The bullsnake is listed as a species of Special Concern and a Species in Greatest Conservation Need in Minnesota.
The bullsnake is largest species of snake in Minnesota. This snake ranges from 37 to 72 inches in length with the record being 100 inches (Conant and Collins 1991). Their ground color varies from straw yellow over the entire body to white on the neck and fore part of body, dull yellow on the body, and a cleaner, brighter yellow on the tail. Bullsnakes have over 40 large, dark body blotches on the body alone. These blotches are usually black on the neck and fore part of the body turning lighter into brown or reddish brown on the body. These blotches turn into black bands on the tail. There are also smaller lateral spots on the sides, sometimes connecting and even forming a network or checkerboard effect. The side scales are also tipped with brown or black giving the snake a speckled appearance. In western portions of its geographical range, the bullsnake takes on a more brownish appearance; the ground color is entirely brown and all the blotches are brown. In the northern and eastern portions of its range (including Minnesota), it displays the black to brown color change described above. This snake has an enlarged rostral scale, keeled scales and a single anal plate.
The bullsnake is a subspecies of the gopher snake, Pituophis catenifer. The bullsnake, Pituophis catenifersayi, is the only subspecies found in Minnesota.
The range of the bullsnake is huge, and it is found from Canada south to Texas and east to Illinois and west to Colorado. In Minnesota, the bullsnake is mostly found in the southern portion of the state. This snake is found along the St. Croix, Minnesota, and Mississippi Rivers; and there are few confirmed records far from these rivers. There are sightings in central and south central portions of the state that need to be investigated further to be sure they are not the similar western fox snake, a Minnesota species that may occur in that region also.
Generally, bullsnakes live in sandy areas that allow burrowing and contain many mammal burrows. Bullsnakes favor open prairies, especially in the northern and central parts of their Minnesota range. Blufflands and open, grassy meadows bordered by woodland are home to many southern Minnesota bullsnakes.
Bullsnakes emerge from winter dormancy in late April. They can be found sunning themselves on top of gopher mounds just outside the opening of the burrow where they spent the winter.
They breed in May; the males may combat with one another for a female. I have observed two males courting a single female in Hennepin County, MN. One male appeared to be close to copulation a few times, but the larger male seemed only interested in keeping the other from breeding as he forfeited advantages a few times. Generally, the male crawls alongside and over the female, making rhythmic motions with his body. Just before copulation, the male may grasp the female's head or neck in his mouth. Sometimes, copulation can become quite violent, both snakes wrapping about each other. Copulation may take from several minutes to hours.
After mating, the pair splits up and the male will wander about the prairie in search of food. Males have much larger home ranges than females. Females are oviparous and lay about a dozen eggs in the sand or other protected areas where they can incubate without the aid of the female. Late June and into July are common egg laying months. The young will hatch in August or September. They are just over a foot at hatching (8 - 18 inches) and differ from the adults in having an all around grayish coloration, which is lost after their first shed.
In spring, bullsnakes spend much of their day sunning outside their burrows, but into the summer they spend most of their time underground. They have a pointed head and the tough rostral scale helps them burrow through loose sand or penetrate mammal burrows. Due to their fossorial habits, they seem less likely to hide under cover such as tin or boards, but a number of these snakes can be found by flipping such junk. Many times there is no junk in prime bullsnake habitat, so observing them out and about (whether it be sunning or hunting in the morning and evening or crossing the roads at night) is the best way to find them. With their yellow and black coloration, they blend in perfectly with the prairie grasses and they can "disappear" before your eyes.
Bullsnakes, like most snakes, have varied ways of reacting to humans in the wild. I have seen more than one bullsnake act completely tame right away as if it had been in captivity for years, but some react badly to disturbances. Escape is their first line of defense, but if they feel cornered, they flatten their head and spread their jaws giving their head a diamond shape, puff their bodies up with air, and let out a hair raising hiss (see video above). No other North American snake can hiss like a Pituophis can! It is not only loud, but very raspy sounding because of a flap of cartilage in front of the trachea vibrates as air passes by it. Furthermore, they vibrate their tails producing a buzzing sound. Sometimes, this is merely a bluff, and they may be slow to actually bite, but many times they will strike and bite with vigor.
Bullsnakes retire into winter dormancy in October. In open sand prairies, they hibernate alone or rarely with garter snakes, hognose snakes, or other bullsnakes in mammal burrows. In bluff prairies, they usually hibernate in rock crevices and may share their hibernacula with eastern racers, timber rattlesnakes, and milk snakes.
Mammals are the number one food item. Pocket gophers, meadow mice, voles, shrews, ground squirrels, rabbits, squirrels, birds and birds' eggs, frogs, and lizards are consumed. They kill larger prey by constriction and simply swallow smaller prey alive. They are powerful snakes and can kill rodents met in a burrow by pressing the rodent against the wall of the burrow with part of its body. I have heard of bullsnakes hanging around chicken coops eating the eggs and young chicks, but these snakes are really one of the most beneficial snakes found in Minnesota. These snakes have appetites! They can easily save a farmer hundreds of dollars every year because of the number of rodents they can eat. They can go into burrows, holes in the walls of barns, weave in between bails of hay, and go places dogs and cats can not go. The smart farmers know this and are glad to see bullsnakes around their farm. The ignorant farmers waste their time killing these snakes, and waste their money buying trap after trap to eradicate a nuisance that the bullsnakes would have eradicated for free.