Discover the Largest Black-tailed Rattlesnake Ever Recorded

Written by Kellianne Matthews
Updated: September 24, 2023
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Key Points:

  • Rattlesnakes play a crucial role in maintaining ecological balance by effectively controlling pests and other animals in their habitats.
  • The coloration of snakes living in desert regions is generally lighter or paler, while those inhabiting mountainous areas tend to have more vibrant and brighter colors.
  • Black-tailed rattlesnakes are venomous snakes with broad heads that are noticeably wider than their necks, which are pit vipers.

What is the largest black-tailed rattlesnake ever recorded? Well, let’s be honest: when you hear the word “rattlesnake,” you probably picture a large, aggressive snake coiled up off the ground and ready to strike at any moment. For many people, rattlesnakes are terrifying creatures to be avoided and eliminated at all costs.

However, rattlesnakes are very beneficial to the environments in which they live, acting as expert pest controllers and keeping ecosystems balanced. In addition, most rattlesnakes do their best to avoid humans, and there are only a few species that are high-strung and aggressive.

Black-tailed rattlesnakes have four subspecies: northern, Mexican, Oaxacan, and San Esteban Island black-tailed rattlesnakes.

This is especially true for the black-tailed rattlesnake (or blacktail rattlesnake). This snake is venomous, but it is not aggressive or temperamental. Black-tailed rattlesnakes are surprisingly calm and relaxed, and it is more likely that you will walk right by one without ever realizing it was there.

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The biggest threat these snakes pose is that because they are so quiet and calm, you must look very carefully so that you do not step on one! Most bites occur because someone accidentally stepped on a rattlesnake.

Let’s take a closer look at these beautiful, laid-back snakes, and discover the largest black-tailed rattlesnake ever recorded!

What Do Black-tailed Rattlesnakes Look Like?

Black-tailed Rattlesnake

Black-tailed rattlesnakes have deep pits on their face between their eyes and nostrils. These pit organs allow the snake to detect heat from nearby animals.

©Rusty Dodson/

Black-tailed rattlesnakes have beautiful and distinct patterns. Snakes that live in desert areas typically have lighter or paler colors, while snakes in mountainous habitats have bolder and brighter colors. In addition, black-tailed rattlesnakes that live in higher elevations often are more yellow, while those in lower elevations have more brown and gray colors.

The background color of black-tailed rattlesnakes can be yellow, olive green, tan, silver, gray, or brown. They have diamond- or rhombic-shaped crossbands running along the length of their bodies with lighter-colored centers and patches.

These patterns can be black, brown, or gray, with light-colored centers. Like their name, the ends of the snakes’ tails are completely black, ending with a large, light-colored rattle. Their rattles are made of segmented portions of keratin, with a new layer added each time the snake sheds. However, snakes shed several times a year, and their rattles can be fragile and break off, so they are not an accurate way to tell a rattlesnake’s age.

Black-tailed rattlesnakes are pit vipers with large heads that are much wider than their necks. Their venom glands are much bigger than many other rattlesnakes, which makes their heads look like large diamonds or hearts. Some snakes have black bands across their faces that look like eyebrows or eye masks and may also have black on their snouts. They also have pronounced scales that hang just over the tops of the eyes which can make the snakes look like they are scowling.

What is the Largest Black-tailed Rattlesnake Ever Recorded?

Black-tailed rattlesnakes are medium-sized snakes, measuring between 30-40 inches in length. On average these snakes are around 36 inches long, and females are often larger than males. However, the largest black-tailed rattlesnake ever recorded was 52 inches long!

Where Do Black-tailed Rattlesnakes Live?

Crotalus molossus is a venomous pit viper species found in the southwestern United States and Mexico. Common names: black-tailed rattlesnake, green rattler, Northern black-tailed rattlesnake.

©Viktor Loki/

Black-tailed rattlesnakes live in the southwestern regions of the United States. They also live as far south as Oaxaca in Mexico and on the San Estéban and Tiburón Islands of the Gulf of California.

There are four subspecies of black-tailed rattlesnakes:

  • The Northern Black-tailed Rattlesnake lives in Mexico, Texas, New Mexico, and Arizona
  • The Mexican Black-tailed Rattlesnake lives in Mexico
  • The Oaxacan Black-tailed Rattlesnake lives in Oaxaca (Mexico)
  • The San Esteban Island Black-tailed Rattlesnake is endemic to San Estéban Island (Gulf of California)

These snakes live in a wide variety of habitats but tend to prefer warm, rocky areas. They often live along the sides of canyons or caves, as well as in desert areas, grasslands, and forests.

