Plains Hog-nosed Snake - Heterodon nasicus
Western Hog-nosed Snake
This is a heavy-bodied snake with a broad neck and dark blotches on the back extending from the back of the head onto the tail. There is a large amount of black pigmentation on the underside of the body, with contrasting patches of white, yellow, and orange. The anal scale is divided. The snout is upturned, with an enlarged rostral scale that is spade-like and keeled. The dorsal scales are also keeled. There are enlarged ungrooved teeth near the rear of the upper jaws. The maximum total length is about 90 centimeters, but most individuals are less than 65 centimeters. Hatchlings are similar to adults in appearance and about 17 to 20 centimeters total length. Eggs are smooth and elongate (usually 26 to 38 millimeters by 14 to 23 millimeters in length and breadth).
The presence of an upturned snout that is spade-like and keeled, in combination with keeled dorsal scales, a dark-patterned belly, a divided anal scale, and the absence of tail rattles and facial pit, distinguishes the Western Hog-nosed Snake from all other snakes native to Montana. The color pattern is described as similar to both the Gophersnake and the Prairie Rattlesnake, but neither of these, nor any other snake in Montana, has an upturned nose like the Western Hog-nosed Snake.
Western Hemisphere Range
Summary of Observations Submitted for Montana
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
No information is available for Montana. Marked individuals in Kansas were usually recovered during the same year within a few hundred meters of their previous capture site; occasionally individuals moved a kilometer or more between years (Platt 1969, Hammerson 1999).
Little specific information for the state is available. They have been reported in areas of sagebrush-grassland habitat (Dood 1980) and near pine savannah in grassland underlain by sandy soil (Reichel 1995, Hendricks 1999).
In other locations, their apparent preference for arid areas, farmlands, and floodplains, particularly those with gravelly or sandy soil, has been noted. They occupy burrows or dig into soil, and less often are found under rocks or debris, during periods of inactivity (Baxter and Stone 1985, Hammerson 1999, Stebbins 2003).
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (high, medium, or low) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2001, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
- Examining the observation records for each species in the state-wide point database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of “observations versus availability of habitat”.
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were associated as using an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignments of habitat quality.
If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at firstname.lastname@example.org
or (406) 444-3655.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species’ known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2001. The wild mammals of Montana. Special Publication No. 12. Lawrence, KS: The American Society of Mammalogists. 278 p.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana’s amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
Little is known about the food habits of this carnivorous species in Montana. Based upon research in other areas that this species is found, the Western Hog-nosed Snake is considered a specialist predator on toads, but other main items in the diet include lizards and reptile eggs, and to a lesser extent frogs, salamanders, snakes, birds, and mammals (Baxter and Stone 1985, Hammerson 1999); young eat proportionally more lizards and lizard eggs than do larger snakes, which sometimes eat birds and other snakes and items not eaten by the young (Platt 1969). It commonly uses its spade-like nose to dig up buried prey detected by odor, such as Painted Turtle and Yellow Mud Turtle eggs (Iverson 1990), and may use toxic saliva to subdue active prey.
Little information is available specific to Montana. However, Western Hog-nosed Snakes are known to be diurnal. Their active period extends primarily from late April to mid-October in Colorado (Hammerson 1999). The active period in Montana is poorly documented, with records from mid-May to the end of September, and mostly from early June to early August (Mosimann and Rabb 1952, Reichel 1995, Hendricks and Reichel 1998, Hendricks 1999). Population density was estimated at about 4 to 6 per hectares in Kansas pasture, about half of this was in an ungrazed area (Platt 1969).
The few confirmed predators include hawks (Buteo spp.), American Crows, and Coyotes (Platt 1969, Hammerson 1999). Predators of the Western Hog-nosed Snake in Montana have not been reported. When disturbed, Western Hog-nosed Snakes may flatten their heads and vigorously strike and hiss. If these methods fail to deter a threat, individuals may exhibit death-feigning behavior that includes writhing, rolling over on the back, letting the tongue hang from the mouth, and remaining limp. If turned right side up, individuals will immediately roll over on their backs again (Hammerson 1999). Montana individuals show this death-feigning behavior (Mosimann and Rabb 1952).
