Fence Lizard
Species Description

The Fence Lizard (Sceloporus undulatus) derives its common name from the species' frequent occurrence on wooden fences, split-rail fencing, and fence posts throughout its range, where they bask and hunt for insects. This behavior makes them one of the most commonly observed lizards in suburban and rural areas across much of the United States. The name "Fence Lizard" is widely recognized, though numerous regional and subspecific names exist including "Pine Lizard," "Prairie Lizard," "Northern Fence Lizard," and "Plateau Lizard" depending on locality and subspecies. The Eastern Fence Lizard and Western Fence Lizard represent the two primary subspecies groups, though multiple additional subspecies have been described based on geographic variation.

Scientifically, Fence Lizards belong to the large genus Sceloporus, which contains over 90 species of spiny lizards distributed throughout North America, Central America, and northern South America. The genus name Sceloporus is derived from Greek words meaning "leg-pore," referring to the prominent femoral pores present on the underside of the thighs in males, which secrete waxy substances for territorial marking. The specific epithet "undulatus" is Latin meaning "wavy" or "undulating," likely referring to the wavy pattern of scales or markings on the body. The species was first scientifically described in the early 1800s during surveys of North American herpetofauna.

Extensive subspecific variation exists within Sceloporus undulatus, with up to 7-8 subspecies recognized by some taxonomists based on geographic distribution and morphological differences, though modern genetic analysis suggests some may warrant elevation to full species status. The Eastern Fence Lizard (Sceloporus undulatus undulatus) is the nominate subspecies occurring in the eastern United States from New York and Pennsylvania southward to Florida and westward to eastern Texas. The Western Fence Lizard (Sceloporus undulatus tristichus) and other western subspecies occur in the Great Plains and western regions. These subspecies show variations in coloration, pattern intensity, scale counts, and size, with western forms often displaying more contrasting patterns and slightly larger size. All subspecies share similar care requirements in captivity, though specific temperature and humidity preferences may vary slightly based on natural range.

Fence Lizards are small, slender lizards with keeled scales giving them a rough, spiny appearance and texture. Adults typically reach 4-7.5 inches in total length from snout to tail tip, with males slightly larger than females. The body is relatively flattened dorsoventrally, an adaptation for pressing into tight spaces under bark or in rock crevices. Adult males commonly weigh 10-15 grams, while females are slightly lighter at 8-12 grams. The tail is long and thin, comprising approximately 50-60% of total length, and is used for balance during climbing and can be autotomized (dropped) as a defense mechanism.

Coloration and pattern in Fence Lizards show considerable geographic and individual variation, but general patterns are consistent. Dorsal coloration consists of gray, brown, or olive base colors with darker wavy or chevron-shaped crossbands running down the back. These bands may be distinct or somewhat faded depending on individual, subspecies, and current physiological state. Lateral coloration often shows blue or blue-green patches particularly visible in males, though intensity varies. The scales have a distinctly keeled appearance with raised ridges running down each scale, creating the spiny texture that characterizes the genus Sceloporus.

Sexual dimorphism is apparent in adult Fence Lizards. Males develop bright blue patches on the throat and sides of the belly, separated by black borders, most visible during breeding season or territorial displays. These blue patches serve important roles in species recognition, female mate choice, and male-male territorial disputes. The blue coloration varies in extent and intensity between subspecies and populations, with some showing brilliant turquoise patches while others display more subdued blue-gray. Females and juveniles lack bright blue coloration, instead showing white, cream, or pale gray undersides with less distinct patterning.

Physical adaptations include well-developed limbs with long toes and sharp claws for climbing rough surfaces including tree bark, fence posts, and rocks. The digits are equipped with keeled scales on the underside providing traction on vertical surfaces. The head is somewhat triangular with a pointed snout, large eyes providing excellent vision for detecting prey and threats, and external ear openings visible behind the eyes. The body scales are arranged in regular, overlapping rows creating an armored appearance. Males possess prominent femoral pores on the underside of the thighs, appearing as a row of waxy or yellowish spots that secrete substances for chemical communication. The overall appearance is alert and athletic, with lizards typically holding their body raised off the substrate on extended legs.

