Animal Diversity Web

Geographic Range

Southern hog-nosed snakes (Heterodon simus) are found in six states (North Caroline, South Carolina, Georgia, Florida, Alabama, and Mississippi) in the southeastern United States. The snakes are found as far north as mid-east North Carolina, just south of Raleigh, and as far south as Lake Okeechobee, FL. Members of this species have been found to inhabit areas from as far east as the Atlantic Coast to as far west as southern Mississippi, reaching just east of the Mississippi-Louisiana state line. There is also a disjunct population of the snakes in central Alabama that ranges between the cities of Anniston and southwest Montgomery. (Hammerson, 2007; Richardson, 2003; Steen, 2010; Tuberville, et al., 2000; Wright and Wright, 1957)

• Biogeographic Regions
• nearctic
  • native

Habitat

Southern hog-nosed snakes are most commonly found in very xeric, upland sand hills. Other habitats may include forests, woodlands, river floodplains, and other dry soil areas. Southern hog-nosed snakes inhabit longleaf pine (Pinus palustris), turkey oak (Quercus laevis), and wiregrass (Aristida stricta) forests and woodlands. These forested areas are maintained by natural or prescribed fire. These snakes also have been found in abandoned agricultural fields.

Southern hog-nosed snakes are fossorial. The burrow depth ranges from 0.20-0.46 m below the surface of the ground. If the snakes do not burrow down into the ground as is most common, they still resort to shelter under piles of brush or in bushes. (Beane, et al., 2010; Beane, et al., 2014; Gibbons and Dorcas, 2005; Jensen, 2008; Palmer and Braswell, 1995; Tuberville, et al., 2000)

• Habitat Regions
• terrestrial

• Terrestrial Biomes
• forest
• scrub forest

• Other Habitat Features
• suburban
• agricultural

Physical Description

Members of the genus Heterodon are most commonly known for their upturned snout. Individuals of Heterodon simus have the most pronounced snout of all the others in the genus, with the tip of their nose curving at a sharper angle. The base of their mouth and neck is wide, which gives their heads a triangular shape; this characteristic is similar to the head shape of the eastern diamondback rattlesnakes (Crotalus adamanteus), for which southern hog-nosed snakes are often misjudged. Keeled scales of the snakes are lined in rows of either 23 or 25 along the body. The keeled scales give the snakes a rough textured body. The anal plate is divided, and the ventral scales are the same width as their body.

Besides the nose angle, southern hog-nosed snakes are separated from other members of the genus Heterodon by their size and coloration. Individuals of Heterodon simus are the stoutest of all others in the genus. These snakes weigh from 46-120g, and their average length is 33.0-56.0cm, with the largest recorded length being 61.0cm. Female southern hog-nosed snakes, averaging between 46.0-56.0cm in length, measured from tip of the nose to the end of the tail, are much larger than the males who average between 33.0-39.0cm. In contrast, the males have a slightly longer tail, but are still shorter in overall length.

The body color of southern hog-nosed snakes is consistently light brown, grey, and tan with dark brown spots (also referred to as blotches) alternating along the dorsal side of the body, larger spots along the top and smaller spots along the sides. The spots do not take up the whole width of the their bodies, but give a patterned mosaic look. The ventral side of southern hog-nosed snakes is solid grey to tan color, and is not distinctly different from the lighter colors on the dorsal side. Oftentimes an orange, yellow, or red line will continue down the dorsal side, setting them apart from all other members of the genus. Eastern hog-nosed snakes Heterodon platirhinos have tails that are much lighter in color than the rest of their bodies, and western hog-nosed snakes Heterodon nasicus have tails that are nearly all black. The tails of southern hog-nosed snakes are always a similar color to the rest of the ventral side. The hatchling snakes resemble the same coloration and blotch patterns of adult southern hog-nosed snakes. ("Species profile: Southern hognose snake (Heterodon sinus) on military installations in southeastern United States", 1998; Beane, et al., 2010; Beane, et al., 2014; Behler and King, 1979; Blair, et al., 1957; Conant and Collins, 1998; Gibbons and Dorcas, 2005; Gibbons and Semlitsch, 1991; Holman, 2000; Jensen, 2008; Jenson, 2004; Palmer and Braswell, 1995; Richardson, 2003; Tuberville, et al., 2000; Wright and Wright, 1957)

