Garter snakes (Thamnophis) are very common throughout North America. They range from southern Alaska and Canada to Central America. It’s one of the northernmost snake species in the world. The garter snake is so successful because of its ability to adapt to many environments and food supplies. The western varieties are more aquatic than the eastern ones.
Garter snakes are carnivorous and will eat about anything they can overpower. Those inhabiting dry land eat slugs, lizards, rodents, insects, and ants. The more aquatic snakes eat fish, tadpoles, frogs, leeches, toads, salamanders, frog eggs, and minnows.
When captured garter snakes may coil and strike, but typically they will go into a defensive mode with their head beneath their body and the tail twitching to attract the attack. They will try to become unpalatable by secreting a musky smell near their cloaca and feces. Although garter snakes are not considered harmful to people they do produce a mild neurotoxin that helps overcome their prey. They have a pair of hooked teeth at the back of their jaws for grasping prey, but no teeth for injecting venom or chewing. They swallow prey whole.
Garter snakes communicate with phermones. Females secrete a phermone that immediately attracts males at mating time. Males on some occasions secrete both male and female phermones. Since mating happens soon after the snakes emerge from bromation — a reptilian low metabolism state similar to hibernation — a male may steal body heat from other males when they attempt to copulate with him because he smells like a female. Indeed, copulation is a group event among garter snakes. One female my be surrounded by as many as 25 males with mating fever in what is appropriately called a “mating ball.”
Before garter snakes enter brumation they stop eating for two weeks to clear any undigested food. Brumation is triggered by low temperatures and lasts until the environment warms up. Mating starts immediately after brumation ends. After mating the females leave the den to find food. They may store sperm for up to three years! Gestation takes about three months; as few and three and as many as 80 young are born live. They are independent from birth.
The Oregon Department of Fish and Wildlife lists four sub-species of garter snake:
- Pacific Coast Aquatic Garter Snake (lives near water such as riparian areas of rivers, ponds, streams, and wetlands)
- Western Terrestrial Garter Snake (found in a large variety of habitats often far from water. Sometimes called the “wandering” garter snake)
- Northwestern Garter Snake (lives in wooded areas of the Willamette Valley, suburbs and parks. Lives mainly on slugs and worms)
- Common Garter Snake (wide range of habitats and prey)
Garter snakes are also food for other animals. The video below is one my wife and I took while on the Fanno Creek Park trail in Beaverton. It shows a Great Blue Heron eating two garter snakes in the space of about 45 minutes.
LINKS ABOUT GARTER SNAKES