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.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
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.
Known Predators:
Anti-predator Adaptations: cryptic
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.
Range length: 50.0 to 115.0 cm.
Other Physical Features: heterothermic
Sexual Dimorphism: female larger
Eastern hog-nosed snakes have been known to live for 11 years in captivity, but how long they live in the wild is unknown.
Range lifespan
Status: captivity: 11.0 (high) years.
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.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: chaparral ; forest ; scrub forest
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.
Biogeographic Regions: nearctic (Native )
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.
Animal Foods: birds; mammals; amphibians; reptiles; insects
Primary Diet: carnivore (Eats terrestrial vertebrates)
Eastern hog-nosed snakes have a significant influence on frog and toad populations.
Eastern hog-nosed snakes are important members of healthy ecosystems. They may contribute to limiting pest populations, such as insects and small mammals.
Positive Impacts: controls pest population
There are no negative effects of eastern hog-nosed snakes on humans.
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.
Communication Channels: visual ; tactile ; chemical
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical
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.
Eastern hog-nosed snakes mate in the spring and sometimes in the fall. In June or July they lay a clutch of 4 to 61 eggs in a shallow burrow. The eggs increase in size during incubation, which lasts for 50 to 65 days. Young hatch in late August or September. Young eastern hog-nosed snakes will expand their necks and hiss, and even play dead, before they have completely freed themselves from their eggshell, if startled. The young grow rapidly at first, but growth slows as they approach maturity at 2 to 3 years old.
Breeding interval: Eastern hog-nosed snakes breed once each year.
Breeding season: Mating occurs in April or May and egg laying in June or July.
Range number of offspring: 4.0 to 61.0.
Range gestation period: 65.0 (high) days.
Range age at sexual or reproductive maturity (female): 2.0 to 3.0 years.
Range age at sexual or reproductive maturity (male): 2.0 to 3.0 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; fertilization ; oviparous
Females lay their eggs in a burrow, there is no further parental care.
Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female)
Like many toad-eating (bufophagous) snakes, H. platirhinos uses death feigning as defense against predation. Before death feigning it may spread is nuchal ribs to flatten its neck, while hissing and mock striking (Tennant, 2003). H. platirhinos will only strike with its nose, it is not known to actually bite. If further harassed, H. platirhinos may hide its head, writhe, regurgitate and defecate, then turn on its back with mouth open and tongue hanging out (Tennant, 2003).
Eastern hognose snake
H. platirhinos can reach a maximum length of 1 m, averaging between 50 to 84 cm. All species of this genus can be recognized by the characteristic upturned and pointed snout. The dorsal coloring in H. platirhinos varies greatly, it can be khaki-green, yellowish-brown, or reddish-brown, all patterned with various combinations of darker spots and splotches. Some individuals are entirely black, but most are yellowish with dark brown blotches (Tennant, 2003). Regardless of age or color, there is always a dark blotch behind the jaw. This blotch extends posteriorly along the sides of the neck. The ventral scales are typically gray (occasionally with orange blotches), and the underside of the tail is usually lighter than the rest of the belly (Tennant, 2003).
The body is H. platirhinos is stocky, with a short head that is not distinct from the wide neck (Tennant, 2003).
H. platirhinos is a toad specialist (Smith and White, 1955; Spaur and Smith, 1971; Tennant, 2007). H. platirhinos, like other toad-eating (bufophagous) snakes, has developed a resistance to the bufadienolide toxins found in the parotoid and skin glands of toads. Additionally, H. platirhinos has enlarged posterior teeth which help to puncture inflated toads (a defense mechanism commonly used by toads that make them too large to swallow) (Tennant, 2003).
Sandy substrate terrestrial environments, mixed hardwood and upland pine forests and forest/grassland boundaries. H. platirhinos will often turn up in recently disturbed areas (Tennant, 2003).
The southern hognose snake (H. simus) has a more upturned snout, and the underside of its tail and belly are the same uniform, pale, color (Tennant, 2003).
The plains hognose snake (H. nasicus), have a sandy ground color more of less uniformly, patterned with brown dorsolateral spots and their ventral scales are heavily pigmented with black spots (Tennant, 2003).
Smith and White (1955) reported that H. platirhinos possesses markedly enlarged adrenal glands. Subsequently, Spaur and Smith (1971) showed that the degree of enlargement is sexually dimorphic, with males possessing significantly larger adrenal glands. Recent observations on other bufophagous species (Rhabdophis tigrinus, Waglerophis merremii) have revealed these same features, suggesting that bufophagy may be related to enlargement, and possibly sexual dimorphism of adrenal glands (Mohammadi et al. unpublished).
The eastern hog-nosed snake[3] (Heterodon platirhinos), also known as the spreading adder[4] and by various other common names, is a species of mildly venomous rear-fanged snake in the family Colubridae. The species is endemic to North America.[5] There are no subspecies that are recognized as being valid.[3]
H. platirhinos is found from eastern-central Minnesota, and Wisconsin to southern Ontario and extreme southern New Hampshire, south to southern Florida and west to eastern Texas and western Kansas.[6]
Studies have shown that H. platirhinos prefers upland sandy pine-forests, old-fields and forest edges.[7] Like most of the genus Heterodon, the Eastern Hognose Snake prefers dry conditions with loose soil for burrowing purposes.[8] These loose soils are preferable habitat components for nesting and egg laying.[9] At the northern end of their range, they have been found to prefer developed lands as their desired habitat followed by mixed forests dominated by hemlock trees.[10] Based on a study in Canada, the average home range size is about 40 hectares.[7] Some individuals will travel outside of their home range in search of mates and nesting sites.
