Jansenii / Oxycephalum

Care Sheet

Condensed Care Sheet

 by Freight Freitas

Habitat and Distribution:

Gonyosoma oxycephala inhabits tropical rainforests and is typically found in lowlands, foothills, mangrove swamps, and in vegetation along riverbanks. Being a predominantly arboreal species this snake is generally found in bushes and trees at elevations up to 750m (Schulz 1996). They are found throughout most of Indonesia, South East Asia, the Philippines, and a few islands off the east coast of India.

Gonyosoma janseni inhabits both low and high elevation rainforests between the elevations of 100-1000m. The black tailed janseni is much more heavy bodied than both the black janseni, and oxycephala, and is believed to live a semi-terrestrial/semi-arboreal lifestyle (Gumprecht, year unknown). The black tailed janseni is found only on the Indonesian island of Sulawesi, and the black janseni is found only on the small Indonesian island of Salayar, which is just off the southern coast of Sulawesi.


Babies and juveniles up to six months of age can be kept in Kritter Keeper cages (18”x12”x7”), 10-20gal aquarium tanks, or similar sized clear Sterlite sweater boxes. Security is of high importance, and therefore a number of secure hide spots, as well as a few plastic plants are necessary to provide a safe haven for younger snakes. Hides can be made from cork bark, or PVC tubing, or simply by cutting access holes into small plastic containers. I generally line the hides, as well as the cage floor with paper towels, as they provide a safe and easy to clean environment, as well as a means to monitor stools for any signs of illness. At six months to one year of age the snakes should be big enough to be moved to a semi-arboreal, or fully arboreal enclosure with dense foliage and lots of climbing branches. There should be hide boxes on the bottom, and top of the enclosure, as well as in the branches to provide maximum security.

Adult Gonyos are generally 5.5-7.5 feet in length, with males generally being smaller than females. Captive bred individuals tend to be much more active and outgoing than w/c Gonyos, and for that reason I suggest a minimum cage size of 36”x18”x36” for adults. I personally have one pair in a 36”x18”x72” cage with grapevine branches, numerous plastic vines and plants, and hide boxes at the bottom, middle, and top of the cage, and the entire cage is utilized. The key is to provide security, space, and freedom of movement to maximize your snake’s quality of life.

Hide boxes can be large plastic shoe boxes or wicker baskets that have access holes cut into them. Humidity boxes, which are simply well ventilated hide boxes with moist sphagnum moss inside are imperative for keeping Gonyos, as they provide moisture, security, and a place for gravid females to lay eggs. Branches made of PVC tubing, grape vine, manzanita, wood dowels, or tree branches that have been weathered, dried, and oven baked, or bleached are all appropriate for climbing. Plastic plants and vines are great for providing security, camouflage, and a semi-naturalistic environment. A large water bowl helps to provide additional humidity, as well as a place to soak, for snakes that wish to do so.


Although Gonyosoma hail from the equatorial region of Indonesia where both day and night temperatures are commonly in the 80’s and 90’s (F), life beneath the shade of the rainforest canopy can be much cooler. All of my Gonyos are kept in a range from 75-85F year round. Daytime temps should reach 80-83F with a cool down at night in the mid to upper 70’s. Overall these snakes appear to be quite tolerant of temperature fluctuations, and can handle temps above 85F for short periods of time, but I strongly suggest minimizing such exposures, especially with babies and juveniles.

Temperatures can be maintained with any number of different reptile heating elements depending on both cage type and keeper preferences (light bulbs, heat pads, ceramic emitters, radiant panels, etc.). I personally use Ultratherm reptile under tank heat pads and white incandescent household light bulbs for a few on my Gonyos that are in rooms that do not heat up above 78-80F during the day. Otherwise, most of my Gonyos are not heated, as they are in rooms that commonly reach into the low-mid 80’s during the day. I particularly prefer heat pads for babies and juveniles, as light bulbs can be very drying to the air, which could promote dehydration, as well as shedding issues.


