The bull snake ( Pituophis catenifer sayi ) is a large, non-venomous snake native to North America. Often mistaken for rattlesnakes due to their defensive behaviors and appearance, bull snakes are valuable members of their ecosystems and can make rewarding pets for experienced reptile keepers. This article provides a comprehensive overview of bull snake biology, diet, care requirements, and conservation status.
Introduction to the Bull Snake
When it comes to top-shelf choices of the most rewarding and easy-to-keep species of snakes to possess in captivity, bull snakes stand out among the champions of Colubrids with exceptional reasons detailed in all aspects. The bull snake, also known as the gopher snake and pine snake, is a subspecies of the gopher snake (Pituophis catenifer). In Mexico, bullsnakes are called cincuate. They are non-venomous snakes found throughout North America, from southern Canada to northern Mexico. They are known for their impressive size, striking patterns, and role in controlling rodent populations.
Natural Habitat and Distribution
Bull snakes ( Pituophis catenifer sayi ) are inhabitants of the central region of North America, being found as far north as Canada, as far south as the northeastern tip of Mexico past the Texas border, in addition to as far west as Montana, and as far east as Indiana. Bullsnakes are found throughout North America - all of the US, central and northern Mexico, and southern Canada. There are a large number of subspecies. The natural habitat of these snakes include desert, woods, plains, prairies and mountain ranges. They are highly adaptable and live in a wide range of environments across their geographic range, from northern Mexico to southern Canada. Their adaptability allows them to thrive in areas with sandy soil, which they use for burrowing. Bull snakes prefer open areas such as prairies and old fields with sandy soil and abundant burrowing rodents. Prairielands, plains, and rich forests are where I have encountered many bulls.
Appearance and Physical Characteristics
The differences of visual characteristics of color and pattern among different locations exemplifies the beauty of variability within this species. Bull snakes come in a vast array of colors. Ground color can be yellow, tan, straw, and red/orange with blotches being brown/chestnut brown outlined in black, or blotches being pure black. In hypomelanistic specimens, blotches can vary from light-silvery black to raspberry/maroon/orange blotches. Bullsnakes have 33 ‒ 66 dark dorsal blotches on the body, usually 41 or more, and 9 ‒ 19 on the tail, which are often darker and bolder on the neck and tail and lighter and faded midbody. The dorsal scale rows range from 27 ‒ 37 at midbody, usually 29, 31, or 33. The bullsnake, as known as a gopher snake, are very long and non-venomous. These snakes have a turtle-shaped head with a protruding scale at the tip of the snout, narrow neck, and large eyes. Their scales are smooth and marked with brown, black and/or reddish blotches on a background of lighter tan to gray.
Adult bullsnakes average about 4 to 6 ft (1.2 to 1.8 m) in length, and specimens of up to 8 ft 4 in (2.5 m) have been recorded. The maximum record for the species is 110 in. (279 cm.). Possibly being the largest subspecies of gopher snake on average, mature specimens can have an average weight in the range of 1-1.5 kg (2.2-3.3 lb), though the heavier known specimens can attain 3.6-4.5 kg (7.9-9.9 lb), with larger specimens being quite bulky for a colubrid snake. Bull snakes are very heavy-bodied snakes with an average length of 4- to 7- feet. Individuals in my experience, have an average length of 5-6 feet. Although extremely long specimens have been found, in the 8- to 9- foot range, those examples are not as common, nor the norm. Interestingly, bull snakes are not sexually dimorphic when it comes to size with males/females being the same length.
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Behavior and Temperament
Bull snakes are solitary creatures, spending most of their lives alone except during the mating season. Bull snakes are known for their impressive defensive displays when they feel threatened.
When bull snakes hiss, the air in the trachea, being forced through the epiglottis, produces a hissing/distorted grunting sound, very similar to an actual bull itself. The hiss volume is extremely notable, and is part of their defense in the wild against predators. Because of this display, bull snakes are mistaken for rattlesnakes by those not knowledgeable of this species.
When threatened by anything as large as a human, a bullsnake's next defensive action is to rear up and make itself look as large as possible, while at the same time hissing at the perceived threat. Bullsnakes can sometimes be mistaken for rattlesnakes and killed. Owing to its coloration, dorsal pattern, and semikeeled scalation, it superficially resembles the western diamondback rattler ( Crotalus atrox ), which is also common within the same range. The bullsnake capitalizes on this similarity by performing an impressive rattlesnake impression when threatened. First, it hisses, or forcibly exhales through a glottis or extension of the windpipe. The end of the glottis is covered by a piece of cartilage known as the epiglottis, which flaps back and forth when air is exhaled from the right lung, producing a convincing rattling sound. It also adopts a rattlesnake-like "S-curve" body posture as though about to strike. It commonly vibrates its tail rapidly in brush or leaves, and flattens its head to resemble the characteristic triangular shape of the rattlesnake.
