Nerodia erythrogaster
Silhouette: Beth Reinke · PhyloPic
In 3 days ~40% in a week ~70%
Nerodia erythrogaster, also known as the plain-bellied water snake or plainbelly water snake, is a common species of semi-aquatic, non-venomous colubrid snake endemic to the United States. The plain-bellied water snake is a large, thick-bodied, mostly patternless snake, with a generally beige underside. Some snakes display a thin, white line between the pale belly and their darker top scales. Subspecies can range from dark brown, gray, and olive-green to greenish-gray or blackish in color. Some lighter-colored individuals have dark dorsal patterns. Plain-bellied water snakes can be distinguished from other water snakes by their "plain", patternless undersides, which vary in color from light reddish hues to beige; this is where they get the common name "plain-bellied", as they typically have no notable markings on their bellies. There used to be recognized subspecies of the plain-bellied water snake, although scientists often had a hard time differentiating between them. This has led to these subspecies no longer being recognized.
The scientific name erythrogaster comes from the Greek word "erythros" (meaning 'red') and "gaster" (meaning 'belly'). This species exhibits... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Congaree National Park | 🇺🇸 United States | |
| 2 | Big Bend National Park | 🇺🇸 United States |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Austin | 🇺🇸 United States | |
| 2 | Dallas | 🇺🇸 United States | |
| 3 | Houston | 🇺🇸 United States | |
| 4 | San Antonio | 🇺🇸 United States |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Cameron Park Zoo | 🇺🇸 United States | |
| 2 | London Zoo | 🇬🇧 United Kingdom | |
| 3 | Museum of Life and Science | 🇺🇸 United States |
With luck
About 10% of wildlife watchers report a Plain-bellied Water Snake sighting in Big Bend National Park on a given day, based on 30 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 27th most-seen of the 48 reptiles we can rate there. Over three days the chance rises to about 40%, and over a week to about 70%, if each day is a fresh chance.
April
In that month about 30% of wildlife watchers report a Plain-bellied Water Snake in Big Bend National Park on a given day, against under 5% in January–February, June and November, the lowest months. That is one of Big Bend National Park's driest months, with about 10 mm of rain against 50 mm in September.
Between 8 and 11 pm
Across all the parks we cover, that three-hour window holds the most Plain-bellied Water Snake sightings with a recorded time, and about 6 in 10 of them come between 6 am and 6 pm: it is seen both by day and at night.
2nd of 2
Of the 2 parks where we can rate Plain-bellied Water Snake sightings, Big Bend National Park ranks 2nd at about 10%. The best odds are in Congaree National Park (United States, about 60%).
Same family: Colubridae
The closest relatives of the Plain-bellied Water Snake that you can see in Big Bend National Park (family Colubridae, Colubrid Snakes) are Trans-pecos Ratsnake (about 30%), Coachwhip (about 20%) and Long-nosed Snake (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Plain-bellied Water Snake is recorded against all the reptiles logged in Big Bend National Park (30 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