From May until the first frost of the year, black-tailed rattlesnakes are active and hunting for food. During the spring and fall months, these snakes are primarily diurnal and hunt during the day. However, during the summer they become nocturnal and hunt at night to escape the heat.

Black-tailed rattlesnakes move using both rectilinear locomotions as well as sidewinding, depending on which is most useful at the time. They also have excellent swimming and climbing skills, although these snakes usually prefer to stay on the ground.

From October through March, black-tailed rattlesnakes brumate in crevices and dens abandoned by other animals. Brumation is similar to hibernation, except that snakes do not completely sleep through the winter. Instead, they slow their metabolism and heat rates to conserve energy. On rare occasions, a snake may even emerge from its den during the winter to warm up in the sun.

Are Black-tailed Rattlesnakes Dangerous?

Black-tailed Rattlesnake

The black-tailed rattlesnake has some of the biggest fangs per body size of any rattlesnake species.

©Joe McDonald/

Black-tailed rattlesnakes are venomous pit vipers and are dangerous to humans. Their venom is primarily hemotoxic and affects blood cells and circulation. However, it is not nearly as potent as many other rattlesnake species. Because of this, black-tailed rattlesnakes must use more venom to subdue their prey, so they have extra-large venom glands on the sides of their heads. They also have some of the biggest fangs of any rattlesnake in comparison to their body size.

Black-tailed rattlesnakes are certainly dangerous, but their bites can be treated and are generally not fatal to humans. In addition, black-tailed rattlesnakes are some of the nicest and most docile rattlesnakes out there. These snakes are curious and calm, so bites are very rare. They rely heavily on their camouflage colors and patterns to keep them out of sight and will try to slither away quietly instead of rattling a warning or fighting.

In fact, black-tailed rattlesnakes are typically so quiet that you will likely never see them. This also makes these snakes dangerous, because it is easy to accidentally step on one and be bitten. If they feel cornered, these snakes will rattle their tails loudly and can strike.

What Do Black-tailed Rattlesnakes Eat?

Black-tailed rattlesnakes are carnivorous ambush predators. These snakes hide out of sight and wait for their prey to walk by. When an unsuspecting prey animal gets too close, the snake springs out from its hiding place and strikes it with a venomous bite. Black-tailed rattlesnakes eat small mammals like rabbits and squirrels, as well as rodents, small reptiles, and birds. Many snakes appear to especially enjoy wood rats, cactus mice, and rock pocket mice. Juvenile snakes often hunt lizards until they are large enough to take down other prey.

Black-tailed Rattlesnakes vs. Diamondback Rattlesnakes

Eastern diamondback rattlesnakes’ pattern often fades towards their tail.

©Chase D’animulls/

The black-tailed rattlesnake can be mistaken for a diamondback rattlesnake because they both have geometric patterns along their backs. However, diamondback rattlesnakes have very distinct and uniform diamond patterns. Black-tailed rattlesnakes, on the other hand, have crossbands that are irregularly diamond-shaped or rhombus-shaped. Diamondback rattlesnakes also have black rings on the ends of their tails, but the end of a black-tailed rattlesnake’s tail is entirely black.

Other Record-Breaking Snakes

According to reports, a construction site in Brazil became the site of a shocking discovery when workers came across what was said to be the largest anaconda ever recorded.

This massive anaconda measured a staggering 33 feet in length and was an astonishing 3 feet across at its widest part, weighing approximately 880 lbs. The discovery of such a creature would have been a rare and awe-inspiring experience for those who came across it.

However, this impressive creature’s fate was tragic. Unfortunately, the snake’s discovery was short-lived as it was either killed in the controlled explosion that followed the construction or by the workers themselves after it emerged.

The loss of such a magnificent animal is not only heartbreaking but also serves as a stark reminder of the need to preserve and protect the natural world and its inhabitants.

The photo featured at the top of this post is © Joe McDonald/

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About the Author

Kellianne Matthews is a writer at A-Z Animals where her primary focus is on anthrozoology, conservation, human-animal relationships, and animal behavior. Kellianne has been writing and researching animals for over ten years and has decades of hands-on experience working with a variety of different animals. She holds a Master’s Degree from Brigham Young University, which she earned in 2017. A resident of Utah, Kellianne enjoys creating, exploring and learning new things, caring for animals, and playing with her cats.

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