Storeria occipitomaculataRedbelly Snake

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Geographic Range

Storeria occipitomaculata, the red-bellied snake, ranges from eastern North Dakota to Nova Scotia, south to Florida, and west to eastern Texas. The Great Plains may act as a barrier to the west, considering that they are also absent from large areas of remnant prairie lands in the parts of the midwest and east. However, a subspecies, Storeria occipitomaculata pahasapae, is found in disjunct populations in the Black Hills of western South Dakota and eastern Wyoming. Another subspecies, Storeria occipitomaculata obscura, is found in Florida and west along the Gulf Coast to eastern Texas. Red-bellied snakes are locally common in woodlands throughout their range (Harding 1997, Smith and Brodie 1982).

Habitat

Red-bellied snakes are most abundant in deciduous and mixed woodlands. They generally like a damp, moist, and cool environment. Unsurprisingly, they are often found in mesic environments, such as river bays, creek bottomlands, and sphagnum bogs where slugs, snails and worms are readily available. They often hide under bark, logs, rocks, and leaf litter. However, they are still common in drier sites such as pastures and grasslands adjacent to woodlands (Harding 1997, Semlitsch and Moran 1984). Quite often they are seen around human habitations. They tend to hide in vacant lots around trash, under boards, and other debris. Occasionally red-bellied snakes are seen basking in the open sun and sometimes climb into low shrubs and other vegetation (Harding 1997).

Physical Description

The red-bellied snake is a very small snake; total body length ranges from 20.3 cm to 40.6 cm (8-16 in) when fully grown. They are usually brown to reddish brown (although sometimes gray and rarely black) with or without 4 faint, dark dorsal stripes. Occasionally there will be only one, light colored, middorsal stripe, or all five stripes may occur together. The belly is usually a striking bright red, but is known to occur in orange, faint yellow, pink, and infrequently in gray or black. The head is usually brown or reddish brown on top with a white throat and chin underneath. There are three light spots around the neck (one on top and one on each side) that can mix together to form a collar. There are 110-133 ventral scales and 35-61 caudal scales. The midbody contains 15 scale rows. They have keeled scales and a divided anal plate. (Behler 1979, Harding 1997, Smith and Brodie 1982).

Red-bellied snakes are just 7-11 cm at birth. Compared with adults, newborn snakes are darker above and lighter below, and the nape spots create a more distinct neck collar (Harding 1997).

Distinguishing the sex of red-bellied snakes is difficult unless the female is pregnant and therefore heavier and larger. However, males generally have longer tails than females. The female tail is approximately 17-22 percent of the total body length and the male's tail makes up 21-25 percent of the total body length (Harding 1997).

Storeria occipitomaculata subspecies are also hard to differentiate. Some have been know to hybridize, and therefore contain characteristics of both parent species (Harding 1997). However, the Florida red-bellied snake, Storeria occipitomaculata obscura, usually has a more distinct neck collar (neck spots more completely fused), while Storeria occipitomaculata pahasapae of the Black Hills region has very small, faint necks spots or they are completely absent (Behler and King, 1979).

Red-bellied snakes can be confused with brown snakes, Kirtland's snakes, ring-necked snakes and garter snakes. However, red-bellied snakes are usually much smaller than these species. Kirtland's snakes also have a red belly, but it contains two rows of black spots. Ring-necked snakes have a more uniform, prominent collar and they have smooth (rather than keeled) scales. The brown snake has a light belly and 17 midbody scale rows. Garter snakes also have a lighter belly and an undivided anal plate (Harding 1997).

  • Sexual Dimorphism
  • sexes shaped differently
  • Range length
    20.0 to 40.0 cm
    7.87 to 15.75 in

Reproduction

Red-bellied snakes typically mate in spring and early summer, but may also mate in late summer and fall. They give birth to live young usually between late July and early September in northern regions and sometimes later in the south. Litter size ranges from 1-21, but normally only 7 or 8 are born (Harding 1997), with approximately equal numbers of each sex (Blanchard 1937). The largest females invest more energy in reproduction, producing a higher number of young (but not necessarily larger young) than smaller females (Brodie and Ducey 1989). Studies have shown that nearly all females captured in the spring are gravid, suggesting that they are very successful breeders (Semlitsch and Moran 1984).

