Yellowstone is among the most breathtaking national parks in the world. This natural wonder spreads over 3,000 square miles and encompasses various geologic features, including mountains, glacier valleys, lakes, rivers, fossil forests, and even its own Grand Canyon! With as much geographic diversity, it’s no surprise that Yellowstone also houses a diverse fauna.
Yellowstone’s undoubtedly the perfect spot for wildlife watching. And if you like snakes, this is your lucky day. Yellowstone is the ideal place to find five fascinating native species in their wild habitat. I cover all of these snakes in great detail in this article. So, keep reading if you’re interested to learn more about Yellowstone’s unique snakes!
Common Garter Snake
- Scientific name: Thamnophis sirtalis
- Venom: Mild neurotoxic venom; harmless to humans; a bite only causes localized inflammation
- Lifespan: 4-10 years
- Adult size: 18-40 inches
- Temperament: Generally shy, calm, and solitary
Garter snakes are small to medium-sized. They can grow up to 40 inches or longer, but most specimens measure 18-26 inches. They have slender bodies, small heads, and round pupils. These snakes are covered in keeled scales, which gives their skin a rough texture.
They have long, vertical stripes traveling from the back of the head to the tail. These range in width, color, and scale patterns. Common garter snakes can be various colors. Besides the obvious browns and greens, these snakes also come in black, yellow, orange, red, or blue, depending on the subspecies.
Specimens in Yellowstone are typically black with pale yellow or blue bellies. The dorsal side is covered with three vertical golden tripes and irregular red spots down the margins of the body. This sub-species is also known as the “valley garter snake” (Thamnophis sirtalis fitchi).
In Yellowstone, this snake’s preferred habitat is near water, especially the Falls and Snake Rivers. There, the snake is most active throughout the day when it hunts for food. Its diet consists mainly of small frogs, toads, earthworms, and fish.
Unfortunately, the local garter snake population is slowly declining. As the number of amphibians decreases, so do their snake predators. When interacting with humans and large animals, garter snakes are mostly docile. They might freeze, make bluff attacks, or try to flee.
Terrestrial Garter Snake
- Other common names: Western terrestrial garter snake
- Scientific name: Thamnophis elegans
- Venom: Mild myotoxic venom; harmless to humans; a bite might cause localized swelling
- Lifespan: Up to 17 years
- Adult size: 18-41 inches
- Temperament: Generally non-aggressive; unlikely to bite humans
The terrestrial garter snake is the most common reptile in Yellowstone. You can see it in many locations throughout the park, especially next to bodies of water. However, they’re difficult to distinguish from the common garter snake. Both species belong to the same genus and share many similarities.
These snakes can be small to medium-sized. Most adult specimens measure 18-30 inches long, but some might grow up to 41 inches. They have slender bodies, small heads and jaws, and rough, keeled scales. Like its sister species, this snake is diurnal and has round pupils.
Their body color varies and can be gray, brown, or dirty green. They have three vertical dorsal stripes, which can be either white, light yellow, or light orange. One stripe travels down the center of the back, while the other two cover the sides. Some specimens also have small, equidistant dark spots along the stripes.
The terrestrial garter snake is a prolific local snake. Its varied diet and breeding strategy allow the species to maintain a stable population. Terrestrial garter snakes prey on frogs, tadpoles, fish, small mammals, leeches, slugs, snails, and even small reptiles. During the breeding season, females can give birth to up to 20 baby snakes.
This snake exhibits a few unique behaviors. Although it can inject venom into its prey, the terrestrial garter snake also relies on constriction. But its constriction is weak and inefficient at killing prey. They’re mostly peaceful around humans, but juveniles are more likely to bite. Adults discharge a foul-smelling musk when threatened.
- Other common names: Great plains rattlesnake
- Scientific name: Crotalus viridis
- Venom: Powerful venom with hemotoxic, myotoxic, and neurotoxic properties; bites are extremely painful and potentially fatal if left untreated
- Lifespan: Up to 20 years
- Adult size: 35-45 inches
- Temperament: Mostly passive but easily irritable; rarely aggressive toward humans
First and foremost, remember the prairie rattlesnake is a venomous pit viper! This is the most potentially dangerous snake in Yellowstone. Luckily, these snakes are unlikely to bite humans unless provoked. Throughout the years, only two bites have been recorded in the park. However, it’s still best to learn how to distinguish these snails to stay safe.
