Animal Diversity Web

Geographic Range

Eastern hog-nosed snakes are native only to the Nearctic. They are found throughout the United States east of the Rocky Mountains and into southern Canada. They are absent from some areas in the Great Lakes region, such as the areas south of Lakes Ontario and Erie and eastern Wisconsin. (Harding, 2000)

• Biogeographic Regions
• nearctic
  • native

Habitat

Eastern hog-nosed snakes prefer areas with dry, loose soils but can be found in a wide variety of habitats, from pine forests or deciduous woodlands to prairies, meadows, and pastures. (Harding, 2000)

• Habitat Regions
• temperate
• terrestrial

• Terrestrial Biomes
• chaparral
• forest
• scrub forest

Physical Description

Eastern hog-nosed snakes are moderately sized, thick-bodies snakes, with a total length ranging from 50 to 115 cm. They are marked, usually, with large darkish blotches on a background of gray, brown, tan, olive, or pinkish. The dark blotches alternate in rows along the length of their body, making them look somewhat like rattlesnakes. Some individuals lack this blotching or are overall black in color. Their most characteristic feature is their wide head, with a flattened, upturned snout. There is often a dark band extending behind their eyes and two, more distinct, large blotches directly behind the head. Belly color is tan, gray, cream, or pinkish. Males are slightly smaller than females, with relatively longer tails. Young eastern hog-nosed snakes are more distinctly marked than adults, with clear blotching even in animals that grow to have no blotches as adults. They hatch at a length of 12.5 to 25.4 cm. Eastern hog-nosed snakes are most often confused with rattlesnake species, but they are completely harmless. They can be distinguished from rattlesnakes because they lack rattles on the tail and do not have facial pits, as do all rattlesnakes. (Harding, 2000)

• Other Physical Features
• heterothermic

• Sexual Dimorphism
• female larger

• Range length

  50.0 to 115.0 cm

  19.69 to 45.28 in

Lifespan / Longevity

Eastern hog-nosed snakes have been known to live for 11 years in captivity, but how long they live in the wild is unknown. (Harding, 2000)

• Range lifespan
  Status: captivity

  11.0 (high) years

Behavior

Eastern hog-nosed snakes are active mainly during the day, though they may restrict activity to mornings and evenings in hot weather. They forage and bask in the open, but are otherwise typically found underground, or sometimes under logs or debris. Eastern hog-nosed snakes are good burrowers, using their wide, upturned snout to push soil from side to side and downward into loose soil. They make their own burrows or enlarge the burrows of other animals. They hibernate in deep burrows or under tree stumps from late October to early April. Eastern hog-nosed snakes are solitary animals. (Harding, 2000)

• Key Behaviors
• fossorial
• diurnal
• sedentary
• hibernation
• solitary

Communication and Perception

Like other snakes, eastern hog-nosed snakes, rely primarily on their sense of smell to sense their environment and communicate with others, mostly during breeding. They also are sensitive to vibrations and have fair eyesight. (Harding, 2000)

• Communication Channels
• visual
• tactile
• chemical

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

Food Habits

Eastern hog-nosed snakes are specialized for eating toads and frogs, though they also sometimes eat salamanders, small reptiles, reptile eggs, small mammals, such as mice, small songbirds, and insects. The majority of their diet, though, is made up of toads. Their digging abilities and wide mouths, flexible jaws, and curved teeth, make them good at finding and grabbing wide-bodied toads. Toads often inflate themselves with air to prevent being eaten by snakes and this snake's wide gape allows them to handle even puffed up toads. They also have a pair of enlarged teeth at the back of their mouth which some say act to puncture inflated toads, though this has never been shown. Eastern hog-nosed snakes also produce hormones that allow them to deal with the toxic skin secretions of toads, making them safe for these animals to eat. They also have specialized salivary glands which secrete a slightly toxic substance that has the effect of subduing amphibians, though it is harmless to humans and other animals. (Harding, 2000)

• Primary Diet
• carnivore
  • eats terrestrial vertebrates

• Animal Foods
• birds
• mammals
• amphibians
• reptiles
• insects

Predation

Eastern hog-nosed snakes are sometimes preyed on by large birds of prey and snake-eating snakes such as milk snakes and blue racers. Few other animals have been observed eating them, despite their conspicuous habits and slow nature. This may be due, in part, to this snake's unique defensive behaviors, which act to startle and discourage other animals from eating them. When startled, eastern hog-nosed snakes will raise their head and neck, breathe in deeply, and flatten their neck into a cobra-like hood. This makes their two, large, neck blotches look something like large eyes, which may scare away many predators. They then begin to lunge and hiss, though they do not try to bite. They also coil and uncoil their tail, spreading feces and a foul-smelling secretion over their bodies. If this doesn't deter an attacker (or curious human), these snakes will begin to writhe and convulse. They drag themselves through the dirt, further smearing themselves with the bad smelling musk and feces, and sometimes throw up their last meal. Eventually they slow their convulsions, turn over on their back with their mouth open and tongue hanging out, and stiffen in a posture that makes them look dead. At this point they look and smell thoroughly disgusting. If turned right side up at this point, they will give themselves away by promptly turning upside down again. Once an attacker has been discouraged, they will eventually flip over and go on their way. (Harding, 2000)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • milk snakes
  • black racers
  • hawks

Ecosystem Roles

Eastern hog-nosed snakes have a significant influence on frog and toad populations. (Harding, 2000)

Economic Importance for Humans

Economic Importance for Humans: Positive

Eastern hog-nosed snakes are important members of healthy ecosystems. They may contribute to limiting pest populations, such as insects and small mammals. (Harding, 2000)

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

There are no negative effects of eastern hog-nosed snakes on humans. (Harding, 2000)

Conservation Status

Eastern hog-nosed snakes are harmless but are often mistaken for venomous rattlesnake species. As a result, most encounters with humans probably end in death for this unique snake. These snakes are also often killed on roadways and by farm machinery or recreational vehicles. Although much of their preferred habitat remains throughout their range (though habitat destruction also affects them), their numbers have declined drastically. Their number may continue to decline as toad populations decline, which seems to be a general trend in eastern North America. (Harding, 2000)

• IUCN Red List

  Least Concern
  More information

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Other Comments

Eastern hog-nosed snakes are known by a variety of names that reflect their unusual defensive mechanism and the fact that most people mistake them for venomous snakes. They are commonly called puff adders, spreadhead, hissing adder, sand adder, spreading viper, blowing viper, and blow snake. 'Viper' and 'adder' are common names for rattlesnakes. (Harding, 2000)

Contributors

Tanya Dewey (author), Animal Diversity Web.

References

Harding, J. 2000. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, Michigan: University of Michigan Press.