There is almost no information specific to Montana. A female collected in Toole County on July 20, 1950 contained seven eggs ready for laying (Mosimann and Rabb 1952).
Information from other locations indicate that Western Hog-nosed Snakes lay clutches of 3 to 23 eggs in shallow burrows or nests a few inches below the surface (Platt 1969). The eggs of a female obtained June 11 measured 13 by 27 millimeters (Stebbins 1954). Eggs are laid in May through August, depending on locality, but mainly during June and July. Females may oviposit in alternate years, and only half of the females in a population may lay eggs in any year. Eggs hatch in about two months; hatchling emergence peaks in late July and early August in Colorado (Hammerson 1999). They reach sexual maturity in the second year (Platt 1969). In a Kansas study, only about 30% of the population was as old as 4 years. Maximum longevity in natural conditions is about 8 years, but captive animals have lived two decades.
The Western Hog-nosed Snake was relatively abundant in Montana during the late 19th Century, at least in some regions; in 1876 it was the third most common reptile (after the Prairie Rattlesnake and Greater Short-horned Lizard) along the Missouri River between Fort Benton and the mouth of the Judith River (Cope 1879). This is no longer the case (Maxell et al. 2003); the few recent records suggest that the species is uncommon throughout Montana, although its status is largely unknown. Even though this snake is still encountered across its historical range, it is less abundant than in the 19th Century. This is probably due to extensive habitat loss associated with conversion of prairie to agricultural landscapes. As in other regions, an unknown percentage of local populations experiences road mortality, as many specimen and observation records are of road-killed individuals. Draining of prairie wetlands may have negative impacts on the prey (toads and frogs particularly, and perhaps turtle eggs) this snake prefers. Management in Montana for this species is hampered by a lack of basic information on abundance, food habits, and habitat associations, but is probably best effected for the long-term by protecting suitable prairie habitats from conversion to agricultural uses. No specific management activities are suggested at this time, but any nests and dens should be protected and left undisturbed.
- Literature Cited AboveLegend: View WorldCat Record View Online Publication
- Baxter, G. T. and M. D. Stone. 1985. Amphibians and reptiles of Wyoming. Second edition. Wyoming Game and Fish Department. Cheyenne, WY. 137 p.
- Cope, E. D. 1879. A contribution to the zoology of Montana. American Naturalist 13(7): 432-441.
- Dood, A. R. 1980. Terry Badlands nongame survey and inventory final report. Montana Department of Fish, Wildlife, and Parks and Bureau of Land Management, Helena, MT. 70 pp.
- Hammerson, G. A. 1999. Amphibians and reptiles in Colorado. University Press of Colorado & Colorado Division of Wildlife. Denver, CO. 484 p.
- Hendricks, P. 1999. Amphibian and reptile survey of the Bureau of Land Management Miles City District, Montana. Montana Natural Heritage Program, Helena, MT. 80 p.
- Hendricks, P. and J. D. Reichel. 1998. Amphibian and reptile survey on Montana refuges: 1996. Montana Natural Heritage Program, Helena, MT. 19 p.
- Iverson, J. B. 1990. Nesting and parental care in the mud turtle, Kinosternon flavescens. Canadian Journal of Zoology 68:230-233.
- Maxell, B. A., J. K. Werner, P. Hendricks and D. L. Flath. 2003. Herpetology in Montana: a history, status summary, checklists, dichotomous keys, accounts for native, potentially native, and exotic species, and indexed bibliography. Society for Northwestern Vertebrate Biology, Northwest Fauna Number 5. Olympia, WA. 135 p.
- Mosimann, J.E. and G.B. Rabb. 1952. The herpetology of Tiber Reservoir Area, Montana. Copeia(1): 23-27.
- Platt, D. R. 1969. Natural history of the hognose snakes Heterodon platyrhinos and Heterodon nasicus. Museum of Natural History. University of Kansas Publications 18(4): 253-420.
- Reichel, J. D. 1995. Preliminary amphibian and reptile survey of the Sioux District of the Custer National Forest: 1994. Montana Natural Heritage Program, Helena, MT. 75 p.
