Animal Diversity Web

Ge­o­graphic Range

Green tree pythons (More­lia viridis) are found only within the Aus­tralian re­gion. These pythons are found through­out New Guinea and sur­round­ing is­lands with the ex­cep­tion of the Bis­marck Arch­i­pel­ago. They also occur in the Cape York Penin­sula of Queens­land, Aus­tralia. The ju­ve­nile yel­low morph of More­lia viridis is found through­out this range, while the ju­ve­nile red morph is only found in parts of New Guinea. (Rawl­ings and Don­nel­lan, 2003; Wil­son and Hein­sohn, 2007; Wil­son, et al., 2007)

• Biogeographic Regions
• australian
  • native

Habi­tat

More­lia viridis is a trop­i­cal rain­for­est species in­hab­it­ing mainly low mon­tane and low­land rain­for­est habi­tat rang­ing from 0 to 2000 m. They may also be found in sec­ondary forests and areas of re-growth. When young, green tree pythons re­strict them­selves to canopy gaps or along the edges of for­est where light can eas­ily reach the ground. As adults, they are gen­er­ally found in closed-canopy rain­forests. (Rawl­ings and Don­nel­lan, 2003; Wil­son, et al., 2006a; Wil­son, et al., 2006b)

• Habitat Regions
• tropical
• terrestrial

• Terrestrial Biomes
• rainforest

• Range elevation

  0 to 2000 m

  0.00 to 6561.68 ft

Phys­i­cal De­scrip­tion

More­lia viridis reaches an av­er­age length of 1.5 me­ters; with the largest recorded spec­i­men being 2.2 me­ters in length. The head scales are ir­reg­u­lar and small and their labial heat-sens­ing pits are only found within the scales on the upper lip. Their tail is pre­hen­sile, help­ing them to climb. Green tree pythons do not ap­pear to ex­hibit sex­ual di­mor­phism in adult­hood; how­ever, at smaller lengths ju­ve­nile fe­males have both wider and longer heads when com­pared to males of sim­i­lar size. (Bartlett, 1995; Torr, 2000; Wil­son, et al., 2006b)

As adults, green tree pythons dis­play a bril­liant green over most of their bod­ies. On the dor­sal sur­face there us a dis­tinct ridge of scales that is usu­ally white to yel­low in col­oration and forms a bro­ken or con­tin­u­ous line down the length of the body. Ven­trally, the scales are gen­er­ally yel­low. How­ever, some in­di­vid­u­als may have ven­tral scales of a more dull yel­low to white and have a blue tinge scat­tered on the scales of the dor­sal sur­face. (Bartlett, 1995; Torr, 2000)

Ju­ve­nile green tree pythons may be ei­ther bright yel­low or brick-red. Along the dor­sal sur­face, they ex­hibit a se­ries of white blotches edged in black or brown. These blotches may be ei­ther sym­met­ri­cal or ran­domly placed on both sides of the body. In both color morphs, a white streak edged in black runs from the nos­tril through the eye and to the back of the head. The dis­tri­b­u­tions of these two color morphs seem to be dif­fer­ent, al­though it is not un­com­mon for both color morphs to be in the same clutch in cap­tive sit­u­a­tions. In the wild, only the yel­low morph has been recorded in Aus­tralia. Al­though poorly stud­ied, the red morph seems to be re­stricted to the is­land of Biak and the Baliem Val­ley in Papua, In­done­sia and in the Sepik basin of Papua New Guinea. In some pop­u­la­tions of More­lia viridis, the adults may not com­pletely change to green and will main­tain some of their ju­ve­nile yel­low col­oration. (Mc­Dow­ell, 1975; Torr, 2000; Wil­son, 2007; Wil­son, et al., 2007; Wil­son, et al., 2006b)

