Heterodon

Diversity

There are multiple species within the genus Heterodon . Heterodon platirhinos commonly known as eastern hognose snake, named for its geographic location. Heterodon nasicus commonly known as the western or plains hognose snake. Heterodon kennerlyi commonly known as the Mexican hognose snake with the specific epithet a patronym to Carl Kennerly who was a surgeon and expeditionist in North America and Mexico. Heterodon simus otherwise known as the southern hognose after its distribution throughout the southern United States. Hognose snakes are different from other snake taxa because of morphology and how they deter predators by playing dead. All species of Heterodon have upturned snouts and stout bodies that allow for to burrow in dirt and leaf litter.

Geographic Range

All species in the genus Heterodon are found throughout North America from Canada through Mexico. Heterodon platirhinos is located in southeast Canada and the southeastern United States (Florida, New York, Minissota, Texas, Oklahoma, Arkansas, Mississippi, Alabama, Georgia, South Carolina, North Carolina, Tennessee, Indiana, Kentucky, Ohio, Virgina, New Jersey, Maryland). Heterodon nasicus is also found throughout Canada (Manitoba, Alberta, Saskatchewan) and the midwest United States (Colorado, Kansas, New Mexico, Montana, North Dakota, South Dakota, Nebraska, Oklahoma, Texas, Illinois). Heterodon simus is found in the southern United States (Mississippi, Alabama, Georgia,Florida, South Carolina, North Carolina, Virgina) (Uetz et al. 2019). Heterodon simus is most abundant in the lower coastal plain. This species has not been found in Alabama in over 15 years with the last recorded observation being in 1970.

Heterodon kennerlyi is found in the southern United States (Arizona, Texas, New Mexico) and Northern Mexico (Coahuila, Aguascalientes, San Luis Potosí, Nuevo León, Tamaulipas, Durango, Jalisco).

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Heterodon platirhinos individuals are commonly found in areas with warmer soil, usually near wetlands with low canopy cover, but high shrub density, rock cover, and ground debris. Heterodon platirhinos individuals are usually found near wetlands because it contains their main food source, amphibians. Developed lands are also a main habitat for the eastern hognose because of the increased solar radiation and therefore increased ground temperature Heterodon simus individuals are usually found in sandy upland habitats and are also commonly observed crossing roads near shrub forests and old fields. They are usually associated with sandy soils and sand bridges, and are commonly found in pine-oak forests in North Carolina. Heterodon simus has been found burrowing up to 30 cm below the ground surface which is common making field observation a challenge.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest
• scrub forest scrub forest

• Wetlands
• marsh marsh

• Other Habitat Features
• suburban suburban
• agricultural agricultural

Systematic and Taxonomic History

The name nasicus is derived from the Latin "nasus" meaning nose, in reference to the upturned snout. The subspecific name kennerlyi is a patronym in honor of Army Surgeon C.B.R. Kennerly.

Physical Description

Snakes in the genus Heterodon are known for their upturned snouts. Compared to other snake taxa, Heterodon species are relatively slow moving and stout bodied (Rouse et al. 2011). Heterodon simus has the smallest body size compared to the other species, and it is usually a tan color with dark brown blotches along its back and sides. Adults range in length from 33 to 56 cm with a max recorded length of 61 cm. Females tend to be larger than males.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

Female Heterodon platirhinos have been observed mating with multiple males during a season.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Heterodon simus lays eggs in clutches of six to 14. Eggs laid in captivity have an incubation period of 60-75 days to hatch. Not much research has been done on incubation of wild hognose eggs.

Heterodon platirhinos have a mean nesting temperature between 23.4 and 26.1 degrees Celsius and have an observed incubation time between 49 to 63 days. They usually lay their eggs in old mammal burrows, under rocks, in sawdust piles, or in small soil depressions. Copulation of H. platirhinos has been observed in both spring and fall in the southern range of habitat.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous oviparous
• sperm-storing sperm-storing

Female Heterodon are extremely specific to where they lay their eggs because the eggs are very sensitive to temperature change. Offspring laid in warmer nests are more likely to be larger and more developed at birth allowing for better survival rate.