All of my baby and juvenile c/b Gonyos are fed with one of two different techniques. For the past two years I have been utilizing tease feeding as my primary technique, but have recently incorporated the feeding box method into my repertoire with excellent results. All frozen rodents are soaked in hot water until they are thawed and warmed all the way through.

For the tease feeding method I simply place each individual snake into a small Kritter Keeper cage and proceed to offer the snake an appropriately sized f/t mouse on a set of tongs through the trap door in the lid. Many of the Oxy-jansen hybrids respond very well to this method, and seem to prefer a little action in their food. Occasionally it is necessary to chase the snake with the mouse, while both stroking and striking the snake lightly to promote an aggressive response. The Kritter Keeper cages are perfect for this technique, as they provide a small yet inescapable chamber to work with individuals, where they can easily be kept in close range to their food.

Due to a total lack of feeding response in all baby oxycephala, and some Sulawesi janseni I decided to try feeding them in small, ventilated butter tubs after many weeks of tease and force-feeding. As it turns out, both species responded immediately to this technique, which now cuts down on feeding time. Individual snakes are simply placed in a butter tub with an appropriately sized freshly thawed mouse, and are left for at least 30min to provide time to settle in and consume their meal. If the snakes do not eat within 45min, and are presumably not in shed, I usually revert to the tease feeding technique, as preferences do change from time to time.

The majority of my adults Gonyos are w/c, and with the exception one female janseni that will take food off tongs, the rest prefer their food be left in a small dish right near them. For snakes that are hiding under their towels or newspapers I place the food in a butter tub with a window cut out of the front, so that the towel is tented up around the food where the snake can find it. My oldest captive bred black janseni prefers to be fed off tongs, but occasionally steals a mouse left in the cage for his mate.

With the exception of my female Sulawesi janseni all of my Gonyos are fed mice, and will never need food larger that jumbo mice. All adult female Sulawesi janseni are fed small to medium sized rats, and some consume two rats at a time. This is convenient for pairs that are kept together, as I feed the males mice, and the females rats, which makes for a nice separation of the food that they are used to.


The gestation period for most Gonyo females is approximately 60 days. Eggs are almost always laid in sphagnum moss, and the female should be left alone as much as possible during egg laying to prevent her from laying them in an inappropriate place. Eggs are incubated between 77-80F (78-79F is optimal) on moist perlite. Once eggs begin to expand in size they are placed on a piece of plastic egg crating, which lies on top of the perlite and helps to prevent over expansion and rupture of the eggs shell from internal hydrostatic pressure buildup. At approximately 100 days of incubation the temperatures are dropped to 76-77F and the eggs are loosely wrapped around the outside of the clutch with moist paper towels to help soften the eggshells before hatching. Hatching for oxycephala, black janseni, and oxy-jansen hybrids has been between 106-137 days, and Sulawesi janseni have been between 125-145 days. The incubation and hatching process of Gonyo eggs tends to be extremely perilous, and is outlined in great detail on my website. I strongly advise consulting this information before attempting to incubate eggs.


While captive bred (c/b) Gonyosoma can be considered relatively easy to care for in captivity they should not by any means be considered for beginners. These snakes do not have a reputation for being well mannered, nor particularly predictable. Most of the c/b Gonyos in my collection have far better demeanors than some of my w/c animals, yet they still require respect, patience, and time to adjust to regular handling. I truly believe that experienced keepers that are willing to patiently work with the progeny from my adults will be rewarded with captives that can be handled, are well adjusted, and in many instances are docile far beyond any former Gonyo keepers wildest dreams. With the exception of my first two c/b clutches of janseni, as well as my first c/b hybrid, I have found the majority of my c/b Gonyos to be quite well mannered, and very easy to work with. While these snakes don’t quite have the docile nature of corn snakes and ball pythons, they have proven to be quite manageable in an appropriate captive setting.