Fence Lizards display typical behavior patterns for small, alert insectivorous lizards, characterized by wariness, quick movements, and high activity levels during optimal conditions. They are nervous around humans and will quickly flee to protected areas when approached, though they can become accustomed to keeper presence in captivity and may even take food from hands with patience. Their temperament is calm rather than aggressive, with defensive behaviors limited to fleeing and, if captured, mild struggling and potentially biting, though their small jaws cause no injury. Individual personalities exist with some individuals becoming relatively bold while others remain perpetually nervous.

Male territorial behavior is most evident during breeding season, typically occurring from April through July in wild populations, though captive breeding cycles may vary. Males perform characteristic push-up displays, raising and lowering their body repeatedly while displaying blue ventral patches to advertise territory and attract females. These displays are fascinating to observe and serve multiple functions including territorial advertisement to rival males, courtship display to females, and possible thermoregulatory assistance by moving air around the body. Males may engage in chasing and occasional physical combat with rival males if territories overlap, though serious injury is rare. Multiple males should not be housed together due to inevitable territorial conflicts.

Fence Lizards are diurnal heliotherms, emerging from overnight retreats shortly after sunrise to bask and raise body temperature for activity. They favor exposed surfaces including tree trunks, fence posts, and rocks where they orient perpendicular to sunlight for maximum heat absorption. Once properly warmed, they begin hunting for insects, moving quickly between perches and using visual cues to detect prey. Hunting strategy involves remaining stationary on elevated positions scanning for movement, then quickly pursuing detected prey. Activity patterns show daily variation, with peak activity during mid-morning and late afternoon in hot weather, and more continuous activity during cooler, overcast conditions.

Seasonal behavior changes are pronounced in Fence Lizards throughout much of their range. Spring emergence from brumation occurs when temperatures consistently exceed 60-65°F, typically March through May depending on latitude. Summer activity continues throughout warm months with potential reduction during extreme heat. Fall activity gradually decreases as temperatures cool, with lizards entering brumation in October through November in northern populations, sometimes later in southern regions. Brumation sites include underground burrows, rock crevices, hollow logs, and building foundations. In captivity, providing seasonal temperature cycling including cooler winter period promotes natural behaviors and may improve breeding success, though some keepers maintain consistent temperatures year-round.

Defensive behaviors emphasize rapid escape over confrontation. When threatened, Fence Lizards immediately run to nearest protective cover including tree trunks where they spiral around to opposite side, crevices, or dense vegetation. Their speed and agility make them difficult to capture. If cornered or captured, they may autotomize (drop) the tail as a distraction while escaping. Tail autotomy should be avoided through proper handling technique, as regenerated tails never match the original. Some individuals become relatively calm with regular exposure to keeper presence, allowing closer observation and even hand feeding, though most retain natural wariness throughout life.

Housing Fence Lizards properly requires providing appropriate temperate conditions with climbing surfaces, basking areas, and secure hiding spots replicating their natural habitat. Adult Fence Lizards require minimum enclosure dimensions of 20 gallon long tanks (30x12x12 inches), suitable for 1-2 individuals with appropriate sexing (one male with one or more females, or multiple females). Larger enclosures such as 30 gallon or 40 gallon breeder tanks provide additional space for territorial displays and natural behaviors. While not large lizards, they are active and benefit from space to move and climb. Glass or screen enclosures work well, with screen providing excellent ventilation important for preventing respiratory issues.