• Parental Investment
• precocial precocial
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female

Lifespan/Longevity

The lifespan of Heterodon nasicus are naturally limited by predators such as hawks, badgers and coyotes. Humans are also a cause of death for the hognose snake because of things like roads, agricultural machinery, insecticides, and loss of habitat. Lots of snakes are killed on roads because of increased traffic and loss of habitat causing hognose snakes to come into contact with humans more often. Farming equipment also causes the death of hognose snakes while they are burrowed under the ground or hiding above ground.

Behavior

When threatened by a perceived predator all species of Heterodon will hiss, puff and strike followed by an intense writhing behavior that ends with a belly up position with mouth open and tongue out with no easily observed breathing. This behavior is known as death feigning and it is considered a way to startle and deter predators.

All species of Heterodon have evolved multiple fangs in order to subdue prey; the front fangs are used to grab while the back row of fangs inject prey with venom.

Heterodon platirhinos enters hibernation in November and emerges in March and are observed to be the most active in spring and fall. The eastern hognose are diurnal and crepuscular and present triphasic activity during part of the year. Heterodon nasicus enters hibernation in October and emerges in May and has been observed to be the most active in late spring and fall. The western hognose are only diurnal and show diphasic activity.

• Key Behaviors
• terricolous
• fossorial fossorial
• diurnal diurnal
• motile motile
• hibernation hibernation
• daily torpor

Communication and Perception

Heterodon nasicus uses visual and olfactory cues in order to locate and catch frogs and lizards. While H. platirhinos relies mostly on olfactory cues. All hognose snakes have touch corpuscles on their head shields and sensory pores on their dorsal body scales.

• Communication Channels
• visual visual
• tactile tactile
• chemical chemical

• Other Communication Modes
• scent marks scent marks
• vibrations vibrations

• Perception Channels
• visual visual
• tactile tactile
• vibrations vibrations
• chemical chemical

Food Habits

Heterodon platirhinos individuals eat invertebrate insects, such as crickets, beetles, grasshoppers, ants, wasps, and bees. They also eat vertebrates such as salamanders, green frogs, cricket frogs, toads, tadpoles, eastern fence lizards, ribbon snakes, lined snakes, mice, rodents, and chipmunks. Toads make up 40% to 75% of their diet. Heterodon nasicus individuals are more likely to eat animals other than amphibians compared to the other species in the genus. In captivity Heterodon platirhinos may get liver disease when placed on a complete mice diet.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • insectivore insectivore

Predation

Not much is known about natural predators of hognose snakes but humans play a large role in deaths of these snakes. Humans kill hognose snakes in the wild fearing they are venomous or confusing them with rattlesnakes because of their similar scale patterns. Reports of predation in the wild are rare, but it is assumed that predators of Heterodon species include larger snakes of other species, birds, large spiders, and predatory mammals.

To avoid predation Heterodon species use a complex series of defense mechanisms. They wiggle their tail, hiss, and flatten their necks. If harassed further, they turn onto their backs in a motionless position usually with the mouth open, feigning death. They may also defecate and vomit to further avoid predation. This death-feigning behavior in hognose snakes has also been observed with the snake repeatedly biting itself. Western hognoses ( Heterodon nasicus ) are the most docile in the genus and are least likely to show this behavior.

• Anti-predator Adaptations
• aposematic aposematic

Ecosystem Roles

Heterodon species prey primarily on toads. There is a correlation between locations of large toad populations and habitats of hognose snakes. Hognose snakes also hibernate in small mammal burrows or burrows dug themselves which loosens the soil and also can provide other organisms shelter in the future. In captivity, it is possible for hognose snakes to be infected with snake mites ( Ophionyssus natricis ).

• Ecosystem Impact
• soil aeration soil aeration

Economic Importance for Humans: Positive

Northern hognose snakes ( Heterodon platirhinos ) has recently entered the pet trade while western hognose snakes ( Heterodon nasicus ) are the most abundant species of hognose within the pet trade. This is because western hognose snakes are the smallest of the other species and they are more flexible in their diet allowing for them to eat mammals other than amphibians, which are not available year round. Every state has different restrictions on selling and trading hognose snakes.

• Positive Impacts
• pet trade pet trade
• controls pest population

Economic Importance for Humans: Negative

Heterodon nasicus individuals possess large venom glands behind the rear fangs which have been observed to have the effect of immobilizing and killing its prey. Heterodon platirhinos also has these venom glands but they are not enlarged and have been concluded to produce no symptoms in humans. Several accounts of Heterodon bites have been reported in literature varying with severity. Bites to humans have been observed to cause edema, swelling, tenderness, and discoloration.

