INTELLAGAMA LESUEURII - (GRAY, 1831)
Intellagama lesueurii, unique représentant du genre Intellagama, est une espèce de sauriens de la famille des Agamidae. Il peut être appelé dragon d'eau australien ou agame aquatique.
Distribution
Cette espèce est endémique d'Australie. Elle se rencontre au Queensland, en Nouvelle-Galles du Sud et au Victoria.
Description
Carnivore, le dragon d'eau est un très bon nageur qui peut rester trente minutes sous l'eau. Les femelles pondent de 6 à 20 œufs au moins une fois par an. L'incubation dure de 70 à 120 jours. La taille adulte pour un mâle peut atteindre de 70 à 90 cm, celle de la femelle étant de 60 cm. Le dragon d'eau est le plus gros spécimen de la famille des agames. Il est de couleur sable. Leur ventre présente un rouge brique, particulièrement saisisant chez les mâles. Des bandes noirs parcourent leur corps. Sa queue puissante, prend le 2/3 de son corps. Elle est mobile et peut afliger des coups lorsque le dragon d'eau se sent en danger. Ses yeux orange possède des paupières. Il possède également un "troisième oeuil" l'oeil pariétal situé sur le dessus de la tête. Ses longues pattes sont doté de griffe qui lui permette de grimper aux arbres mais aussi de nager lorsque ce dernier plonge dans les rivières près desquel il habite.
Dismorphie sexuel
Le mâle possède une crète très apparente sur la tête et le dos. Il est aussi plus gros que la femelle qui ne possède pas de crète aussi grosse. Le mâle possède aussi une bande noir marqué proche des yeux ainsi qu'un ventre rouge brique particulièrement facile à remarquer.
Systématique
Cette espèce avait été placée dans le genre Istiurus par Townsend & al., 2011 mais celui-ci avait été créé par Cuvier pour Lacerta amboinensis, elle est donc placée dans le genre Intellagama par Amey, Couper, Shea, 2012. Il est proche du Physignathus cocincinus, qui vit en Asie.
Étymologie
Cette espèce est nommée en l'honneur de Charles Alexandre Lesueur.
Liste des sous-espèces
Selon Reptarium Reptile Database (29 avril 2012)
Intellagama lesueurii howittii (Mccoy, 1884)
Intellagama lesueurii lesueurii (Gray, 1831)
Synonymes
Lophura lesueurii (Gray, 1831)
Istiurus lesueurii (Gray, 1831)
Physignathus lesueurii (Gray, 1831)
Amphibolurus maculiferus (Girard, 1857)
Amphibolurus heterurus (Peters, 1866)
Amphibolurus branchialis (De Vis, 1884)
Physignathus lesueurii howittii (Mccoy, 1884)
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The Australian water dragon (Intellagama lesueurii), which includes the eastern water dragon (Intellagama lesueurii lesueurii) and the Gippsland water dragon (Intellagama lesueurii howittii) 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.
Description
Australian water dragons have long powerful limbs and claws for climbing, a long muscular laterally-compressed tail for swimming, and prominent nuchal and vertebral crests. (A nuchal crest is a central row of spikes at the base of the head. These spikes continue down the spine, getting smaller as they reach the base of the tail). Including their tails, which comprise about two-thirds of their total length, adult females grow to about 60 cm (2 feet) long, and adult males can grow slightly longer than one metre (3 feet) and weigh about 1 kg. Males show bolder colouration and have larger heads than females. Colour is less distinct in juveniles.
Species variation
The Australian water dragon is the only species of the genus Physignathus in Australia. There are two subspecies; Intellagama lesueurii lesueurii (eastern water dragon) and Intellagama lesueurii howitti (Gippsland water dragon). Intellagama lesueurii lesueurii tends towards white, yellow and red on the throat and possesses a dark band behind its eye; Intellagama lesueurii howitti lacks this and instead has dark bands on either side of its throat, which is blotched with yellow, orange, or blue. Both subspecies are light greenish grey in overall colour with black bands running across their back, tail and legs.
