Plain-bellied Watersnake (Nerodia erythrogaster)

Plainbelly Water Snake  Nerodia erythrogaster

by Jeff LeClere

A plain belly water snake from Louisa County, Iowa



ENDANGERED. It is illegal to kill or collect this species by law in Iowa. One of Iowa’s rarest snakes, the copperbelly water snake may be found in swampy habitats in southeastern Iowa. Records are few for this snake and any reports would be appreciated. Please send reports to us or the Iowa DNR.


Plainbelly water snakes are a medium sized Iowa snake. They range in length from 30 to 48 inches (Conant and Collins, 1998) and may be quite heavy bodied as adults. Adult plainbelly water snakes have a dark brown or black dorsum with no markings, even when wet. The belly is orange or red and is unmarked except for dark pigment that is sometimes present on the edges of the ventral scales. The labials also share the distinct coloration of the belly, and may also have dark suture lines.

A plain belly water snake from Louisa County, Iowa

Newborn plainbellies look much like northern water snakes and have a gray or very light brown ground color with striking black or dark brown bands and blotches. The crescents on the belly of the young usually have no red but are solid black or brown instead, and there may be a light pink wash on the belly. They change to the adult coloration quickly; specimens only one or two years old are marked like adults.


I list the copperbelly water snake, Nerodia erythrogaster neglecta, as the subspecies found in Iowa (LeClere, 1998). Christiansen and Bailey (1991) and the State list the yellowbelly water snake, Nerodia erythrogaster flavigaster as the subspecies found in Iowa, however, there is much debate as to which one is found here. Please see the Subspecies Remarks found at the end of this account for more information.

A juvenile plain belly water snake from Louisa County, Iowa


The plainbelly water snake is found in only a few scattered locations close to the Mississippi River in southeastern Iowa. This is one of Iowa’s rarest snakes and any specimens seen in Iowa should be reported to us or the DNR. Ventral coloration is extremely important in the identification of this species and reports should include photos or a clear description of the belly. Incidental roadkills should be frozen until someone can pick them up. Remember, it is illegal to keep, harm, or kill these snakes in Iowa.

Range map for the plain belly water snake in Iowa


The plainbelly water snake may be found in the Mississippi river itself, or on one of the islands. Inland habitats consist of backwaters, pools in wet woodlands, rivers, ponds, sloughs, lakes, dams; any waterway closely associated with the Mississippi River.

Ventral surface of a Louisa County plain belly water snake

Ventral surface of a Louisa County plain belly water snake


Plainbelly water snakes are similar to the other water snakes in habits. They are active from April to October and begin breeding soon after emergence. Many males may court one female at the same time. The females are usually quite a bit larger than the males. The pair usually will select a basking perch such as a shrub or branch overhanging water for copulation. Matings have been observed on the banks or even in the water, however. During breeding, both snakes may make undulating movements with their bodies and the pair may remain locked up for an hour or more.

Young are born alive in late June into August. They are roughly 6 – 10 inches at birth and are pugnacious like the adults. Minton (1972) reports litters of 8 to 37 from specimens from Indiana.

A neonate plain belly water snake from Louisa County, Iowa

Plainbelly water snakes are reported to wander farther distances from the waters edge than other water snake species. Specimens may be encountered in wet forests moving from pool to pool. They are most likely seen basking in shrubs, fallen trees, or vegetation over the water. They may also bask on the banks and use rocks, logs, or other debris for shelter. They seem to be more wary than northern water snakes and will slide into the water at any disturbance. They are also more likely to stay submerged after fleeing. They are mainly diurnal.

When caught, they will flatten their jaws and bodies. They release musk and strike viciously. Their bite will draw blood. Even after some time in captivity, they will still strike, although a very few may calm down. Plainbelly water snakes are nonvenomous!! The famous, and venomous, cottonmouth (or water moccasin), Agkistrodon piscivorus, is not found in Iowa. The farthest north cottonmouths have been recorded is central Missouri.