• Negative Impacts
• injures humans
  • venomous venomous

Conservation Status

Heterodon nasicus is a species of least concern, with a widespread and stable population. Heterodon simus populations have seen a sharp decline in range and population and are classified as vulnerable by the IUCN, and a species of concern by the U.S. Fish and Wildlife Service. Lack of documentation on Heterodon simus has caused it not to be listed as endangered, but multiple states have classified it as S3 or “rare or uncommon in state.” Heterodon nasicus is currently on the “blue list” in Alberta, Canada which means it is at risk of population decline.

Additional Links

Encyclopedia of Life

Contributors

Sarah Shassetz (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Averill-Murray, R. 2006. Natural History of the Western Hog-nosed Snake (Heterodon nasicus) with Notes on Envenomation. SONORAN HERPETOLOGIST , 19:9: 98-101. Accessed March 07, 2020 at https://www.researchgate.net/profile/Roy_Averill-Murray/publication/242470243_Natural_History_of_the_Western_Hog-nosed_Snake_Heterodon_nasicus_with_Notes_on_Envenomation/links/54be9d1c0cf28ce68e69e950/Natural-History-of-the-Western-Hog-nosed-Snake-Heterodon-nasicus-with-Notes-on-Envenomation.pdf .

Beane, J., S. Graham, T. Thorp, L. Pusser. 2014. Natural History of the Southern Hognose Snake (Heterodon simus) in North Carolina, USA. Copeia , 1: 168-175. Accessed February 01, 2020 at https://doi.org/10.1643/CH-13-044 .

Buchanan, S., B. Timm, R. Cook, L. Hazard. 2017. Spatial ecology and habitat selection of eastern hognose snakes. The Journal of Wildlife Management , 81: 509-520. Accessed February 01, 2020 at https://wildlife-onlinelibrary-wiley-com.ezproxy2.library.colostate.edu/doi/full/10.1002/jwmg.21218 .

Burghardt, G., H. Greene. 1988. Predator simulation and duration of death feigning in neonate hognose snakes. Animal Behaviour , Vol 36, Issue 6: 1842-1844. Accessed February 02, 2020 at https://www-sciencedirect-com.ezproxy2.library.colostate.edu/science/article/pii/S0003347288801271 .

Cunnington, G., J. Cebek. 2005. Mating and Nesting Behavior of the Eastern Hognose Snake (Heterodon platirhinos) in the Northern Portion of its Range. The American Midland Naturalist , 2: 474-478. Accessed February 01, 2020 at https://bioone-org.ezproxy2.library.colostate.edu/journals/The-American-Midland-Naturalist/volume-154/issue-2/0003-0031(2005)154[0474:MANBOT]2.0.CO;2/Mating-and-Nesting-Behavior-of-the-Eastern-Hognose-Snake-Heterodon/10.1674/0003-0031(2005)154[0474:MANBOT]2.0.CO;2.full .

Didiuk, A., J. Wright. 1998. Status of the Plains Hognose Snake (Heterodon nasicus nasicus) in Alberta . Alberta, Canada: Alberta Environment. Accessed February 23, 2020 at http://www.assembly.ab.ca/lao/library/egovdocs/1998/alen/65850.pdf .

Durso, A., S. Mullin. 2013. Intrinsic and Extrinsic Factors Influence Expression of Defensive Behavior in Plains Hog‐Nosed Snakes (Heterodon nasicus). International Journal of Behavioral Biology Ethology , Vol 120 Issue 2: 140-148. Accessed February 02, 2020 at https://onlinelibrary-wiley-com.ezproxy2.library.colostate.edu/doi/full/10.1111/eth.12188 .

Durso, A., S. Mullin. 2017. Ontogenetic shifts in the diet of plains hog-nosed snakes (Heterodon nasicus) revealed by stable isotope analysis. Zoology , Vol 120: 83-91. Accessed February 01, 2020 at https://www-sciencedirect-com.ezproxy2.library.colostate.edu/science/article/pii/S094420061630068X .

Edgren, R. 1955. The Natural History of the Hognose Snakes, Genus Heterodon, a Reveiw. Herpetologica , Vol 11 No. 2: 105-117. Accessed March 01, 2020 at www.jstor.org/stable/3889972. .

