Captive Husbandry of Spilotes sulphureus

by Roy Arthur Blodgett

Disclaimer

It is important to begin by stating that what follows is largely a work of opinion, deeply informed by the author’s own experiences and sometimes by those of other keepers who have been willing and generous enough to share their successes and failures. As with all endeavors, there are many ways of achieving success working with animals in captivity - and just as many ways of determining what qualifies as success. I don’t claim to know the best way, and want to make it clear that I have no intention of offering the only way. I aim simply to offer what I have observed and what has worked for me, with the driving intention of demystifying how to give these animals the quality of care and attention which I feel they, and all captive animals for that matter, profoundly deserve. The keeping of animals in captivity is a complicated and often paradoxical prospect - something that I do not expect to entirely reconcile - but one thing to me is clear: if I am to be responsible for the well being of a life which is not my own, then I intend to undertake that responsibility with as much care and sensitivity as I can muster. The privileges of this undertaking and arrangement have come with their ample shares of gratitude, and occasionally, regret at mistakes I have made. I think the best one can do is to learn from both ends of that spectrum.

 

Introduction and Natural History

Spilotes sulphureus (formerly classified as Pseustes sulphureus) is one of the largest species of neotropical colubrid snake, and among the largest colubrid species in the world, with adults routinely attaining (and reportedly exceeding) ten feet in length. Common names for the species include the Yellow-bellied or Amazon puffing snake and the Giant bird snake, among a myriad of regional monikers. Close relatives of the species include at least one other species in the Spilotes genus, in addition to the neotropical bird snakes of the genus Phrynonax (also formerly classified as Pseustes). An incredibly variable species in terms of morphology, adult sulphureus can display a wide range of pattern and coloration, expressing a broad array of yellows, greens, reds, browns, and black, or any mixture of these colors. Despite this polymorphism as adults, neonates are almost invariably born patterned in black and gray, or varying shades of brown (presumably affording better camouflage from predators) before gradually assuming an ontogenetic shift into their permanent adult coloration. Lean and powerful snakes, their dorsal scales are large and heavily keeled, and their bodies are laterally compressed granting them an aided capacity to thrust over long distances - a physiological trait which suggests their semi-arboreal habits. Similarly, their large eyes suggest a keen attention to movement, which they put to good use in pursuing highly mobile prey in the thick vegetation of their native environments. It is not uncommon for specimens to practice liana mimicry, a form of crypsis, if spotted or approached. When threatened, they are wont to rattle their tails and inflate their fore-bodies, especially their throats, exposing the interstitial skin between their scales (which is commonly bright yellow). If these measures fail to dissuade their would-be-antagonist, and retreat is not a viable option, they will not hesitate to defend themselves by bluff striking or biting as a last resort. All of these characteristics and more contribute to making sulphureus an especially charismatic and impressive species.

A wide-ranging snake, sulphureus is found throughout the Amazonian region of South America, from Venezuela and Colombia in the north, the eastern slope of Ecuador in the west all the way to the Atlantic slope of Brazil in the east, and south to Bolivia, as well as the islands of Trinidad and Tobago. Though primarily associated with lowland primary rainforest, they are also reported to occur in savannah, dry forest, and disturbed habitats, possessing both terrestrial and semi-arboreal habits, with wild specimens commonly observed both on the forest floor and within trees. The vast majority of sulphureus in captivity trace to the Guyana or Suriname regions of the Guiana Shield, where they are collected from the wild and exported to the United States, and occasionally Europe.

Despite their extensive range and impressive appearance, the natural history of sulphureus is poorly documented, and I’ve been unable to find much literature expressly concerning the species. The image I can deduce of their habits is largely drawn from anecdotal accounts, and only from firsthand experience observing them within captivity, which is to admit it is limited at best. That said, there are some clear consistencies to be seen in the scant observations I’ve excavated and in the experiences of those who have worked with the species in captivity. For one, all accounts confirm that the species is chiefly diurnal and most active during peak daylight hours. They are alert creatures and display a level of attention that is widely characterized as an intelligence uncommon to the majority of snakes. As predators, they are opportunistic and have been recorded to consume small mammals, birds (especially nestlings and eggs), and occasionally amphibians and reptiles. An oviparous (egg-laying) species, breeding behavior in sulphureus is thought to commence during the onset of the wet season, timing which assures ideal environmental conditions for incubation and abundant prey for neonates after emerging from their eggs.