• Other Physical Features
• heterothermic

• Sexual Dimorphism
• sexes alike

• Range length

  2.2 (high) mm

  0.09 (high) in

• Average length

  1.5 mm

  0.06 in

De­vel­op­ment

Green tree pythons are about 30.5 cm in length when they hatch. At this stage, they are ei­ther bright yel­low or brick-red. They must un­dergo on­to­ge­netic color change in order to ac­quire their adult green col­oration. This gen­er­ally oc­curs be­tween six months and a year of age, but does not co­in­cide with sex­ual ma­tu­rity, as might be ex­pected. In­stead, at this age, the ju­ve­nile python will be be­tween 53 and 59 cm in length and is large enough to change its for­ag­ing be­hav­ior and habi­tat. Each color stage ap­pears to pro­vide cam­ou­flage suit­able to its im­me­di­ate habi­tat. As a young snake, the red or yel­low color blends in bet­ter in for­est gaps or edges, where smaller an­i­mals re­side. Adult green col­oration blends in best in the closed canopy of the rain­for­est, where larger prey live. The change does not gen­er­ally as­so­ci­ate with a shed­ding event and may hap­pen as quickly as overnight or take as long as sev­eral months. Red in­di­vid­u­als of More­lia viridis take longer to un­dergo this change as they first lighten to a yel­low color, sev­eral patches at a time, and then sub­se­quently change to their adult green color. (Bartlett, 1995; Ross and Marzec, 1990; Torr, 2000; Wil­son, et al., 2007; Wil­son, et al., 2006b)

Re­pro­duc­tion

Re­pro­duc­tion in the wild has never been re­ported for More­lia viridis and the mat­ing sys­tem is un­known. (Ross and Marzec, 1990; Wil­son, 2007)

A ma­jor­ity of avail­able in­for­ma­tion on re­pro­duc­tion has been pub­lished from hob­by­ists in the cap­tive pet trade, though some spec­u­la­tion can be made from sci­en­tific re­search in situ. The lack of sex­ual di­mor­phism and the pres­ence of an equal sex-ra­tio in green tree pythons sug­gests that males do not com­pete phys­i­cally in male-male com­bat in order to mate with fe­males. In­stead, a male’s abil­ity to ob­tain a mate may be pri­mar­ily de­ter­mined by how well they can search out a fe­male. This is ap­par­ently why males do not main­tain sta­ble home ranges. Males ap­pear to stop feed­ing when search­ing for a mate. Once the male has found a sex­u­ally ma­ture fe­male he will stim­u­late her with his cloa­cal spurs (ves­ti­gial dig­its) to make her re­cep­tive for mat­ing. (Ross and Marzec, 1990; Torr, 2000; Wil­son, et al., 2006a; Wil­son, et al., 2006b)

Green tree pythons have a highly sea­sonal breed­ing cycle; how­ever, few off­spring are en­coun­tered in any one year sug­gest­ing that these pythons do not breed every year. The ac­tual mat­ing sea­son in the wild is not known, though in cap­tiv­ity it can range widely from Au­gust to Jan­u­ary and tends to be stim­u­lated by the onset of low pres­sure fronts and storms. As is true for all pythons, More­lia viridis is oviparous. In the wild, fe­males lay their clutches in Oc­to­ber and then brood them for ap­prox­i­mately 50 days, but this can range from 39 to 60 days. Hatch­ing takes place in No­vem­ber, cor­re­spond­ing to the start of the wet sea­son in the Aus­tralian re­gion. At hatch­ing, green tree pythons are ap­prox­i­mately 30.5 cm in length and can be ei­ther brick-red or bright yel­low. Reach­ing sex­ual ma­tu­rity can take sev­eral years and can be long after they have changed into their adult green col­oration. In males, sex­ual ma­tu­rity re­port­edly oc­curs after 2.4 years and in fe­males, sex­ual ma­tu­rity oc­curs after 3.6 years. (Bartlett, 1995; O'Shea, 2007; Ross and Marzec, 1990; Wil­son, et al., 2006b)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• sexual
• oviparous

• Breeding interval

  Green tree pythons have a highly seasonal breeding cycle; however, few offspring are encountered in any one year suggesting that these pythons do not breed every year.

• Breeding season

  Mating has not been recorded for green tree pythons in the wild. It can be inferred that egg laying occurs in October, as hatching takes place in November.