Despite their past reputation of being difficult to handle, Bull snakes, with their high intelligence, awareness, and mental adaptation of their environment around them, are extremely docile regarding handling. While many baby bulls can be hissy, many, if not most, outgrow that behavior. Unlike kingsnakes and milksnakes, captive bull snakes regularly do not musk when picked up for handling, nor do they randomly bite. While some may be initially flighty when first picked up, most calm down quickly.
Diet and Feeding Habits
Bull snakes are very powerful constrictors that eat small mammals, such as mice (including Peromyscus and Reithrodontomys spp.), moles, voles, rats (including Dipodomys spp.), pocket gophers, ground squirrels (including Spermophilus spp.), young rabbits and bats, as well as ground-nesting birds, birds' eggs, smaller snakes (including Crotalus spp.), lizards (including Uta spp.) and insects. Their climbing proficiency enables them to raid bird nests (and birdhouses) to eat the nestlings or sitting mother. One snake can eat five small birds within 15 minutes.
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Bullsnakes eat a variety of small mammals including mice, rats, gophers, squirrels, and rabbits. They will also eat birds and their eggs; and occasionally they will take lizards and other snakes. Bullsnakes kill their prey by constriction but are at risk when trying to overpower a large rodent. Bull snakes have a varied diet that primarily includes small mammals like ground squirrels, mice and rats, making them valuable allies to farmers by controlling rodent populations. Bull snakes are powerful constrictors, meaning they subdue their prey by wrapping their heavy bodies around victims and squeezing until the prey can no longer breathe.
In captivity, it is common to feed mice/rats/chicks from various frozen rodent suppliers. The size of the food should be 1.5 times as big as the largest part of their body, at the very most. Like many snakes of North America, the bull snake consumes small rodents like mice and rats. In captivity frozen then thawed mice and rats are healthier because they cannot fight back or spread disease. Adult snakes need to eat only once every 7-10 days. The size of rodent you should feed varies depending on the size of your snake. A rule of thumb is to provide a mouse or rat that will make a noticeable lump at the snake's thickest point, but not awkwardly protruding. A 6' bull snake can eat full sized rats, but hatchlings should be eating pinkie mice. Do not handle your snake within 48 hours of its last meal to avoid regurgitation of undigested food. While many keepers feed with different frequencies and amounts, I personally feed one item once a week, or multiples if I have smaller food items, from babies to small-young adults. My biggest adults get fed every 7-10 days.
Housing and Enclosure Requirements
Bulls can be kept in a wide array of cage types. Some keepers enjoy keeping bulls in enclosures with naturalistic displays, using dirt/sand as substrate, along with rock/branch cage additions, as they do enjoy climbing. A 4’ x 2’x 2’ enclosure is an ideal size for an adult bull snake. Others keep their bull snakes in large plastic sweater/blanket boxes that can be bought at various stores. Substrates with this way of keeping include shredded aspen. Aspen bedding is what I prefer as it is cheap, comes in big packages, and bulls like to burrow in it. In addition, spot cleaning is easy using aspen. Although many keepers have success with pine shavings, it has been known to produce a bleach-like chemical when pushed into water bowls, and mixed with the water. For baby bulls, plastic shoe boxes are fantastic and then as the snake grows, the size of the enclosure is increased. Adult bulls, being active as they are, thrive in the largest possible enclosure. I personally use Animal Plastics CB70 plastic tubs with racks for many of my adult bulls and for my biggest specimens, I do have bigger plastic tubs for them.
At a minimum, a 6 foot long bull snake needs to be kept in a 55 gallon enclosure with a screen lid. Snakes are solitary animals and do best on their own, but if you plan to breed two snakes, a 70 gallon enclosure will be enough room. When it comes to cage size, the more room the better. If you are looking for the perfect setup for a small to medium sized Bull Snake, then you might want to check out the Large Glass Reptile Snake Terrarium 48" x 24" x 24" sold at ReptiZoo.
Hide boxes are vital to their security and health and many items can be used, such as hides sold from reptile suppliers/pet stores, to then producing your own at home. Creative hides can range from using various boxes such as cereal/food/cardboard boxes, to plastic containers of all kinds, to even PVC plumbing pipe sections. A minimum of two hide boxes should be used in the enclosure. These hide boxes should be dark and snug so the snake has a place to feel safe and secure. Provide large, sturdy branches for the bull snake to climb on and explore.
