Bullsnakes ( Pituophis catenifer sayi) are large, heavy-bodied, nonvenomous snakes found throughout North America from southern Canada into Mexico. Bullsnakes are probably the most widespread snake in New Mexico, according to William G. Degenhardt, Charles W. Painter and Andrew H. Price in the book "Amphibians and Reptiles of New Mexico" (University of New Mexico Press,1996). They have been found in dry deserts at elevations of 3,000 feet and mixed conifer forests at much higher elevations up to 9,000 feet.
There are actually five species of bullsnakes in North America. All of them are large, powerful, muscular bodied snakes with keeled scales. They are daunting to look at, are popular with amateur snake keepers and they are bred in fairly large numbers. The snakes have a number of color and pattern variations.
Bullsnakes, also known as gopher snakes, eat a wide variety of small mammals like voles, deer mice, shrews, rabbits and ground squirrels, according to researchers at the Arizona-Sonoran Desert Museum. They are commonly found in areas where lots of small mammals live because these rodents are their primary food source and because bullsnakes will also often use their old burrows for shelter.
Bullsnakes will also feed on birds and their eggs and nestlings, frogs and lizards. They are "constrictors," which means that they squeeze their food until they die, but they may also swallow small animals without killing them first.
Bullsnakes are active mainly during the day, but it is not unusual to see them in the evenings or even at night. During the hottest parts of the summer, they are actually more active at night. Some people confuse bullsnakes - which are not poisonous - with rattlesnakes, because of their defensive posture and similar appearance. Bullsnakes, like rattlesnakes, will show defensive behavior when threatened. They flatten their head, puff up their bodies and coil up. They will even hiss and shake their tails.
Bullsnakes play an important role in controlling the population size of small mammals, particularly rodents, according to researcher Robert C. Stebbins, in his book "A Field Guide to Western Reptiles and Amphibians" (Houghton Mifflin Company, 2003). Since bullsnakes are common predators of the deer mouse, which is a known carrier for hantavirus, healthy Pituophis populations are beneficial to humans.
Ultimately, it is good to have bullsnakes around neighborhoods to keep disease-carrying rodents like deer mice away.
Steve Tapia is a biologist who loves talking and writing about wildlife.
The Spanish version of this column is on Page C4.