Though widely classified as non-venomous, recent studies confirm that sulphureus is opistoglyphous (rear fanged) with a venom containing two separate toxins: sulmotoxin, lethal to small mammals but not birds or reptiles, and sulditoxin, lethal to birds and reptiles but not mammals. Despite this development, they are not considered dangerous to humans and no known serious envenomations or fatalities have resulted from their bite, likely due in part to a relatively unsophisticated venom delivery system and a general reluctance on their part to deliver prolonged bites. Regardless, it is sensible to take care when handling them and avoid being bitten, as with any venomous species.

Housing

Given their size and activity level, Spilotes sulphureus fare best in large enclosures with a vertical orientation to support their arboreal habits. For their first year, young snakes can be kept in simple, small enclosures, but by their second or third year, most will be ready to occupy their adult quarters, for which an enclosure no smaller than 48” by 24” by 72” (length by depth by height) for a single adult or pair is advisable, in my opinion. Larger enclosures are even better, as the snakes will make good use of whatever space they are afforded. Personally, I recommend an enclosure of 72”- 96” in length, by 30”- 36” in depth, by 72” in height to provide the snakes ample opportunity to make use of the space and to afford the keeper the opportunity to observe a much broader range of natural behaviors. In determining the appropriate size of the enclosure, an important factor to consider is the baseline foot traffic in the surrounding area. Larger enclosures are especially preferred in areas with higher foot traffic, and many keepers consider depth to be the critical dimension in offering security. All that said, some have been successful keeping and even breeding sulphureus within smaller confines than those I recommend, suggesting that there are many factors to success in this regard.

One of the author's enclosures - this design is composed of two stacking units with a pass-through, which allows for separating snakes if needed.

Given the humidity and security requirements that sulphureus demand, the best commercially available enclosures are those made from PVC or HDPE - they’re strong, opaque materials which don’t rot under high humidity, as wood cages are wont to do over time - and they can be ordered in sizes up to 48” by 24” by 72”. They’re also much easier to clean and sterilize than wood enclosures, and are less hospitable to harboring pests such as mites. Glass enclosures are usually unsuitable for adult sulphureus as they don’t provide adequate security given their transparent sides, and they’re also rarely available in the required dimensions. The primary challenge posed by providing appropriate housing is that few options are commercially available in the dimensions needed for adult specimens. For the largest enclosures, custom made is often the best (or only) option.

Whatever the enclosure (although it is perhaps especially true in smaller enclosures) it is imperative to provide adequate security, as sulphureus are sensitive snakes that generally cannot tolerate persistent stress. In my experience, heightened security can be provided in the form of hide boxes or cork rounds, in which the snake can comfortably retreat when necessary. I offer my snakes large cork rounds, elevated within the branches of their enclosures at varying heights, which they use frequently for both hiding and basking. I vary the height options of the cork rounds to allow the snakes to thermoregulate without having to sacrifice security. I also make a point never to bother the snakes or remove them from their cork rounds when they are hiding, as I feel it is important to honor these particular parts of their enclosures as sanctuaries of some kind, in which they can be assured they will not be bothered. The snakes in my care often rest within their cork rounds leaving just their heads extended, surveying their enclosures and following the movement of anything within the room - always curious about the goings on within their domain.

Cork rounds make for excellent arboreal hides. 

To facilitate climbing opportunities, I provide a network of madrone or live oak branches in my enclosures of which the snakes make nearly constant use. Beginning with the branches firmly anchored in place, I use them as a framework from which to design the rest of the enclosure, making sure to include elevated hiding and basking areas - usually in the form of the aforementioned large cork rounds. Greenery in the way of live or synthetic plants aids in creating more security for the snakes and in providing a more naturalistic display. Though not strictly necessary, the benefit of using live plants when possible is clearly evident to me by the way in which the snakes in my care interact with them. After incorporating live plants into some of my enclosures, I noticed a clear shift in activity level with my snakes, and a pronounced tendency in them to incessantly tongue flick any new leaves or flowers. If live plants are utilized, hardy species are a must, as the enclosure inhabitants will inadvertently trample anything too delicate - some plants I have used with success include Aechmea fasciataPhilodendron scandensPeperomia serpens, and Monstera deliciosa.

