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Eastern fence lizard

The Eastern fence lizard (Sceloporus undulatus) is a medium-sized spiny lizard native to North America, characterized by rough, keeled scales, a stout body, and a total length of 10–19 cm (4–7.5 in), including the tail.^[1]^[2] It typically exhibits grayish to brown dorsal coloration with 5–8 irregular dark wavy bands, a pale belly often edged in blue or greenish-blue, and, in breeding males, prominent bright blue patches on the throat and underside bordered by black.^[1]^[2]^[3] This species occupies a broad geographic range from southern New York and Pennsylvania westward to eastern Colorado, and southward through the eastern and central United States to north-central Mexico, favoring dry, open woodlands, rocky hillsides, forest edges, and sunny clearings with ample basking sites such as logs, stumps, fences, or rock piles.^[3]^[1]^[2] It avoids dense, humid forests and barrier islands but thrives in xeric pine-hardwood habitats and disturbed areas like old fields or building sites.^[4]^[1] Eastern fence lizards are diurnal and primarily terrestrial or semi-arboreal, often perching on elevated structures to bask and forage for insects, spiders, and other invertebrates, which they capture via quick dashes or tongue flicks.^[1]^[2]^[4] Males perform conspicuous territorial displays involving push-ups and head-bobbing to attract females or deter rivals, especially during the breeding season from April to June.^[5]^[2] When threatened, they evade predators like snakes and birds by sprinting to trees or crevices, circling trunks to stay out of sight.^[1]^[4] Reproduction is oviparous, with females laying 3–16 eggs in clutches buried in sandy soil, rotting logs, or under debris during late spring or early summer; eggs incubate for about 60 days, hatching in late summer as juveniles measuring 4–5 cm.^[1]^[2]^[4]

Taxonomy

Etymology

The genus name Sceloporus originates from the Greek words skelos, meaning "leg," and poros, meaning "pore" or "passage," alluding to the prominent femoral pores on the lizard's hind legs, which are used for scent marking in communication and territorial behavior.^[6]^[7] The species epithet undulatus derives from the Latin term for "wavy" or "undulated," a reference to the distinctive dark, wavy crossbands that pattern the lizard's dorsum.^[8] The common name "eastern fence lizard" reflects the species' frequent perching and basking behavior on fences, logs, and other elevated structures in its eastern North American range, while alternative regional names include "prairie lizard" in open grassland areas and "spiny lizard" due to the genus's characteristic rough, keeled scales.^[1]^[9]

Classification

The eastern fence lizard (Sceloporus undulatus) belongs to the family Phrynosomatidae within the order Squamata and class Reptilia.^[10]^[11] In 2002, molecular phylogenetic analyses by Leaché and Reeder revealed deep genetic divergences within the former Sceloporus undulatus species complex, leading to its reclassification into four distinct species: S. undulatus (eastern fence lizard, occupying the eastern United States), S. consobrinus (prairie lizard, in central and southern Great Plains), S. tristichus (plateau fence lizard, in the southwestern United States), and S. cowlesi (southwestern fence lizard, in the Chihuahuan Desert region).^[12] This revision was based on mitochondrial DNA data showing monophyletic clades with significant genetic differentiation, despite morphological similarities across the group. Currently, S. undulatus is recognized as a monotypic species with no formally accepted subspecies.^[10] Although older literature proposed variants such as S. u. hyacinthinus and S. u. elongatus based on regional morphological differences, these have not been adopted in modern taxonomy due to lack of genetic support and failure to delineate discrete populations.^[13] Within the diverse genus Sceloporus, which comprises over 90 species of spiny lizards, S. undulatus plays a prominent role in evolutionary research, particularly studies examining sexual dichromatism—such as hormone-mediated color development in males—and local adaptations to environmental pressures like temperature and predation.^[14] These investigations highlight its utility as a model for understanding phenotypic plasticity and sexual selection in squamates.^[15]