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Fresh water must be available at all times using water bowls with a heavy base. Clean and refill the water daily because they are known to defecate and swim in their water bowl.
Substrate
If you are looking for a simple, inexpensive and clean substrate use butcher paper, paper towels or newspaper for your bull snake. If you want a more natural look, options like aspen bedding or cypress mulch. When given the opportunity, bull snakes will burro a couple of inches into loose substrates. Do not ever use cedar or pine chips of any kind because they are toxic to all reptiles.
Temperature and Lighting
Bulls prefer cooler temperatures than what some may keep North American colubrids, such as kingsnakes, milksnakes, and corn snakes. As a keeper, my bulls enjoy a range from 74 to 82 degrees Fahrenheit (23.3 to 27.8 degrees Celsius), with 78 degrees Fahrenheit (25.6 degrees Celsius) being most favorable, making them extremely handleable and calm, which makes them such a pleasure to hold. It is strongly thought that in the past, bulls were kept much warmer than needed, thus bringing forth the reputation that all bulls were hissy/flighty, and untamable. As years went by, it was determined that bullsnakes simply did better with cooler temperatures. Maintaining temperatures include utilizing heat tape for thermoregulation in their rack systems, or using only ambient temperatures most of the year, which is what I prefer. I use heat tape for my breeding adults only in the spring, while they are developing eggs. A basking spot of 85F should be located on one end of the enclosure. If you need to provide heat to reach 85F, a heat bulb or a heat pad will work. If you are using a heat pad make sure that it is made for reptiles and you have a thermometer in the cage at all times. The other end on the cage can be kept at room temperature. Snakes are exothermic so if there is not enough heat, their bodies will literally stop. No additional UVA or UVB rays are required for this species of snake.
Bullsnakes are ectothermic reptiles and need to regulate their body temperature via thermoregulation. One study on northern populations in Canadian grasslands found that they can often be observed basking in sunny areas when needing to warm up and will retreat into their burrows when needing to cool down. Research indicates that bullsnakes actually prefer burrows in open grassland areas as opposed to shaded woodland areas. This is because living in an open space makes thermoregulation easier. Rather than avoiding trees and overhanging vegetation to reach a sunny area bullsnakes can simply bask in the sun at the mouth of their burrows. Thermal gradients also play a role in bullsnake thermoregulation as different temperatures at different locations will determine where the snake will travel throughout the day to maintain its preferred body temperature.
Humidity
No extra humidity is required for bull snakes.
Cleaning
Paper substrates need to be replaced when soiled and loose substrates need to be replaced every three months. Spot clean the enclosure and clean the water bowl daily.
Brumation
In northern regions of their range, bullsnakes will enter a dormant state called brumation in order to conserve energy during the winter months. Bullsnakes will brumate in their burrows below the frostline typically from October to April. They will often nest in large colonies even with various species of snakes like rattlesnakes and garter snakes in order to conserve heat.
Preparing bulls for brumation is quite simple. Properly fed bulls should have their feedings stopped two to three weeks before brumation, allowing their digestive systems to be cleared of all food. Temperatures are gradually lowered to my preferences of 50 to 60 degrees Fahrenheit (10 to 15.6 degrees Celsius), even allowing colder temperatures below 50 to take place, in short increments. I give them access to water at all times available during brumation, along with a completely dark room. The brumation length of time that I prefer is three to four months. In my opinion, brumation is critical for breeding success.
Breeding
Bull snakes, in my opinion, should be at least 3 to 4 years old, AND averaging 4 to 7 feet, when it comes to being ready to breed. Some Northern Range bulls tend to be smaller, such as Montana specimens, while many, if not, most other localities, are larger. I personally prefer females to be at least 5 feet, if not 6 feet long for many reasons. For one, bull snake eggs are much larger eggs compared to most other Colubrids, and the egg amount can be large, in which the female bull needs to be as large and mature as possible.
In captivity a male and a female can be introduced at any time during the year. Make sure that they are both at least 2 years old and are fully matures so neither one is harmed. Most snakes will mate right away or within the week. Once they have mated, separate the male and the female so the male does not try to mate again because this will cause problems for the female. Females should be fed medium portions every 5 days until the bulge of the eggs is very noticeable. Right before she is ready to lay her eggs, the female will stop eating.