The average adult H. platirhinos measures 71 cm (28 in) in total length (including tail), with females being larger than males. The maximum recorded total length is 116 cm (46 in).[11]
The generic name Heterodon is derived from the Greek words heteros meaning "different" and odon meaning "tooth". The specific name platirhinos is derived from the Greek words platys meaning "broad or flat" and rhinos meaning "snout".[12]
The most distinguishing feature is the upturned snout, used for digging in sandy soils.
The color pattern is extremely variable. It can be red, green, orange, brown, gray to black, or any combination thereof depending on locality. Dorsally, it can be blotched, checkered, or patternless. The belly tends to be a solid gray, yellow, or cream-colored. In this species the underside of the tail is lighter than the belly.[13]
Although H. platirhinos is rear-fanged, it is often considered nonvenomous because it is not harmful to humans. Heterodon means "different tooth", which refers to the enlarged teeth at the rear of the upper jaw. These teeth inject a mild amphibian-specific venom into prey. The fangs receive the venom from the snake's Duvernoy's gland.[14] Bitten humans who are allergic to the saliva have been known to experience local swelling, but no human deaths have been documented.
Common names for H. platirhinos include eastern hog-nosed snake,[3] spreading adder, spread'em outer, hog-nosed snake, adder, bastard rattlesnake, black adder, black blowing viper, black hog-nosed snake, black viper snake, blauser, blower, blowing adder, blowing snake, blow(ing) viper, blow snake, buckwheat-nose snake, calico snake, checkered adder, checquered adder, chunk head, common hog-nosed snake, common spreading adder, deaf adder, eastern hognose snake, flat-head, flat-head(ed) adder, hay-nose snake, hissing adder, hissing snake, hog-nosed adder, hog-nosed rattler, hog-nose snake, hog-nosed viper, hissing viper, (mountain) moccasin, North American adder, North American hog-nosed snake, pilot, poison viper, puff(ing) adder, red snake, rock adder, rossel bastard, sand adder, sand viper, spotted (spreading) adder, spread nelly, spread-head moccasin, spread-head snake, spread-head viper, flat-head adder (spreading) viper.[4]
This species, H. platirhinos, is classified as Least Concern (LC) on the IUCN Red List of Threatened Species (Year assessed: 2007).[15] However, it is a species of increasing conservation concern, especially in the northeastern part of its range.[16][17][18][19] Of the five states in the northeast U.S. where the eastern hognose snake occurs, it currently has "listed" conservation status in four (Connecticut, New Hampshire, New York, and Rhode Island).[20] Noted declines are believed to be the result of direct anthropogenic pressures including habitat loss and fragmentation, road mortality, environmental degradation, and intentional killing.[21][22] Some of this habitat fragmentation may be due to eastern hognose snakes having a reluctance to cross paved roads.[23]
When the eastern hognose snake is threatened, the neck is flattened and the head is raised off the ground, like a cobra. It also hisses and will strike with its mouth closed, but it does not attempt to bite. The result can be likened to a high speed head-butt. If this threat display does not work to deter a would-be predator, an eastern hognose snake will often roll onto its back and play dead, going so far as to emit a foul musk from its cloaca and let its tongue hang out of its mouth.[13][24][25] One individual was observed playing dead for 45 minutes before reanimating and moving away.[26] This death-feigning behavior was also observed often in water habitats.[27]
The eastern hognose snake feeds extensively on amphibians, and has a particular fondness for toads. This snake has resistance to the toxins toads secrete. This immunity is thought to come from enlarged adrenal glands which secrete large amounts of hormones to counteract the toads' powerful skin poisons. At the rear of each upper jaw, it has greatly enlarged teeth, which are neither hollow nor grooved, with which it punctures and deflates toads to be able to swallow them whole.[11][24][28] It will also consume other amphibians, such as frogs and salamanders. Because it is a toad feeding specialist, its venom has been modified to be greatly effective against toads and has not been found to be harmful to humans.[29]
Eastern hognose snakes are occasionally available in the exotic pet trade, but due to their specific dietary requirements, they are not as readily available as other species. Generally, they refuse feeder rodents unless they are scented with amphibians. In Canada, Eastern hognose snakes are considered to be a species-at-risk (COSEWIC designation: Threatened), and consequently capture or harassment of these animals, including their captive trade, is illegal.
These snakes live for approximately 12 years. They shed their skin periodically to grow and develop.
Eastern hognose snakes mate in April and May. Females lay their eggs in small soil depressions, mammal burrows, or under rocks.[9] Some females have been observed traveling past viable nesting conditions in order to reach communal nesting sites.[30]The females, which lay 8–40 eggs (average about 25) in June or early July, do not take care of the eggs or young. The eggs, which measure about 33 mm × 23 mm (1+1⁄3 in × 1 in), hatch after about 60 days, from late July to September. The hatchlings are 16.5–21 cm (6.5–8.3 in) long.[25] They have an average nest temperature of 23-26 degrees Celsius incubating for an average of 49-63 days.[9]
H. platirhinos eating a toad.
H. platirhinos.
H. platirhinos dark color pattern.
H. platirhinos in a Florida orange grove.
The eastern hog-nosed snake (Heterodon platirhinos), also known as the spreading adder and by various other , is a species of mildly venomous rear-fanged snake in the family Colubridae. The species is endemic to North America. There are no subspecies that are recognized as being valid.