Description

Morphology

The eastern fence lizard (Sceloporus undulatus) is a medium-sized lizard, with adults typically measuring 4.0–7.5 inches (10–19 cm) in total length, including the tail.^[16] The snout-to-vent length (SVL) of adults averages 6–7 cm, though maximum SVL can reach 8.6 cm in some populations.^[17]^[18] This robust body structure supports an active lifestyle in varied terrains, with the overall build providing stability during movement.^[1] The body is covered in keeled, overlapping scales on the back and sides, which are pointed and give the lizard a rough, spiny appearance. These scales offer protection against predators and environmental abrasion.^[19]^[20] The lizard possesses strong limbs equipped with five toes each, featuring sharp claws that enhance grip for climbing on rocks, trees, and fences.^[21] The tail is long, comprising up to 60% of the total body length, and serves functions such as balance during agile maneuvers and fat storage for energy reserves.^[17] Located on the underside of the thighs are femoral pores, specialized glands that secrete pheromones for chemical signaling in territorial and reproductive contexts.^[17]^[22]

Coloration and sexual dimorphism

The Eastern fence lizard (Sceloporus undulatus) exhibits a base coloration of gray to brown on the dorsal surface, often accented by dark, wavy transverse crossbands that provide cryptic camouflage against bark and leaf litter. These crossbands are typically more prominent and conspicuous in females and juveniles, enhancing their ability to blend into forested habitats, whereas adult males display a more uniform reddish-brown dorsal hue during the breeding season. Ventrally, the lizard is pale white or cream-colored with scattered black flecks, serving as a neutral background for sexually dimorphic traits.^[1]^[21]^[23] Sexual dichromatism is pronounced in this species, particularly during the breeding period from spring to summer, when adult males develop vibrant blue or turquoise patches bordered by black on the throat and belly, while females generally lack these or show only faint, reduced versions. These male-specific ventral badges function in intraspecific signaling for territory defense and mate attraction, contrasting with the females' dorsal stripes that prioritize concealment from predators. Hormonally, testosterone drives this dimorphism; in juvenile males, elevated plasma levels trigger the development of blue and black ventral coloration as well as the male-typical dorsal reddish-brown shift, with castration preventing these changes and exogenous testosterone implants inducing them even in females.^[11]^[24] In males, coloration is also temperature-dependent, with short-term changes in dorsal hue and ventral badge intensity occurring in response to environmental shifts.^[25]

Distribution and habitat

Geographic range

The Eastern fence lizard (Sceloporus undulatus) is native to much of the eastern United States, with its range extending from southern New York and Pennsylvania southward through the Atlantic Coastal Plain to central Florida, and westward across the Piedmont and interior plains to eastern Texas and Oklahoma.^[12]^[11] The northern limit reaches southern portions of Ohio, Illinois, and Indiana, while the western boundary follows the eastern edges of the Great Plains.^[9] It is notably absent from the extreme northeastern states, such as Massachusetts and Maine, and from much of the Midwest, including areas north of southern Illinois and east of central Ohio.^[12]^[2] Introduced populations occur outside this native distribution, most notably on Staten Island, New York, where a self-sustaining colony was established in the 1950s, likely transported via shipping routes from southern localities.^[26]^[27] A smaller introduced presence has also been documented on Long Island, New York.^[12] Historically, the species' distribution has expanded northward and into disturbed landscapes due to European settlement and associated forest clearing, which generated abundant edge habitats and secondary growth in pine and hardwood forests—preferred environments that facilitated population growth and range extension.^[11] Within its overall range, the eastern fence lizard occupies elevations from sea level along coastal plains to approximately 1,550 meters in the Appalachian Mountains, though it is more abundant at lower elevations.^[4]^[28]

Habitat preferences

The eastern fence lizard (Sceloporus undulatus) primarily inhabits open, dry environments that provide ample opportunities for thermoregulation and predator avoidance. It favors sunny, exposed areas such as dry open woodlands, forest edges, pine barrens, grasslands, and shrublands, where it can access elevated perches like fences, fallen logs, rocks, stumps, and retaining walls for basking and observation.^[29]^[2] These habitats typically feature rocky outcrops, talus slopes, or south-facing hillsides that maximize solar exposure, essential for the lizard's ectothermic physiology.^[29]^[30] Essential microhabitat elements include abundant cover for refuge, such as leaf litter, brush piles, crevices in rocks or logs, and coarse woody debris, which the lizards use to escape threats and for hibernation during cooler months.^[29]^[30] They actively select sites with reduced canopy and litter cover to facilitate basking, showing a negative association with dense vegetation layers that obstruct sunlight.^[30] The species avoids dense forests and wetlands, preferring disturbed or open conditions that enhance visibility and thermal gradients over shaded, humid areas.^[2]^[29] This adaptability extends to human-modified landscapes, where eastern fence lizards commonly occupy suburban and urban edges, utilizing woodpiles, old lumber stacks, and concrete retaining walls as surrogate perches and refuges.^[31] In such settings, they thrive amid oak-hickory forests interspersed with development, demonstrating resilience to moderate habitat fragmentation as long as basking sites and cover persist.^[31]^[29]

