mechanisms, characterized by the evolutionary transition to genetic sex determination or temperature-dependent sex determination from the opposite mechanism, has frequently and readily occurred among multiple taxa across a transitionary continuum.
Western Bearded Dragon, Pogona minor minor