Enclosure design should emphasize vertical surfaces for climbing and basking. Include pieces of cork bark positioned vertically against enclosure walls, branches at various angles, flat rocks or slate pieces for basking platforms, and background materials providing texture for climbing. Fence Lizards naturally bask on vertical or angled surfaces rather than horizontal basking spots, so positioning cork bark or branches appropriately is important. Provide at least one secure hiding spot per lizard, positioned at both warm and cool ends of the enclosure. Live or artificial plants add visual security and enrichment. Ensure all climbing structures are stable and cannot collapse, as falling can cause injury.

Substrate options include cypress mulch, coconut fiber, topsoil/sand mixtures, or paper towels. Natural substrates like cypress mulch or coconut fiber appear most natural and maintain moderate humidity, though they require regular replacement. Topsoil/sand mixtures allow for some digging behavior. Paper towels or newspaper provide practical, easy-to-clean options that eliminate impaction risk, though they appear less natural. Avoid pure sand or fine particulate substrates that pose impaction risks. Substrate depth of 1-2 inches suffices for most setups. Some keepers use bioactive setups with springtails and isopods for waste management, creating low-maintenance naturalistic environments.

Temperature regulation requires creating appropriate thermal gradients. Basking areas should reach 90-95°F, measured at the basking surface, while ambient temperatures throughout most of the enclosure should range 75-85°F with a cool end around 70-75°F. These relatively modest temperatures are easily achieved with low to medium wattage basking bulbs (40-60 watts) positioned over one end of the enclosure. Under-tank heaters can supplement ambient temperatures if needed, though overhead heating is preferable. Nighttime temperatures should drop to 60-70°F, mimicking natural conditions and promoting healthy circadian rhythms. Most homes provide appropriate nighttime cooling with lights off. Thermostats prevent dangerous overheating, though lower wattage bulbs used for Fence Lizards are less likely to cause temperature problems than high-wattage systems.

UVB lighting is essential for Fence Lizard health, enabling vitamin D3 synthesis and calcium metabolism. Use linear fluorescent UVB bulbs such as T5 HO 5.0 or T8 5.0/10.0 positioned 8-12 inches from basking areas. Since Fence Lizards bask on vertical surfaces, ensure vertical climbing structures receive adequate UVB exposure by positioning bulbs appropriately. The entire length of the basking surface should receive UVB coverage. Replace UVB bulbs every 6-12 months as UV output degrades before visible light diminishes. Outdoor exposure to natural unfiltered sunlight during appropriate weather provides excellent UVB supplementation and behavioral enrichment, though secure outdoor enclosures preventing escape are essential.

Humidity requirements are low to moderate at 30-50%, easily maintained in most homes without special equipment. A small water dish provides drinking opportunities and adds slight humidity. Brief misting once or twice weekly provides additional drinking opportunities for lizards that prefer licking droplets and supports proper shedding. Avoid excessive humidity above 60%, which can promote respiratory infections and skin problems in these temperate species. Proper ventilation through screen tops or ventilation panels prevents humidity accumulation. Monitor humidity with digital hygrometers, adjusting misting frequency or water dish size based on readings and observation of shedding quality.

Fence Lizards are insectivores consuming various small arthropods encountered while foraging in their territories. In the wild, their diet includes small crickets, beetles, flies, ants, spiders, small grasshoppers, caterpillars, and other insects proportional to their small size. They are visual hunters that detect prey movement from elevated positions, then quickly pursue and capture prey with their sticky tongues. Their small size limits prey size to relatively small insects compared to larger lizards. In captivity, their enthusiastic appetite and active hunting behavior make feeding straightforward and entertaining to observe.

Appropriate feeder insects for Fence Lizards include small crickets (1/8 to 1/4 inch), fruit flies, small dubia roaches, phoenix worms (black soldier fly larvae), small waxworms, small mealworms, and small hornworms. Prey items must be appropriately sized for their small mouths, generally no larger than the space between the lizard's eyes. Small crickets form the primary staple food for most keepers, as they are readily available and eagerly accepted. Variety improves nutritional completeness and maintains feeding interest. Avoid prey items that are too large, which can cause choking, regurgitation, or refusal to feed.