The average size of adult specimens is 40-45 inches. However, some specimens are even larger. The largest prairie rattlesnake recorded measures just shy of 60 inches (aka 4.97 feet)! To complete the threatening appearance, this snake also has a dense, muscular body, keeled scales, and a wide triangle-shaped head with a strong jaw.
Like all rattlesnakes, Crotalus viridis has the signature rattle at the tip of the tail. The body color ranges from light brown to tan, typically with a greenish hue. The dorsal side has large brown blotches with thin white borders. These go down the back and sides from head to tail.
The prairie rattlesnake prefers drier habitats, so it’s most common in the lower Yellowstone River area. Unlike other snakes in Yellowstone, this species doesn’t usually prey on amphibians. Instead, they prefer small mammals like mice, rats, squirrels, and birds. Like other rattlesnakes, this species will emit a rasping warning sound when it feels threatened.
- Other common names: Gopher snake, Pine snake
- Scientific name: Pituophis catenifer sayi
- Venom: Nonvenomous
- Lifespan: Up to 12 years
- Adult size: 4-6 feet
- Temperament: Irritable and defensible, but rarely aggressive
The bullsnake is a subspecies of the colubrid snake Pituophis catenifer. Pituophis catenifer sayi is the largest of all gopher snakes and the largest reptile in Yellowstone. Most adult specimens measure 4-6 feet long, but some grow up to 8 feet and 4 inches.
Ironically, this very large snake is among the least dangerous. That makes it even sadder to know that bullsnakes are often mistaken for dangerous rattlesnakes and killed in self-defense. They do look quite threatening due to their large size and muscular bodies. Bullsnakes have large, turtle-like heads with small eyes and blocky snouts.
They have rough, keeled scales and are a bright yellow color. They have alternating brown, black, and reddish blotches along the dorsal side. The blotches resemble the scale pattern of diamondback rattlesnakes. The darkest shades are on the upper body. The blotches become narrower towards the tail, where they resemble horizontal rings.
These snakes prefer warmer environments at lower elevations; they’re most common near Yellowstone’s Mammoth hot springs area. There, they feed on small rodents and ground-nesting birds. They’re proficient climbers and can often be spotted in trees. Since this snake is nonvenomous, it relies on its powerful constriction to kill prey.
Bullsnakes are mostly harmless to humans. They’re unlikely to attack, but they’re easily threatened by animals on objects larger than them. Their defense strategies include threat displays, hissing, mock attacks, freezing, or fleeing. Bullsnakes can also imitate rattlesnake sounds by vibrating their tails against the ground.
- Other common names: Northern rubber boa
- Scientific name: Charina bottae
- Venom: Nonvenomous
- Lifespan: 12-25 years
- Adult size: 15-28 inches
- Temperament: Docile
Charina bottae is a true boa species in the family Boidae. Despite this, rubber boas are very different from other boas you might’ve heard about. For starters, these snakes are small, measuring less than 30 inches long. They also have small heads, tiny eyes, and short, blunt snouts.
The tail end is also blunt and rounded— it’s undistinguishable from the head at first glance. Then there’s the skin texture and color. Rubber boas have very small and smooth scales. This makes their skin appear elastic and wrinkly.
The body color ranges from tan to dark brown with no dorsal patterns. The underside is a paler block color, either tan, yellow, green, or orange. I wouldn’t blame you if you mistook this snake for an oversized worm. Just look up some pictures without zooming in on the snake, and you’ll see what I mean. Rubber boas prefer humid areas with shrubs, trees, or rocks.
Like any veritable worm snake, this species spends most of its time partially buried in the soil, rodent burrows, or foliage. Despite stable populations in Yellowstone, its burrowing habits and nocturnal nature mean you won’t see this snake too often. They feed primarily on young rodents but eat salamanders, small frogs, birds, and sometimes reptile eggs as well.
They’re not well-equipped to fend off predators. Their defense strategy is exposing their tail to mimic their head. This lures attackers away to attack a less sensitive spot. Well, they fooled me! Rubber boas are the most docile snakes around humans and will never bite, even when threatened.
If you want to see wild snakes in their natural habitat, Yellowstone is the perfect location for that. This natural park houses five unique native species, including garter snakes, boas, rattlesnakes, and gopher snakes. Most species are at least mildly venomous but unlikely to bite humans.
Such is the case for the common garter snake, terrestrial garter snake, and the potentially deadly prairie rattlesnake. These snakes are mostly calm and docile but can envenomate you when biting. Yellowstone also houses docile nonvenomous species like the bullsnake and the least threatening boa in the world— the rubber boa.