The Smooth green snake is a "small medium" North American nonvenomous snake. It gets its common name from its smooth dorsal scales. It is uniform light green on its back, with a yellow or white belly. At birth, its dorsal coloration is different than when it matures. At first, it can be olive green, blue-gray, or even brown, but after it sheds its skin for the first time, it becomes the characteristic bright green. The dorsal coloration can also vary depending on location: bluish in Kansas, olive-tinted light brown in southeastern Texas, and bronze in northern Wisconsin. A non-aggressive snake, it seldom bites and usually flees when threatened.
Smooth green snakes are native to the Nearctic region. Their range spreads through southeastern Canada, west to Saskatchewan, and south through Illinois and Virginia. They can also be found in other areas, such as Wyoming, New Mexico, Iowa, Missouri, Colorado, Kansas, Texas, Mississippi, and northern Mexico. Smooth green snakes live in many different habitats, including marshes, meadows, the edges of streams, and open woods. They prefer moist habitats and areas near permanent water sources, usually staying in green areas for camouflage.
Smooth green snakes are generally solitary creatures. During months when the weather is warmer, they tend to be active both day and night; while in the colder winter months, they hibernate. During hibernation, these snakes look for burrows, ant hills, and other dug-out underground areas, normally gathering in large numbers. Being cold-blooded, during periods of activity these snakes prefer warm areas, lying in the sun on rocks and logs; they also use them for hiding. Smooth green snakes rely on an environment matching their green scales for camouflage to protect themselves from predators. If threatened, they will usually flee. These snakes are docile; they seldom bite and usually allow humans to come close. If provoked, they can secrete a substance from their anal gland, causing a foul smell. When handled by humans, they usually show excited behavior and calm down after wrapping themselves around a finger. When these snakes hunt, they turn their head from side to side, finding prey with their tongue and an organ on the roof of their mouth that interprets chemical signals. Smooth green snakes have no ears, relying on vibrations to figure out their surroundings. Their sight is relatively strong over short distances.
Smooth green snakes mate in the late spring or summer, and females lay eggs from June to September. Usually, two clutches are laid, each containing four to six eggs. Females usually lay their eggs in rodent burrows, mounds of rotting vegetation, sawdust piles, or rotting logs. In the northern parts of their range, female Smooth green snakes may nest communally. The eggs are white and oval; they have thin shells and are about one inch in length. They have an average mass of 2.6 grams. Once the eggs are laid, the female leaves the nest. The eggs usually hatch 4 to 23 days later. Snaklets are completely independent at birth and become reproductively mature at 2 years of age.
Smooth green snakes are hunted by various predators, including the Red-tailed hawk, Great blue heron, Rough-legged buzzard, bears, raccoons, foxes, and the Common house cat. Humans also find these snakes in the wild and keep them for pets. They are subjected to the commercial collection because of their nice skin coloration, passive nature, and small size. However, this snake is not known to survive well in captivity. Because their populations are usually isolated and small in size, this commercial collection can greatly affect the overall population. The Smooth green snake population is also declining due to the use of pesticides, as well as the destruction of habitats. Pesticides are particularly harmful to the snake when used in riparian areas, mountain foothills, and meadows. Habitat destruction is caused by road building, logging, cattle grazing, and the draining of streams. Roads and highways are a major cause of deaths, especially those near streams or other habitats the snake occupies. Flooding, freezing, and destruction of dens can destroy large numbers of Smooth green snakes, as well as other species of snake with which they may hibernate. Human recreational activities, such as off-road vehicles near wetlands, are also damaging the habitat of these snakes. Lakes and streams are enjoyable areas for recreation, but human activity in these areas can degrade them. The use of off-road vehicles in or around wetlands, however, is the most damaging recreational activity.
According to IUCN, the Smooth green snake is locally common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.
Smooth green snakes play an important role in the ecosystem they live in as they control populations of their prey species and in turn, are an important food source for local predators.