An adult female puffing snake investigating new leaves.

For substrate, a myriad of commercial options are available, and truly anything suitable for a tropical species can be used. In my enclosures, I use a mixture of ground coconut fiber, decomposed granite, charcoal, and New Zealand long fiber sphagnum moss as a base layer, with an added layer of leaf litter (in my case, madrone or magnolia leaves - which I harvest and boil) to emulate the forest floor of a neotropical rainforest. This method of layering substrate promotes natural foraging behavior in some species, and is also suitable for bioactive enclosures, which include the addition of microfauna as a ‘clean-up-crew’ to help eliminate waste and detritus, thereby reducing odors and maintaining a tidier environment.

A sturdy water bowl that is kept clean and filled with fresh (dechlorinated) water at all times is a must. I observe my snakes drinking frequently from their bowls - sometimes even while the rest of their bodies are suspended up in the branches. A bowl large enough to allow for the animal to submerge in is a plus, as some Spilotes have been observed to enjoy soaking in their water bowls - though I wouldn’t consider it a necessity.

Heating, Lighting and Humidity

In their native environment, Spilotes sulphureus live in the near-constant heat and humidity of the Amazonia region, making specific heating, lighting, and humidity important requirements for their care in captivity. Failure to provide appropriate conditions in these realms can lead to a whole host of issues, from digestion problems to respiratory infections, and there are few aspects of husbandry with greater potential consequences.

There are many ways to achieve optimal temperatures - standard incandescent or halogen bulbs, deep heat projectors, and radiant heat panels are among the best options. I utilize a combination of halogen bulbs and deep heat projectors, which provide a broad area of radiant heat and infrared wavelengths, while creating a vertical thermal gradient. I aim to provide upper basking temperatures of over 90 degrees, leaving the floor of the enclosures at temperatures in the low-to-mid 70s, thereby allowing the snakes to thermoregulate by moving up or down within the branches of their enclosures. Though I initially used radiant heat panels to heat my enclosures, I have moved away from them as a primary source of heat, because they provide only a narrow wavelength of infrared, which does not adequately reproduce the benefits of sunlight, in my opinion. This assertion is strongly supported by a number of studies, and by my own observations of the animals in my care. Whatever the heat element, a reliable thermostat is advisable to maintain preferred temperatures and ensure that the inhabitants are not exposed to potentially hazardous temperature extremes. I have had excellent results with proportional and dimming thermostats made specifically for the purposes of herpetoculturists.

Despite extensive research proving that snakes benefit from ultraviolet wavelengths, there is still some debate in the mainstream about whether or not captive snakes should be outfitted with UVA and UVB producing bulbs, as other reptiles are shown to require. There is little doubt, however, that simulating a day and night cycle through the use of artificial lighting is an important aspect of keeping diurnal snakes. To simulate the light of equatorial South America, I have my lights on a twelve hour cycle, utilizing LED fixtures on timers to provide bright light (~6000K) sufficient for plant growth. Additionally, my snakes are exposed to fluorescent UVB emitting bulbs for six hours each day, during the peak of the standard twelve hour cycle created by the LEDs. This also simulates (to some degree) the gradual increase and decrease of light throughout the day, as would be experienced by the arc of the sun’s path through the sky. I came to the decision to provide the sulphureus in my care with UVB lighting simply because I have noticed their propensity to bask for long periods of time during the peak hours of the day - an observation also supported by accounts of wild specimens, which are often recorded basking in patches of sunlight breaking through the forest canopy. The health benefits to me are clear, and as an added benefit for those aesthetically inclined, I have also noticed that the colors of my snakes appear brighter and richer beneath such light.

An adult male puffing snake basking beneath dappled light.

Achieving appropriate humidity levels of sixty to ninety percent, for keepers in temperate or arid climates, is attainable through automatic misting systems, or misting enclosures by hand. Because I enjoy the process of misting my enclosures by hand, I use a simple pump sprayer, but there are many benefits to using automated systems, most of which come with a myriad of options. I prefer to simulate the climate of the Amazonian region by creating artificial wet and dry seasons, alternating between periods of heavy misting - usually twice per day - and light misting - usually once every other day. There are likely many benefits to simulating such cycles, not least of which is encouraging natural behaviors such as breeding, which for tropical species is often triggered by fluctuations in precipitation given the more constant year-round temperatures and daylight cycles.