Behaviour
Australian water dragons are extremely shy in the wild, but readily adapt to continual human presence in suburban parks and gardens. They are fast runners and strong climbers. When faced with a potential predator, they seek cover in thick vegetation, or drop from an overhanging branch into water. They are able to swim totally submerged, and rest on the bottom of shallow creeks or lakes for up to 90 minutes, to avoid detection. Both males and females display typical agamid behaviour such as basking, arm-waving and head-bobbing. Fast arm-waving signals dominance, while slow arm-waving signals submission. Males are territorial, and in areas of higher population density, males exhibit displays of aggression toward other males including posturing and chasing.
Breeding
Australian water dragons living in cooler Australian climates hibernate over winter. During spring, usually in early October, the female excavates a burrow about 10–15 cm (3.9–5.9 in) deep and lays between 6 and 18 eggs. The nest is usually in sandy or soft soil, in an area open to sun. When the mother has laid the eggs, she backfills the chamber with soil and scatters loose debris over it. Australian water dragons exhibit temperature dependant sex determination; the sex of the hatchlings is determined by the temperature of the nest site. When the young are born they stay near the entrance of the burrow for some time before leaving home. When they finally leave the nest, they tend to group together away from the adult population.
Habitat
As its name suggests, the Australian water dragon is associated with water and is semi-aquatic. It can be found near creeks, rivers, lakes and other water bodies that have basking sites such as overhanging branches or rocks in open or filtered sun. The species is so common in the rainforest section of Brisbane Botanic Gardens, Mount Coot-tha in Queensland that a monument has been built to them there. There are anecdotal reports of a small colony living on the Sixth Creek in the Forest Range area of South Australia, which were probably introduced there during the 1980s by a local reptile enthusiast. This is many hundreds of miles outside their natural range.
Predators, threats and diet
Australian water dragons are prey to snakes, cats, dogs and foxes. Nestlings and smaller juvenile water dragons are vulnerable to predation by kookaburras, currawongs, butcherbirds and other carnivorous birds. They are also prone to becoming road kill due to the attraction of warm bitumen and concrete for basking. The Australian water dragon's diet depends on its size. Juveniles and yearlings tend to feed on small insects such as ants, spiders, crickets, and caterpillars. When they get bigger, so does their prey. An adult diet includes small rodents such as baby mice, although insects are still the most commonly consumed.
Distribution
Cette espèce est endémique d'Australie. Elle se rencontre au Queensland, en Nouvelle-Galles du Sud et au Victoria.
Description
Carnivore, le dragon d'eau est un très bon nageur qui peut rester trente minutes sous l'eau. Les femelles pondent de 6 à 20 œufs au moins une fois par an. L'incubation dure de 70 à 120 jours. La taille adulte pour un mâle peut atteindre de 70 à 90 cm, celle de la femelle étant de 60 cm. Le dragon d'eau est le plus gros spécimen de la famille des agames. Il est de couleur sable. Leur ventre présente un rouge brique, particulièrement saisisant chez les mâles. Des bandes noirs parcourent leur corps. Sa queue puissante, prend le 2/3 de son corps. Elle est mobile et peut afliger des coups lorsque le dragon d'eau se sent en danger. Ses yeux orange possède des paupières. Il possède également un "troisième oeuil" l'oeil pariétal situé sur le dessus de la tête. Ses longues pattes sont doté de griffe qui lui permette de grimper aux arbres mais aussi de nager lorsque ce dernier plonge dans les rivières près desquel il habite.
Dismorphie sexuel
Le mâle possède une crète très apparente sur la tête et le dos. Il est aussi plus gros que la femelle qui ne possède pas de crète aussi grosse. Le mâle possède aussi une bande noir marqué proche des yeux ainsi qu'un ventre rouge brique particulièrement facile à remarquer.
Systématique
Cette espèce avait été placée dans le genre Istiurus par Townsend & al., 2011 mais celui-ci avait été créé par Cuvier pour Lacerta amboinensis, elle est donc placée dans le genre Intellagama par Amey, Couper, Shea, 2012. Il est proche du Physignathus cocincinus, qui vit en Asie.
Étymologie
Cette espèce est nommée en l'honneur de Charles Alexandre Lesueur.