• Range number of offspring

  6 to 32

• Range gestation period

  39 to 65 days

• Average gestation period

  50 days

• Average age at sexual or reproductive maturity (female)

  3.6 years

• Average age at sexual or reproductive maturity (male)

  2.4 years

Green tree pythons ex­hibit some ma­ter­nal care by brood­ing their eggs be­fore they hatch. In cap­tiv­ity, fe­males have been ob­served coil­ing around their clutches. They will often shiver and con­tract their coils, ap­par­ently to pro­duce meta­bolic heat and thus main­tain an ideal brood­ing tem­per­a­ture, which ranges from 84 to 88 de­grees Fahren­heit. Once the young hatch, how­ever, there does not ap­pear to be any parental care. (Ross and Marzec, 1990; Torr, 2000)

• Parental Investment
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female

Lifes­pan/Longevity

In­for­ma­tion on ac­tual ages in the wild is lim­ited for More­lia viridis. How­ever, a pop­u­la­tion at Iron Range on Cape York Penin­sula, Aus­tralia had an av­er­age age of 3.4 years. It is pre­dicted that these pythons could live for at least 15 years, with a max­i­mum age of 19. Green tree pythons in cap­tiv­ity have lived only slightly longer with the record age set at 20 years old. (Wil­son and Hein­sohn, 2007; Wil­son, et al., 2006b)

• Range lifespan
  Status: wild

  12 (high) years

• Average lifespan
  Status: wild

  3.4 years

• Range lifespan
  Status: captivity

  20 (high) years

• Typical lifespan
  Status: wild

  15 to 19 years

• Average lifespan
  Status: captivity

  20.6 years

  AnAge

Be­hav­ior

More­lia viridis is the most ar­bo­real python species, though it may be found on the ground oc­ca­sion­ally. As adults, they are noc­tur­nal and hunt pri­mar­ily at night when larger noc­tur­nal prey are ac­tive as well. Be­fore on­to­ge­netic color change, green tree pythons are di­ur­nal, co­in­cid­ing with smaller prey that are ac­tive dur­ing the day. (Wil­son, et al., 2006b)

Green tree pythons ex­hibit two dif­fer­ent pos­tures de­pend­ing on whether they are rest­ing or hunt­ing. In a rest­ing pos­ture, the snake’s body is coiled up and hang­ing on a hor­i­zon­tal branch or vine. This is how the an­i­mal is gen­er­ally de­picted in pho­tographs. When rest­ing, green tree pythons often take shel­ter in tree hol­lows or epi­phytic veg­e­ta­tion. In a hunt­ing pos­ture, the an­te­rior end of the body is ex­tended from the branch and folded like an ac­cor­dion, ready to strike at the ground or at a lower branch, while the pos­te­rior end is wrapped se­curely around its perch. Green tree pythons typ­i­cally change be­tween these pos­tures only dur­ing dusk or dawn to avoid giv­ing away their lo­ca­tion. (Cog­ger, 1983; Torr, 2000; Wil­son, 2007)

Ac­tiv­ity rates are dif­fer­ent be­tween the sexes. Fe­males are more likely to change their po­si­tion from day to day than are males. They are also more ac­tive and move fur­ther in the month of Feb­ru­ary. In con­trast, males are more ac­tive in Jan­u­ary and March. How­ever, from about April until the start of the next breed­ing sea­son in Oc­to­ber, both sexes are seden­tary and in­ac­tive. When mov­ing, dis­tances trav­eled by adult snakes are equal to the dis­tances trav­eled by ju­ve­niles, re­gard­less of their com­par­a­tively smaller size. (Wil­son, et al., 2006a; Wil­son, et al., 2006b)

• Key Behaviors
• arboreal
• diurnal
• nocturnal
• sedentary
• solitary

• Average territory size

  62100 m^2

Home Range

Only fe­male green tree pythons have dis­tinct home ranges. Though it varies by the length of the snake, the av­er­age size of this range is 6.21 hectares. Nei­ther adult males nor ju­ve­niles have dis­tinct home ranges; males adopt a mate-search­ing strat­egy, while ju­ve­niles pre­sum­ably dis­perse from the nest. Fe­males are not ter­ri­to­r­ial as they may share a large por­tion of their home range with other fe­males as well as with roam­ing males and ju­ve­niles. (Wil­son, et al., 2006a; Wil­son, et al., 2006b)

