Garter snakes, belonging to the genus Thamnophis, are among the most widespread reptiles in North America. These slender, striped snakes are frequently encountered in various habitats, from forests to suburban gardens. Garter snakes are not nocturnal; they are primarily diurnal, meaning they are active during the day. This daytime activity is a direct consequence of their physiological needs as a cold-blooded species.
The Garter Snake’s Primary Activity Cycle
The activity cycle of a garter snake is fundamentally dictated by its status as an ectotherm, an animal that relies on external sources to regulate its body temperature. Unlike mammals, these snakes cannot generate sufficient internal heat, forcing them to seek warmth from the environment. They must reach a specific range of body temperatures, often between 26 and 32 degrees Celsius, to enable proper digestion, movement, and metabolic function. While generally diurnal, their activity often shifts toward crepuscular hours, which are dawn and dusk, particularly during specific environmental conditions.
Temperature and Environmental Triggers
Temperature is the single most important factor governing when a garter snake is active, forcing behavioral adjustments to avoid thermal extremes. During the spring and fall, the snakes spend the early morning hours basking to raise their body temperature from the low overnight levels. They flatten their bodies and orient themselves perpendicular to the sun’s rays to maximize heat absorption.
In the peak of summer, the intense midday sun can quickly lead to overheating, with body temperatures above 35 degrees Celsius causing inactivity. To prevent this, garter snakes shift their routine, becoming most active in the cooler, crepuscular periods of the morning and late afternoon. During the hottest part of the day, they retreat to shaded areas or underground to avoid the heat, a behavior that might mistakenly suggest they are nocturnal.
Rainfall, cloud cover, and seasonal changes also influence their activity levels. A cold, cloudy day may suppress activity entirely, as the snakes cannot achieve their preferred thermal range for movement. Conversely, a mild winter day can draw individuals out of their communal hibernacula for brief periods of basking near the den entrance.
Daily Behaviors: Hunting and Shelter
During their active, diurnal hours, the garter snake’s primary focus is foraging for food. They are active hunters that use a combination of sight and a highly developed sense of chemical detection to locate prey. The snake’s forked tongue flicks out to sample chemical cues in the air, transferring them to the Jacobson’s organ to “smell in stereo” and pinpoint the direction of a scent trail.
Their diet typically consists of earthworms, slugs, leeches, amphibians, and sometimes small fish, which they grab and swallow whole without constricting. As the sun begins to set and air temperatures drop, garter snakes must seek secure and insulated shelter to survive the night. They retreat under cover objects like rocks, logs, boards, or into burrows and foundations to avoid the cold and hide from nocturnal predators.