PLAINS hog-nosed snakeHeterodon nasicus
(HARMLESS) REAR-FANGED VENOMOUS 
Photo: Graham Zephirin
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Map accurate as of 1/31/2024
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General Distribution: In Colorado, the Plains Hog-nosed Snake can be found along the eastern half of the state at elevations less than 6,000 feet. There is an isolated population in northwestern Colorado in Moffat County at about 6,000 feet. The range of the Plains Hog-nosed Snake reaches from western Minnesota, southwestern Manitoba, southern Alberta and Saskatchewan, south to central and eastern Texas, and eastern New Mexico. Isolated populations are also found in southeastern Minnesota, northwestern Iowa, and eastern Nebraska, the prairies of western Illinois, northwestern and southeastern Missouri, central Wyoming, and northwestern Colorado (Ernst & Ernst 2003).
Activity: Plains Hog-nosed Snakes are diurnal. At night, this species retreats to a temporary burrow that the snake makes out of loose soil with its up-turned snout. The Plains Hog-nosed Snake occasionally takes shelter under rocks or logs (Stebbins, 2003). In the southern United States, the annual activity of H. nasicus most likely begins in late March or early April. Activity ceases in October or November. Farther north, or at higher elevations, this species may have a shorter period of annual activity. A hibernacula is usually within the home range and underground below the frost line. Hibernation occurs in individual burrows that the snake digs for itself or in burrows made previously by mammals (Ernst & Ernst 2003).
Habitat: The Plains Hog-nosed Snake digs out its prey in sandy or gravely soils in the prairie. It also occurs in suburbs, cultivated fields, pastures, floodplains, canyon bottoms, scrub brush, creosote deserts, and montane woodlands. Rangewide, H. nasicus has been found at elevations ranging from sea level to 2,400 m (7,874 ft), but occurs below about 1,830 m (6,000 ft) in Colorado.
Size: The maximum Total Body Length (TBL) is 154 cm for this species, however, most individuals are smaller and range from 38 to 92 cm. males are smaller than females and have a TBL up to 67 cm and tail lengths of 12-19% of the TBL. Larger females have a TBL up to 154 cm and tail lengths of 9-13% of their TBL. Hatchlings range in TBL from 14 to 20 cm (Ernst & Ernst 2003).
Conservation Status: Designated as a Non-game Species in Colorado. This species can be taken into captivity (up to 4 individuals annually) following state regulations (see State of Colorado regulations here). NatureServe rank: G5 (Globally Secure), S4 (State Secure). Because the Plains Hog-nosed Snake is tolerant of habitat changes typically brought by rural ranching and semi-agricultural landscapes, this species has continued to occupy its historic range in Colorado. In areas with a high density of agricultural activities, the Plains Hog-nosed Snake has probably been eliminated or its populations have been greatly reduced despite it being locally common. Especially along the eastern Front Range, urbanization and heavy road traffic have most likely been the cause of declines (Hammerson, 1999). In northwestern Colorado, the current distribution and abundance of H. nasicus is uncertain but records of this species marked the first confirmed appearance of this species on the west side of the Continental Divide in Colorado.
Coloration / Markings
- Body color is buffy gray, brown, or olive.
- Series of 23-52 dark brown dorsal blotches.
- Two longitudinal rows of smaller dark brown blotches run down the sides of the body.
- On the head, a dark line runs between the eyes and extends downward, behind each eye, to reach the corners of the mouth.
- Another set of extended blotches runs from the parietal scales to the neck.
- The venter is mostly black in color, including under the tail, with scattered yellow or whitish blotches.
- Both sexes and all age-classes are similarly patterned.