Feeding

Due to their voracious appetites and preference for rodents and birds, Spilotes sulphureus are rarely difficult feeders in captivity. The vast majority of specimens will accept live or frozen-thawed mice, rats, or chicks without hesitation, but most prefer smaller prey items than some might expect. I offer my adults (which are between nine and ten feet in length) prey items no larger than a large rat, whereas a boa or python of similar length might accept much larger prey without difficulty. On average, sulphureus is a larger and more heavily-bodied species than it’s close relative Spilotes pullatus, capable of accepting slightly larger prey items. However, most keepers report both species faring better with multiple small prey items over one large prey item, as they are prone to regurgitating prey that is too large for them to easily digest.

As sulphureus are sight-hunters (meaning they cue primarily off of the movement of their prey), it may sometimes be necessary to offer live prey, or to wiggle frozen-thawed prey items to attract attention. In my experience, once the first prey item is accepted, sulphureus become extremely responsive and keepers must be careful to avoid being bitten from a hyper-active feeding response. Accidental bites can be avoided by using tongs to offer frozen-thawed prey, while using common sense and staying focused during feeding. Upon seizing a prey item, most sulphureus typically consume it within seconds - faster than any other species I’ve worked with. This is a feeding strategy which would prove useful when raiding the nests of rodents and birds, which are often actively defended by protective adults. In my opinion, the voracious appetites sulphureus possess are one of the many aspects which make them such enjoyable snakes to work with and observe in captive conditions.

Though the majority of sulphureus will accept frozen-thawed or live prey without difficulty, occasionally one may encounter a reluctant feeder - this is especially true with freshly imported wild-caught specimens. Usually, I approach such snakes with persistence using the above methods, and find that most will accept food when sufficiently acclimated to their new environment. As a last resort, tease feeding has proven an effective way to get particularly stubborn sulphureus eating when all other methods fail. Given the inherently stressful nature of tease feeding, it is rarely a sustainable method for feeding snakes, and has sometimes reportedly backfired, resulting in snakes becoming nervous around the presence of food. Regardless, in cases where snakes are reluctant to accept live or frozen-thawed prey, I have employed the method with success for brief periods, only until the snakes begin accepting live or frozen-thawed prey through less stressful means.

A rapid metabolism and frequent feeding also comes with more frequent defecation as a consequence, which has much to do with the ‘messy’ reputation with which Spilotes and other large colubrids are often labeled. In my opinion they’re really not so intolerable in this realm, and I suspect much of the unsavory reputation applies to snakes which are kept in cramped enclosures where they cannot easily move away from their waste. The sulphureus in my care typically defecate within 48 to 72 hours after eating, and I remove their waste as soon as possible to avoid foul odors and maintain as sanitary an environment as possible. Even in bioactive enclosures immediately removing large segments of solid waste is a good practice to ensure cleanliness, leaving the urates and less solid waste to be dealt with by the microfauna.

Conclusion

Spilotes sulphureus is without question the most rewarding species I have worked with in a captive setting. The combination of their housing and habitat requirements, impressive appearance, and curious disposition makes for a unique and endlessly fascinating observational experience. As shy, sensitive, and inquisitive animals, I feel continuously grateful for the presence and attention they demand from me as I interact with them. Though not suitable for beginning keepers, given their size and demands, they pose challenges and rewards that make them an excellent species to work with for those experienced keepers who are fascinated by large, active colubrids. With the continued efforts of a select few who have sought to learn from them in recent days, they could become more of an establishment in the realm of reptile hobbyists in the United States and Europe in coming years, hopefully with an ever-increasing understanding of their behaviors and requirements, as well as their varied morphology.

Acknowledgements

Special gratitude to John Andermann for generously sharing his insights and experience working with Spilotes, for tolerating my many questions after a long time away from keeping snakes, and for granting me the opportunity to work with these snakes again.

And above all, thanks to the snakes themselves for their teachings.