Regional variation

The Eastern fence lizard (Sceloporus undulatus) displays notable latitudinal variation in body size and growth, reflecting adaptations to climatic gradients across its range. Northern populations, such as those in New York, achieve larger adult body sizes—often exceeding 60 mm in snout-vent length (SVL)—due to delayed maturation and elevated juvenile survivorship, which allow individuals to allocate more resources to growth before reproduction in shorter, cooler seasons.^[32] This countergradient pattern compensates for environmental constraints, with northern lizards exhibiting slower overall growth rates compared to southern counterparts, as limited thermal opportunities restrict activity and foraging periods.^[33] Reproductive traits also vary regionally, with northern females producing larger eggs (averaging 0.35–0.40 g) to support enhanced embryonic development and hatching success in colder nest environments.^[32] In contrast, southern populations in Florida feature smaller body sizes (typically 50–55 mm SVL) and more vibrant dorsal coloration, including richer brown or rusty hues that may aid thermoregulation and signaling in warmer, sunnier conditions. Southern females lay smaller first clutches (around 4–6 eggs) but are more likely to produce multiple clutches per season (up to two or three), resulting in higher overall reproductive output adapted to extended breeding periods.^[34]^[11] Clinal variation occurs in morphological features like dorsal scale counts and limb length, which correlate with habitat openness. Populations in more open, arid environments show higher scale counts (37+ dorsal scales) and longer hindlimbs (up to 20% relative length increase), facilitating rapid sprinting for predator evasion, whereas forested or closed-canopy areas favor shorter limbs and fewer scales for climbing efficiency.^[20]^[35]

Behavior

Locomotion

The eastern fence lizard (Sceloporus undulatus) primarily employs quadrupedal locomotion characterized by a sprawling gait, where the limbs extend laterally from the body to generate propulsive force through ground contact. This mode of movement enables bursts of sprint speed reaching up to approximately 2.1 m/s, particularly during short-distance pursuits or evasions, with performance peaking at body temperatures between 30–35°C.^[36]^[37] Sprint speeds decline modestly on inclines, but the lizard maintains effective locomotion on slopes up to 45°, demonstrating adaptations for navigating uneven terrain such as rocky outcrops or forest floors.^[38] The hindlimbs provide the primary propulsion, with efficient muscle contractions allowing sustained bursts despite the biomechanical demands of climbing. The tail contributes to overall locomotor dynamics by aiding propulsion during acceleration and serving as a counterbalance for steering and stability on irregular surfaces.^[39] In defensive scenarios, the lizard can voluntarily autotomize its tail at fracture planes, detaching it to distract predators and facilitate escape, though this temporarily impairs balance and speed until regeneration occurs.^[40] Perching is a key aspect of its movement repertoire, with individuals frequently ascending and positioning on vertical substrates like tree trunks, stumps, or fence posts to overlook potential threats or prey. This behavior leverages claw morphology for secure grip on rough bark or wood, enabling rapid vertical traversal when grounded locomotion is compromised. Such adaptations support both foraging ambushes and predator avoidance in arboreal-edge habitats.^[11]

Territoriality

Male eastern fence lizards establish and defend territories during the breeding season in spring, with average home range sizes of 47 to 61 m², which can expand based on food availability.^[11]^[17] These territories often overlap with the smaller home ranges of multiple females, allowing resident males priority access to potential mates within them.^[41] To assert dominance and deter intruders, males perform ritualized displays consisting of rapid head-bobbing and push-ups lasting 4–5 seconds, which prominently expose their bright blue ventral patches.^[11]^[16]^[17] These visual threats typically escalate to physical confrontations, including chasing and biting, if the display fails to repel rivals; such aggressive interactions occur in about 14% of male encounters, often near females, with victorious males securing greater mating opportunities.^[42]^[41] Females exhibit less territorial behavior overall, maintaining smaller home ranges without extensive defense against conspecifics, though they briefly protect nest sites during the egg-laying period, increasing their vulnerability to predators.^[11]^[17]