Com­mu­ni­ca­tion and Per­cep­tion

Green tree pythons are soli­tary snakes, so the ma­jor­ity of com­mu­ni­ca­tion is in­ter­spe­cific. They use their labial pits as well as sight when search­ing for prey. Labial pits allow for in­frared imag­ing, which is par­tic­u­larly im­por­tant given their noc­tur­nal habits as adults. Labial pits may also serve to help these snakes find suit­able am­bush and ther­moreg­u­la­tion sites as well as help them avoid pos­si­ble preda­tors. When find­ing po­ten­tial mates, green tree pythons most likely use chem­i­cal pheromones as op­posed to vi­sual cues. (Wil­son, 2006; Wil­son, 2007; Wil­son, et al., 2006b)

• Communication Channels
• chemical

• Other Communication Modes
• pheromones

• Perception Channels
• visual
• infrared/heat
• tactile
• vibrations
• chemical

Food Habits

As with all other snake species, More­lia viridis is ex­clu­sively car­niv­o­rous. They are ob­lig­ate am­bush preda­tors feed­ing on small rep­tiles, in­ver­te­brates, mam­mals, and birds through­out their lives. There is a dis­tinct change in their feed­ing habits that co­in­cides with the color change from red or yel­low into their adult green col­oration. Once they hatch out of the egg, their main prey con­sists of Car­lia longipes and di­ur­nal in­ver­te­brates. In cap­tiv­ity, how­ever, hatch­lings have been known to can­ni­bal­ize nest mates. Ju­ve­nile green tree pythons eat mostly small an­i­mals, such as lizards. As they grow in size, their gape gets larger and they are sub­se­quently able to in­gest larger ver­te­brate prey. In adult­hood, green tree pythons eat mainly mam­mals and birds. For ex­am­ple, the main prey species for pop­u­la­tions in the Iron Range of Cape York Penin­sula, Aus­tralia are the ro­dents Rat­tus leu­co­pus and Melomys capen­sis. Since they are am­bush preda­tors, green tree pythons do not move often and may use the same am­bush site for up to 14 days, wait­ing for ac­tively for­ag­ing prey to come within range. Cau­dal lur­ing has been ob­served, es­pe­cially in ju­ve­niles, where the tip of the tail is used to at­tract small an­i­mals. While an am­bush feed­ing strat­egy does not yield prey often, green tree pythons have ef­fi­cient di­ges­tive sys­tems and do not re­quire fre­quent feed­ing. (Cog­ger, 1983; O'Shea, 2007; Ross and Marzec, 1990; Torr, 2000; Wil­son, 2007; Wil­son, et al., 2007; Wil­son, et al., 2006a; Wil­son, et al., 2006b)

• Primary Diet
• carnivore
  • eats terrestrial vertebrates

• Animal Foods
• birds
• mammals
• reptiles
• insects

Pre­da­tion

The main preda­tors of green tree pythons are ru­fous owls, black butcher­birds, and an as­sort­ment of di­ur­nal rap­tors. Other preda­tors in­clude man­grove mon­i­tors, din­goes, and New Guinea quolls. (Wil­son, 2006; Wil­son, 2007; Wil­son, et al., 2007)

The main anti-preda­tor strat­egy of More­lia viridis is to avoid pre­da­tion using its cryp­tic col­oration and hid­ing be­hav­ior, which is es­pe­cially ef­fec­tive against its vi­su­ally-ori­ented avian preda­tors. As ju­ve­niles, the yel­low col­oration blends in well in the rain­for­est edges where they are found. In ju­ve­niles with brick-red color, their col­oration cam­ou­flages them bet­ter than yel­low morphs against non-leafy back­grounds. It should be noted that in other species, red and yel­low are typ­i­cal warn­ing col­ors to preda­tors, how­ever, green tree pythons do not ap­pear to have any chem­i­cal de­fenses nor is there a dan­ger­ous model that they would be mim­ic­k­ing. As adults, green tree pythons in­habit the canopy of the for­est and their bril­liant green col­oration blends in much bet­ter than ei­ther red or yel­low. This sug­gests an adap­tive basis for on­to­ge­netic color change in this species. (Wil­son, 2006; Wil­son, et al., 2007; Wil­son, et al., 2006b)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • black butcherbirds (Cracticus quoyi)
  • grey goshawks (Accipiter novaehollandiae)
  • long-tailed buzzards (Henicopernis longicauda)
  • Doria's hawks (Megatriorchis doriae)
  • Meyer's hawks (Accipiter meyerianus)
  • New Guinea harpy eagles (Harpiopsis novaeguineae)
  • grey-headed goshawks (Accipiter poliocephalus)
  • black-mantled goshawks (Accipiter melanochlamys)
  • chestnut-shouldered goshawks (Accipiter buergersi)
  • rufous owls (Ninox rufa)
  • mangrove monitors (Varanus indicus)
  • dingoes (Canis lupus dingo)
  • New Guinea quolls (Dasyurus albopunctatus)

