Rattlesnakes do not possess the physical ability to dig their own burrows, making the idea of a rattlesnake “hole” a misunderstanding. They lack the limbs and claws necessary to excavate soil. Instead, rattlesnakes are opportunistic, relying on pre-existing structures created by other animals or geological processes for shelter from extreme temperatures and predators.
The specific term for a rattlesnake’s winter shelter is a “hibernaculum,” often simply called a den. This underground space is used for brumation, a state of dormancy similar to hibernation in mammals, allowing the snake to survive below the frost line where temperatures are stable. Rattlesnakes utilize natural rock crevices, fissures in canyon walls, or the abandoned burrows of various mammals, such as prairie dogs, gophers, or ground squirrels. Many species exhibit strong fidelity, returning to the same den site annually, sometimes traveling miles to do so.
Identifying the Key Features of a Den Entrance
A rattlesnake den entrance is typically an irregular opening or crevice rather than a perfect hole. The openings usually range from two to four inches wide, accommodating the snake’s body size. These entrances are frequently found under rocky outcroppings, at the base of talus slopes, or within rock piles that offer a deep network of protected spaces.
The surrounding environment provides important clues for identification. Hibernacula are often situated on south or southwest-facing slopes, maximizing sun exposure for basking and temperature regulation. A tell-tale sign of long-term use is a depression or “disk” of smoothed, flattened earth immediately outside the entrance, created by the snake repeatedly coiling there to warm up. Another strong indicator is the presence of dried, shed skin, known as a slough, which snakes leave behind as they exit the den or utilize the rough edges to help them molt.
Telling a Rattlesnake Den from a Rodent Burrow
Distinguishing a rattlesnake den from the burrow of its original digger, typically a rodent, depends on recognizing the lack of mammalian activity. Rodent burrows, such as those made by gophers or squirrels, are characterized by fresh, loose soil piled at the entrance from continual excavation. These holes may also show distinct claw or paw prints in the soft dirt around the perimeter.
A rattlesnake den, by contrast, shows no signs of recent digging because the reptile does not displace soil. The entrance will appear clean, lacking a fresh dirt mound or “plug” of soil, as the snake is merely using a ready-made tunnel or natural fissure. While a rodent burrow entrance may be round and uniform, a den used by a rattlesnake is often an irregular shape, such as a narrow crack in rock or an oval opening in the ground. If you observe an opening that is clean of debris and surrounded by smoothed earth or dried shed skin, it is likely a shelter used by a snake. Always maintain a safe distance when encountering a suspected den, as these locations concentrate rattlesnakes.