If you live in an area that is inhabited by rattlesnakes, you may have heard the rumor that they can interbreed with other species. The most common rumor is that rattlesnakes can breed with gopher snakes (or bullsnakes), to create a venomous gopher snake lookalike.
Rattlesnakes can only breed with other rattlesnakes – members of their genus. They belong to the family Viperidae, whereas most non-venomous snakes belong to the family Colubridae. Rattlesnakes are too biologically different for it to be possible to breed with non-venomous snakes. There is no such thing as a bull snake rattlesnake hybrid.
We’re going to discuss what hybrid snakes are, and which species of snake can interbreed. We’re going to examine whether different venomous snakes can breed with each other, and whether any venomous snakes could ever breed with non-venomous snakes.
What is a Hybrid Snake?
Under usual circumstances, only animals of the same species breed with one another. However, when they are similar enough, two animals of different species can occasionally come together and mate. These pairings sometimes produce living offspring. Such animals are known as hybrids, or crossbreeds. Hybrids are often, but not always, sterile (unable to produce offspring of their own).
You are probably already familiar with certain hybrids within the animal kingdom. But what you may not know is that certain snakes can also interbreed, and produce viable hybrid offspring.
There are some limitations as to which species can successfully interbreed. Generally speaking, the two snakes must:
- Live in the same geographic region and habitat
- Be active and fertile during the same time of year
- Produce similar sex pheromones and engage in similar mating cues
- Be morphologically similar, so that they can have intercourse
- Be genetically similar, so that the sperm and egg cells can create a viable embryo.
As you can imagine, this means that snake hybrids are not especially common in the wild. However, they have certainly been documented. So, which snake species can interbreed? Let’s find out.
Which Snake Species Can Interbreed?
Most species that can interbreed belong to the same genus. The genus is the taxonomical rank just above species, which contains animals that are quite similar, but not the same (such as horses and donkeys). However, in some cases, two species may belong to different genera and yet still be able to breed, as long as they are part of the same family (the next rank up).
For example, sheep and goats – both members of the Bovidae family – can interbreed, despite belonging to different genera (Ovis and Capra). This is called intergeneric hybridization.
So, which species of snake can produce viable hybrid offspring?
There are many rumors concerning hybrids between different species. Few of them, however, have been confirmed or documented. Most confirmed examples come from DNA testing of wild-caught specimens, or deliberate crossbreeding of captive species.
The hybrids that we do know of include:
- Bullsnakes (Pituophis catenifer sayi) and Fox Snakes (Pantherophis vulpinus). According to the Journal of Herpetology, these two colubrids have been known to interbreed in the wild, though they belong to different genera.
- King Snakes (Lampropeltis ) and Corn Snakes (Pantherophis guttatus). It is unlikely that these species would interbreed in the wild. However, snake owners have successfully bred pet king snakes with corn snakes in captivity. The offspring are known as “jungle corns.” Interestingly, jungle corns are usually fertile.
- Pythons (Python) According to the United States Geological Survey, some of the Burmese pythons living in the Florida Everglades actually have Indian python DNA, meaning the two species must have naturally interbred at some point.
- Garter snakes (Thamnophis ). There are many species of garter snake. Because they are all so similar, they have been known to interbreed (both in the wild and captivity).
Can Venomous Snakes Cross Breed?
Now that we know that some species of snake can interbreed, what about venomous snakes? Could they potentially breed with other venomous snakes? Let’s take a look at the venomous snakes found in the US.
All rattlesnakes in the U.S. – except for pygmy rattlesnakes and massasaugas – are members of the same genus (Crotalus). They are genetically and biologically very similar to one another, and often inhabit the same areas.
It has been scientifically documented that certain species, such as Mojave rattlesnakes and Southern Pacific rattlesnakes, have interbred in the laboratory and captive environments. Whether they would interbreed in the wild is not known, but it is possible.