- Stebbins, R. C. 2003. A field guide to western reptiles and amphibians. 3rd Edition. Houghton Mifflin Company, Boston and New York. 533 p.
- Stebbins, R.C. 1954. Amphibians and reptiles of western North America. McGraw-Hill, New York. Xxii + 528 pp.
- Additional ReferencesLegend: View WorldCat Record View Online Publication
Do you know of a citation we're missing?
- [EI] Econ Incorporated. 1984. Terrestrial wildlife inventory for the Lame Jones and Ismay coal lease tracts. Econ Incorporated. Helena, MT.
- [PRESI] Powder River Eagle Studies Incorporated. 1998a. Big Sky Mine 1997 wildlife monitoring studies. Powder River Eagle Studies Incorporated. Gillete, WY.
- [PRESI] Powder River Eagle Studies Incorporated. 1998b. Spring Creek Mine 1997 wildlife monitoring studies. Powder River Eagle Studies Incorporated. Gillete, WY.
- [VTNWI] VTN Wyoming Incorporated. No Date. Second year's analysis of terrestrial wildlife on proposed mine access and railroad routes in southern Montana and northern Wyoming, March 1979 - February 1980. VTN Wyoming Incorporated. Sheridan, WY. 62 p.
- [WESCO] Western Ecological Services Company. 1983b. Wildlife inventory of the Southwest Circle known recoverable coal resource area, Montana. Western Ecological Services Company, Novato, CA. 131 p.
- [WESTECH] Western Technology and Engineering Incorporated. 1998. Wildlife monitoring Absaloka Mine area 1997. Western Technology and Engineering, Inc., Helena, MT.
- Alberta Environmental Protection. 1996. The status of Alberta wildlife. Natural Resources Service, Wildlife Management Division. 44 pp.
- Allen, J.A. 1874. Notes on the natural history of portions of Dakota and Montana Territories, being the substance of a report to the Secretary of War on the collections made by the North Pacific Railroad Expedition of 1873, General D.S. Stanley, Commander. Proceedings of the Boston Society of Natural History 17: 33-85. Pages 68-70.
- Allen, R. 1994. A profile of the western hognose snake (Heterodon nasicus). Rephiberary 199: 9-10.
- Bakker, J. 1997. Striking nest behaviour of Heterodon nasicus nasicus. Litteratura Serpentium English Edition 17(1):10-11.
- Bauer, Delane, 2002, 2002 Four Seasons Wildlife Study. Savage Mine Report, Richland County, Montana.
- Blake, P. 1993. Success with odour manipulation and western hognose snakes, Heterodon nasicus nasicus. Herptological Review 18(2): 60-61.
- BLM. 1982b. Moorhead baseline inventory - wildlife. Bureau of Land Management, Miles City District Office. Miles City, MT. 29 pp.
- Braddell, D.L. 1984. A western record for the plains hognose snake in Manitoba. Blue Jay 42(4): 196.
- Bragg, A.N. 1960. Is Heterodon venomous? Herpetologica 16(2): 121-123.
- Brant, R. 1993. A failed attempt to breed the western hog-nose snake, Heterodon nasicus nasicus. Herptological Review 18(2): 62-64.
- Brant, R. 1993. Successful breeding of the western hog-nosed nake, Heterodon nasicus nasicus. A case of double clutching. Herptological Review 18(3): 130-132.
- Brown, C., C. Foster, J. Spivey-White, and J. Hesletine. 2003. Feeding behaviour in monitor lizards and snakes; does direction of prey ingestion influence prey handling? Herpetological Bulletin 83:26-29.
- Brunson, R.B. 1955. Check list of the amphibians and reptiles of Montana. Proceedings of the Montana Academy of Sciences 15: 27-29.
- Burghardt, G.M. and H.W. Greene. 1988. Predator simulation and duration of death feigning in neonate hognose snakes. Animal Behaviour 36: 1842-1843.
- Carlson, J. (Coordinator, Montana Animal Species of Concern Committee). 2003. Montana Animal Species of Concern. Helena, MT: Montana Natural Heritage Program and Montana Fish, Wildlife, and Parks. In Press. 12p.