Male bullsnakes reach maturity in one or two years, while females reach maturity in three to five years, both at a total length of 90 ‒ 96 cm. Bullsnakes breed in March or April (depending upon their location) and usually lay their eggs in April, May, or June (again, depending upon when the snakes breed). In northern regions of their distribution mating usually takes place near the hibernaculum.
Once bulls are brought up out of brumation, feeding starts after two weeks, with the first meal being slightly smaller than average. Once feedings are on schedule, then male/female pairs are introduced together starting at week 4. Three to four days after a meal to allow digestion, I put male/female pairs together for breeding. Shed cycles regarding egg-laying are then followed. Once they shed during the gestation period, the eggs are commonly laid around 10 days after, on average.
Egg Laying and Incubation
They typically lay 12 eggs in sand or other protected areas and leave the eggs to incubate unprotected. Clutches of five to 22 eggs have been observed. The eggs are elliptical, leathery, rough, sticky, and up to 70 mm (2+3⁄4 in) long. The eggs typically hatch in August or September but, June 30 to November 7 hatching have been recorded.
In getting ready for the eggs, for my bigger cages, I put in cat litter boxes, with side holes for access and fill them with vermiculite with a 50-50 mixture of water/vermiculite with the perfect mix producing a damp ball in hand with no water coming out, and green/peat moss. Size of clutches are variable, ranging anywhere from four eggs to upwards of 30 eggs, with 12 to 15 eggs for larger bulls being the average. Shoeboxes with the aforementioned vermiculite-water mix serve as incubation boxes, with temperatures ranging from 76 to 82 degrees Fahrenheit (24.4 to 27.8 degrees Celsius). I halfway bury the eggs in the vermiculite, as well. Incubation periods can vary from 8 to 11 weeks. Once the eggs are laid, they should be moved as soon as possible into an incubator and keep them at 85F until they hatch.
Hatchling Care
Baby bullsnakes are 20-55.5 cm (7.9-21.9 in) at hatching. A hatchling bull snake only needs a 10 gallon enclosure for the first couple months of its life. It will eat frozen thawed pinkie mice every 5 days and should be kept on a newspaper substrate. Young bull snakes can be jumpy and nippy, so watch out for your fingers. A hot spot of 85F needs to be maintained and give them enough water to soak in.
Baby bullsnakes emerge from the eggs within one to two days of pipping, living off of their yolk for several weeks, resulting in not needing to be fed before the post-hatching shed. Hatchling size ranges from 15 to 20 inches, and housing hatchlings is similar to other colubrids.
Handling and Aggression
When startled in the wild, a bull snake will lift itself up and shake the tip of its tail on the ground to act like a rattlesnake. Although they have no venom, they have a powerful bite and should be treated with respect. Hatchlings are difficult to tame, but as they get older, they mellow out and can become very friendly to you. Many snakes only are aggressive when they are startled or threatened.
Regarding handling in captivity, especially with babies who display this behavior, the key point with calming them down is to focus on being direct, yet firm, in gently picking them up and making them feel well supported by your hands and arms. Once they are “broken” from this defense posture, they will then often go into “flee-mode,” in which you then firmly, yet gently, handle them like any other snake. Bullsnakes are generally gentle but they can be very defensive, particularly when they perceive an object as a predator, i.e., too big to be prey. They will coil up, hiss, and shake their tails imitating a rattlesnake. Bull snakes are generally tolerant of handling and can become accustomed to human interaction with regular, gentle handling.
Conservation Status and Threats
Bull snakes are not currently listed as an endangered species, but they face threats from habitat loss and human persecution. Because people often mistake them for venomous rattlesnakes, bull snakes are sometimes killed out of fear. Conservation efforts focus on educating the public about the importance of these nonvenomous snakes and protecting their habitats from further destruction.
Interactions with Humans
Bullsnakes, as important predators on rodents, are considered a “friend” by farmers. I have enjoyed field herping for bulls in various states such Colorado and Kansas. Finding them is always a pleasure, during road cruising or field herping, with their peak activity during the morning/early evening hours. My experience with working with bulls has been invaluable and such a treasure! The fun produced with breeding and hatching both locality and morph specimens, has been such a joy and a celebration of our amazing hobby, and the future, in so many ways, looks promising with these fine animals. These amazing snakes truly are exceptional, with so many qualities making them superior captives with not only visual appeal, but with their intelligence outlined in their behavior.
Lifespan
If cared for properly a bull snake will live from 15-25 years of age so be ready for a long term commitment. Bullsnakes are long-lived in captivity, with one reported living 22 years. With proper care, Bullsnakes can live 20-25 years in captivity.