Rat snakes are medium-to-large, nonvenomous snakes that kill by constriction. They pose no threat to humans, and as their name implies, rats are one of their favorite foods. There are Old World (Eastern Hemisphere) and New World (Western Hemisphere) rat snakes, and the two types are genetically different.
New World rat snakes are found throughout North America. One such species of rat snake is the corn snake (Pantherophis guttatus), a docile animal and popular pet.
What is a rat snake?
In the past two decades, the question "What is a rat snake?" has become increasingly complicated to answer. Until the early 2000s, both Old and New World rat snakes were generally thought to belong to the same genus, Elaphe, according to Alan Savitzky, a professor of biological sciences at Utah State University who specialises in the biology of snakes.
"There was a time not that long ago when all rat snakes were considered closely related," Savitzy told Live Science. "We know now that the rat snakes in North America are more closely related to the king snakes than the Old World rat snakes."
New technologies for studying evolutionary biology at the molecular level have enabled scientists to look at the DNA differences between snakes, Savitzy said. This has caused a great deal of upheaval in snake classification, and snakes are being moved into different genuses. In 2002, herpetologist Urs Utiger published findings in the Russian Journal of Herpetology and proposed reclassifying North American rat snakes as members of the genus Pantherophis.
The proposal met with mixed reactions. Some authorities adopted the classification. For example, the Global Biodiversity Information Facility (GBIF), a collaborative network of researchers, accepts Pantherophis, as does the Society for the Study of Amphibians and Reptiles (SSAR), an international non-profit organization that supports herpetological research and education.
However, the International Commission on Zoological Nomenclature (ICZN), recognized as the arbiter for the correct use of the scientific names of animals, does not recognize Pantherophis; nor does the Convention on International Trade in Endangered Species (CITES).
What do rat snakes look like?
According to Reptiles Magazine, rat snakes can vary widely in appearance. They can have blotches, stripes, a combination of both or be single-colored. They can be black, red, brown, yellow, gray or black-and-white colored. They have keeled scales — scales with a ridge running down the center — slender bodies and wedge-shaped heads. Their pupils are round, as are those of most nonvenomous snakes.
Some species of rat snakes reach lengths of 10 feet (3 meters), though 4 to 6 feet (1.2 to 1.8 m) long is more common, according to the Smithsonian National Zoological Park.
Here are descriptions of the appearances of some common rat snake species.
Eastern rat snake/black rat snake (Elaphe obsoleta or Pantherophis alleghaniensis)
According to the Virginia Herpetological Society, this is a shiny, primarily black snake. It has a white chin and many individuals have white bellies. When their skin is stretched, such as after a meal, a spotted pattern may be visible. Spots might be white, yellow, red or orange. Bellies are sometimes checkered in gray, brown, white or yellow. Juveniles are more blotchy and have white or gray bodies.
Yellow rat snake (Elaphe obsoleta quadrivittata or Pantherophis alleghaniensis quadrivittata)
According to the Cincinnati Zoo, yellow rat snakes are the most common rat snake in the Florida peninsula. Their coloration is a morph — a visual difference between populations, caused by a genetic mutation — of the eastern rat snake (also known as the black rat snake) that produces yellow or orange hues over the snake's entire body. Their eyes typically have yellow irises, and the snakes have four narrow brown stripes going down their backs.
Red rat snake (Elaphe guttatus or Pantherophis guttatus)
According to Savitzky, "red rat snake" is an old-fashioned synonym for corn snake. Red rat snakes vary in color but have yellowish or orange bodies with large red blotches on their backs, dark marks on their bellies, and a "V" shape on the tops of their heads.
Gray rat snake (Pantherophis spiloides or Elaphe spiloides)
According to Ontario Nature, gray rat snakes are the longest snakes in Canada, measuring up to 7 feet (2 m) in length. They have grayish coloring with black or dark gray blotches on their backs and bellies. Juveniles are vividly patterned, but that fades somewhat with adulthood.
Where do rat snakes live?
Rat snakes are found throughout North America, from Central America to Southern Canada. Their habitats vary by species. The following is a list of some common rat snake species' ranges and habitats.
Eastern rat snake/black rat snake (Elaphe obsoleta or Pantherophis alleghaniensis)
This snake lives throughout New England and south to Georgia. They are found as far west as Northern Louisiana and as far north as Southern Wisconsin. They can live in a variety of forests and grasslands but a deciduous forest surrounded by grass is their preferred habitat, according to Pennsylvania State University.
Texas rat snake (Elaphe obsoleta lindheimeri or Pantherophis obsoleta lindheimeri)
As their name implies, Texas rat snakes are found throughout Texas, though they also live in Louisiana, Oklahoma and Arkansas. According to the University of Texas at Arlington, they can live in a wide variety of habitats, including forests, grasslands, suburbia and urban areas.
Yellow rat snake (Elaphe obsoleta quadrivittata or Pantherophis alleghaniensis quadrivittata)
According to the Cincinnati Zoo, these snakes are found along the coasts of North and South Carolina, Georgia and Florida. They live in pine flatlands and shrubs, forests and cypress swamps, as well as citrus groves, abandoned buildings and pastures.