- Censky, E.J. and C.J. McCoy. 1985. Geographic distribution. Heterodon nasicus nasicus (Plains hognose snake). Herpetological Review 16(2): 60.
- Cobb, V.A. and L.M. Cobb. 1991. New county records for amphibians and reptiles of east Texas. Herpetological Review 22(1): 27-28.
- Conant, R. and J.T. Collins. 1991. A field guide to reptiles and amphibians of eastern and central North America. Third edition. Houghton Mifflin Company. Boston, MA. 450 pp.
- Cooper, S.V., C. Jean, and P. Hendricks. 2001. Biological survey of a prairie landscape in Montana’s glaciated plains. Report to the Bureau of Land Management. Montana Natural Heritage Program, Helena, MT. 24 pp. plus appendices.
- Cope, E.D. 1875. Check-list of North American Batrachia and Reptilia; with a systematic list of the higher groups, and an essay on geographical distribution. Based on the specimens contained in the U.S. National Museum. U.S. Natioanl Museum Bulletin 1: 1-104.
- Coues, E. and H. Yarrow. 1878. Notes on the herpetology of Dakota and Montana. Bulletin of the U.S. Geological Geographic Survey of the Territories 4: 259-291.
- Crother, B.I. (ed.) 2008. Scientific and standard English names of amphibians and reptiles of North America north of Mexico. SSAR Herpetological Circular No. 37:1-84.
- Dichow, A. 2000. Keeping and breeding Heterodon nasicus nasicus. Nordisk Herpetologisk Forening 43(1):2-6.
- ECON, Inc. (Ecological Consulting Service), Helena, MT., 1977, Colstrip 10 x 20 Area wildlife and wildlife habitat annual monitoring report, 1977. Proj. 164-85-A. December 31, 1977.
- Edgren, R.A. 1952. A synopsis of the snakes of the genus Heterodon, with the diagnosis of a new race of Heterodon nasicus Baird and girard. Natural History Miscellanea 112: 1-4.
- Edgren, Richard A. 1955. The natural history of the hognosed snakes, genus Heterodon: a review. Herpetologica 11: 105-117.
- Fjell, Alan K., 1986, Peabody Coal Company Big Sky Mine, Rosebud County, MT. Wildlife monitoring report: 1985 field season. March 1986.
- Fjell, Alan K., and Brian R. Mahan, compilers., 1984, Peabody Coal Company Big Sky Mine, Rosebud County, MT. Wildlife monitoring report: 1983 field season. February 1984.
- Fjell, Alan K., and Brian R. Mahan., 1983, Peabody Coal Company Big Sky Mine, Rosebud County, MT. Wildlife monitoring report: 1982 field season. May 1983.
- Fjell, Alan K., and Brian R. Mahan., 1985, Peabody Coal Company Big Sky Mine, Rosebud County, MT. Wildlife monitoring report: 1984 field season. February 1985.
- Fjell, Alan K., and Brian R. Mahan., 1987, Big Sky Mine, Rosebud County, MT. Wildlife monitoring report: 1986 field season. April 1987.
- Flath, D.L. 1998. Species of special interest or concern. Montana Department of Fish, Widlife and Parks, Helena, MT. March, 1998. 7 p.
- Flath, Dennis L., 1979, Nongame species of special interest or concern: Mammals, birds, reptiles, amphibians, fishes. January 1979.
- Fuller, S.R. 1981. A case of envenomation by a western hognose snake, Heterodon n. nasicus. Northern Ohio Association of Herpetological Notes 9(1): 11.
- Gates, M.T. 2005. Amphibian and reptile baseline survey: CX field study area. Report to Billings and Miles City Field Offices of Bureau of Land Management. Maxim Technologies, Billings, MT. 28pp + Appendices.
- Gildart, R.C. and J. Wassink. 1982. Montana wildlife. Montana Geographic Series. Number three. Montana Magazine, Inc. Helena, MT. 128 p.
- Goldberg, S.R. 2004a. Reproduction in the western hognose snake, Heterodon nasicus (Serpentes: Colubridae) from the southwestern part of its range. Texas Journal of Science 56(3):267-273.
