Breeding Trans-Pecos Rat Snakes

Breeding Trans-Pecos rat snakes (Bogertophis subocularis) starts with proper care and feeding. Before being able to breed this beautiful species, you must first ensure that your snakes are properly housed, properly fed and properly identified, not to mention you need to be certain that you have an accurately sexed male and female.

Choosing the Right Trans-Pecos Rat Snakes For Your Breeding Project

Trans-Pecos rat snakes– like most serpents – can be challenging for the inexperienced snakekeeper to sex. I will not detail in this article any of the ways in which gender is determined because some are invasive and/or require considerable experience to safely perform. For reliable procedures regarding gender determination, consult rat snake books, reptile magazines, Internet forums with peer-reviewed content, veteran breeders and veterinarians.

Photo by Don Soderberg

Crucial for the captive success of Trans-Pecos rat snakes is offering them the maximum ventilation achievable.

Maturity, therefore size, varies from one rat snake species to another, but generally Trans-Pecos rat snakes are considered sexually mature when they exceed 36 inches in length. I’ve known males that were only 30 inches long, weighing as little as 225 grams, to successfully sire viable embryos, but females smaller than 250 grams seldom even accept the advances of males. Personally, I would not even try to breed a female who is below 300 grams in body weight, as it is possible for her to have difficulties laying egg, which could result in her death. Seldom does age affect their sexual maturity as much as size, but regardless, sexual maturity is usually achieved, with weekly feedings, in 2 to 3 years, depending on cage conditions, genetics and feeding regimens.  

The Right Breeding Enclosure For Your Trans-Pecos Rat Snakes

Appropriate caging and good maintenance practices are essential in preparing captive snakes for reproduction. Because Trans-Pecos rat snakes require cage conditions slightly different from those of most North American rat snakes, some Trans-Pecos rat maintenance will be briefly cited in this breeding article. (To read more about rat snake captive care, see my article in the April 2013 issue of REPTILES magazine.)

Although general maintenance for Trans-Pecos rat snakes varies from that of most North American rat snakes, do not deduce that their cage conditions should emulate the climate of the Southwestern U.S. and adjacent Mexican deserts from which they originate. This is largely because we humans think of those deserts as being harsh, arid regions, but at night, when most snakes are active, this is not the case. Given the nocturnal habits of Trans-Pecos rat snakes, and other desert denizens, they require shelter from the heat and light of day. To do this, they hole up during the warm days in underground and cave settings, where it is cooler and less arid.

Crucial for the captive success of Trans-Pecos rat snakes is offering them the maximum ventilation achievable. In most glass aquarium-type cages, nylon or wire mesh lids are the only means of ventilation.

Given that it is virtually impossible to maintain necessary cage temps and ambient humidity in cages with screen sides, glass aquaria with complete screen closures are recommended. While cross ventilation from opposing cage walls would be more efficient, captive snakes often seriously injure their rostrums when trying to escape through mesh panels on cage sides. Take caution not to constrict ventilation through the screen top; Trans-Pecos rat snakes don’t fare well in overly humid conditions. If the room in which your Trans-Pecos rat snakes are kept has high ambient humidity, I recommend using a particulate wood pulp substrate, such as Aspen bedding, which wicks ambient moisture away from the air space of the cage. Should your snake experience feeding or digestion problems or show signs of breathing problems – usually evidenced by mouth gaping – the stimulus of such problems could be excessive ambient cage humidity.

Ideal cage temperatures for Trans-Pecos rat snakes range from 82 to 85 degrees Fahrenheit on the warm side of the cage to low 70s to 81 degrees on the cool side. This is traditionally achieved by heating one end of the cage with an undertank device, and no heat source on the other end. We recommend two or three hides in the cage that are only slightly larger than the snake. Most snakes are not normally attracted to cavernous hides. Even properly tempered zones in the cage are often only utilized by snakes if such zones offer a place to hide. In the absence of eyelids, nocturnal snake species – like the Trans-Pecos rat snake– instinctively avoid resting in open spaces. Not only does ultraviolet radiation (light) damage their eyes, but they instinctively reason that they cannot evade detection from prey, predator or wandering herds of deer or cattle when in open spaces. It is a myth that most North American rat snakes will burn themselves by lying directly on hot glass beneath the substrate. Although I have never witnessed this, I find that adequate hides and proper cage temperatures negate the need to burrow down to the glass floor of the cage. That said, male rat snakes can seriously deplete sperm stores if in contact with hot surfaces for prolonged periods, so if your Trans-Pecos rat snakes are prone to burrowing, it is usually because the substrate depth is too deep, thereby preventing enough heat to rise to the substrate surface. Virtually all snakes are capable of burrowing, but evidenced by the shape and construct of the Trans-Pecos rat snake head, burrowing is not a natural practice. They will burrow only if their cage needs are not met—proper temperature at the top level of the substrate and an adequate hide.