Another ventral shot of a plain belly water snake from Louisa County, Iowa


Plainbelly water snakes are active hunters. They feed on a wide variety of animals associated with water. Amphibians seem to be the favored food, but fish, baby turtles, young snakes, worms, leeches, insects, crayfish, and mammals have also been reported as being consumed. A wider variety of prey is utilized at higher temperatures. They probably eat small meals every day or every other day and hunt by patrolling the water next to the shore for food. These snakes are not constrictors and simply swallow prey alive.

Subspecies Remarks

Although Christiansen and Bailey (1991) and the State of Iowa list the subspecies flavigaster as occurring in Iowa, Joe Monahan and I feel this is not entirely true. Clark(1903) first separated erythrogaster from sipedon as a distinct species. Conant (1943) described two new geographic races of erythrogaster which shed much light on populations found in the north and northeastern part of its range. Both workers separate these races by coloration. In fact, all references state only coloration as the definitive character in these races. Only a plain, bright yellow venter is diagnostic of the subspecies flavigaster (Dundee and Rossman 1985; Tennant 1997; Tennant 1985).

I have heard of only two reports of a water snake with a plain yellow belly seen in Iowa and no one has been able to provide evidence. The only water snake with a yellow belly that I have seen in Iowa was an aberrant northern water snake, N. sipedon, I found in Clayton County (well outside of recorded erythrogaster range) that had some gray dots that are not found on erythrogaster. Preserved specimens lose their color, and ventral coloration is an important key in identifying erythrogaster subspecies (Conant, 1943; Conant and Collins, 1991; Smith, 1961; Minton, 1972; Johnson, 1992; Holman et, al. 1993; Mount, 1975; Wright and Wright, 1957). Therefore, specimens must be described while alive and cannot be reliably identified from dated holdings.

Iowa material seems to fit the descriptions of the copperbelly water snake, N. e. neglecta, quite well thus far (Holman et. al. 1993; Minton, 1972; Smith, 1961) or at least as intergrades with this subspecies. Specimens found in the late 1970s had bright orange red bellies and labials (Christiansen, pers. comm.). There is recorded evidence of this in the photo here, which also appears in the Snakes of Iowa publication (Christiansen and Bailey, 1991), in that the labials are bright orange red, not yellow. The belly was the same color as the labials.

Joe Monahan found several specimens in 1993 in Muscatine and Louisa Counties that had bright orange red labials which can be seen in the photos. The belly was red with no trace of yellow on it. I found a roadkilled erythrogaster in Louisa County in 1996 about 18 inches in length. This snake, though badly mangled, definitely had no dorsal markings and was plain black above. The venter was orange red with black pigment along the edge of each ventral scale. This fits neglecta descriptions (Holman et. al. 1993; Minton, 1972; Smith, 1961). I have seen the flavigaster subspecies and this was not it. Smith (1961) records a neglecta from an island in the Mississippi River between Rock Island County, Illinois, and Muscatine County, Iowa.

If these snakes are found to be neglecta, this population may be eligible for protection under the Federal Endangered Species Act (Levell, 1997). Also, there exists the possibility that these snakes are intergrades between flavigaster and neglecta.

Smith (1961) mentions that most specimens found along the Mississippi River in extreme southwestern Illinois are such intergrades. There are no differences in scalation between the erythrogaster subspecies (Mount, 1975; Wright and Wright, 1957). Genetic work should be performed for additional clues, however, the live specimens needed for the Iowa sample size are extremely difficult to procure. If Iowa populations are intergrades, they are no more flavigaster than the other intergrading subspecies. The copperhead in Iowa is assigned a dual subspecies status and the same might be considered for this snake.

Again, this is one of Iowa’s rarest snakes. Any sightings should be reported! A photo is very important. If possible, try to get a good belly photo as well. If this is not possible, at least try to get a good shot of the labials!

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