• Other Physical Features
• ectothermic
• bilateral symmetry

• Sexual Dimorphism
• female larger

• Range mass

  46 to 120 g

  1.62 to 4.23 oz

• Range length

  33 to 61 cm

  12.99 to 24.02 in

• Average length

  33-56 cm

  in

Development

Gestation period has not been reported in southern hog-nosed snakes, but the incubation period, the time from egg laying to hatching, ranges from 65-70 days. The size of the eggs ranges from from 13-20mm in width and 24-36mm in length with a mass of 2.1-2.5g. Hatchings of the fully developed snakes in genus Heterodon have been seen to take 40-60 hours to fully come out of the eggs and range in size from 13.0cm-17.0cm in length, Weight at hatching has not been reported. When western hog-nosed snakes (Heterodon nasicus) break from the egg, they use an egg-tooth that is on the tip of their nose. These egg-teeth are used to break the surface of the eggs and have been noted to be swallowed by the young snakes after use. Although specific studies have not been done on the hatching process of southern hog-nosed snakes, it's likely that the processes are similar to that of western hog-nosed snakes. Shedding in members of the genus Heterodon takes place within an hour of emergence from the egg.

Color patterns in young southern hog-nosed snakes are the same as color patterns seen in the adult snakes. Southern hog-nosed snakes display indeterminate growth patterns.

As the snakes develop, sex is determined as either male or female by observing the physical anatomy of the snakes. Comparison to other species in the genus Heterodon suggests that the age of sexual maturity for southern hog-nosed snakes ranges from 2-3 years and that generation length is estimated from 5-10 years. It's likely that growth is indeterminate, as it the case for most reptiles. However, no literature has confirmed this for southern hog-nosed snakes. (Beane, et al., 2010; Behler and King, 1979; Edgren, 1955; Gibbons and Dorcas, 2005; Jensen, 2008)

Reproduction

During the mating season, two males may exhibit a combat behavior described as a dance, as they compete for one female. Female snakes have been known to have multiple mates, making southern hog-nosed snakes polyandrous. Because of the bifurcated spiny hemipenes of male southern hog-nosed snakes, females have been found to be in copula with two different males simultaneously. Lasting about 3 hours total, one male in copula will insert his right hemipenis and one will insert the left. Under a few instances females have been observed mistakenly mating with multiple male eastern hog-nosed snakes (Heterodon platirhinos).

Nests of southern hog-nosed snakes have been reported 10-15cm below the surface. Females are responsible for this preparation of the nests as seen in captive environments. In captivity, females were observed making U-shaped burrows and took about 3.5 hours to complete the nests (Edgren, 1955). (Edgren, 1955; Wright and Wright, 1957)

• Mating System
• polyandrous

Breeding most commonly occurs once a year but has been reported less commonly twice a year. Copulation in southern hog-nosed snakes most commonly occurs from mid May to early June, but mating has been observed less frequently in the fall between September and October. In late-season mating instances, it’s unknown if there is delayed fertilization.

Gestation period for southern hog-nosed snakes has not been reported, but the incubation period, the time from egg laying to hatching, is 65-70 days. The eggs are laid in clutches of 6-14 eggs in shallow burrows. The maximum number of eggs laid in a single clutch was observed at 42 eggs, but is not common. Female southern hog-nosed snakes may have up to 6 clutches. The eggs are elliptical in shape and are soft and leathery. The eggs weigh 2.1-2.5g, are 13-20 mm wide, and are 24-36mm long. These eggs can be laid from May to September, but are most commonly laid between June and July. Hatching can occur from August to November, but the most common time being mid September to mid October. Hatchling size ranges from 130-170mm in length, with equal numbers of sex in each clutch. The snakes are born independent. Age of sexual maturity is unknown, but the similarities between species in the genus Heterodon suggests that the age is between 2-3 years, as seen in western hog-nosed snakes (Heterodon nasicus). Generation length as compared to other members of Heterodon is estimated to be 5-10 years. (Beane, et al., 2010; Behler and King, 1979; Edgren, 1955; Gibbons and Dorcas, 2005; Gibbons and Semlitsch, 1991; Jensen, 2008; Jenson, 2004; Oliver, 1955; Palmer and Braswell, 1995; Wright and Wright, 1957)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• sexual
• oviparous

