Common Name:
Sonoran gopher snake
Erroneously called bullsnake in some areas
El Cincuate in Mexico, which seems to be a catch all term for all Pituophis of that region.

Scientific Name:
Pituophis catenifer affinis (Hallowell, 1852)

    Hatch: 9 to 12 inches (occasionally up to 14 inches from exceptionally large eggs)
    Adult: 4.5 to 5 feet on average (up to just over 8 feet in length); 6' feet in length is an exceptionally large affinis in any area despite rumors of larger specimens.

Scalation: (based on Stull's study)

Dorsal rows (mid-body): maximum number of scale rows 28 to 35, with an average of 29; rows at neck 25 to 33, most often 29; minimum number anterior to the vent 20 to 25, most often 23 (125).

Ventrals: 215 to 260 [average 233.1] (125)

Caudals: 51 to 71 [average 61.0] (125)

Supralabials: 8 or 9, with the fourth, fifth or none entering the eye (125).

Infralabials: 11-15, usually 12-13 (125)

Prefrontals: four (125)

Anal Plate: Single, undivided

Range: Southeastern California; central and southern Arizona; central, western, and southwestern New Mexico, especially Dona Ana and Otero counties; far west Texas in El Paso and Hudspeth counties; and northern Mexico. Contiguous with Pituophis catenifer sayi in Texas, New Mexico, and northern Mexico where intergrades occur.

Text by Shannon Hiatt

Coloration and Description:

General: Pattern is a series of brown, black or reddish brown blotches that sometimes lighten at mid dorsum. Those blotches at the anterior and posterior are generally darker black or brown. This variation in blotch color is one of the most attractive characteristics of affinis. Ground color is most often yellow but ranges from beige and creamy white to tan, depending upon the region and, many times, this varies within populations from the same region. The affinis from White Sands National Monument tend to have the creamy white ground color with a few specimens displaying an off white to grayish white coloration that complements the white sands of that habitat. Other affinis from White Sands are as yellow as those found further south in El Paso county.

Head and Neck: Stull describes affinis: "The top of the head is a reddish brown, only slightly dappled with dark brown or black, and the throat is white" (126). A dark, bold line usually runs from the corner of the jaw through the eye, although a few specimens have faint markings.

Ventral: Varies from yellow to creamy white, although it is generally a yellowish white and Stull indicates: "The belly bears on each side a series of small dark spots, which are each 1 to 2 scutes long and are separated from one another by 1 to 4 scutes (126).

Habitat: Although this species prefers grasslands and more open terrain, it is found in desert flats covered with sagebrush, along the edge of coniferous forests in meadows, open brushy areas, and in cultivated crop and pasture lands. Not generally associated with rocky talus slopes even though specimens have been found at altitudes above 8500 feet. The Sonoran prefers sandy soils where it locates rodent burrows. Found in and around abandoned or seasonal houses and farm buildings where rodent populations abound.

Prey: Predominately small rodents (with the pocket gopher being the prey of choice), young nestling rabbits, lizards, sometimes (although rarely) other snakes, a few young birds from nests, and occasionally bird eggs taken from ground nests or low lying nests in bushes.

Behavior: Diurnal in most habitats with limited movement during the hot summer months in desert areas; then most often seen at daybreak and just after sunset. Remains hidden in rodent burrows during the heat of the day. At higher altitudes may remain diurnal even in the summer.

They will put on an effective and intimidating display if cornered or encountered unexpectedly in the wild. Juveniles will rarely bite, but occasionally a large affinis will bite if handled roughly. I have encountered Sonorans in the field that are calm and easily handled while others are seemingly terrorized by every movement, continue closed-mouth biting, loud open-mouthed hissing, and rapid buzzing of their tails until the threat is lessened. Then the neck often remains in the rigid "s"-shaped threat display while the snake's tongue slowly tests the air. Some affinis will drop to the ground and make a hasty retreat at that point; others will hold their ground until the threat leaves.

Captive Behavior: One of the more easily handled Pituophis in my estimation, wild caught affinis become increasingly less likely to hiss and buzz the longer they are in captivity. Others hiss and buzz until taken into the hand and then quiet quickly. Captive bred affinis are a joy to cultivate even though all specimens, wild caught or captive bred, can have "off" days. This occurs when they are in the "blue" or in the spring when males are following nature's call and searching for females in adjacent trays. I recommend a fairly deep substrate, three to four inches, and a hide of some sort for this species. CareFresh is the substrate I use in a 32-quart plastic container with a couple layers of newspapers placed over the substrate to serve as a hide. The water bowl is placed on top of the newspaper at the cool end; when the snake is in the "blue," however, the water bowl is placed at the end of the container over the heat tapes to increase the humidity. If you use CareFresh, make sure that water is available at all times to prevent any possible dehydration in juveniles.

Captive Breeding: With albino and hypomelanistic specimens available to herpetoculturists, Sonorans will remain a worthy prize in a Pituophis breeder's collection. In fact, the beauty of the wild type coloration alone is worth including a pair of Sonorans in any snake collection. Brumation from November to March is expected to increase breeding success with females being introduced to the male's container in April. I remove the females to their own trays and introduce egg chambers (plastic shoeboxes filled with peat moss) shortly after the second pre-egg laying shed. Females will lay clutches in late summer in most regions with neonates emerging in the fall. Most clutches range from six up to 24 eggs, with egg size depending upon the size of the female. Neonates are able to eat pinkie mice after their first shed and are generally good feeders from that point on.

Literature Cited:

Mara, W.P. Pine Snakes: A Complete Guide, Neptune City, NJ: TFH Publications, Inc., 1994. [Photos of an albino affinis, page 46.]

Rodriguez-Robles, Javier A. and Jose M. De Jesus-Escobar. 2000. Molecular Systematics of New World Gopher, Bull, and Pinesnakes (Pituophis: Colubridae), A Transcontinental Species Complex. Molecular Phylogenetics and Evolution. 14 (1), January: 35-50. [see bibliography for wide range of scientific sources and the text for some insights into relationships among the Pituophis group.]

Stull, Olive Griffith. Variations and Relationships in the Snakes of the Genus Pituophis,United States National Museum, Bulletin 175, Washington, D.C., Smithsonian Institution, 1940. [An old study but it remains the classic of all Pituophis studies.]


Power 1998