Quick Answer
Rattlesnakes and bullsnakes are frequently confused because they share similar color patterns and both can inflate their bodies and hiss when threatened. The key differences: rattlesnakes have a triangular head, vertical (cat-like) pupils, heat-sensing pits between the eye and nostril, and a rattle on the tail. Bullsnakes have a narrower head, round pupils, no heat pits, and a pointed tail without a rattle. Bullsnakes also have a dark stripe running from the eye to the corner of the mouth, which rattlesnakes lack. In practical terms, if you see a segmented rattle at the tail tip, it is a rattlesnake — a bullsnake's tail simply tapers to a point.
Rattlesnake vs Bullsnake: Why Identification Matters
Bullsnakes are often mistaken for rattlesnakes and killed unnecessarily. This is unfortunate because bullsnakes are beneficial predators that control rodent populations. At the same time, mistaking a rattlesnake for a bullsnake can lead to a dangerous encounter. Accurate identification is essential for safety and conservation.
If you are in Texas, see our Texas Rattlesnake Species Guide and Texas Rat Snake vs Copperhead guide. For the Southeast, see our Copperhead vs Rat Snake guide.
Quick Comparison Table
| Feature | Rattlesnake | Bullsnake |
|---|---|---|
| Head Shape | Triangular, broad, arrow-shaped | Narrower, slightly wider than neck |
| Pupils | Vertical (cat-like, elliptical) | Round |
| Heat-Sensing Pits | Present (between eye and nostril) | Absent |
| Tail End | Rattle (segmented, keratin) | Pointed, no rattle |
| Eye Stripe | Absent | Dark stripe from eye to mouth corner |
| Body Pattern | Diamonds or blotches on lighter background | Dark blotches on tan/yellow, smaller near tail |
| Maximum Length | 2-6 feet (0.6-1.8 m), species-dependent; Western Diamondback averages 4-5 ft | 3-7 feet (0.9-2.1 m), average 4-6 ft; rare specimens to 8 ft |
| Adult Weight | Western Diamondback averages 5-10 lbs (2.3-4.5 kg) | Typically 4-8 lbs (1.8-3.6 kg) |
| Defensive Behavior | Rattle tail, coil, strike | Hiss loudly, flatten head, mimic rattle against ground |
| Venomous | Yes | No (constrictor) |
| Geographic Range | Americas, widespread in US | Central and western US, north into Canada |
Size and Weight: Overlapping but Distinct
Both species grow large enough to cause alarm, and their size ranges overlap — which is exactly why length alone never settles the ID. An average Western Diamondback rattlesnake runs 4-5 feet and 5-10 lbs, though a 6-foot, 15-lb adult is possible in South Texas. Bullsnakes average 4-6 feet and 4-8 lbs, with exceptional individuals reaching 8 feet. In general, a bullsnake looks longer and leaner for its weight, while a rattlesnake is heavier-bodied for the same length, with a blunt tail. If the snake is longer than a standard door frame (6 ft 8 in), you are likely looking at a bullsnake — most rattlesnakes stay shorter.
Head Shape: The Most Reliable Identifier
The head shape is the single most reliable visual identifier. Rattlesnakes have a distinct triangular head that is much wider than the neck. This is because their venom glands are located at the back of the head, giving it a broad, arrow-shaped appearance. Bullsnakes have a narrower head that is only slightly wider than the neck. However, be aware that bullsnakes can flatten their heads when threatened, making them appear more triangular.
Pupil Shape
Rattlesnakes have vertical, elliptical pupils (like a cat's eye). Bullsnakes have round pupils. This is a reliable identifier, but you need to be close enough to see it clearly. Use binoculars or a zoomed camera photo if you are unsure.
The Rattle vs Tail Behavior
The presence of a rattle is definitive for rattlesnakes. However, rattlesnakes can lose their rattles and young rattlesnakes may have only a small button (the first segment). Bullsnakes do not have a rattle, but they will vibrate their tail against dry leaves, grass, or ground when threatened, which can produce a buzzing sound that mimics a rattle. This is the primary reason for confusion between the two species.
Defensive Behaviors
Both species display defensive behaviors that can look similar:
| Behavior | Rattlesnake | Bullsnake |
|---|---|---|
| First warning | Rattle tail audibly | Hiss loudly, inflate body |
| Body posture | Coiled, ready to strike | Coiled or flattened, mouth open |
| Bluffing | Less common | Common — may strike with closed mouth |
| Strike | Fast, with venom injection | Rarely strikes; if so, no venom |
Geographic Range
In the western US, both species overlap in many areas. Bullsnakes are found from the Great Plains through the Rocky Mountains and into the Pacific Northwest. Rattlesnakes (primarily Western Diamondback, Prairie, and Great Basin species) overlap significantly with bullsnake range. In the eastern US, bullsnakes are not present — if you see a large snake in the eastern US with a rattle-like tail, it is more likely a rattlesnake or a mimic.
What to Do If You Encounter One
- Stay calm and do not approach
- If you cannot identify the snake, treat it as venomous
- Back away slowly — give the snake at least 6 feet of space
- Do not try to kill or handle the snake (most bites occur during attempts to kill or handle)
- If it is in your yard, keep pets and children away
- Call a professional for removal if needed
FAQ: Rattlesnake vs Bullsnake
Can a bullsnake kill a rattlesnake?
Yes, bullsnakes are known to eat rattlesnakes. They are immune to rattlesnake venom and will constrict and consume rattlesnakes they encounter. This is one reason why bullsnakes are beneficial to have around.
Do bullsnakes rattle their tails?
Yes, bullsnakes vibrate their tails when threatened, and if they are in dry leaves or grass, it produces a buzzing sound similar to a rattlesnake's rattle. This is a form of mimicry that helps them deter predators.
Sources: US Fish and Wildlife Service, USDA Wildlife Services, state wildlife agencies, CDC, academic extension services. This guide is for informational purposes only and does not constitute professional wildlife management advice.