Reproduction: In 2-3 years, females of the H. nasicus species have gained maturity with a TBL of 38-43 cm. Males gain maturity in 1-2 years and with a total body length of 38-40 cm. Because this species does not hibernate communally, males likely find scent trails of females. Mating usually occurs in late March to May. Mating has also been observed later in August and even into the fall and females can store this sperm over the winter (Ernst & Ernst 2003). Females dig out nests in early June to late in loose or sandy soils using their spade-like snouts (Hammerson, 1999). Most eggs are laid in July and sometimes, the eggs are laid in a row in a tunnel rather than as a cluster in a nest. Clutches range from 2 to 24 eggs that are ovular in shape and white or cream in color. Eggs for this species have smooth leathery shells and they usually hatch between mid-August and mid-September. Hatchlings have a brighter coloration than adults and typically range in TBL from 14 to 20 cm (Ernst & Ernst 2003).
Feeding & Diet: The Plains Hog-nosed Snake uses sight and smell to find prey. H. nasicus moves rapidly toward its target and quickly seizes it in its mouth. Often, this species will also try to hold its prey in a coil of its body (Ernst & Ernst 2003). Hog-nosed Snakes will use their upturned snouts to dig out prey such as small turtles from their burrows (Hammerson, 1999). It should be noted that this species is mildly venomous - which can aid in subduing its prey - but it is rear-fanged and reluctant to bite so poses little risk to humans. Prey for the Plains Hog-nosed Snake consists of amphibians such as toads and spadefoots, reptiles such as lizards, smaller snakes, and small turtles and their eggs. The large and flexible mouth of the Plains Hog-nosed Snake is especially adapted to eat large inflated toads. H. nasicus also eats birds such as sparrows, Western Meadowlarks, and eggs of ground nesting birds, mammals such as mice and voles, and insects such as ants, beetles and grasshoppers. (Ernst & Ernst 2003).
Defenses from Predation: Common predators of the Plains Hog-nosed Snake include hawks, crows, and coyotes (Hammerson, 1999). To avoid predation, this species will display a defensive posture with the tail poised as 'head' to 'strike' above, and the head hidden under thicker body coils. H. nasicus also has a dramatic defensive display that involves spreading its neck, hissing loudly, and occasionally striking with its mouth closed. Furthermore, this snake will contort is body, writhe about, vomit up food, and even roll over onto its back and play dead with its tongue extended and seep blood from its mouth (Ernst & Ernst 2003; see photo to right). Many predators will only attack live prey, making this death display a way for the snake to escape (Hammerson, 1999).
Cited & Additional Resources
Ernst, C. H., and E. M. Ernst. 2003. Snakes of the United States and Canada. Simthsonian Books, Wsahington and London. 141 pp.
Hammerson, G. A. 1999. Amphibians and reptiles in Colorado. 2nd ed. University Press of Colorado, Boulder, Colorado. 305 pp.
Stebbins, R. C. 2003. Western reptiles and amphibians. 3rd ed. Houghton Mifflin Company, New York, New York. 347 pp.
Hammerson, G. A. 1999. Amphibians and reptiles in Colorado. 2nd ed. University Press of Colorado, Boulder, Colorado. 305 pp.
Stebbins, R. C. 2003. Western reptiles and amphibians. 3rd ed. Houghton Mifflin Company, New York, New York. 347 pp.
Account compiled by: Beth Wittmann
Reviewed by: Lauren Livo (text & map)
Last updated: 4/13/2022 by Rémi Pattyn
Reviewed by: Lauren Livo (text & map)
Last updated: 4/13/2022 by Rémi Pattyn
Suggested Citation
Colorado Partners in Amphibian and Reptile Conservation. 2014. Species account for Plains Hog-nosed Snake (Hereodon nasicus). Compiled by Beth Wittmann. http://www.coparc.org/plains-hog-nosed-snake.html [accessed date here]. Editor: Lauren Livo.
Colorado Partners in Amphibian and Reptile Conservation. 2014. Species account for Plains Hog-nosed Snake (Hereodon nasicus). Compiled by Beth Wittmann. http://www.coparc.org/plains-hog-nosed-snake.html [accessed date here]. Editor: Lauren Livo.
