How to Tell a Bullsnake from a Rattlesnake

Snakes in the House!

As a resident of Eastern Washington for the past 10 years learning to live with snakes has become a reality for me. I've come across a super mean rattle on a hike and my husband was even struck while on the job in construction. Recently we decided to build a house a little ways out of town and we know for a fact our neighbors have occasionally had a snake in the house. It's simply a fact of life.

Fortunately the vast majority of serpentine visitors have been bullsnakes, the non-venomous lookalikes of the western rattlesnake. However, they can be a pretty convincing lookalike and nature had even given them the ability to mimic the sound of a rattle! How then, is a gal like me to figure out the difference? Why shouldn't I just kill them all?

Let's explore both of those questions.

A Bullsnake

Source

Bullsnake (Pituophis catenifer sayi)

The bullsnake is a non-venomous member of the colubrid family and is considered a type of gopher snake. They are a powerful constrictor and squeeze their prey to death. Said prey mostly consists of various rodents, including mice, gophers and rabbits. They will also eat birds and lizards, especially the juveniles. Most importantly however, they have been known to kill and eat rattlesnakes! Here's a huge reason to avoid killing a bullsnake, in my opinion. Sure, they may look a little creepy and it's no fun finding one in the guest bed when changing the sheets (sorry neighbors) but the fact that they can face off with a rattlesnake is a huge bonus. Even setting that aside, having a bullsnake prevent a rodent infestation in your house is also pretty helpful.

As you can see in the picture above the bullsnake's coloration and dorsal pattern mimic a western diamondback's with fair accuracy. The bullsnake can even produce a rattling sound when it hisses through an extension of its wind pipe. It will curve into the signature S-shape of the diamondback and vibrate its tail the create additional noise. All of this occurs when the snake feels threatened, such as in the presence of a human being. At first glance these guys could pass for the real deal and it might be very tempting to kill them. However, wouldn't it be better to just let them go deal with other snakes and mice?

Western Rattlesnake

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Western or Prarie Rattlesnake (crotalus viridis)

The Western Rattlesnake (crotalus viridis), also called the Prairie Rattlesnake, is exactly the kind of fellow I might someday find in my backyard. Roaming the western US and Canada this pitviper subspecies is the dangerously venomous counterpart to the bullsnake. Though they may look alike, the Western Rattlesnake boasts a powerful neurotoxic and hemotoxic venom that may not always prove fatal but can definitely send a grown man to the hospital. At their maximum length they can reach a terrifying four-plus feet.

Generally the rattlesnake subsists on the same rodent based diet at the bullsnake. This is another great reason to keep bullsnakes around, because if they are consuming the local prey they will edge out the competition- there won't be enough food left for the rattlesnake.

As you can see the color and patterning of a Western Rattlesnake is very similar to the bullsnake at first glance. But look carefully at his head, it had the telltale triangular shape of a pit viper. To me this is one of the most striking differences. The rattles on his tail are also a dead giveaway. One difference between the bullsnake and rattlesnake is that when threatened, the rattlesnake will coil into an s-shape and will raise his rattle in the air to sound a more clearly audible warning . A bullsnake on the other hand will keep his tail to the ground to create noise with it on the ground cover. The high, raised tail is a clear indicator of a rattlesnake.

Living With Nature

Ultimately if you live in an area where snakes are part of the natural landscape then you have to get used to the idea you're probably going to encounter one. Be smart, don't go running around barefoot in rocky crevices or sticking your hands in holes you can't see into, and you should be fine. But on the chance that you may encounter a snake remember, it probably wants nothing more than to get far away from you. I can't say I blame you if you do determine the snake is poisonous and decide to kill it, I have small children so I probably would too. But hopefully the tools above will give you the opportunity to at least try to identify the snake, and if it is harmless, release it to do its job for Mother Nature.

Crotalus viridis-Western Rattlesnake

Bullsnake
Rattlesnake
no rattle
visible rattle
rounded head
triangular head
keeps tail down
holds tail up

Have you ever encountered a poisonous snake?

  • Yes- I killed it with swift justice!
  • Yes- I left it well alone
  • Yes- it bit me
  • No- thank goodness!
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