- Hammack, S.H. 1991. Heterodon nasicus kennerlyi (mexican hognose snake). Oophagy. Herpetological Review 22(4): 132.
- Hendricks, P. and J. D. Reichel. 1996. Preliminary amphibian and reptile survey of the Ashland District, Custer National Forest: 1995. Montana Natural Heritage Program, Helena, MT. 79 p.
- Hossack, B. and P.S. Corn. 2001. Amphibian survey of Medicine Lake National Wildlife Refuge Complex: 2001. USGS Northern Rocky Mountain Science Center, Aldo Leopold Wilderness Research Institute, Missoula, MT. 13 p.
- Humphris, Michael., 1993, Wildlife Monitoring Report. Spring Creek Coal Company 1993 Mining Annual Report. Appendix I. April 11, 1993.
- Humphris, Michael., 1994, Wildlife Monitoring Report. Spring Creek Coal Company 1994 Mining Annual Report. Appendix I. April 1994.
- Hunziker, R. 1990. The best defense: an introduction to hognose snakes. Tropical Fish Hobbyist 39(4): 106-108, 110-115.
- Iverson, J.B. 1995. Heterodon nasicus (western hognose snake). Reproduction. Herpetological Review 26(4): 206.
- Kapus, E.J. 1964. Anatomical evidence for Heterodon being poisonous. Herpetologica 20(2): 137-138.
- Kolbe, J.J. 1999. Size and demographic structure of an isolated population of western hognose snakes, Heterodon nasicus, in northwestern Illinois. Bulletin of the Chicago Herpetological Society 34(6):149-152.
- Kroll, J.C. 1973. Comparative physiological ecology of eastern and western hognose snakes (Heterodon platyrhinos and H. nasicus). Ph.D. Thesis, Texas A&M University 261p. 1973.
- Kroll, J.C. 1977. Self-wounding while death feigning by western hognose snakes (Heterodon nasicus). Copeia 1977(2): 372-373.
- Kugelberg, A. 1991. Western hognosed snake, Heterodon n. nasicus. Newsletter of the Australian Society of Herpetologists Incorporated 34(7): 147-149.
- Lazcano, D., Jr. 1988. Life history notes. Heterodon nasicus kennerlyi (Mexican hognose snake). Coloration. Herpetological Review 19(2): 36.
- Leavesley, L.K. 1987. Natural History and Thermal Relations of the Western Hognose Snake (Heterodon nasicus) in Southwestern Manitoba. M.S. Thesis. University of Manitoba, Winnipeg, Manitoba. 160 pp.
- Lowe, D. 1997. Keeping and breeding the western hognose snake (Heterodon nasicus). Herptile 22(2):89-92.
- Martin, P.R. 1980b. Terrestrial wildlife inventory in selected coal areas of Montana. Montana Department of Fish, Wildlife and Parks and Bureau of Land Management, Helena, MT. 84 p.
- Martin, P.R., K. Dubois and H.B. Youmans. 1981. Terrestrial wildlife inventory in selected coal areas, Powder River resources area final report. Montana Department of Fish, Wildlife and Parks and Bureau of Land Management, Helena, MT. 288 p.
- Matthews, W.L. 1979. Wibaux-Beach wildlife baseline study - nongame species. Bureau of Land Management, Miles City, MT. 93 p.
- Matthews, W.L. 1980b. Wildlife of Prairie County Terry study area. Bureau of Land Management, Miles City, MT. 52 p.
- Matthews, W.L. 1981. Broadus-Pumpkin Creek baseline inventory - wildlife. Bureau of Land Management, Miles City, MT. 83 p.
- Mattison, C. 1992. Reproduction in the dusty hognose snake, Heterodon nasicus gloydi. Litteratura Serpentium English Edition 12(5): 98-101.
- McAlister, W.H. 1963. Evidence of mild toxicity in the saliva of the hognose snake (Heterodon). Herpetologica 19: 132-137.
- McCallum, M.L. 1995. Heterodon nasicus (western hognose snake). Herpetological Review 26(1): 46.
- McEneaney, T. and J. Jensen. 1974. The reptiles and amphibians of the Charles M. Russell National Wildlife Range - 1974. Charles M. Russell National Wildlife Refuge. Lewistown, MT. 3 p.
