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
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. 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.
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. 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. 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. Storeria occipitomaculata subspecies are also hard to differentiate.
Some have been know to hybridize, and therefore contain characteristics of both parent species. 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. 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.
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, with approximately equal numbers of each sex. The largest females invest more energy in reproduction, producing a higher number of young (but not necessarily larger young) than smaller females. Studies have shown that nearly all females captured in the spring are gravid, suggesting that they are very successful breeders. Newborn snakes grow quickly, often doubling their length within the first year.
By their second year they are sexually mature and begin mating. Minimum length for sexual maturity is 22 cm. It is not known how long they live in the wild, but captives may live at least four years . Red-bellied Snakes have been known to live 4 years in captivity. They may live longer in the wild but this is poorly known.
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. 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. 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. 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. 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. Occasionally they may even play dead by going completely limp until they think the coast is clear. 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. It is not known if this is actually a death-feigning display or a stress induced seizure.
Red-bellied snakes are specialized feeders of gastropods. Stomach content analysis has revealed that at certain times they may feed exclusively on slugs. Earth worms and snails are also very common food items, while insect larvae and pill bugs, and possibly young salamanders serve as food items 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. Their skulls are also proportionately smaller than other snakes, which may aid in extracting snails from their shells.
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.