Newborn snakes grow quickly, often doubling their length within the first year (Harding 1997). By their second year they are sexually mature and begin mating. Minimum length for sexual maturity is 22 cm (Blanchard 1937). It is not known how long they live in the wild, but captives may live at least four years (Harding 1997).

  • Breeding interval
    Red-bellied Snakes breed once or twice each year.
  • Breeding season
    Red-bellied Snakes have their young in late summer and fall.
  • Range number of offspring
    1.0 to 21.0
  • Average number of offspring
    7.0
  • Average age at sexual or reproductive maturity (female)
    2.0 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    730 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    2.0 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    730 days
    AnAge

Female Red-bellied Snakes nurture their young in their bodies until they are born. At that point there is no further parental care.

Lifespan/Longevity

Red-bellied Snakes have been known to live 4 years in captivity. They may live longer in the wild but this is poorly known.

  • Range lifespan
    Status: captivity
    4.0 (high) years
  • Average lifespan
    Status: captivity
    4.6 years
    AnAge

Behavior

Red-bellied snakes are typically diurnal, but may become nocturnal during hot or dry weather. They tend to be more active after rainfall, most likely because their main prey is more active at these times (Harding 1997). However, in South Carolina surface activity was found to increase during periods of hot dry weather and low water levels. This is presumably because drying of their home range forces them to seek moist areas to escape desiccation and to find slugs, snails, and worms. During this type of weather red-bellied snakes may be encountered more often because they are forced to follow soil moisture gradients (Semlitsch and Moran 1984).

Red-bellied snakes are quite cold tolerant, as many are locally common in northern portions of their range. They remain active year-round in the south and from April to October or November in the north. In the north activity may increase during large migrations to and from hibernating sites. They hibernate underground in anthills, building foundations, abandoned animal burrows, and other suitable cavities. They usually hibernate in large numbers with their own kind as well as with other snake species (Carpenter 1953, Harding 1997). An excavated ant mound in Manitoba Canada yielded 257 hibernating snakes of which 101 were red-bellied snakes, 148 smooth green snakes and 8 Great Plains garter snakes (Oliver 1955).

The red-bellied snake exhibits a curious behavior known as "lip-curling." While both ingesting prey and being threatened, they flick their tongue and curl their lips upward to show their small maxillary teeth. This is thought to have some benefit for prey seizure, but it may be just as important as a deterrent to predators. When handled roughly they will sometimes exhibit the lip-curling, then rub their head sideways on the captor scratching their teeth against the flesh. The teeth are too small for this to be harmful to humans and is barely even noticeable. As with many other snakes when captured, they often release musk and smear the captor with cloacal matter (Amaral 1999). Occasionally they may even play dead by going completely limp until they think the coast is clear (Watermolen 1991). A much more dramatic display of death-feigning has been recorded. The particular snake wiggled its tail, twitched the back of its body, rolled over exposing the red belly, held its mouth open, protruded its tongue, contorted its body, and then went completely stiff instead of the usual limp display (Jordan 1970). It is not known if this is actually a death-feigning display or a stress induced seizure (Harding 1997).

Communication and Perception

Red-bellied Snakes communicate with each other primarily through touch and smell, especially during breeding. Outside of the breeding season they do not interact much with other snakes. They use their forked tongues to collect chemicals from the air and insert these forks into a special organ in the roof of their mouth, which interprets these chemical signals. Snakes are also sensitive to vibrations and have reasonably good vision.

Food Habits

Red-bellied snakes are specialized feeders of gastropods. Stomach content analysis has revealed that at certain times they may feed exclusively on slugs (Brown 1979, Semlitsch and Moran 1984). Earth worms and snails are also very common food items, while insect larvae and pill bugs, and possibly young salamanders serve as food items (Harding 1997).

They have a number of adaptations to aid their specialized gastropod diet. The teeth of S. occipitomaculata are especially slender and in-curved so they can more easily grasp and hold on to the slimy, soft bodies of slugs and snails (Amaral 1999). Their skulls are also proportionately smaller than other snakes, which may aid in extracting snails from their shells (Rossman and Myer 1999). It is possible that they release very weak venom from their Duvernoy glands during prey seizure. This venom may serve to both weaken the prey (reducing prey-handling time) and reduce the effects of the snail's mucous secretions (Amaral 1999).