• Breeding interval

  Most likely once a year, but may occur twice.

• Breeding season

  Most common mid May to early June but has been reported from September to October.

• Range number of offspring

  6 to 14

• Average time to independence

  0 minutes

Southern hog-nosed snakes are oviparous and do not care for their eggs or hatchlings. Once the eggs are deposited in shallow burrows, the parental investment stops. Southern hog-nosed snakes have not been seen to return to the young or invest in the young once the eggs are laid.

Edgran (1995) observed a female eastern hog-nosed snake (Heterodon platirhinos) defending a nearby clutch, but that is the only time a protective behavior has been seen by any member of genus Heterodon. (Beane, et al., 2010; Edgren, 1955; Gibbons and Dorcas, 2005; Jensen, 2008; Palmer and Braswell, 1995)

• Parental Investment
• no parental involvement

Lifespan/Longevity

Little is known about the longevity of southern hog-nosed snakes. Eastern hog-nosed snakes (Heterodon platirhinos), a closely related species in genus Heterodon, have a maximum longevity of 9.1 years. The assumed generation time of the southern hog-nosed snakes is 5 years. Annual mortality rates are unknown. ("Partners in Amphibian and Reptile Conservation", 2011; Hammerson, 2007; Tuberville, et al., 2000)

Behavior

Southern hog-nosed snakes are known for their death-feigning behavior and their inflated body defense towards predators. When faced with a threat, the snakes flatten their head and neck to form a hood shape, inflate their body just below the back of their neck, and hiss loudly. This inflating and hissing behavior has led to the common names hissing adder, blowing viper, puff adder, and spreading adder. If this initial response does not deter the predators, the snakes will then play dead. Snakes roll onto their dorsal side, convulse, and remain limp and still with their mouth open and tongue sticking out. If picked up during this death-feigning behavior the snakes will remain limp. The only way to tell whether the snakes are truly dead or not is to turn them over onto their ventral side. If the snakes are still alive, they will turn back over onto their dorsal side.

Southern hog-nosed snakes are not venomous and will rarely ever bite, even when provoked. The main purpose for their sharp posterior fangs are to ensure capture of prey and to deflate any toads that may inflate themselves when consumed.

These snakes are diurnal, are active mostly from May-October, and burrow underground at night classifying them as fossorial. It is proposed that eastern hog-nosed snakes (Heterodon platirhinos) do hibernate or possibly go into pseudohibernation in the winter from October to April (Edgren, 1955). Months of hibernation are reported for other members of genus Heterodon, but are still unknown for southern hog-nosed snakes and may depend on location.

Males and females interact with one another during mating seasons. Males have been reported displaying a combat dance-like behavior to compete for a female mate, and females can mate with one or multiple mates. ("Species profile: Southern hognose snake (Heterodon sinus) on military installations in southeastern United States", 1998; Beane, et al., 2010; Beane, et al., 2014; Behler and King, 1979; Conant and Collins, 1998; Edgren, 1955; Gibbons and Dorcas, 2005; Jensen, 2008; Jenson, 2004; Oliver, 1955)

• Key Behaviors
• fossorial
• diurnal

Home Range

No home range is reported for southern hog-nosed snakes.