However,, there has been no documented case of a rattlesnake breeding with any other kind of snake (whether venomous or non-venomous). They are not similar enough to other snakes, even other pit vipers, to breed with them.
Copperheads and Cottonmouths
Copperheads and cottonmouths belong to the same genus of pit viper (Agkistrodon). They are very similar to one another. For example, both species give birth to live young. They both have similar colors and markings as juveniles, including a bright green-yellow tail tip. They grow to similar sizes and have similar physical characteristics, such as their heat-sensing pit organs. And, of course, their geographical range does overlap.
There have been several documented instances of copperheads breeding with cottonmouths, to produce what is colloquially known as a “cottonhead” or “coppermouth.” Hybrids usually share some features of both parents, such as the body shape and scale count of a cottonmouth with the color and markings of a copperhead.
Coral snakes belong to the family Elapidae, along with cobras and mambas. They are the only elapid in the U.S., and are very biologically different from the rest of our native species.
For that reason, it’s not possible for coral snakes to interbreed with any other snake in our country (whether venomous or nonvenomous). It could, however, be possible for a Texas coral snake to breed with an Eastern coral snake. As the two species are so similar, you likely wouldn’t even notice a hybrid if you saw one.
Can Venomous Snakes Breed with Non-Venomous Snakes?
So, now we’re aware that some venomous snakes can interbreed, we need to ask ourselves: can any venomous snakes breed with non-venomous snakes?
We need to look at venomous and non-venomous snakes in a bit more detail. What makes a snake venomous or non-venomous?
It all comes down, usually, to the taxonomical family that the snake belongs to. There are 18 families in the suborder Serpentes, containing all known snakes.
The main families, containing the majority of species, are as follows:
- Viperidae, containing venomous vipers such as rattlesnakes
- Elapidae, containing venomous elapids such as coral snakes, mambas, and cobras
- Colubridae, made up of non-venomous snakes, such as rat snakes and gopher snakes
- Pythonidae (non-venomous pythons)
- Boidae (non-venomous boids)
As we know, snakes in different families cannot interbreed. It is not possible for a colubrid to breed with a viper, for example. So, in the U.S. at least, there is no way that a venomous snake could breed with a non-venomous snake.
The only venomous colubrids in the US contain such weak venom that they pose no risk to humans (such as garter snakes), and even these have not been noted to interbreed with any snakes from different genera.
There are some highly venomous colubrids in the world, but they do not live in the US. For example, the boomslang is a dangerous colubrid living in Africa. It is hypothetically possible that, in other parts of the world, venomous colubrids could potentially crossbreed with nonvenomous colubrids. However, there has been no scientific documentation of such an event.
Can Rattlesnakes Breed with Bullsnakes?
If you live in a part of the country that has wild bullsnakes (also known as gopher snakes) and rattlesnakes, you may have heard that the two species can interbreed, producing a venomous bullsnake lookalike. Could this be true?
Rattlesnakes belong to the Viperidae family, whereas bullsnakes are Colubrids. They look different and are also distinct from one another biologically. For example, rattlesnakes give birth to live young, whereas bullsnakes lay eggs.
Genetically, bullsnakes and rattlesnakes are about as similar as bears are to raccoons. While the two species have similarities, they are far too different to be able to breed. Even if a bullsnake tried to mate with a rattlesnake, they would not be able to produce viable embryos.
So, how did this rumor start? Bullsnakes are examples of Batesian mimics: they have evolved to mimic rattlesnakes when threatened, to ward off predators. Usually, bullsnakes have narrow, oval-shaped heads. When confronted, however, they can flatten out their heads to a triangular shape and vibrate their tails like a rattlesnake. It’s possible that somebody saw this display, and concluded that the snake was some sort of hybrid.
If you ever spot a bullsnake in the wild, you have no reason to fear it. However, because of their similarity to rattlesnakes, we’d still recommend staying away. After all, it might only take one mistaken identity to give you a bite that would send you to hospital.