Ecosys­tem Roles

As preda­tors, green tree pythons help to re­duce pop­u­la­tions of sev­eral prey species of ro­dents, birds, and lizards. They also serve as food for sev­eral avian and ter­res­trial preda­tors. (Wil­son, 2006)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

The bright red or yel­low col­oration of green tree pythons as ju­ve­niles and bril­liant green col­oration as adults has made them one of the most pop­u­lar species of snake kept in the pet in­dus­try today. For this rea­son, In­done­sia cap­tively breeds More­lia viridis for ex­port into the cap­tive pet trade each year. How­ever, even with cap­tive breed­ing, wild pop­u­la­tions are still under strain be­cause a small num­ber of snakes are cap­tured il­le­gally each year and en­tered into the trade. Green tree pythons are also hunted by the in­dige­nous peo­ples of New Guinea for food. (Wil­son, et al., 2006b)

• Positive Impacts
• pet trade
• food

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

As with most an­i­mals, green tree pythons may bite in self-de­fense. How­ever, there are no known ad­verse ef­fects of this species on hu­mans. (Bartlett, 1995)

Con­ser­va­tion Sta­tus

The sta­tus of the More­lia viridis is un­de­ter­mined as it is not listed on the IUCN Red List or CITES. How­ever, pop­u­la­tions may be vul­ner­a­ble to har­vest for the cap­tive pet trade. A ma­jor­ity of the pet trade for the United States and Eu­rope is sup­plied by pop­u­la­tions in Irian Jaya, al­though there has been re­cent suc­cess in breed­ing in­di­vid­u­als in cap­tiv­ity. In Aus­tralia, it is il­le­gal to col­lect green tree pythons or im­port in­di­vid­u­als that orig­i­nated in New Guinea. Aside from the pet trade, these pythons are also vul­ner­a­ble to habi­tat degra­da­tion through log­ging and slash and burn agri­cul­ture. Nev­er­the­less, until their num­bers can be ac­cu­rately counted, it may be im­pos­si­ble to de­ter­mine the sta­tus of this species in the wild. (Bartlett, 1995; Rawl­ings and Don­nel­lan, 2003; Wil­son, et al., 2006b)

• IUCN Red List

  No special status
  More information

• IUCN Red List

  No special status
  More information

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Other Com­ments

Green tree pythons were once known by the name Chon­dropy­thon viridis and was placed in its own genus. When sci­en­tists no­ticed the sim­i­lar­i­ties with Aus­tralian and New Guinea car­pet pythons, it was placed in the genus More­lia and given the sci­en­tific name More­lia viridis. In the pet trade, how­ever, green tree pythons still go by the nick­name “chon­dro” and this is un­likely to change soon. (Bartlett, 1995; Ross and Marzec, 1990)

There can be con­sid­er­able vari­a­tion in color and pat­tern­ing in green tree pythons. Be­cause of this, some her­petol­o­gists and many hob­by­ists in the pet trade sep­a­rate the species into vari­ants or races. These in­clude the Aru, Sorong, Biak, and Yapen. While these races aren’t rec­og­nized cur­rently, ad­di­tional re­search may sug­gest these vari­a­tions war­rant sub­species or species sta­tus. (O'Shea, 2007)

