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Bites, Sub-species, Predation, Combat dance, Encounters and Life-cycle

It is common belief that all rat snakes are non-venomous. However, recent studies (Fry et al. 20031) show that some rat snakes, such as the asian rat snake (Elaphe radiata), are venomous indeed.

Even though most rat snakes may be slightly venomous, their venom is not a problem for humans. As predators, rat snakes are known as constrictors only.

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)2, 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. 1 month, and up to 30 eggs are laid in a clutch, with variation between sub-species.

Predation Pattern

A study by Stake et al. (2005)3 explained how rat snakes behaved during predation at a songbird's nest. First of all, they ate all 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.

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.

A black rat snake ready to enter a home

                                                                            







                                                                      

Close encounters

Rat snakes enter people's homes rather frequently, the reason being that they are good climbers and their prey are in abundance close to residential areas. Ratsnakes are not dangerous and mostly not aggressive although they will vibrate their tails and behave aggressively towards anybody trying to corner them.

When threatened, Rat snakes freeze, and many are killed in traffic because of this habit. Their bite looks very much like a human bite, and as they can grow rather large, a bite can be very painful.

Constrictors & non-venomous

Rat snakes are constrictors and feed on a varied diet of rodents, birds, frogs, squirrels, and eggs. They play an important role in many ecosystems by keeping the population of rodents (some of which are disease carriers) at a constant, low level. Therefore rat snakes are liked by farmers. Rat snakes use their sight and their Jacobsen's organ inside their mouth to detect prey and are experts at finding and killing small rodents.

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 US, whereas several common Pantherophis species are prominent throughout most of the southeastern US. The table below shows where the different Pantherophis species are found.

A distribution map of rat snakes in the USA

A Black Rat snake. Looks almost like a Rat snake.

A Black Racer - very common snake

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, so they 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.

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 or under rocks searching for prey. 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 night and 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 have a gray hue with 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, or 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.

Combat Dance

Something called a «combat dance» has been observed (Rigley, 19714) in male Rat snakes where the snakes have their tails intertwined, and the rest of their bodies are coiled and twisted. 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 feel 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.

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-bred corn snakes at respected pet-stores. At the page about snake care you will 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. 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)
3. 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)
4. Rigley, L. "Combat Dance" of the Black Rat Snake, Elaphe o. obsoleta Journal of Herpetology 5(1/2) pp. 65-66 (1971)

Web links

Rat snakes - (Georgia)
Texas rat snake

Acknowledgements

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


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