Communication and Perception

Little is known about the perception of southern hog-nosed snakes specifically, but it's likely that their perception is similar to others in the family Colubridae and genus Heterodon. Perception in the snakes is most commonly through the senses of sight and smell. The members of the Heterodon genus do not see clear pictures, colors, or shapes, but rather respond to changes in light. The snakes will perceive changes in light and dark. Because the snakes can not clearly see the prey they are hunting, especially for the burrowing snakes, other methods of sensory reception are heightened. The strongest and most useful sense is the sense of smell, which they use by flicking their tongue.

Eastern hog-nosed snakes (Heterodon platirhinos) have an extremely keen and specific sense of smell and ability to pick up chemical signals from prey by flicking their tongue. It is believed that the chemosensory qualities in southern hog-nosed snakes are most closely related to those of the eastern hog-nosed snakes due to their genetic similarities in body structure and similarities of prey choice. The tongue is flicked and picks up vomodors, or chemical signals, from nearby prey. Those signals enter the mouth via the tongue and are received by the vomeronasal organ. In eastern hog-nosed snakes, the speed and number of tongue flicks increases greatly when southern toads (Anaxyrus terrestris) are present. Anaxyrus terrestris is a common prey item for both eastern and southern hog-nosed snakes. Reception and response of the snakes are dependent on the signals received from prey in the surrounding areas. When burrowing down into the ground, the snakes use their tongues to smell the prey. Once the prey is located the number of tongue flicks increases until the snakes respond by biting the prey. This smell sense allows the hunt to be accurate and specifically tells the snakes the type and location of the prey. More research is needed to show the different chemical signals given off by different prey species and to show the reception of those chemicals by the snakes. (Cooper and Secor, 2007; Daghfous, et al., 2012; Davies, et al., 2009)

• Communication Channels
• tactile
• chemical

• Perception Channels
• visual
• tactile
• chemical

Food Habits

Southern hog-nosed snakes have diets consisting of toads, lizards, frogs, and small vertebrates. Toads are the most common prey and include eastern spadefoot toads (Scaphiopus holbrookii) and southern toads (Anaxyrus terrestris or Anaxyrus terrestris). Members of the genus (Lithobates), barking tree frogs (Hyla gratiosa), and ornate chorus frogs (Pseudacris ornata) are frogs that southern hog-nosed snakes consume. Lizards eaten by these snakes include six-lined racerunners (Cnemidophorus sexlineatus) and ground skinks (Scincella lateralis). Although extremely uncommon, rough stinkbugs (Brochymena arborea) have been found in the stomach of few captured southern hog-nosed snakes.

The presence of the upturned snout in the southern hog-nosed snakes allows the species to dig up their prey. Their large posterior maxillary teeth puncture the prey; this is specifically important for the southern hog-nosed snakes due to the prey (many toads and frogs) inflating themselves when attacked. The act of puncturing the prey deflates the toads or frogs and makes the animal easier for the snakes to swallow. (Beane, et al., 2010; Edgren, 1955; Gibbons and Dorcas, 2005; Jensen, 2008; Oliver, 1955; Tuberville, et al., 2000; Wright and Wright, 1957)

• Primary Diet
• carnivore
  • eats terrestrial vertebrates

• Animal Foods
• amphibians
• reptiles
• insects

Predation

Potential predators of southern hog-nosed snakes include common kingsnakes (Lampropeltis getula), eastern indigo snakes (Drymarchon couperi), red-tailed hawks (Buteo jamaicensis), and other various carnivorous mammals and birds. Eggs and hatchlings specifically have seen predation by red imported fire ants (Solenopsis invicta).

Anti-predator behaviors displayed by southern hog-nosed snakes include body puffing and death feigning. In the former behavior snakes will flatten their heads creating a hood and puff up their body to try and scare away predators. Their latter anti-predator behavior is seen when the snakes roll on their dorsal side and play dead. (Beane, et al., 2010; Edgren, 1955; Gibbons and Dorcas, 2005; Jensen, 2008)

• Known Predators

  • common kingsnakes (Lampropeltis getula)
  • eastern indigo snakes (Drymarchon couperi)
  • red-tailed hawks (Buteo jamaicensis)
  • red imported fire ants (Solenopsis invicta)

Ecosystem Roles

Southern hog-nosed snakes prey on regional frogs, toads, lizards. The presence of southern hog-nosed snakes in the ecosystem affects the population of those prey. Southern hog-nosed snakes are prey to various snakes, carnivorous mammals, and birds.

