The genus Gonyosoma includes a group of arboreal rat snakes native to Southeast Asia, known for their vibrant coloration, slender build, and highly alert behavior. These snakes are often associated with species such as the red-tailed green ratsnake (Gonyosoma oxycephalum), one of the most recognizable arboreal colubrids in the region.
Unlike heavier-bodied snakes, Gonyosoma species are highly active and visually oriented, moving through branches with speed and precision. Their behavior reflects a true arboreal predator, making them a unique group of snakes for keepers interested in active, display-oriented species.
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🥈 QUICK FACTS
Quick Facts – Gonyosoma (Rat Snakes)
• Scientific Name: Gonyosoma spp.
• Common Name: Red-tailed Green Ratsnake
• Origin: Southeast Asia
• Size: 5–7+ feet (species dependent)
• Behavior: Arboreal, diurnal, highly alert
• Diet: Rodents, birds
NATURAL HISTORY
Here is another snake that was largely ignored by the masses pretty much the majority of my life involved with reptiles.
The common name of this snake is the red-tail green ratsnake and they occur in Myanmar, Thailand, Malaysia, Singapore, Indonesia and also the Philippines. There are some individuals that are silver, yellow and mixes of both but these seem to occur in Indonesia and the Philippines and the other localities are generally the standard color scheme. These snakes are very arboreal and seem to often times share habitat with the Mangrove Snakes being in trees and over rivers and streams. While these snakes can retreat into the water, they are more prone to climbing to evade threats or predators. They are diurnal which means they are active during the daytime and they feed on birds, eggs and some mammals in the wild. Young tend to feed on lizards and frogs and this is probably because they have to grow into their prey. When threatened they will inflate the forward portion of their bodies to appear more imposing but will bite if provoked….they are not venomous but the physical bites of large adults does not feel good.
CAPTIVE CARE/ACCLIMATION
The history of this species in the hobby is mostly represented by wild-caught animals. They often arrive stressed, dehydrated, with nose rubs and internal parasites. If all of these issues can be addressed and corrected before they turn into comlicated issues, they do very well in captivity. Many of the same things apply as with the Ptyas genus with the same things mentioned in those masterclass videos we have done. They have the good eyesight, are easily agitated or stressed by visual cues so we prefer to use hideboxes, branches, good cover and little to no interaction. While we will try to offer live rat pups as first meals, f/t chicks can also be readily accepted. Once these guys are acclimated, they usually have no issues with taking f/t rodents or birds. These snakes do well with higher humidity which will remedy any dry shed issues and direct spraying or misting usually prompts drinking so I recommend you start this from the beginning and continue as a regular practice. Treating wild caught animals with flagyl and panacur is highly recommended in first meals. We keep these with a warm spot in the mid-upper 80’s.
BREEDING
Gonyosoma will breed readily in captivity if your breeding adults are healthy and conditioned for it. There does not seem to be any cannibalism in this species so you can either palpate for follicles or pair intermittently. These will double clutch and will breed year round. Clutches number around 6-8 on average and eggs are good size.
ESTABLISHING BABIES
One thing that I experienced in this species is that they will lay their eggs off the ground in branches if you provide somewhere for them to do so. I have had females also lay clutches on the ground like other snakes but it was interesting for me to see eggs laid in branches. We incubate these eggs in the low 80’s and they will take approximately 115 days. As the date gets close, I watch the eggs for signs of a pip and as soon as I see it happen I will manually pip all the eggs. These eggs can be very thick so I like to assist with a small incision just to help things along. They will sit in the eggs for a couple of days most of the time breathing air and absorbing their yolk sac…they will come out on their own when ready. Babies can be a little tricky with these guys and I have had decent results with live pinky mice and stubborn babies sometimes will start feeding on live fuzzy mice which you would normally think are too big for these babies to feed on but sometimes it triggers feeding for some reason. Other more difficult animals may require scenting with lizard or bird, offered actual lizards or even assist fed if things become more challening.
FINAL THOUGHTS
Gonyosoma species are highly active, visually driven snakes that differ significantly from more sedentary or heavy-bodied species. These snakes are constantly aware of their surroundings and are quick to react to movement.
In captivity, they spend much of their time elevated, utilizing branches and vertical space. Their movement is fluid and precise, reflecting their adaptation to arboreal environments.
When disturbed, Gonyosoma may display defensive behavior such as rapid movement, striking, or body inflation. This is especially common in younger or newly established animals. With time and consistent handling, many individuals become more manageable, though they typically retain a high level of alertness. It is nice for me to see the strong interest in Gonyosoma for both wild-caught adults and also captive bred babies. While we are no longer breeding red-tail green rats in the states, we do have some adults set up for breeding in our facility in Malaysia and we should have both wc and cb coming in our June shipments. We may have Gonyosoma janseni coming from Indonesia as well.
👉 For additional species and care information, explore our other care sheets covering a range of Southeast Asian pythons and colubrids, including arboreal species, large active rat snakes, and other advanced husbandry subjects.