The garter snake, belonging to the genus Thamnophis, is one of the most widely distributed and commonly encountered snakes across North America, ranging from Canada down to Central America. These slender snakes are highly adaptable, inhabiting diverse environments like forests, grasslands, and suburban areas, often near water sources. Though generally considered harmless to humans, garter snakes possess a mild neurotoxic venom that they use to immobilize their small prey. This venom is not medically significant to people and typically causes only minor irritation or slight swelling.
Primary Natural Prey
The foundation of a garter snake’s diet in the wild consists of soft-bodied invertebrates and small amphibians, which are easy to overpower and swallow whole. Earthworms, particularly common nightcrawlers, are a staple food source for many species and are often the first prey item for young snakes. Slugs and leeches also form a regular part of the menu due to their slow movement.
Small frogs, toads, and their tadpoles are heavily preyed upon, especially in aquatic or semi-aquatic habitats. Garter snakes locate their prey using a keen sense of smell, flicking their tongue to sample chemical cues. The mild venom is particularly effective on amphibians, helping to subdue them quickly. This reliance on small, slow-moving prey aligns with the garter snake’s relatively small size.
Specialized and Occasional Food Sources
The garter snake’s diet exhibits significant variability based on the specific species, its geographical location, and the opportunistic availability of prey. For populations living near streams, ponds, or marshes, small fish, such as minnows, can become a frequent part of the diet. These snakes are skilled swimmers and will actively hunt aquatic prey, complementing their terrestrial feeding habits.
Certain garter snake species have evolved specialized adaptations, allowing them to consume newts, which are highly toxic to most other predators. For example, some western species have developed a resistance to the potent neurotoxins found in the rough-skinned newt. Less frequently, garter snakes may consume insects like grasshoppers, small lizards, or even very small, young rodents or baby birds if they are discovered in nests.
Feeding Garter Snakes in Captivity
The dietary needs of a captive garter snake are managed differently from their wild counterparts to ensure proper nutrition and prevent the introduction of parasites. Feeding wild-caught amphibians or invertebrates is strongly discouraged because they often carry parasites that can cause serious illness in a pet snake.
The safest and most nutritionally complete option for larger snakes is frozen/thawed “pinky” mice, which provide a balanced source of protein and fat. For snakes that prefer fish, certain species are recommended, such as frozen/thawed silversides, trout, or salmon, which can be cut into appropriately sized pieces.
It is important to avoid feeding feeder fish like goldfish or rosy reds, as these contain high levels of an enzyme called thiaminase. Thiaminase breaks down thiamine (Vitamin B1), and a diet heavily reliant on these fish can lead to a severe and potentially fatal neurological condition known as Vitamin B1 deficiency.
Snakes that are fed a diet primarily of earthworms or fish fillets should also receive a calcium and vitamin supplement to ensure a complete nutritional profile.