Trans-Pecos Rat Snake Shedding

The shedding process is eight to 10 days long. During this time, it is safe to increase ambient cage humidity via slightly dampening the substrate around the warm hide each day. Don’t dampen to the point of encouraging fungal or bacterial growth. Slightly dampening that small zone of the substrate rarely facilitates unsafe ambient cage humidity. During shedding episodes, moderate dampening of substrate near the warm hide will help rat snakes remain metabolically hydrated during the long days when most of them are reluctant to leave their hide for a drink of water. Therefore, it is acceptable to emulate the semi-humid hides of their natural caves and crevices for most of each year, but don’t allow such dampened substrate zones to remain moist for entire days. Undertank heating is recommended because most over tank heating devices can unsafely dehydrate the air space of the cage. As it is with anything, moderation will result in better cage conditions.

Water bowl diameters should be small. Some Trans-Pecos rat snake breeders only offer water for one 24 hour period, once or twice weekly. Change the bedding substrate partially or entirely upon discovery of spilled water or feces. Bedding materials, such as aspen, are ideal (and non-toxic) because of their natural desiccating properties. You will find natural wood products to be aesthetic as they are functional.

Preparing Your Rat Snake For Brumation

Prior to brumating, allow the snakes 10 to 14 days to evacuate their digestive system. Contrary to popular belief, gradual transition from nominal cage temperatures to cooler brumating temperatures is not necessary. I have encountered wild rat snakes that, at first, appeared to be dead, lying on frost-covered grass between patches of fallen snow, only to revive them to activity in minutes with the warmth of my hands. During the changes from summer to fall and from fall to winter, there are many warm days and nights that are abruptly followed by cold days or nights, but rat snakes are designed to adjust to temperature extremes in mere hours. And yes, Trans-Pecos rat snakes are also found at montane elevations where it snows.

Brumation is essentially the reptile equivalent of mammalian hibernation. Captive Trans-Pecos rat snakes breed more reliably when we emulate their annual seasonal changes. This equates to fertile reproduction being more successful if rat snakes are bred in the summer months. This does not imply that they cannot breed from the stimulus of artificial seasons, but in so much as you may not live in a part of the world with the same annual climates of the Chihuahuan Desert of the U.S. southwestern states of Texas and New Mexico (and adjacent Mexico), it is beneficial to utilize the help that winter months offer to achieve safe brumal temperatures with the least amount of artificial resources. Surely, there is a part of your home that is cooler than areas heated for human comfort? While brumation increases the chances for successful reproduction, it is not mandatory.

The ideal brumation conditions for adult Trans-Pecos rat snakes involve cooling them between temperatures of 45 to 65 degrees for 60 days prior to your reproduction schedule. Depending on temperatures, the duration of brumation can be shorter or longer than 45 to 80 days, but temperatures above 70 degrees can cause illness and below 35 degrees for periods of more than a day or two can be potentially lethal. That said, my snakes once experienced an unexpected drop to 30 degrees that resulted in no casualties.

Most snakes are safely brumated in containers smaller than their everyday cages, as long as adequate ventilation is provided. Monitor brumation conditions each week to ensure that temperatures are correct and the substrate is not damp. Change their drinking water routinely or whenever it is fouled from substrate material, sloughed skin or feces. Note that when screen tops are employed for brumation, because snakes sometimes seek warmth or feel the need to avoid something in their brumation enclosure (usually excessive humidity), they can damage their rostrums from pushing against the screen to escape. Consider containers with well-spaced holes that don’t have sharp peripheries. Holes made from a pointed soldering device are safer than those that are drilled or reamed. I recommend only offering them a small water bowl once or twice a week for 24 hours during brumation. Because I’ve always practiced high-ventilation brumation conditions, none of my Trans-Pecos rat snakes have died during brumation. I attribute that success to never allowing their enclosures to have high ambient humidity.

Many rat snakes can be successfully bred without brumating, so if you are unable to maintain temperatures lower than 70 degrees, I recommend not brumating them. If snakes are excessively burning calories that they refuse to replenish (i.e., fasting from inferior body temperatures and consequent reduced metabolism) their immune systems may be compromised – sometimes resulting in illness that could lead to death.