Gut-loading feeder insects improves nutritional value transferred to lizards. Feed insects high-quality diet for 24-48 hours before offering to lizards. Commercial gut-load products are available, or provide fresh vegetables including collard greens, mustard greens, squash, carrots, and commercial cricket feed. Well-nourished insects provide significantly better nutrition than nutritionally depleted insects consuming only poor-quality foods. The gut contents of insects directly impact the nutritional value received by lizards, making proper gut-loading an essential practice.

Supplementation is important for captive Fence Lizards to prevent calcium deficiency. Dust insects with calcium powder (without vitamin D3 if proper UVB is provided) at most feedings, approximately every other day. Use multivitamin supplement or calcium with D3 once or twice weekly to provide additional vitamins. The exact supplementation schedule depends on UVB quality and diet variety, but consistent moderate supplementation prevents deficiencies without over-supplementation problems. Growing juveniles require more frequent calcium supplementation than adults. Monitor growth and overall condition, adjusting supplementation if deficiency signs appear including slow growth, lethargy, or metabolic bone disease symptoms.

Feeding frequency depends on age and growth rate. Juvenile Fence Lizards should be fed daily, offering as many appropriately sized insects as they will consume in 10 minutes. Their rapid growth requires frequent feeding with well-supplemented prey. Adult Fence Lizards can be fed every other day or 3-4 times weekly, offering 3-6 small insects per feeding depending on prey size and lizard condition. Some keepers prefer feeding smaller amounts more frequently. Monitor body condition, adjusting feeding frequency if lizards become too thin (visible ribs, sunken appearance) or overweight (round abdomen, reduced activity). A shallow water dish should be available at all times, cleaned and refilled daily. Brief misting provides additional drinking opportunities, as some individuals prefer licking water droplets from leaves and surfaces.

Fence Lizards are generally hardy, resilient lizards when provided with appropriate care, though they face several potential health challenges in captivity primarily stemming from improper husbandry. Common health problems include metabolic bone disease from inadequate UVB exposure or calcium supplementation, respiratory infections from excessive humidity or inadequate ventilation, parasites particularly in wild-caught specimens, injuries from improper handling or enclosure hazards, and tail loss from stress or improper capture. Their small size means health problems can progress quickly, requiring prompt attention and veterinary care when issues are identified. Establishing relationship with a qualified reptile veterinarian familiar with small lizards is beneficial, though in practice, basic preventive husbandry prevents most health issues. Their relatively short 4-7 year lifespan means consistent care from the start is important for maximizing longevity.

Fence Lizards are excellent beginner to intermediate reptiles when provided with proper care including appropriate UVB lighting, temperature control, and small insect prey. Their hardy nature, manageable size, and straightforward care requirements make them ideal for keepers interested in North American herpetofauna. Most health problems in captivity result from inadequate UVB exposure, improper supplementation, or excessive humidity, all easily prevented through proper husbandry from the start. With appropriate care, these engaging lizards provide years of enjoyment as they display natural behaviors including basking, hunting, and territorial displays in appropriately designed enclosures.

Handling Fence Lizards should be minimal due to their nervous nature, small size, and high stress response to restraint. These are display animals best appreciated through observation rather than physical interaction. Their speed and agility combined with fragile tails that can autotomize (drop) make handling challenging and potentially harmful. When handling is necessary for health checks, enclosure maintenance, or veterinary transport, proper technique minimizes stress and injury risk. Many individuals never become truly comfortable with handling despite regular gentle exposure, maintaining their instinctive escape response throughout life.

Proper handling technique requires patience and gentle movements. When handling is necessary, move slowly to avoid startling the lizard. Cup hands around the lizard or allow it to walk onto your hand rather than grabbing. Support the body gently with both hands, never restraining tightly or grabbing the tail which easily breaks off. Be prepared for quick movements and potential escape attempts, handling over secure surfaces or within the enclosure to prevent falls or escape. Some individuals bite defensively when restrained, though their small jaws cause no injury beyond minor pinching sensation. If a lizard shows extreme stress including frantic thrashing, mouth-gaping, or severe color darkening, return it to the enclosure immediately.

