Rat snakes

Previously, the Latin name for the genus rat snakes was Elaphe, meaning deer-skin. The rat snake species are Elaphe obsoleta while corn snakes are Elaphe guttata. Because of mitochondrial DNA analysis, and re-evaluation of phylogenetic relationships, rat snakes have been moved to the genuses Pantherophis and Bogertophis. The name Elaphe is however still widely used.

Rat snakes enters people homes rather frequently. Bites from rat snakes are painful, and should be avoided because it hurts and because of the risk of bacterial infection. Rat snakes are not dangerous and mostly not aggressive although they will vibrate their tails and behave aggressively towards anybody trying to corner them.

Constrictors & non-venomous

Rat snakes are constrictors by nature, and they feed on a varied diet of rodents, birds, frogs, squirrels, and eggs. Rat snakes play an important role in many ecosystems by keeping the population of rodents (some of which are disease carriers) at a constant, low level. That's also why rat snakes are liked by farmers and others that prefer rat snakes to rats. Rat snakes use their sight and their Jacobsen's organ inside their mouth to smell any prey in their surroundings, and they are experts at finding and killing small rodents.

Entering people's homes

It is black rat snakes that enter US homes most frequently. The reason is that they are very abundant and that their prey is abundant close to homes too. Also, black rat snakes are good climbers and they can easily get around in people's homes.

When threatened, rat snakes freeze - and many rat snakes are killed in traffic because of this behavior, which is not suitable for dealing with modern day traffic. When cornered, there is a risk they will bite. Their bite looks very much like a human bite, and as rat snakes can grow rather large, a bite from a rat snake can be very painful.

Species

Rat snakes in North America belong to either the genus Pantherophis or the genus Bogertophis. Pantherophis are the more abundant of the two. In fact, only Bogertophis rosaliae, the Baja California Rat snake, and the Bogertophis subocularis, can be found in small confined habitats (in the USA), whereas several very common Pantherophis species are throughout most of the southeastern US. The table below shows where the different Pantherophis species are found.

Venom - in relation to rat snakes

It is a common belief that all rat snakes are non-venomous. However, recent studies show that some rat snakes, such as the Asian Rat snake (Elaphe radiata), are venomous indeed ¹.

Even though some rat snakes may be slightly venomous, their venom is not a problem for humans - and rat snakes are constrictors by nature.

Eastern rat snakes

The black rat snake is one of five subspecies of the eastern rat snake and is one of the largest snakes in the US reaching lengths of more than eight feet. They are not venomous, and kill their prey by constriction. They are uniformly black except for a white underside, and are found on the ground, in trees and in water. They enter their hibernacula in November and hibernate on southern exposed areas until March/April, sometimes with other species such as black racers, to get the most benefit from the sun, and can often be seen basking in the fall and in the late autumn.

Other Eastern rat snake sub-species include the yellow rat snake, the gray rat snake, everglades rat snake, and the Texas rat snake.

Yellow rat snakes are yellow (or variations of yellow) with four dark stripes. They are the same size as black rat snakes and are known to interbreed with black rat snakes. They are often found in trees searching for prey or under rocks. They will bite if they feel threatened, and rat snakes tend to have a low threshold with respect to people handling them carelessly. They are most active during the night and they are often found in suburban areas.

Gray rat snakes are smaller than black and yellow rat snakes, as they only reach a length of six feet. They can be quite aggressive and must be handled with caution. They are grayish with blotches of orange and yellow and are also called silver racers, and may interbreed with gray, yellow, and black rat snakes.

Everglades rat snakes are found in Florida only. They are orange with four grey longitudinal stripes. They are also called glades rat snakes, and orange rat snakes, and interbreed with yellow rat snakes. Unfortunately, the population of everglades rat snake is in decline.

Texas rat snakes are quite aggressive and will bite anyone coming too close. They are constrictors and non-venomous. Some mistake the Texas rat snake with the western rat snake, but they are not the same sub-species.

Life-cycle

Rat snakes hibernate every year. They hibernate in hibernacula on rocky, south-facing slopes, preferably with some trees for basking. In a study by Prior and Weatherhead (1996) ³, it was found that per rat snake, 0-11 trees were used for basking, and that their preferred trees were older oaks, as they have numerous cavities and trunks for cover.

Their lifespan in the wild is up to 15 years, males living a little longer than females. In captivity they can live up to 25 years, reaching maturity after 18-24 months.

The gestation period of females is approx. 1½ month, and up to 30 eggs are laid in a clutch, with variation between sub-species.

Combat dance

Something called a «combat dance» has been observed in male rat snakes ² where. The snakes have their tails entwined, and the rest of the body coiled and twised. The role of this strange behavior is not known.

Rat snake bites

Rat snakes, such as the black rat snake or the everglades rat snake, are more aggressive than corn snakes and will bite if handled incorrectly or if they feels uncomfortable.

Although rat snakes are not venomous and they lack two fangs seen in venomous species, a bite from any rat snake can be rather painful, as the saliva of the snake may contain bacteria causing an infection that must be treated.

Furthermore, rat snakes can secrete an ill-smelling substance they can release on any predator. The substance, a musk, acts as a deterrent.

Predation pattern

A study by Stake et al. 2005 explained how rat snakes behaved during predation at a songbird's nest. First of all, they were usually very thorough about eating all the eggs. Secondly, they spent an average of 13½ minutes at the nest, and it took them on average two minutes before eating the first egg ⁴. The same study also showed that predation on nestling songbirds were higher the older the nestlings, the reason being that the older the nestlings, the more noise from the nest to attract rat snakes. Secondly, odor from the nests may attract the snakes.

Red rat snakes or corn snakes

Corn snakes are more popular as pets than rat snakes, and for beginners corn snakes are easier pets than any other rat snake. They come in a number of beautiful colors and varieties. Keepers should buy captive-breed corn snakes at respected pet-stores. At the site about snake care you'll find a list with tips on how to keep corn snakes. Please visit the listed web-resources on that page to find a local pet store.

References

1. Fry, B.G., Lumsden, N.G., Wuster, W., Wickramaratna, J.C., Hodgson, W.C., Kini, R.M. Isolation of a neurotoxin (alpha colubritoxin) from a nonvenomous colubrid: Evidence for early origin of venom in snakes JOURNAL OF MOLECULAR EVOLUTION 57(4) pp. 446-452 (2003)
2. Rigley, L. "Combat Dance" of the Black Rat Snake, Elaphe o. obsoleta Journal of Herpetology 5(1/2) pp. 65-66 (1971)
3. Prior, K.A and Weatherhead, P.J. Habitat Features of Black Rat Snake Hibernacula in Ontario Journal of Herpetology 30(2) pp. 211-218 (1996)
4. Stake, M.M., Thompson, F.R., Faaborg, J. and Burhans, D.F. Patterns of Snake Predation at Songbird Nests in Missouri and Texas Journal of Herpetology 39(2) pp. 215-222 (2005)

Acknowledgements

Thanks to Jonathan, Ryan, Sonja, Patrick and Jacob for giving me the permission to use their photos.

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