Red rat snake (Elaphe guttatus or Pantherophis guttatus)
These snakes are found throughout the southeastern United States, particularly in Florida. They live in pine flatlands, mangrove swamps, forests and urban areas, according to the Florida Fish and Wildlife Conservation Commission.
Gray rat snake (Pantherophis spiloides or Elaphe spiloides)
Gray rat snakes are found in the central United States, from Indiana to Florida and west to the Mississippi River. They are also found in southern Ontario. According to Ontario Nature, gray rat snakes spend their time in forests, venturing out into grassy areas when it is warm enough.
What are rat snakes' habits?
Rat snake behavior varies among species. Some species, such as the black rat snake/eastern rat snake, are known to be shy but aggressive when cornered, according to Marshall University's Herpetology Lab in Huntington, West Virginia. They produce a bad-smelling musk when touched by a predator or picked up by a person, and they spread the scent around with their tail. On the opposite end of the spectrum are corn snakes, some of the most docile serpents in the world.
All species of rat snakes may vibrate their tails in an attempt to trick a predator into confusing them with a rattlesnake. "This type of mimicry, where a harmless species mimics a harmful species, is known as Batesian mimicry," said Bill Heyborne, a herpetologist and professor of biology at Southern Utah University. While such behavior may be helpful for keeping predators away, Batesian mimicry can cause problems for rat snakes. Humans often kill them after mistaking them for venomous rattlers.
Rat snakes are semi-arboreal, which means they spend some of their time in trees, said Savitzky. While rat snakes are nocturnal in warm areas, they are still active during the day fairly frequently. You may see them lying out in the sun or foraging in the forest or on the plains. They also take shelter in tree cavities to wait for prey. Rat snakes are often found in barns, where farmers appreciate their rodent-eating habits.
Rat snakes are excellent swimmers, and the Everglades rat snake is known for swimming to escape from predators, according to the Smithsonian National Zoological Park.
In cold climates, rat snakes typically hibernate in the winter, according to Marshall University.
How do rat snakes hunt and what do they eat?
Rat snakes are constrictors, squeezing their prey to death and swallowing it whole. There are some common misconceptions about how constricting works, said Heyborne. One is that constrictors crush or break the bones of their prey. Another is that they suffocate it, squeezing the prey's lungs too tightly for the prey to breathe. "It turns out that the squeezing overwhelms the circulatory system," explained Heyborne. "Blood cannot get to the brain, and the animal dies within seconds due to ischemia."
Rat snakes often feed on small rodents, such as mice, rats, chipmunks and voles, but they are also known to eat frogs, lizards, birds and bird eggs. Juveniles are more likely to eat cold-blooded prey, while adults stick almost exclusively to warm-blooded animals, according to Marshall University. Some species of rat snake are called chicken snakes because they like to eat chicken eggs.
Rat snakes are known to wait for and ambush their prey as well as actively hunt it, according to Savitzky.
According to Penn State, sometimes after killing their prey, rat snakes continue hunting. They do this because once they are cloaked in their prey's scent, other prey is less likely to notice them. Rat snakes might kill more prey and then return to their original kill, devouring many animals in a single meal.
How do rat snakes reproduce?
Rat snakes are oviparous, meaning they lay eggs that spend little to no time incubating inside the mother, said Savitzky. If conditions are right, females may lay two clutches of eggs per year. Otherwise, they usually lay one. In cold climates, they may lay eggs even less frequently.
Mating season is often in the late spring, though it depends on the climate. Males attract females through pheromones and will sometimes fight other males for the same female, according to Penn State University.
Five weeks later, females lay clutches of about 12 to 20 eggs in a hidden spot, such as in a hollow log or pile of compost. According to Penn State University, the burying beetle (Nicrophorus pustulatus) commonly parasitizes rat snake eggs. The beetle lays its eggs in the snake's eggs, and the baby beetles eat the snake embryos.
Rat snake young hatch after about two months and are quite long as hatchlings, measuring around 13 inches (33 centimeters) from nose to tail. Rat snakes offer no parental care to their young, and their babies are often eaten by hawks and other snakes.
Are rat snakes endangered?
Some species of rat snakes are endangered. Canadian grey rat snakes are either endangered or threatened, depending on the location (a population in Ontario's Carolinian forest is endangered, while a population in the Frontenac Arch region is threatened, according to the Government of Ontario). Eastern/black rat snakes are considered endangered in Massachusetts, and red rat snakes are part of the Imperiled Species Management Plan in the Florida Keys, according to the Florida Fish and Wildlife Conservation Commission.
Additional resources
When temperatures drop during the winter, rat snakes enter a state of reduced metabolic activity, called brumation; the Discovery Place in Charlotte, North Carolina, explains how brumation differs from hibernation. Check out Pennsylvania State University's website to learn more about beetles that parasitize rat snake eggs, and the Florida Museum of Natural History describes how to identify the Eastern ratsnake, which is also known as the chicken snake, the yellow rat snake and the Everglades rat snake.
This article was updated on Feb. 15, 2022 by Live Science Senior Writer Mindy Weisberger.
Editor's note: This article has been corrected after previously stating the eastern rat snake was the largest species of rat snake.
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