Courtship

Males of the eastern fence lizard (Sceloporus undulatus) court receptive females through a series of conspicuous visual and olfactory signals, typically initiated upon encountering a female within the male's territory. The primary display involves rapid push-ups and head-bobs, performed in bursts lasting 4–5 seconds, which accentuate the male's bright blue ventral badges on the throat and abdomen. These movements are often combined with lateral body orientations to fully expose the coloration and occasional tongue flicks to detect female pheromones, while males also release scents from anal glands to enhance attraction.^[11]^[43] Female mate selection favors larger males exhibiting more saturated and vivid blue badges, traits that honestly signal superior body condition, elevated testosterone levels, and immunocompetence, thereby correlating with higher reproductive success and siring rates.^[15]^[44] Brighter coloration and greater body size enable males to outcompete rivals and more effectively court multiple partners, though direct female discrimination may also incorporate behavioral cues from the displays.^[45] Courtship interactions generally escalate to mounting after repeated displays, with the female either submitting or attempting to flee, and occur primarily during the breeding season from April to August, peaking in May and June shortly after emergence from winter hibernation.^[11] Territorial push-up displays toward same-sex intruders can transition into courtship sequences when redirected at females, blending rivalry and attraction in the same behavioral repertoire.^[17]

Reproduction

Mating system

The eastern fence lizard (Sceloporus undulatus) exhibits a polygynous mating system, in which individual males mate with multiple females while females typically mate with a single male.^[46] This system is facilitated by genetic sex determination, resulting in a population sex ratio close to 1:1 at hatching and in adults.^[47] Males engage in intense intrasexual competition, including aggressive displays and physical contests, to secure access to females within overlapping home ranges, with larger and more aggressive males achieving higher reproductive success by monopolizing multiple mates.^[46] Females can store viable sperm in oviductal tubules and vaginal folds for extended periods, enabling delayed fertilization and the production of multiple clutches from a single mating event.^[48] Sperm viability declines gradually, remaining functional for up to 12–25 weeks post-mating, which aligns with the species' seasonal breeding pattern and supports single-season reproduction without necessitating repeated matings.^[48] Clutch frequency varies from 1 to 4 per reproductive season, influenced by environmental resources such as food availability and latitude, with higher frequencies observed in southern populations where longer growing seasons allow for iterative oviposition at intervals of approximately 6 weeks.^[49]^[48] Female mate choice plays a key role in the mating system, with preferences directed toward males exhibiting larger body size and more vigorous courtship displays, such as push-up signaling, which correlate with male quality and offspring fitness.^[50] In experimental trials, females consistently associated longer with larger males over smaller counterparts, and display intensity further modulates acceptance, as more energetic performances signal superior genetic or condition-based traits that enhance progeny survival.^[50] This selective pressure reinforces sexual size dimorphism, as successful males pass on alleles for larger stature, ultimately influencing population-level reproductive dynamics.^[46]

Egg-laying and clutch dynamics

Females of the eastern fence lizard (Sceloporus undulatus) oviposit in shallow nests excavated in moist, sandy soil, typically 3–15 cm deep, often under cover objects such as rotting logs, rocks, or stumps to provide protection and maintain suitable microclimates for embryonic development.^[11]^[4] These nests are dug by the female using her hind limbs, and eggs are deposited without further parental care, with the female covering the clutch afterward to conceal it. Clutch sizes range from 3 to 16 eggs, though averages vary regionally, with smaller clutches (around 5–6 eggs) in southern populations and larger ones (up to 11–12 eggs) in northern areas.^[49]^[51] This variation is positively correlated with female body size, as larger individuals allocate more resources to reproduction.^[49] Mature females typically produce 2–4 clutches per reproductive season, spaced 2–6 weeks apart, allowing for multiple bouts of egg production from late spring through summer.^[49] The total annual reproductive output can reach up to 40 eggs for older, larger females in favorable environments, though younger females often lay only a single clutch of 3–13 eggs.^[11]^[49] Clutch size and frequency are influenced by environmental factors, including latitude and temperature, with northern populations exhibiting higher per-clutch investment due to shorter activity seasons and cooler conditions that promote larger maternal sizes.^[51] Under suboptimal conditions such as cool temperatures or dry substrates, females may exhibit extended egg retention in the oviducts, delaying oviposition to await more favorable nesting opportunities and thereby optimizing hatching success. This plasticity results in heavier eggs with slightly more advanced embryos at laying but generally incurs minimal costs to overall reproductive output.^[53]

