The typical position of a Green Tree Python - coiled over a branch with its head resting on the centre coils.
Green Tree Pythons are found on the Indonesian Islands, in Papua New Guinea, Western New Guinea and Australia. Their main habitat is trees, bushes and shrubs found in humid, warm tropical regions.
Green Tree Python juveniles are of various colours and only change to the adult green colour as they mature.
Female Green Tree Python at the NZG's Reptile Park. The female incubates and protects the eggs by wrapping the eggs with her coils and uses tiny muscular contractions to raise the temperature. This is quite unique among reptiles as most reptiles, being cold-blooded, do not stay with their eggs. (Picture: Michael Adams)
The scales around their mouth have thermo-receptive pits which enable them to track down warm-blooded prey. (Picture: Michael Adams)
The Green Tree Python (Morelia viridis) is an arboreal species which spends a great deal of its time in trees, as its common name suggests.
Adult Green Tree Pythons are bright green in colour with a broken vertebral stripe of white or yellow. They may also have blue, white or yellow spots scattered over their body, their colour patterns varying according to their different locations. They can reach lengths of between 1.2 and 2.2 metres and have a slender shape with a prehensile tail enabling them to hold on to and move easily between tree branches.
Juvenile Green Tree Pythons vary in colour from brick red, orange, yellow, to dark brown-black, all in the same clutch. As they mature at between six and eight months old, they change to the adult bright green colour, but some may take up to two years to make the full change to green. It can be an exciting pastime to watch their colour change as each colour pattern is unique to each individual snake.
Behaviour and diet
Green Tree Pythons are solitary and only descend to the ground to hunt or to move between trees. They have a particular way of curling up on tree branches, in a saddle position placing their head on the middle of their coils. This trait and their physical appearance are similar to the Emerald Tree Boa (Corallus caninus) of South America, which causes people to confuse the two, especially when seen outside their natural habitat.
The large head of the species is wider than the body and has thermo-receptive pits in the scales around the mouth which detect relative changes in temperature. These thermo-receptive pits help the snake detect warm-blooded prey when hunting at night when they are most active. Their diet mainly consists of rodents, rabbits and other small mammals and reptiles.
They use their tails as a hunting strategy, attracting prey by wriggling their tail to resemble a worm or small snake to birds and lizards. They grab their prey from a distance. Using their wide jaws and enlarged front teeth to hold on to fast-moving prey, they coil around and suffocate the prey. Another method of capture is by holding onto a branch using their prehensile tail and striking out in an s-shaped position to grab their prey before constricting it.
Reproduction and breeding
Green Tree Pythons are oviparous. Between 20-24 days after mating, the female lays 1-30 viable eggs per clutch in a tree hole or among tree roots on the ground. The female incubates and protects the eggs by wrapping the eggs with her coils and uses tiny muscular contractions to raise the temperature. This is quite unique among reptiles as most reptiles, being cold-blooded, do not stay with their eggs.
After 45-52 days the eggs hatch with independent young snakes. At the age of two years old, they reach sexual maturity. Most mating occurs from August to December. November to February is the period during which they lay their eggs. These snakes can live up to their mid-20s in the wild and up to 35 years in captivity.
Predators and conservation
Predators are mostly birds of prey, but the largest threat to this species is habitat destruction such as logging of forests. In native countries this species is classified as threatened (least concern) by the IUCN, due to exploitation for the skin trade and being hunted. Illegal pet trade is also a major threat to these snakes.
At the NZG
Currently, the Reptile Park has one female Green Tree Python on display that has been in the NZG's reptile collection since 2009. She was confiscated at OR Tambo International Airport after being illegally smuggled into the country. In February 2012, this striking reptile was officially donated to the NZG after the court case had been finalised.
She is 1.4 m in length and is fed a number of small mice or one rat once a week. Zookeepers are careful not to over feed her as this species naturally has a slender body and lives a sedentary lifestyle coiled up on a branch, only being active at night.
This attractive snake is of a manageable adult size as a pet, but is known to be temperamental and have very specific husbandry requirements. Many so-called 'captive bred' Green Tree Pythons are in fact wild caught snakes, illegally smuggled into the country.
By Claire Fordred, Intern, NZG
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