Dr. Michael Dorcas is a professor of biology at Davidson College and author of A Guide to the Snakes of North Carolina. Here he lays out the facts about this shy snake common to rural and suburban backyards. Questions and answers have been edited.
Q. How did rat snakes get their name?
A. These long black snakes are called rat snakes because they frequently feed on mice and rats. They also eat birds and bird eggs and when young, feed on small frogs like tree frogs.
Q. Are they dangerous?
A. If they are threatened, they might bite, but they are not venomous and thus pose essentially no danger to people. Normally they will freeze to avoid being detected. And if that doesnt work they will crawl away as quickly as possible. They can also release a smelly musk that presumably tastes bad, to deter predators.
Q. How can you tell the difference between a rat snake and other poisonous snakes that might show up in our backyard?
A. Thats a common question and there is no easy answer. Adult rat snakes are black, but the young are patterned and often mistaken for copperheads. Copperheads have distinctive hourglass-shaped cross bands on their bodies. However, no single characteristic works well for telling venomous from nonvenomous snakes. My strongest recommendation is that people become familiar with identifying local snakes. Good resources are www.herpsofnc.org or the book A Guide to the Snakes of North Carolina.
Q. Do rat snakes ever end up in houses?
A. Yes, they are often found around houses and barns looking for rats and mice. They are good climbers, so they sometimes end up in attics. They are actually beneficial to have around, particularly near barns or farming communities, because they help keep the rat and mice population down.
Q. I have heard that black rat snakes mate for life, and if one gets killed in the road, the other wraps itself around the corpse so it can die as well. Is that true?
A. Thats a myth. Males typically seek out a new mate in the fall or shortly after they emerge from hibernation each spring. The females lay their eggs in June, and the babies hatch about two months later.
Q. How do you track black rat snakes in the wild? What are you learning about them in your research?
A. We use surgically-implanted radio transmitters to track their movements. Its a simple surgery and the snakes do great afterward. We have found that some snakes can move long distances and all really know their environment and where they are going. One snake we tracked would spend each winter hibernating in the same stump hole and then go about a mile north each spring to a barn where it would feed on rodents, then return to the same stump hole each fall. Pretty cool!