Embryonic development and hatching

The eggs of the eastern fence lizard (Sceloporus undulatus) undergo incubation in underground nests, where environmental conditions influence embryonic development. Incubation typically lasts 50–70 days, averaging about 10 weeks, under optimal soil temperatures of 25–30°C, which support high hatching success rates exceeding 70%. ^[54] ^[11] In northern populations, eggs are often larger and experience prolonged incubation periods compared to those in southern regions, allowing for developmental synchronization with seasonal conditions and faster post-hatching growth rates. ^[55] ^[56] Embryos develop into fully formed juveniles within the eggs, emerging as independent hatchlings with no parental care. Hatchlings measure 24–28 mm in snout-to-vent length (SVL) and are immediately capable of foraging and thermoregulating on their own. ^[17] ^[57] ^[11] Hatching primarily occurs from July through August, coinciding with late summer warmth that aids juvenile survival. The residual yolk sac serves as the initial nutrient source, enabling rapid assimilation of energy to support early growth before active feeding begins. ^[11] ^[56]

Ecology

Diet and foraging

The eastern fence lizard (Sceloporus undulatus) is primarily insectivorous, with its diet consisting mainly of arthropods such as ants (Formicidae), beetles (Coleoptera), grasshoppers (Orthoptera), spiders (Araneae), and ticks (Ixodidae).^[11] Ants form a substantial portion of the diet, comprising approximately 80% for juveniles and 50% for adults, while other invertebrates like beetles contribute significantly to the remainder.^[58]^[59]^[11] Juveniles occasionally consume small amounts of plant matter, such as cheatgrass (Bromus tectorum) and needlegrass (Stipa spp.), though this is incidental and not a primary food source.^[11] These lizards employ a sit-and-wait ambush foraging strategy, typically perching on elevated structures like logs, fences, or rocks to scan for prey within striking distance. Prey capture involves rapid tongue projection, facilitated by the hyobranchial apparatus, which allows precise prehension without leaving the perch in most cases; if necessary, short bursts of locomotion may be used to pursue escaping prey. Foraging activity peaks in the morning following thermoregulatory basking, when body temperatures are optimal for performance, and occurs diurnally until late afternoon.^[60]^[61] Ontogenetic shifts occur in prey selection, with juveniles focusing on smaller, more abundant items like ants due to gape limitations and higher metabolic demands, while adults target larger prey such as beetles and grasshoppers for greater energy yield. Seasonal variation influences diet composition, with ants dominating in summer when their abundance is high, and greater diversity—including more beetles—observed in late seasons as invertebrate communities change. These adaptations optimize energy intake across life stages and environmental conditions.^[62]^[63]

Predators and defense mechanisms

The eastern fence lizard (Sceloporus undulatus) faces predation from a variety of native species across its range. Avian predators include raptors such as hawks and corvids, as well as smaller birds like shrikes and Carolina wrens that target juveniles and hatchlings.^[17] Snakes, particularly colubrids like eastern rat snakes (Pantherophis alleghaniensis) and black racers (Coluber constrictor), frequently prey on adults and subadults by ambushing them on perches or during foraging.^[17] Mammalian predators encompass small to medium-sized carnivores, including foxes, raccoons, and domestic cats, which opportunistically capture lizards in open habitats.^[64] Additionally, eggs laid in shallow soil nests are highly vulnerable to predation by small mammals such as rodents and native ants that excavate and consume them.^[1] To counter these threats, eastern fence lizards employ a suite of anti-predator strategies emphasizing evasion and deterrence. Their mottled brown and gray coloration provides effective crypsis against bark and leaf litter, allowing them to blend into woodland and scrub environments and avoid detection by visually hunting predators.^[16] When threatened, individuals often freeze in place to minimize movement cues, relying on immobility to enhance camouflage until the danger passes. If pursued, they exhibit rapid flight, sprinting bipedally at speeds up to 10 km/h to reach tree trunks or rock crevices, where they circle to the opposite side to evade climbing predators.^[16] Physical and behavioral defenses further bolster survival. Tail autotomy enables the lizard to voluntarily detach its caudal appendage when grasped, distracting the predator with the wriggling tail while the lizard escapes; the tail regenerates over several months, though regrown versions are often shorter and less effective.^[1] Against smaller or less committed predators, lizards perform push-up displays—rapid extensions of the forelimbs accompanied by head bobbing—to signal alertness and fitness, potentially deterring attacks by indicating that the prey is vigilant and not an easy target.^[65] These combined tactics contribute to the species' resilience in predator-rich habitats.