  • Primary Diet
  • carnivore
    • eats non-insect arthropods

Predation

Red-bellied snakes are eaten by a number of predators, including American crows, milk snakes, hawks, shrews, thirteen-lined ground squirrels, raccoons, and domestic cats. They do not bite in response to a threat but will flatten their bodies and curl their upper 'lips' as a form of warning. These snakes are very small, though, and their teeth wouldn't harm any but the tiniest of predators. They can emit a foul-smelling substance and smear it on their attacker if harassed. Some will stiffen and roll onto their backs when harassed, playing dead. This exposes their bright red belly and may be enough to startle a predator momentarily and allow escape.

Ecosystem Roles

Red-bellied Snakes help to control populations of slugs, snails, and earthworms. They are also a valuable food source for the animals who prey on them.

Economic Importance for Humans: Positive

Although seemingly insignificant, red-bellied snakes may be important to us in any number of unforseen ways. They are likely an important link in the food web as both predator and prey, and are therefore important in sustaining the integrity of our natural ecosystems. The condition of our ecosystems will likely, in time, be reflected in our economy.

In addition to food web relationships, their consumption of slugs, snails, and occasionally insects and larvae, may aid in controlling these pests in our farmlands and gardens (Harding 1997).

  • Positive Impacts
  • controls pest population

Conservation Status

Red-bellied snakes often turn up around lumber, sheet metal, and other debris around homes, abandoned buildings, and trash dumps. Their proximity to humans can often result in death by some fearful person.

Red-bellied snakes are, currently, locally common in areas of suitable habitat. However, habitat fragmentation is probably reducing their numbers to some degree. They are often killed in large numbers while crossing roadways during migrations to and from their hibernacula. People should be educated on the harmlessness and value of this species (Harding 1997).

Contributors

Matthew Gates (author), Michigan State University, James Harding (editor), Michigan State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

diurnal
  1. active during the day, 2. lasting for one day.
female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

young precocial

young are relatively well-developed when born

References

Amaral, J. 1999. Lip-curling in Redbelly Snakes (Storeria occipitomaculata): Functional morphology and ecological significance. Journal of Zoology, 248(3): 289-293.

Barret, G., M. Villarroul. 1994. Storeria occipitomaculata occipitomaculata (Northern Red-bellied Snake). Predation. Herpetological Review, 25(1): 29-30.

Behler, J., F. King. 1979. National Audubon Society Field Guide to North American Reptiles and Amphibians. New York, NY: Chanticleer Press and Alfred A. Knopf, Inc..

Blanchard, F. 1937. Data on the natural history of the Red-bellied Snake, Storeria occipitomaculata (Storer), in northern Michigan. Copeia, 1937: 151-162.

Brown, E. 1979. Stray food records from New York and Michigan snakes. American Midland Naturlaist, 102(1): 200-203.

Carpenter, C. 1953. A study of hibernacula and hibernating associations of snakes and amphibians in Michigan. Ecology, 34(1): 74-80.

Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, Michigan: University of Michigan Press.

Jordan, R. 1970. Death-feigning in a captive Red-bellied Snake, Storeria occipitomaculata (Storer). Herpetologica, 26: 466-468.

Knapik, P., J. Hodgson. 1986. Life history notes. Serpentes. Storeria occipitomaculata (Red belly Snake). Herpetological Review, 17(1): 22.

Oliver, J. 1955. The Natural History of North American Amphibians and Reptiles. Princeton, New Jersey: D. Van Nostrand Company.

Rossman, D., P. Myer. 1990. Behavioral and morphological adaptations for snail exraction in the North American Brown Snakes (Genus Storeria). Journal of Herpetology, 24(4): 434-438.

Semlitsch, R., G. Moran. 1984. Ecology of the Redbelly Snake (Storeria occipitomaculata) using mesic habitats in South Carolina. American Midland Naturalist, 111(1): 33-40.

Smith, H., E. Brodie Jr.. 1982. A Guide to Field Identification: Reptiles of North America. Racine, Wisconsin: Western Publishing Company.

Watermolen, D. 1991. Storeria occipitomaculata occipitomaculata (Northern Red-belly Snake). Behavior. Herpetological Review, 22(2): 61.