Green tree pythons are often men­tioned in dis­cus­sions of con­ver­gent evo­lu­tion in rep­tiles. This is be­cause More­lia viridis shares sim­i­lar ecol­ogy and mor­phol­ogy with emer­ald tree boas, de­spite their rel­a­tively dis­tant com­mon an­ces­try. Both species live in trop­i­cal rain for­est habi­tats and are ar­bo­real am­bush preda­tors. They ex­hibit sim­i­lar diets and switch from a di­ur­nal lifestyle as ju­ve­niles to a noc­tur­nal lifestyle as adults. Green tree pythons and emer­ald tree boas also share the same rest­ing and hunt­ing pos­tures and, re­mark­ably, both species un­dergo on­to­ge­netic color change from a red or yel­low ju­ve­nile to a bright green adult. This can make it quite dif­fi­cult to dif­fer­en­ti­ate be­tween the two species. One of the few ways to tell them apart is the po­si­tion of the labial pits. In emer­ald tree boas, the pits are on the upper and lower lip. Green tree pythons only have labial pits on the upper lip sur­face. Emer­ald tree boas are found in the trop­i­cal rain­forests of South Amer­ica. (Bartlett, 1995; Torr, 2000; Wil­son and Hein­sohn, 2007; Wil­son, et al., 2006b)

Con­trib­u­tors

Michael Hill­man (au­thor), Michi­gan State Uni­ver­sity, James Hard­ing (ed­i­tor, in­struc­tor), Michi­gan State Uni­ver­sity, Tanya Dewey (ed­i­tor), An­i­mal Di­ver­sity Web.

Ref­er­ences

Bartlett, R. 1995. Pop­u­lar Pythons and Boas: Com­plete guide for own­ers of larger snake species. Mis­sion Viejo, Cal­i­for­nia: Bowtie Press.

Cog­ger, H. 1983. Rep­tiles and Am­phib­ians of Aus­tralia. Sani­bel, Florida: Ralph Cur­tis Books.

Mc­Dow­ell, S. 1975. A Cat­a­logue of the Snakes of New Guinea and the Solomons, with Spe­cial Ref­er­ence to Those in the Ber­nice P. Bishop Mu­seum. Part II. Anil­ioidea and Python­i­nae. Jour­nal of Her­petol­ogy, 9/1: 1-79.

O'Shea, M. 2007. Boas and Pythons of the World. Prince­ton, New Jer­sey: Prince­ton Uni­ver­sity Press.

Rawl­ings, L., S. Don­nel­lan. 2003. Phy­lo­geo­graphic analy­sis of the green python, More­lia viridis, re­veals cryp­tic di­ver­sity. Mol­e­c­u­lar Phy­lo­ge­net­ics and Evo­lu­tion, 27: 36-44.

Ross, R., G. Marzec. 1990. The Re­pro­duc­tive Hus­bandry of Pythons and Boas. Des Moines, Iowa: Gar­ner Print­ing, Inc..

Torr, G. 2000. Pythons of Aus­tralia: A Nat­ural His­tory. Mal­abar, Florida: Krieger Pub­lish­ing Com­pany.

Wil­son, D. 2007. For­ag­ing ecol­ogy and diet of an am­bush preda­tor: the green python More­lia viridis. Pp. 141-150 in R Hen­der­son, R Pow­ell, eds. Bi­ol­ogy of the Boas and Pythons. Eagle Moun­tain, Utah: Eagle Moun­tain Pub­lish­ing.

Wil­son, D. 2006. On green tree pythons: The ecol­ogy and con­ser­va­tion of More­lia viridis - PhD The­sis. Aus­trail­ian Na­tional Uni­ver­sity, 1: 1-127.

Wil­son, D., R. Hein­sohn. 2007. Ge­o­graphic range, pop­u­la­tion struc­ture and con­ser­va­tion sta­tus of the green python (More­lia viridis), a pop­u­lar snake in the cap­tive pet trade. Aus­tralian Jour­nal of Zo­ol­ogy, 55: 147-154.

Wil­son, D., R. Hein­sohn, J. Endler. 2007. The adap­tive sig­nif­i­cance of on­to­ge­netic colour change in a trop­i­cal python. Bi­ol­ogy Let­ters, 3: 40-43.

Wil­son, D., R. Hein­sohn, S. Legge. 2006. Age- and sex-re­lated dif­fer­ences in the spa­tial ecol­ogy of a dichro­matic trop­i­cal python (More­lia viridis). Aus­tralian Ecol­ogy, 31: 577-587.

Wil­son, D., R. Hein­sohn, J. Wood. 2006. Life-his­tory traits and on­to­ge­netic colour change in an ar­bo­real trop­i­cal python, More­lia viridis. Jour­nal of Zo­ol­ogy, 270: 399–407.