Interactions with invasive species

The red imported fire ant (Solenopsis invicta), an invasive species introduced to the southeastern United States, exerts significant predation pressure on the eastern fence lizard (Sceloporus undulatus), particularly targeting eggs and juveniles. Fire ants readily occupy nesting microhabitats shared by fence lizards, leading to direct attacks on eggs where they can penetrate intact shells and consume contents, rendering embryos non-viable. In experimental studies across southern ranges, approximately 61% of artificial nests were potentially vulnerable to fire ant predation over the full 55–70-day incubation period, highlighting a substantial threat to recruitment in invaded areas.^[66] Juveniles face similar risks, as small numbers of fire ants can envenomate and kill them within minutes, contributing to population declines in heavily infested regions.^[58] Eastern fence lizards have evolved behavioral adaptations to mitigate fire ant predation, including rapid escape responses that vary by life stage and exposure history. Juveniles exhibit innate fleeing upon initial encounters, with about 60% escaping on first contact, and a single exposure prompts increased flight propensity in subsequent trials, enhancing survival without requiring long-term learning.^[67] Both juveniles and adults perform body twitching—known as "fire ant dancing"—to dislodge attacking ants, with twitch frequency rising in proportion to the number of assailants. In populations evolutionarily adapted to long-term fire ant presence, these responses are more pronounced, reducing envenomation risk by roughly 50% compared to naïve individuals from uninvaded sites; genomic studies as of 2025 have identified specific genetic signatures underlying these adaptations.^[68]^[69] While fire ants represent the primary invasive threat, other non-native species such as introduced anole lizards (Anolis sagrei) overlap in distribution and may compete for resources like insect prey and perch sites in the southeastern U.S., though documented impacts on eastern fence lizard populations remain minimal and indirect.

Conservation

Global and regional status

The eastern fence lizard (Sceloporus undulatus) is classified as Least Concern on the IUCN Red List, with this assessment made in 2007 based on its wide distribution across the eastern United States and stable population levels overall. The species receives no federal protection under the U.S. Endangered Species Act, reflecting its generally secure status across much of its range.^[16] Regionally, conservation designations vary, particularly at the northern periphery of the range. In New York, the eastern fence lizard was added to the state's threatened species list in April 2025 due to ongoing habitat loss and limited populations.^[70] It is also designated as a Species of Greatest Conservation Need in several northeastern states, including Connecticut, New Jersey, and Pennsylvania, where peripheral populations face heightened vulnerability. In contrast, populations in core southeastern areas, such as Virginia and North Carolina, are typically considered secure without special state protections.^[17] Population trends for the eastern fence lizard are stable globally, supported by its adaptability to a broad range of habitats. However, local declines have been observed in fragmented habitats, such as isolated forest patches, where habitat loss can lead to extirpation of small populations.^[17] Conversely, the species has thrived in human-modified edge habitats, including forest clearings and suburban areas created by development and logging, which provide increased basking sites and foraging opportunities.^[11]