Goulet, C., M. Marchand, J. Litvaitis. 2015. Habitat Associations of the Eastern Hognose Snake at the Northern Edge of Its Geographic Distribution: Should a Remnant Population Guide Restoration?. Northeastern Naturalist , Vol 22 issue 3: 530-540. Accessed February 09, 2020 at https://doi.org/10.1656/045.022.0309 .

Goulet, C. 2010. A multi-scale evaluation of eastern hognose snake (Heterodon platirhinos) habitat selection at the northern extent of its range . Ann Arbor, Ml: Dissertations Publishing. Accessed February 01, 2020 at https://search-proquest-com.ezproxy2.library.colostate.edu/docview/744072447/?pq-origsite=primo .

Kasumi, K., K. Hiroshi, M. Akimichi. 2019. A case of Western hognose snake bite. Journal of Cutaneous Immunology and Allergy , Vol 2: 37-38. Accessed February 01, 2020 at https://onlinelibrary.wiley.com/doi/full/10.1002/cia2.12041 .

Kroll, 1997. Self-Wounding While Death Feigning by Western Hognose Snakes (Heterodon nasicus). Copeia , Vol 1997 No.2: 372-373. Accessed February 23, 2020 at DOI: 10.2307/1443918 .

Kroll, J. 1973. Comparative Physiological Ecology Of Eastern And Western Hognose Snakes (heterodon Platyrhinos And Heterodon Nasicus). ProQuest Dissertations & Theses Global : 1-5.

Kroll, J. 1976. Feeding Adaptations of Hognose Snake.

The Southwestern Naturalist

Rouse, J., R. Wilson, R. Black, R. Brooks. 2011. Movement and Spatial Dispersion of Sistrurus catenatus and Heterodon platirhinos: Implications for Interactions with Roads. Copeia , 2011 issue 3: 443-456. Accessed February 15, 2020 at https://doi.org/10.1643/CE-09-036 .

Stallins, A., L. Kelley. 2013. The Embeddedness of a North American Snake in the Wildlife Pet Trade and the Production of Assemblage Biogeographies. Annals of the Association of American Geographers , 104:1: 151-165. Accessed March 07, 2020 at https://doi.org/10.1080/00045608.2013.765770 .

Thomasson, V., G. Boulin-Demers. 2015. Using Habitat Suitability Models Considering Biotic Interactions to Inform Critical Habitat Delineation: An Example with the Eastern Hog-nosed Snake (Heterodon platirhinos) in Ontario, Canada. Canadian Wildlife and Biology Management , vol 4: 2-13. Accessed March 01, 2020 at https://mysite.science.uottawa.ca/gblouin/articles/098_2015_ehs_hsm.pdf .

Tuberville, T., R. Bodie, J. Jensen, L. Laclaire, J. Gibbons. 2000. APPARENT DECLINE OF THE SOUTHERN HOG-NOSED SNAKE, HETERODON SIMUS.

Journal of the Elisha Mitchell Scientific Society

Uetz, P., J. Hallerman, J. Hosek. 2019. "Heterodon platirhinos" (On-line). The Reptile Database. Accessed February 09, 2020 at http://reptile-database.reptarium.cz/species?genus=Heterodon&species=platirhinos&search_param=%28%28search%3D%27heterodon%27%29%29 .

Uetz, P., J. Hallerman, J. Hosek. 2019. "Heterodon kennerlyi" (On-line). The Reptile Database. Accessed February 09, 2020 at http://reptile-database.reptarium.cz/species?genus=Heterodon&species=kennerlyi&search_param=%28%28search%3D%27heterodon%27%29%29 .

Uetz, P., J. Hallerman, J. Hosek. 2019. "Heterodon nasicus" (On-line). The Reptile Database. Accessed February 09, 2020 at http://reptile-database.reptarium.cz/species?genus=Heterodon&species=nasicus&search_param=%28%28search%3D%27heterodon%27%29%29 .

Uetz, P., J. Hallerman, J. Hosek. 2019. "Heterodon simus" (On-line). The Reptile Database. Accessed February 09, 2020 at http://reptile-database.reptarium.cz/species?genus=Heterodon&species=simus&search_param=%28%28search%3D%27heterodon%27%29%29 .