- Montgomery, C. and S.P. Mackessy. 1999. Heterodon nasicus nasicus (plains hognose snake). Lack of paralysis following vertebral disjunction. Herpetological Review 30(4):227-228.
- Moore, J.E. 1953. The hog-nosed snake in Alberta. Herpetologica 9: 173.
- Morris, M.A. 1985. Envenomation from the bite of Heterodon nasicus (Serpentes: Colubridae). Herpetologica 41(3): 361-363.
- Painter, C.W., B.R. Tomberlin, and J.P. Brastad. 1996. Serpentes: Heterodon nasicus kennerlyi (Mexican hognose snake): Maximum size. Herpetological Review 27(4): 203-204.
- Pendlebury, G.B. 1976b. The western hognose snake, Heterodon nasicus nasicus, in Alberta. Canadian Field Naturalist 90(4): 416-422.
- Perez-Ramos, E. 1987. Heterodon nasicus. Herpetological Review 18(3): 56.
- Platt, D.R. 1989. Seasonal activity of snakes on a sand prairie. Proceedings of the North American Prairie Conference 11: 251-254.
- Plummer, M.V. and N.E. Mills. 2000. Spatial ecology and survivorship of resident and translocated hognose snakes (Heterodon platirhinos). Journal of Herpetology 34(4): 565-575.
- Powder River Eagle Studies, Inc., Gillette, WY., 1994?, Big Sky Mine 1993 wildlife studies. Date???
- Rauscher, R.L. 1998. Amphibian and reptile survey on selected Montana Bureau of Reclamation impoundments. Montana Department of Fish, Wildlife and Parks, Nongame Program. Bozeman, MT. 24 pp.
- Rehak, I. 1990b. On the reproductive biology of Heterodon nasicus. Akvarium Terarium 33(8): 30-32.
- Reichel, J. and D. Flath. 1995. Identification of Montana's amphibians and reptiles. Montana Outdoors 26(3):15-34.
- Reichel, J.D. 1997. Amphibian, reptile and northern bog lemming survey on the Rocky Mountain Front: 1996. Montana Natural Heritage Program, Helena, MT. 81 p.
- Roedel, M.D. and P. Hendricks. 1998. Amphibian and reptile survey on the Bureau of Land Management Lewistown District: 1995-1998. Montana Natural Heritage Program, Helena, MT. 53 p.
- Roth, J.J., B.J. Johnson, and H.M. Smith. 1989. The western hognose snake, Heterodon nasicus, west of the continental divide in Colorado, and its implications. Bulletin of the Chicago Herpetological Society 24(9): 161-163.
- Russell, A. P. and A. M. Bauer. 1993. The amphibians and reptiles of Alberta. University of Calgary Press. Calgary, Alberta. 264 p.
- Ruzicka, I. 2000. Curious facts from keeping the western hog-nosed snake Heterodon nasicus. Akvarium Terarium 43(3):61-62.
- Sexton, O.J. 1979. Remarks on defensive behavior of hognose snakes, Heterodon. Herpetological Review 10: 86-87.
- Smith, H.M. 1991a. Range extensions of three reptile species in northern Mexico. Bulletin of the Maryland Herpetological Society 27(4): 216-218.
- Smith, H.M. and F.N. White. 1955. Adrenal enlargement and its significance in the hognose snakes. (Heterodon). Herpetologica 11: 137-144.
- Smith, P.W. and H.M. Smith. 1962. The sytematic and biogeographic status of two Illinois snakes. C.C. Adams Center of Ecological Studies Occasional Papers 5: 1-10.
- Smith, W. and C. Wershler. 1989. Pilot project on the study of the Western Hognose Snake in Alberta. Paper for Alberta Forestry, Lands and Wildlife by Sweetgrass Consultants Ltd., Calgary, AB. 17pp.
- Spring Creek Coal Company., 1992, Wildlife Monitoring Report. Spring Creek Coal Company 1992 Mining Annual Report. Appendix I.