Emerge From Brumation

Resume normal feeding regimens upon emergence from brumation. Just as it is not necessary to gradually cool them prior to brumation, you do not need to gradually warm them after brumation. If not exhibiting some stage of shedding, you may feed your Trans-Pecos rat snake three to seven days after emergence from brumation. The first two post-brumal meals should be smaller than they are normally capable of digesting. After that, feed them rodents that are appropriate for their body size. An accelerated feeding regimen (perhaps two rodents per week instead of one) is recommended to speed the process of replacing fat stores that were spent during brumation. Males will fatten quickly, even when fed less than females, so the increased feeding regimen is primarily prescribed for females that need extra fat to facilitate egg production.

Shedding events for adult rat snakes after brumation are often regarded as reproductive signal events. Most Trans-Pecos rat snakes will shed after three to seven weeks of steady post-brumal feeding in the nominal temperate range of 80 to 85 degrees. The first shedding event after brumation is sometimes referred to as the post-brumal or post-brumation shed. It usually signals that the female has recently ovulated or soon will. Do not rely on this shed to signal that you should introduce the male, but in so much as no two snakes are alike and because you get just one chance of breeding your snakes each year, I recommend introducing the male after the female’s post-brumal shed.

While not all sheds alert us to reproduction stages, after brumation, most sheds certainly do. More than 80 percent of all females that have been maintained via emulation of natural annual seasons will be in some stage of egg production after the first post-brumal shed. If ovulation has not occurred by the second post-brumal shed, it should occur in the following weeks, but almost certainly by the time of the third post-brumal shed. There are underlying stimuli that dictate the processional timing of, and/or failure of, reproductive processes, but most are related to improper temperatures and off-seasonal event timing. Therefore, it is wise to introduce the pair of adults immediately after each shed in the spring and summer seasons, just in case the female is on an atypical reproductive schedule.

Introducing Rat Snakes For Breeding

When introducing snakes to breed, the male may be introduced to the female’s cage or vice-versa. I have not observed notable breeding advantages regarding introducing the female to the male’s cage versus the male to the female’s cage. Generally speaking, it is wise not to feed either snake within hours prior to a breeding introduction for at least two good reasons: fear of mistaken identity (are you introducing my mate or feeding me?), and in rare instances, regurgitation from proximity stress or excess motion during breeding.

If you do not need the male to breed a second female, communal housing is relatively safe. Trans-Pecos rat snakes are not known for cannibalism within their species, but in rare situations, the male could fail to retract one of his hemipenes (plural for the paired penises of a male snake) after copulation. If communally housed, you would likely not react to such a potentially catastrophic malfunction in time to correct it. Historically, I put the odds of this happening at one in every 100 breeding cases, but of course, that’s only based on the way I maintain my snakes during breeding seasons. One of the most common reasons for failure to retract a hemipenis (one of the paired penises of a male snake) after mating is from particulate substrate material irritating and therefore preventing painless retraction. Should this happen, the result is often the loss of that hemipenis. Hence, you may want to introduce the breeding pair to a bare cage floor or a layer of newsprint on the cage floor. It is not uncommon for a male to be incapable of safely breeding for up to two years after such a tragedy. We therefore recommend conjugal management by monitoring each breeding event, to ensure that there are no such problems.

If you do need the male to breed other females, there is another reason it is recommended that you do not let them remain together in the cage indefinitely. Mature rat snakes can copulate up to five times in a 24-hour period, so after several days the male’s sperm stores could be seriously depleted.

Observation by humans is tolerated by most mating snakes, but you should keep distractions to a minimum. Most receptive pairs will copulate as soon as just a few minutes to one hour after introduction, but Trans-Pecos rat snakes often take considerably longer. When they do mate, it often lasts for 30 to 60 minutes. If no riding or parallel positioning occurs after one hour, I separate them and try again after several days. When females emit pheromones, signaling males that they are receptive to breeding, it often only takes minutes for the male to successfully court the female by trying to subdue her and achieve a position directly atop most of her body.

After one to three copulations over a seven-day period, the female should show obvious signs of increased appetite. It is extremely rare for a female to have reduced appetite or completely stop eating prior to egg-laying, but don’t be alarmed if this occurs, even when you are certain that cage conditions are nominal. Our goal is for them to consume more calories at this time in the breeding cycle, but should your female fast during this period, fertile reproduction is not all-together impossible. 

Trans-Pecos Rat Snake Egg Laying

Her next post-brumal shed should signal that she is preparing to lay eggs, but copulation is not necessarily an assurance that she will lay fertile eggs. Nor is providing a natural breeding schedule and optimal conditions any guarantee that reproductive success will result. It is, therefore, a good idea to re-introduce the male after this second post-brumal shed. If she allows the male to copulate within one hour, the indication is that this shed is not her pre-partum shed (the shed that occurs four to 12 days prior to the laying of eggs). If she spurns his advances for up to a 60-minute period, the likelihood is that egg-laying is eminent within a few days. After the pre-partum shed, she should not have an appetite, but regardless, she must not be fed. Conflict between her digestive and reproductive systems can cause egg impaction and could lead to her death.

