Online Field Guide to The Reptiles and Amphibians of Arizona

Mexican Hog-nosed Snake (Heterodon kennerlyi) Arizona
Cochise County, AZ

Heterodon kennerlyi (Mexican Hog-nosed Snake) Arizona
Cochise Co., AZ
Heterodon kennerlyi (Mexican Hog-nosed Snake) Arizona
Death-feigning. Cochise Co., AZ
Mexican Hog-nosed Snake (Heterodon kennerlyi) Arizona
Cochise Co., AZ

 MEXICAN HOG-NOSED SNAKE  Heterodon kennerlyi
Mildly Venomous
DESCRIPTION: A medium (up to 760 mm or 30″ in total length), stocky, yellowish-tan snake with 23-43 brown to orange-brown dorsal blotches. The large mid-dorsal blotches are often somewhat muted. A row of small, dark brown, crisp-edged blotches runs along each upper side. Below this row, an additional row of large, muted, blotches runs along each side, followed below by one or two more rows of small muted blotches or spots. The dorsal blotches morph into bands on the tail. Two large, crisp-edged, dark brown blotches mark the neck and are separated at the mid-dorsum by a third, smaller nuchal blotch. Two dark brown bars cross the top of the head between the eyes, the posterior-most of which runs past the back of the eye and down to the corner of the mouth. The underside of the body is checkered with large, rectangular, yellow-orange and black blotches. Many specimens have a nearly solid black venter. The underside of the tail is usually black. The pupils are round. The head is large but is barely distinct from the thick neck. The scale on the snout (rostral) is enlarged, flat on bottom, upturned, keeled on top, and shovel-like. Adult females attain larger sizes than males. The dorsal scales are keeled. The similar looking Chihuahuan Hook-nosed Snake has smooth (not keeled) dorsal scales and a pale venter.

DISTRIBUTION: This snake is found in the valleys of southeastern Arizona at elevations ranging from ca. 1,100 m to 1,560 m (3,600′ – 5,100′).

HABITAT: Heterodon kennerlyi is usually found within Semidesert Grassland, Chihuahuan Desertscrub, and grassland communities. It seems to prefer open areas with loose, well-drained, sandy or gravelly soil. It is typically found in open valleys, flatlands, rolling plains, and gentle bajadas.

The Mexican Hog-nosed Snake is normally active from May through October in Arizona. It is a slow-moving primarily diurnal and crepuscular ground-dweller that is occasionally active into the night during particularly warm periods. Its plow-like snout and shortened head, body, and tail are adaptations for burrowing. It uses its snout to unearth prey, bury itself for temporary shelter, and create deeper, habitually used shelter burrows. It probably hibernates singly in a burrow below the frost line during the cold months of late fall and winter. When threatened this snake may remain motionless or it may try to escape. The next line of defense is “bluffing”, followed by death feigning. Bluffing consists of inflating the body, flattening the neck and posterior head, coiling the tail, elevating the head and neck, and making repeated false strikes, each accompanied by a sharp hiss. Although dramatic, bluffing is purely defensive and H. kennerlyi rarely bites. If bluffing fails to alleviate the threat the snake may feign death by turning belly up, gaping the mouth, extending the tongue, expelling foul smelling waste, and then remaining motionless. While death feigning some snakes regurgitate, hemorrhage from the lining of the mouth, and smear the body with feces and blood.

DIET: Prey is located by smell and sight. The shovel-like snout is used to root around in the soil for prey which includes toads, frogs, lizards, small snakes, rodents, reptile eggs, salamanders, hatchling turtles, birds and their eggs, and insects. There are two enlarged teeth on the posterior of each upper jaw bone (maxilla) which are used to inject a mild venom into prey. The venom might be mildly toxic to humans. Prey is grasped by the jaws and is not constricted but may be partially restrained by a body coil. Heterodon kennerlyi is resistant to the toxic secretions of toads, a major prey item.

REPRODUCTION: Most mating takes place in the spring and some might occur in late summer or fall. A clutch of up to 23 eggs is laid, usually in June or July, in a nest excavated from sandy or loamy soil. Incubation lasts 50 to 64 days and hatchlings appear in late July, August, and September.

REMARKS: The proliferation of roads through its habitat might negatively impact some populations of H. kennerlyi. This snake frequently basks on warm roads making it particularly susceptible to road mortality.

By Thomas C. Brennan

Bartlett. 2000. Snakes of North America: Western
Gulf Publishing Co. Houston, TX

Brennan, T. C., and A. T. Holycross. 2006. A Field Guide to Amphibians and Reptiles in Arizona. Arizona Game and Fish Department. Phoenix, AZ

Degenhardt, W. G., Painter, C. W., and Price, A. H.. 1996. Amphibians and Reptiles of New Mexico. University of New Mexico Press. Albuquerque.

Fowlie. 1965. The Snakes of Arizona. Azul Quinta Press, Fallbrook, California

Lowe, Schwalbe, Johnson. 1986. The Venomous Reptiles of Arizona. Nongame Branch
Arizona Game and Fish Department. Phoenix, AZ

Stebbins. 1985. Western Reptiles and Amphibians. Houghton Mifflin. New York, NY

Heterodon kennerlyi (Mexican Hog-nosed Snake) Arizona Range Map

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