Liste des sous-espèces
Selon Reptarium Reptile Database (29 avril 2012)
Intellagama lesueurii howittii (Mccoy, 1884)
Intellagama lesueurii lesueurii (Gray, 1831)
Synonymes
Lophura lesueurii (Gray, 1831)
Istiurus lesueurii (Gray, 1831)
Physignathus lesueurii (Gray, 1831)
Amphibolurus maculiferus (Girard, 1857)
Amphibolurus heterurus (Peters, 1866)
Amphibolurus branchialis (De Vis, 1884)
Physignathus lesueurii howittii (Mccoy, 1884)
----------------------------------------------
The Australian water dragon (Intellagama lesueurii), which includes the eastern water dragon (Intellagama lesueurii lesueurii) and the Gippsland water dragon (Intellagama lesueurii howittii) 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.
Description
Australian water dragons have long powerful limbs and claws for climbing, a long muscular laterally-compressed tail for swimming, and prominent nuchal and vertebral crests. (A nuchal crest is a central row of spikes at the base of the head. These spikes continue down the spine, getting smaller as they reach the base of the tail). Including their tails, which comprise about two-thirds of their total length, adult females grow to about 60 cm (2 feet) long, and adult males can grow slightly longer than one metre (3 feet) and weigh about 1 kg. Males show bolder colouration and have larger heads than females. Colour is less distinct in juveniles.
Species variation
The Australian water dragon is the only species of the genus Physignathus in Australia. There are two subspecies; Intellagama lesueurii lesueurii (eastern water dragon) and Intellagama lesueurii howitti (Gippsland water dragon). Intellagama lesueurii lesueurii tends towards white, yellow and red on the throat and possesses a dark band behind its eye; Intellagama lesueurii howitti lacks this and instead has dark bands on either side of its throat, which is blotched with yellow, orange, or blue. Both subspecies are light greenish grey in overall colour with black bands running across their back, tail and legs.
Behaviour
Australian water dragons are extremely shy in the wild, but readily adapt to continual human presence in suburban parks and gardens. They are fast runners and strong climbers. When faced with a potential predator, they seek cover in thick vegetation, or drop from an overhanging branch into water. They are able to swim totally submerged, and rest on the bottom of shallow creeks or lakes for up to 90 minutes, to avoid detection. Both males and females display typical agamid behaviour such as basking, arm-waving and head-bobbing. Fast arm-waving signals dominance, while slow arm-waving signals submission. Males are territorial, and in areas of higher population density, males exhibit displays of aggression toward other males including posturing and chasing.
Breeding
Australian water dragons living in cooler Australian climates hibernate over winter. During spring, usually in early October, the female excavates a burrow about 10–15 cm (3.9–5.9 in) deep and lays between 6 and 18 eggs. The nest is usually in sandy or soft soil, in an area open to sun. When the mother has laid the eggs, she backfills the chamber with soil and scatters loose debris over it. Australian water dragons exhibit temperature dependant sex determination; the sex of the hatchlings is determined by the temperature of the nest site. When the young are born they stay near the entrance of the burrow for some time before leaving home. When they finally leave the nest, they tend to group together away from the adult population.
Habitat
As its name suggests, the Australian water dragon is associated with water and is semi-aquatic. It can be found near creeks, rivers, lakes and other water bodies that have basking sites such as overhanging branches or rocks in open or filtered sun. The species is so common in the rainforest section of Brisbane Botanic Gardens, Mount Coot-tha in Queensland that a monument has been built to them there. There are anecdotal reports of a small colony living on the Sixth Creek in the Forest Range area of South Australia, which were probably introduced there during the 1980s by a local reptile enthusiast. This is many hundreds of miles outside their natural range.
Predators, threats and diet
Australian water dragons are prey to snakes, cats, dogs and foxes. Nestlings and smaller juvenile water dragons are vulnerable to predation by kookaburras, currawongs, butcherbirds and other carnivorous birds. They are also prone to becoming road kill due to the attraction of warm bitumen and concrete for basking. The Australian water dragon's diet depends on its size. Juveniles and yearlings tend to feed on small insects such as ants, spiders, crickets, and caterpillars. When they get bigger, so does their prey. An adult diet includes small rodents such as baby mice, although insects are still the most commonly consumed.