Once you are reasonably certain this is her pre-partum shed, prepare two plastic containers: a nest box of damp sphagnum moss in which she may lay her eggs and an incubation container with slightly damp vermiculite and/or perlite. These two containers are prepared in advance so you can monitor the crucial temperature and humidity conditions necessary for successful oviposition (egg-laying) and subsequent incubation.

The nest box should be roughly 9 to 14 inches long, 6 to 10 inches wide, and at least 6 inches high. Place enough damp sphagnum moss in the nest box to fill half the inside space and secure it with a relatively tight-fitting lid. Provide an entrance hole that is twice the diameter of the snake in either the lid or one or more sides of the container. Set this nest box inside her cage and ensure that she always has fresh drinking water. The water bowl should be small enough so as not to accommodate eggs being tragically laid therein. She will inspect inside the nest box for a few days, but thereafter should remain outside that box until one to two days prior to oviposition. Check the moss every few days to ensure that it is slightly damp and otherwise accommodating of her eggs. When in doubt, slightly dry nest medium is better than nest medium that is too damp.

The egg incubation container should be prepared so there are several days prior to oviposition so that you may evaluate the moisture content of the hatch medium (water, vermiculite, and/or perlite are recommended) prior to the day they are laid. I recommend no ventilation holes, as over-hydration of eggs is more deadly to incubating snake eggs than slightly dry incubation substrates. Set this box where you intend to incubate the eggs (at a recommended temperature between 78 and 85 degrees) to allow time for temperature stabilization and so as to afford you several days to evaluate the moisture content of the incubation substrate. After 24 hours, if there are several small concentrations of condensation on the sides and/or ceiling inside the container, proper humidity is indicated. If more than 60 percent of the sides or lid displays obvious condensation, the ambient humidity may be too high. Condensation is little more than an indication that the temperature inside the incubation container is warmer than the air outside the container, thereby forming moisture droplets on the inside surface. If the incubation box were the same temperature as the room it is in, there would obviously be no condensation, but given that rooms are usually cooler, take advantage of the condensation being an indication of proper substrate hydration.

While the eggs are being laid, I recommend giving the female as much privacy as possible. Oviposition of the eggs can take from just a few hours to an entire day. If the eggs are positioned in formation, I recommend leaving them together. If the eggs are not in contact with each other, you may place them anywhere you wish atop the incubation substrate. Nestle them partially into the substrate, but do not fully cover them with substrate medium. Instead, it helps to place a covering of damp sphagnum moss over the entire egg clutch. Moss that is too damp could clog micro pores in the egg shells, thereby potentially smothering the embryos.

Trans-Pecos Rat Snake Hatching

Under proper conditions, hatching generally occurs in 65 to 80 days after oviposition, but it is possible for them to hatch in less than 65 days from lower incubation temperatures or up to 90 days after being laid if temperatures were higher than 85 degrees. Eggs incubated above 90 degrees will usually hatch, but all manner of problems usually plague those hatchlings. Some may be less human-tolerant, under-sized, anatomically deformed, poor feeders or all the above. Color and pattern anomalies may also result from high-temperature incubation. At lower incubation temperatures (lower than 80 degrees), hatchling can take from 85 to 95 days. When temperatures are at the lower end of the 78- to 85-degree range (or below) hatchlings can have some of the same maladies as those hatched at higher temperatures, but they are almost always larger hatchlings with superior appetites. In other words, eggs incubated under 85 degrees but above 75 degrees usually yield more robust neonates.

Check the eggs weekly to determine proper humidity and temperature. Each week (or perhaps every other week) open the incubation container for a minute while fanning the container to exchange the inside air. Generally, if the average incubating temperature is 82 degrees but rarely and briefly below 79 degrees, they should hatch in 85 days (plus or minus a few days). These are generalities, and different genetics and incubation conditions can result in skewing of these incubation duration ranges.

After the eggs have hatched, the neonates will shed in seven to 13 days, depending on cage temperature and humidity. Any time after this, you may begin offering food. Under nominal cage conditions, approximately 50 to 70 percent of them will eagerly eat unaltered frozen/thawed pinky mice on the first attempt and up to another 15 to 20 percent of them should eat within the next two to three offerings. Hatchlings that have not eaten anything within four to six weeks usually perish or will have sustained irreversible anatomical deformities and terminal digestive and nutritional damage.

Cage conditions and maintenance are essentially the same for neonates and adults.