Shedding occurs regularly, particularly in growing juveniles, with adults shedding every 4-8 weeks depending on growth rate and season. Lizards shed in pieces rather than whole skin, with the process typically completing within several days to a week. During shedding, lizards may show reduced appetite, duller coloration, and slightly increased wariness. While Fence Lizards tolerate low ambient humidity, they benefit from brief misting or access to a humid hide box during shedding to facilitate skin removal. Most lizards remove shed skin themselves by rubbing against rough surfaces. Avoid pulling shedding skin, as this damages underlying scales. If shed remains stuck, particularly around toes or tail tip, brief soaking in shallow lukewarm water or increased misting helps loosen stubborn pieces.

Daily care routines include feeding every other day or several times weekly depending on age, removing any dead insects or waste from enclosure, checking and refilling water dish, monitoring basking and ambient temperatures using reliable thermometers, and observing lizards for normal activity, alert posture, and healthy appearance. Weekly tasks include thorough spot cleaning or substrate replacement if needed, sanitizing water dish, checking all equipment function, and detailed health assessment looking for retained shed, injuries, or concerning changes. Monthly tasks include weighing to monitor growth or detect changes, deep cleaning decorations, UVB bulb inspection, and general maintenance. Maintaining records of feeding, shedding, weight, and any health concerns helps track patterns and provides information for veterinary consultation if needed.

Fence Lizards are excellent beginner to intermediate reptiles suitable for keepers interested in North American species and willing to provide appropriate care including UVB lighting, temperature control, and small live insect prey. They are appropriate for responsible older children with adult supervision, dedicated beginners willing to research proper care, and experienced keepers looking for manageable native species. Their small size, hardy nature, straightforward care requirements, and interesting behaviors make them ideal introductions to reptile keeping. However, they are display animals with minimal handling tolerance, making them unsuitable for anyone expecting interactive, handleable pets.

Financial considerations for Fence Lizard ownership are modest compared to larger reptiles. Initial setup costs range from $200-400 including appropriate enclosure (20 gallon long minimum), UVB and basking lighting, substrate, decorations including vertical climbing surfaces, water dish, thermometers, and initial supplies. Monthly costs include electricity for lighting ($10-20), small feeder insects ($15-30), supplements, and occasional substrate replacement. Annual costs are minimal beyond possible veterinary exams ($75-150 if needed) and UVB bulb replacement ($20-35 every 6-12 months). These modest costs make Fence Lizards accessible for budget-conscious keepers throughout their 4-7 year lifespan.

Time commitment is minimal compared to many reptiles. Daily care includes feeding several times weekly (5-10 minutes per feeding), basic observation and monitoring (5 minutes), and water dish maintenance (2 minutes). Weekly cleaning and maintenance requires 20-30 minutes. The straightforward care makes vacations manageable with basic pet sitter instructions, though sitters must be comfortable handling small live insects. Overall time commitment is well-suited for busy individuals, students, or families introducing responsible pet care to children.

Legal considerations vary by location. Fence Lizards are native to much of the United States, and collection from wild populations is regulated by state wildlife agencies. Many states prohibit or restrict collection of native reptiles, requiring permits for possession or prohibiting collection entirely. Always verify specific regulations for your state, county, and city before acquiring any native reptile. Some jurisdictions require proof that specimens are captive-bred rather than wild-collected. Captive-bred specimens are strongly preferred over wild-caught as they are healthier, parasite-free, already acclimated to captivity, and place no pressure on wild populations. Check rental agreements and homeowner association rules, as some prohibit reptile keeping. Fence Lizards face few restrictions compared to exotic species in most jurisdictions, but compliance with all applicable laws is essential.