- Thompson, L.S. and P.S. Nichols. 1982. Circle West wildlife monitoring study; fourth annual report for period March 1, 1981 - May 31, 1982. Circle West Technical Report No. 10. Montana Department of Natural Resources and Conservation, Helena, MT.
- Travis, C.A., D. Chiszar, and H.M. Smith. Heterodon nasicus (western hognose snake). Herpetological Review 27(4): 212.
- Vitt, L.J., J.P. Caldwell, and D.B. Shepard. 2005. Inventory of amphibians and reptiles in the Billings Field Office Region, Montana. Sam Noble Oklahoma Museum of Natural History and Department of Zoology, University of Oklahoma, Norman, OK. 33 pp.
- VTN Colorado, Inc. Decker Coal Company., 1975, Draft environmental impact assessment for the proposed North Extension of the West Decker Mine.
- Waage, B.C. 1998. Western Energy Company Rosebud Mine 1997 annual wildlife monitoring report December 1, 1996 to November 30, 1997 survey period. Western Energy Company, Colstrip, MT.
- Waage, Bruce C., 1995, Western Energy Company Rosebud Mine, Colstrip, Montana:1994 Annual Wildlife Monitoring Report; December 1, 1993 - November 30, 1994. February 27, 1995.
- Waage, Bruce C., 1996, Western Energy Company Rosebud Mine, Colstrip, Montana: 1995 Annual Wildlife Monitoring Report; December 1, 1994 - November 30, 1995. February 28, 1996.
- Waage, Bruce C., 1999, Western Energy Company Rosebud Mine, Colstrip, Montana: 1998 Annual Wildlife Monitoring Report; December 1, 1997 - November 30, 1998 Survey Period. February 24, 1999.
- Waage, Bruce C., 2000, Western Energy Company Rosebud Mine, Colstrip, Montana: 1999 Annual Wildlife Monitoring Report; December 1, 1998 - November 30, 1999. February 2000.
- Walcheck, K. 1976. Montana Wildlife 170 years ago. Montana Outdoors 7(4): 15-30.
- Walley, H.D. and C.M. Eckerman. 1999. Reptilia: Squamata: Colubridae. Heterodon nasicus. Catalogue of American Amphibians and Reptiles 698:1-10.
- Webb, R.G. and C.M. Eckerman. 1998. Neotype and type locality of the western hognose snake, Heterodon nasicus (Serpentes: Colubridae). Texas Journal of Science 50(2): 99-106.
- Werner, J.K., B.A. Maxell, P. Hendricks and D.L. Flath. 2004. Amphibians and Reptiles of Montana. Mountain Press Publishing Company: Missoula, MT. 262 pp.
- Western Technology and Engineering, Inc. (WESTECH)., 1994, Wildlife Monitoring Absaloka Mine Area Annual Report, 1994. Montana SMP 85005. OSMP Montana 0007D. Febr. 24, 1994.
- Western Technology and Engineering, Inc. (WESTECH)., 1997, Wildlife Monitoring Absaloka Mine Area Annual Report, 1996. Montana SMP 85005. OSMP Montana 0007D. Mar. 1997.
- Western Technology and Engineering, Inc. (WESTECH)., 1999, Wildlife Monitoring Absaloka Mine Area Annual Report, 1998. SMP 85005. OSMP Montana 0007E. April 1999.
- Westmoreland Resources, Inc., Hardin, MT., 1981, 1981 Wildlife Report. April 1982.
- Wilkie, B. 1996. Force feeding snakes. My experience with rat snakes and western hognose snakes. Rephiberary 221:10.
- Wright, J. 1998. Status of the plains hognose snake (Heterodon nasicus nasicus) in Alberta. Alberta Environmental Protection, Fisheries & Wildlife Management Divison, and Alberta Conservation Association, Wildlife Status Report No. 15, Edmonton, AB. 26pp.
- Yarrow, H.C. 1882. Check list of North American reptilia and batrachia, with catalogue of specimens in the U.S. National Museum. United States National Museum Bulletin 24. 249 p.
- Young, R.A. 1992. Effects of Duvernoy's gland secretions from the eastern hognose snake, Heterodon platyrhinos, on smooth muscle and neuromuscular junction. Toxicon 30(7): 775-779.