No parasites have been observed in Heterodon simus, but observed parasites and trematodes including Renifer ellipticus and Neorenifer validus have been found in eastern hog-nosed snakes (Heterodon platirhinos) (Beane, et al., 2014; Edgren, 1955)

Economic Importance for Humans: Positive

There are no known positive economic benefits to humans by Heterodon simus.

Economic Importance for Humans: Negative

Southern hog-nosed snakes are not venomous, yet some humans believe them to be and will kill them on contact. They rarely ever bite humans. If they do, it is not a common behavior. There are no known negative economic effects of Heterodon simus on humans. (Weinstein, et al., 2011)

• Negative Impacts
• injures humans
  • bites or stings

Conservation Status

Tuberville et al. (2000) showed that southern hog-nosed snakes have declined over the past few decades. The main reason for this decline is loss of natural habitat. Habitats for the snakes have been disrupted by logging, agriculture, housing, pine plantations, and fire exclusion. Longleaf pine (Pinus palustris) ecosystems have been altered by the restriction of prescribed fire and have contributed to their decline. Southern hog-nosed snakes rely heavily on the ecosystem of longleaf pines and their decline has been directly correlated to the decline of those forests. Another area of decline for the snakes is through the attack of the invasive red imported fire ant (Solenopsis invicta) brought to the snakes habitat around the 1980s (Bean et al. 2014). The introduction of these ants to southern hog-nosed snakes' ecosystem has greatly affected their young survival and overall population.

The IUCN Red List cites southern hog-nosed snakes as "Vulnerable" with a decreasing population trend, and Beane et al. (2014) stated that southern hog-nosed snakes are the "rarest and most threatened snakes in North America." Ranking and protection of the species varies from state to state. In North Carolina and Georgia the National Heritage Program and Georgia Natural Heritage Program rank it as S3 "rare or uncommon" (Tuberville, 2000). The Nature Conservancy as stated by Tuberville (2000) ranks the snakes as G2, meaning "imperiled because of rarity or because other factors demonstrably make it very vulnerable to extinction." In Mississippi southern hog-nosed snakes are an endangered species and in Alabama they are state-protected. No species status is recorded by US Federal List, CITES, or State of Michigan List.

Roadkill has been the main source of mortality for southern hog-nosed snakes and is opportunistically used as the main way to record snake populations.

Ways to ensure the survival of the species are increased prescribed fires, better regulation of invasive species, protection of the pine forests, limiting pesticide use in their habitats, and further education of humans to show that the snakes are not harmful. ("Species profile: Southern hognose snake (Heterodon sinus) on military installations in southeastern United States", 1998; Beane, et al., 2014; Edgren, 1955; Hammerson, 2007; Tuberville, et al., 2000)

• IUCN Red List

  Vulnerable
  More information

• IUCN Red List

  Vulnerable
  More information

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Contributors

Grace Smiley (author), Radford University, Alex Atwood (editor), Radford University, Marisa Dameron (editor), Radford University, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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Strategic Environmental Research and Development Program. Species profile: Southern hognose snake (Heterodon sinus) on military installations in southeastern United States. 98-4. Chapel Hill, North Carolina: The Nature Conservancy. 1998.

Beane, J., A. Braswell, J. Mitchell, W. Palmer. 2010. Amphibians and Reptiles of the Carolinas and Virginia, 2nd Ed. Chapel Hill, North Carolina: University of North Carolina Press.

Beane, J., S. Graham, T. Thorp, L. Pusser. 2014. Natural history of the southern hognose snake (Heterodon simus) in North Carolina, USA. Copeia, 2014/1: 168-175.

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