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Gopher Snake - Pituophis catenifer (Bullsnake) PDF Print E-mail
 A Field Guide to Amphibians and Reptiles of Iowa
  

 

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See the Minnesota HerpNet Site for more information on the Bullsnake  

Synonyms: Gophersnake.

Status

 
 

SPECIAL CONCERN. It is illegal to kill or collect this species by law in Iowa. These large, beautiful snakes are disappearing from Iowa's grasslands and prairies, although they are still common in some areas. Bullsnakes are a species of special concern in Iowa and any reports are welcomed.

Description

The bullsnake is largest species of snake in Iowa. This snake ranges from 37 to 72 inches in length with the record being 100 inches (Conant and Collins 1991).

Bull snake, bullsnake, Pituophis cantifer sayi, Iowa specimen
Bullsnake, Pituophis catenifer sayi, from Allamakee County, Iowa

The ground color varies from straw yellow over the entire body to white in the neck region, dull yellow-brown on the midbody, and a cleaner, brighter yellow on the tail. Bullsnakes have over 40 large, dark, body blotches. These blotches are usually black in the neck region turning to lighter brown or reddish brown on the midbody. These blotches turn into dark black bands or rings on the tail. There are also smaller lateral spots on the side of the bullsnake, sometimes connecting, and even forming a network or checkerboard effect. The side scales are also tipped with brown or black. This often gives the bullsnake a speckled appearance on the sides.

Bullsnake, Pituophis cantifer sayi
Bullsnake, Pituophis catenifer sayi, from Muscatine County, Iowa
 

The head is yellow or brown and boldly marked with black, including a stripe across the top of the head from eye to eye, barring on the labial scales, and a stripe from the eye to the corner of the mouth. The belly is porcelain white on the throat and fore part of the belly becoming yellowish with brown squares or spots thereafter.

In the southern and 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 Iowa), it displays the black to brown color change described above.

Bullsnake, Pituophis cantifer sayi
Bullsnake, Pituophis catenifer sayi, head, from Allamakee County, Iowa
 

This snake has an enlarged rostral scale, keeled scales and a single anal plate. Confusing species are the prairie kingsnake and especially the western fox snake. Prairie kingsnakes are brown overall and have smooth scales. Western fox snakes are brown or yellow overall with no pronounced color change or speckling on the sides, a rounded snout, and a divided anal plate.

Subspecies

The bullsnake is a subspecies of the gopher snake, Pituophis catenifer, which contains about six subspecies, five occurring west of the bullsnake's range. The bullsnake, P. c. sayi, is the only subspecies found in Iowa.

County distribution map, Bullsnake, Pituophis cantifer sayi in Iowa
County distibution map for Pituophis cantifer sayi
 

Range

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 Iowa, the bullsnake is found statewide. It is a prairie species and because Iowa was mostly prairie in the past, it was common throughout the state. Cultivation and development of these inviting, flat prairie areas began by early settlers continues today and have substantially reduced the number of many prairie adapted species, including bullsnakes.

Habitat

Bullsnakes favor open prairies, and sand prairies especially. Bluff lands and open, grassy meadows bordered by woodland are home to many bullsnakes as well. Generally, bullsnakes prefer loose, sandy soil that allows easy burrowing. Today, less than 0.1 percent of these prairie remnants remain (Prior, 1991) causing a serious decline in this species in Iowa. The addition of roads fragment the existing habitat further.

Strike pose, Bullsnake, Pituophis cantifer sayi
Bullsnake, Pituophis catenifer sayi, bluffing by flattening head and jaws, from Muscatine County, Iowa
 

Bullsnakes are large snakes that need a lot of space and many individuals cannot all live in one small area of suitable habitat. When they attempt to seek out new homes, they are forced to cross roads that surround the small prairies and their journey often ends there. Box turtles and western hognose snakes, which share the same areas, are faced with identical obstacles (LeClere, 1998).

Habits

Bullsnakes emerge from hibernation in April. They can be found sunning themselves on top of gopher mounds just outside the opening of the burrow where they spent the winter. 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 to not use cover (such as tin or boards) quite as much as other snake species, but nevertheless, 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, bullsnakes blend in perfectly with the prairie grasses and can disappear before your eyes.

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. Bullsnakes 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. I find the highest number of gravid bullsnakes around early June in Linn County. The eggs will hatch in August or September. Baby bullsnakes 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.

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 the majority 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.

No other North American snake can hiss like a Pituophis can! The hiss is not only loud, but very raspy sounding because a flap of cartilage in front of the trachea vibrates as air passes by it. Sometimes, the hissing striking is merely a bluff, and they may be slow to actually bite, but many mean business and will strike and bite with vigor. Furthermore, bullsnakes vibrate their tails producing a buzzing sound when in contact with leaves or dry grass. This causes many of them to be killed as rattlesnakes. However, timber rattlesnakes have black tails with tan rattles. Both timber and prairie rattlesnakes hold their tails high in the air while rattling; bullsnakes must hold their tails close to the ground to produce noise.

Bullsnakes retire into winter dormancy in October. In open sand prairies, they hibernate alone or with garter snakes, hognose snakes, or other bullsnakes in mammal burrows. In bluff prairies, they usually hibernate in rock crevices and share their hibernaculums with racers, timber rattlesnakes, and milk snakes.

Food

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 just a part of their 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 Iowa. These snakes have appetites! They can easily save a farmer hundreds of dollars every year because of the amount 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 cannot 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.

 
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