Garter snakes (Thamnophis species) are one of the most recognized and widespread groups of reptiles across North America. They are frequently seen in various habitats, from forests and meadows to suburban gardens. These slender, diurnal snakes are known for their distinct striped patterns, leading to questions about their movement and behavior.
Are Garter Snakes Arboreal
Garter snakes are not classified as a true arboreal species, meaning they do not spend the majority of their lives living and hunting in trees. They are fundamentally terrestrial and semi-aquatic, preferring to stay on the ground or near water sources like ponds and marshes. The term “arboreal” refers to species with specialized physical adaptations for navigating high in a canopy, which garter snakes lack.
Despite their terrestrial classification, garter snakes exhibit facultative arboreality, meaning they can climb when specific needs arise. This behavior is opportunistic rather than habitual, distinguishing them from dedicated climbing snakes. Occasionally ascending low vegetation provides a survival advantage, allowing them to temporarily expand their usable habitat range.
Motivations for Climbing
The decision for a garter snake to climb vertically is usually driven by two primary ecological needs: finding food and regulating body temperature. Foraging often involves ascending low bushes or shrubs to seek out specific prey items that live off the ground. This may include eggs or nestlings from ground-nesting birds, or insects found on plant stems.
Thermoregulation is another strong motivator for climbing, especially in cooler regions or adverse weather. Researchers have observed that red-sided garter snakes (Thamnophis sirtalis parietalis), for example, will ascend low trees to bask when the air temperature is slightly warmer than the ground temperature. This behavior is noticeable following rain, which cools the soil surface, prompting the snakes to climb to a dry, warmer location to raise their body heat.
Climbing can also be a reactive behavior, serving as a temporary escape from danger. This includes avoiding a terrestrial predator or escaping localized flooding on the ground.
Physical Constraints and Climbing Technique
Garter snakes lack the specialized anatomical features seen in dedicated climbers, which limits the height and type of surfaces they can effectively ascend. Dedicated climbers, such as rat snakes, possess highly keeled ventral scales for friction or prehensile tails for grasping branches. Garter snakes have a more generalized morphology, including a slender body and only moderately keeled scales.
Their climbing technique relies heavily on finding rough, textured surfaces that provide adequate grip, such as tree bark, tangled shrubs, or a coarse wooden fence. Due to these limitations, their climbing efforts are typically restricted to low heights, often between 20 to 80 centimeters above the ground. Their physical structure prevents them from efficiently navigating the smooth, vertical trunks or high, unsupported branches characteristic of a truly arboreal habitat.