Threats and management

The eastern fence lizard faces several anthropogenic threats, primarily habitat fragmentation and loss due to urban and suburban development, which disrupts its preferred open woodland and rocky habitats across its range. Road mortality is a significant concern, as lizards crossing roadways for foraging or dispersal are frequently killed by vehicles, exacerbating population isolation in fragmented landscapes. In the southern portions of its range, invasive red imported fire ants (Solenopsis invicta) pose a major risk by preying on lizard eggs in nests, with studies showing that fire ants can detect and consume intact eggs, leading to high rates of nest failure even in areas with established lizard populations. Climate change contributes to altered environmental conditions, including increased flooding that can inundate nests and warmer temperatures affecting egg development and overall population dynamics, though the species is assessed as presumably stable under projected changes in some regions. In the Northeast, particularly New York, recent urbanization has heightened concerns, with the species listed as threatened due to ongoing habitat loss and fragmentation. Management efforts focus on preserving suitable woodland habitats with open canopies and sunny exposures to support basking and nesting, including protection of rocky outcrops and forest edges in conservation areas. In southern ranges where fire ants are prevalent, control measures such as targeted baiting and mound treatments help reduce predation pressure on lizard nests, though lizards have shown adaptive responses like behavioral changes to mitigate impacts. Post-2025, monitoring programs in states like New York track population trends and habitat quality following its threatened listing, emphasizing surveys in remnant populations on Staten Island and the Hudson Highlands. Due to the species' adaptability and widespread distribution, no large-scale recovery programs are currently implemented, with conservation relying on localized habitat management rather than broad interventions. Human interactions with eastern fence lizards are generally minimal but include occasional persecution based on misconceptions that the lizards are poisonous or venomous, despite being completely harmless to humans. Conversely, the species provides ecological benefits by serving as a host for blacklegged ticks (Ixodes scapularis), where lizard blood proteins can kill or remove Borrelia burgdorferi, the causative agent of Lyme disease, thereby reducing transmission risk in endemic areas.

