Confused about the differences in bullsnakes and rattlesnakes? Bryon Shipley, Denver Zoo keeper and rattlesnake researcher at the Plains Conservation Center in Aurora, Colorado, can help clear up some myths and misconceptions about these two snakes. Read his comments below:
Typically, myths about rattlesnakes vs. bullsnakes are one of the following:
- Bullsnakes eat rattlesnake eggs.
- Bullsnakes eat rattlesnakes.
- Bullsnakes and rattlesnakes breed together.
- Bullsnakes chase away rattlesnakes.
- Bullsnakes kept in your tent keep rattlesnakes away.
- Bullsnakes kill rattlesnakes for sport.
- Bullsnake bites are worse because of the infection that results.
- Bullsnakes are venomous.
- Bullsnakes eat all of the rattlesnakes’ food.
Reasons for myth creation between these two snakes:
- Bullsnakes eat rattlesnake eggs: Since rattlesnakes do not lay eggs, this cannot be true. Rattlesnake eggs hatch within their bodies; consequently young rattlesnakes are born live.
- Bullsnakes eat rattlesnakes: A thorough search of the literature and discussions with researchers who study both snakes has revealed next to nothing that supports the idea that bullsnakes eat rattlesnakes. Bullsnakes are primarily consumers of warm-blooded prey. In one instance, the body of a small rattlesnake showed up in the gut of a bullsnake, but no information exists on whether the ingested rattlesnake was already deceased or even what species it was. It is possible that a young bullsnake may eat a lizard, but no rattlesnake population could be significantly affected by bullsnakes. The natural mortal enemy of rattlesnakes is, in fact, the kingsnake. Additional information, Nov. 27, 2013: An article I ran across says that it happens, but rarely and largely opportunistically. In the particular study, looking at the guts contents of over 1000 bullsnakes, 2 rattlesnakes were found. This is 0.5% of the entire list of prey items found. We don’t know if the rattlers were constricted alive and eaten or scavenged, unfortunately. The take home lesson is still that even eating one or two rattlers during its lifetime, for a bullsnake, this consumption rate is too small to exact any population control over rattlesnakes.
- Bullsnakes and rattlesnakes breed together: Rattlesnakes and bullsnakes commonly hibernate together, along with other snakes and amphibians. Rattlesnakes are live-bearers and bullsnakes are egg layers, and even within the reptile group, where breeding between species of like physiology can happen (i.e. egg layers with egg layers, live-bearers with live-bearers), successful breeding between egg layers and live-bearers could never occur due to the biology involved.
- Bullsnakes chase away rattlesnakes: Bullsnakes and rattlesnakes have always coexisted in their habitat. Their activity schedules in a season can be very different. The sudden disappearance of rattlesnakes in mid-spring results from their switching to a nocturnal schedule, when they are not as noticeable as they were in early spring.
Differences in Ecology and Biology that Enable these two Snakes to Coexist:
- Rattlesnakes have a more variable diet (snakes, lizards, amphibians, and all types of warm-blooded prey). Bullsnakes favor primarily warm-blooded prey and bird eggs. Although bullsnakes eat many of the same prey as rattlesnakes, they eat them in different proportions. Bullsnakes are more of an opportunistic generalist than rattlesnakes, because rattlesnakes tend to focus on one species at any one time, depending on availability and abundance.
- Rattlesnakes have a more efficient digestive system, requiring fewer meals per year than bullsnakes. Bullsnakes eat smaller prey, but more of them.
Rattlesnakes are mostly ambush hunters, preferring to wait for opportunities, once an area of active prey is found. Bullsnakes are active foragers, investigating rodent holes, moving frequently, using more energy.
- Bullsnakes lay several large, calcified, shelled eggs that require lots of energy to produce. Also, energy is required to dig a hole in which the eggs are laid and then covered up.
- Rattlesnakes give birth to live young after their eggs hatch internally, and these young are not encased inside a shelled egg. The rattler does not have to expend energy digging a burrow for the eggs in a suitable environment. The female merely carries them around, protects them, and provides them with adequate heat for embryonic development by moving her body in and out of the sun.
- Rattlesnakes are nocturnal most of the season, while bullsnakes remain mostly diurnal. This difference in foraging schedules reduces competition for shared resources.
- Bullsnakes are constrictors, and rattlesnakes envenomate their prey. Bullsnakes can subdue and eat an entire nest of rodents simultaneously, while rattlesnakes track down their prey after a strike, later consuming that animal after the venom has already begun to digest it.
- Bullsnakes breed annually in the spring, and eggs hatch in the summer. Annual breeding requires being able to ingest lots of prey during the spring and summer to maintain high levels of energy for egg production. A female rattlesnake will breed once every 1 1/2 – 2 years, beginning at about age 3, and deliver babies in the fall. The energy requirement for rattlesnake baby production is still a factor, but spread over longer time span.
Harmless snakes are frequently depicted as being kindly and timid, while rattlesnakes are described as being vicious and aggressive. It is easy to see why an aggressively responding bullsnake, who has a flattened head, can be easily mistaken for a rattlesnake. You can see that these two snakes are very different in almost all respects. Food gathering, energy maintenance, and reproduction in time and space are differences that allow resources to be shared so that both snakes can coexist.
Primarily we are referring to the Prairie rattlesnake or the Western rattlesnakes, as taxonomy stands now, where they occur with bullsnakes in grassland ecosystems, but could include other rattlesnake species. Rattlesnakes in rocky and/or montane habitats may not fully address these same issues as with Prairie rattlesnakes.