The Eastern Fence Lizard (\(Sceloporus\) \(undulatus\)) is a common reptile found across the eastern United States, ranging from New York to Florida and west to Arkansas. Despite their rough appearance, these lizards are definitively not poisonous and pose no threat to humans or pets. Concerns about their safety often stem from a general misunderstanding about how reptiles can cause harm. This species, also called the prairie lizard or fence swift, plays a beneficial role in its local ecosystem by controlling insect populations.
Understanding Poisonous Versus Venomous
The core of the safety question rests on the difference between being poisonous and being venomous. A creature is considered poisonous if its toxins are ingested or absorbed through the skin, such as a poison dart frog. A venomous animal, however, injects its toxins into a victim through a specialized delivery mechanism, like fangs or a stinger.
The Eastern Fence Lizard is neither poisonous nor venomous. They do not produce toxins, meaning they cannot harm a person or pet if eaten or absorbed through the skin. Furthermore, the species completely lacks the biological machinery for venom delivery.
Physical Characteristics and Identification
The Eastern Fence Lizard is a relatively small species, typically measuring between 4 and 7.5 inches in total length. They are easily identified by their rough, spiny scales, which gives them the common name “spiny lizard.” Their coloration is generally gray or brownish-gray, providing excellent camouflage against tree bark and woodpiles where they often bask.
A key identification feature is the difference between the sexes, known as sexual dimorphism. Males have bright patches of iridescent blue scales on their throat and abdomen, which they flash during territorial displays. Females typically have dark, wavy, horizontal patterns on their backs and lack these prominent blue markings.
Behavior and Safe Interaction
Eastern Fence Lizards are diurnal, meaning they are active during the day, spending time basking in the sun to regulate body temperature. They are highly arboreal, preferring habitats with trees, logs, stumps, or fences, which explains the “fence” part of their name. Their primary defense mechanism is flight; they quickly dash up a tree trunk or under debris when disturbed.
If captured or handled, a bite is possible, but it is superficial and harmless. Their tiny teeth are designed for crushing small invertebrates like ants, beetles, and spiders, which comprise their diet. Any bite will feel like a slight pinch and does not require medical attention. Basic hygiene, like washing hands afterward, is recommended when handling any reptile. These lizards are beneficial in controlling garden pests and should be left alone to continue their natural function.