Things that will eat slugs are a welcome sight in any garden. The Common Garter Snake, along with most snakes in Oregon, is considered ‘beneficial’ because of their diet. The Common Garter Snake will eat slugs, grubs, mice, voles, earthworms, rats, frogs and tadpoles, and generally anything they can overwhelm.
Species in Oregon
There are four species of Garter snakes in Oregon: The Common Garter and Western Terrestrial Garter are abundant throughout Oregon, except the mountains. The Northwestern Garter resides in western Oregon. The Aquatic Garter resides in southwestern Oregon. Snakes are usually black, dark brown or green with a light-colored or red stripe and can reach 48-inches in length.
Where to look
You can find Garter snakes in a variety of habitats such as urban lawns, forests, woodlands, fields, and grasslands. Look for Garters near water, such as a wetland, stream, or pond. Water provides a place to hunt amphibians and as a potential escape strategy.
When disturbed, a garter snake may coil and strike. Typically, the Garter will hide its head and flail its tail. It may also discharge a malodorous, musky-scented secretion or slither into the water to escape a predator. Garters do not have the capacity to seriously injure humans, even though they have small amounts of a mild venom.
Garter snakes give birth to live and independent young. Gestation lasts a couple of months with birth rates reaching nearly 100. Juvenile snakes are often killed by predators, cars, and lawnmowers! Predators include birds of prey, crows, egrets, herons, cranes, raccoons, otters, bull frogs, shrews, and other snake species (such as the coral and king snakes).
Garter snakes use a complex communication system using pheromones. The pheromones cues are communicated through tongue-flicking behavior. This system helps them find other snakes through pheromone-scented trails and making it key to breeding.
Snakes slither through the garden eating slugs, grubs and other pests (https://extension.oregonstate.edu/news/snakes-slither-through-garden-eating-slugs-grubs-other-pests)
Garter Snakes, Wikipedia (https://en.wikipedia.org/wiki/Garter_snake)
Oregon Department of Fish & Wildlife (https://myodfw.com/wildlife-viewing/species/snakes)