References

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Range and Habitat: Fence lizards range across the Southeast and are common in many habitats from the mountains to the coast. Unlike other lizards, though, fence ...Missing: distribution | Show results with:distribution
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Habitat: Rocky, wooded areas, dry hillsides, and sunny, open woodlots. Natural History: Mating occurs in April or May. Five to 15 eggs are laid in soil and ...
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Fence Lizard
The Fence Lizard has a very wide geographic distribution, from Pennsylvania west to Utah and south into north-central Mexico, including all of the southeastern ...
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Eastern fence lizard
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Word History. Etymology. New Latin, from scel- (from Greek skelos leg) + -porous (from Greek poros passage, pore); ...
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rom Greek skelos (σκελός), “leg,” and poros (πόρος), “pore,” referring to the ...
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Also called “rusty-back” or “fence swift,” this conspicuous animal gets its name from its tendency to bask and forage in the open on logs and wooden fences.
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Eastern Fence Lizard. Sceloporus undulatus. Status: Not Listed. Classification ... Fence lizards are relatively common and their populations are stable.
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Eastern Fence Lizard Sceloporus undulatus ; Etymology: ; Genus: Sceloporus is derived from the Greek word scelos meaning "leg" and the Latin word porus meaning " ...
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A medium-sized (4.0 to 7.25 inches in length), wide-bodied grayish to brown lizard with keeled, pointed scales. Females are larger than males.Missing: morphology limbs tail femoral pores
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[24]
Sceloporus undulatus - Eastern Fence Lizard
Mickey. Taxonomy. Class: Reptilia, Order: Squamata, Family: Phrynosomatidae. Taxonomic Comments: The Eastern Fence Lizard is one of twenty-two species in this ...
[25]
(PDF) Temperature‐dependent colour change is a function of sex ...
We found that skin colour (hue) in both sexes changed with temperature. Only ventral patch colour in males changed visibly to human observers.
[26]
[PDF] Eastern Fence Lizard Species Status Assessment - NY.gov
Jan 3, 2025 · Status Discussion: The eastern fence lizard is a southern species that reaches the northern extent of its range in a small area of extreme ...Missing: geographic | Show results with:geographic
[27]
Have you seen lizards on Staten Island? - SILive.com
Aug 19, 2014 · There no native species of lizards on Staten Island, but colonies of two introduced species, the eastern fence lizard and Italian wall lizard, are found here.
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eastern fence lizard (Priority species - iNaturalist
The elevational range extends from sea level to around 3,050 m (10,000 feet) (Stebbins 2003). Habitat and ecology. Habitat and Ecology. Habitat varies ...Missing: Appalachians | Show results with:Appalachians
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[PDF] Species Assessment for Eastern fence lizard - NY.Gov
Its distribution is widespread across much of the southern United States, but its status is poorly understood.Missing: geographic | Show results with:geographic
[30]
None
### Summary of Habitat and Microhabitat Use by Eastern Fence Lizards (Sceloporus undulatus) in Southeastern Pine Forests
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[PDF] Lizards of New York State - NY.Gov
It adapted well to urban and suburban settings, and is now permanently established on western Long Island and in isolated pockets in New York City as far ...
[32]
Body Size Clines in Sceloporus Lizards: Proximate Mechanisms and ...
Body size within Sceloporus does vary greatly within and among species. Although adult body size varies over tenfold among species, from 4 grams to 60+ grams, ...Missing: counts | Show results with:counts
[33]
Environmental causes of between-population difference in growth ...
Sep 24, 2018 · Ectothermic animals living in cold (high latitude or high elevation) regions are predicted to grow slower due to limited thermal opportunities ...
[34]
Latitudinal and seasonal variation in reproductive effort of the ...
Oct 21, 2013 · We collected gravid female lizards (Sceloporus undulatus) from northern (Indiana), central (Mississippi) and southern (Florida) populations ...
[35]
(PDF) Latitudinal and climatic variation in body size and dorsal scale ...
Aug 7, 2025 · (PDF) Latitudinal and climatic variation in body size and dorsal scale counts in Sceloporus lizards: A Phylogenetic perspective.
[36]
[PDF] Geographic Variation in the Effects of Heat Exposure on Maximum ...
Oct 13, 2011 · Sprint speed (m/s):. BC. 1.537 (.110)A .709 (.070)B .693 (.930)B. KHS. 1.576 (.076)A. 1.326 (.188)A. 1.020 (.131)B. TM. 1.326 (.095)A. 1.131 (.
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Effects of Temperature and Slope on the Sprint Speed and Stamina ...
Dec 1, 2003 · The broad thermal breadth of performance suggests that the lizards are capable of sustaining near optimal levels of locomotor performance at ...<|control11|><|separator|>
[38]
[PDF] Tail autotomy and subsequent regeneration alter the mechanics of ...
It is clear from recent work that the lizard tail is important in a number of locomotor behaviors. Jusufi et al. (Jusufi et al., 2008) showed that the tail ...
[39]
[PDF] Eastern Fence Lizard Sceloporus undulatus - Emperor Ken's World
their tails through a process called “autotomy”. ... This tactic is employed by lizards to allow them to escape when a predator captures them by the tail.
[40]
(PDF) Home-Range Analysis in Sceloporus undulatus (Eastern ...
Aug 6, 2025 · Here, we couple a comprehensive analysis of home range with demographic information and focal behavioral observations of Sceloporus undulatus ( ...
[41]
[PDF] Eastern Fence Lizard | NC Wildlife
The fence lizard is one of the most common and widespread lizards in North Caro- lina. Many populations in urban and suburban areas have been reduced or ...
[42]
eastern fence lizard - Illinois Department of Natural Resources
The eastern fence lizard averages four to seven and one-fourth inches in length. It has keeled (ridged), overlapping, pointed scales on the back.
[43]
https://dnr.illinois.gov/education/wildaboutpages/wildaboutlizards/walzeasternfencelizard.html
[44]
Mate choice and competition in the eastern fence lizard, Sceloporus ...
Notably, fence lizards perform dramatic physical displays when courting and defending resources, and males bear vibrant blue throat and abdominal badges used in ...
[45]
[PDF] natural history and endocrine experiments on a lizard (Sceloporus ...
Jul 13, 2009 · We then discuss fitness in terms of reproductive success, which we estimated via DNA fingerprinting, and finally we close with statistical ...
[46]
[PDF] 9 Temperature-dependent sex determination
Jan 6, 2004 · Sceloporus undulatus ... Stars denote the pivotal temperatures that correspond to constant temperatures that produce a population-wide 1:1 sex ...
[47]
[PDF] decline in functional short-term sperm storage and reproduction in ...
Apr 30, 2021 · Here, we examine functional sperm storage in two oviparous lizard species (Sceloporus undulatus and. S. woodi; Fig. 1) by assessing reproductive ...
[48]
[PDF] Intraspecific Life History Variation in Sceloporus undulatus
In this study we consider the covariation of life history traits in the eastern fence lizard, Sceloporus undulatus, one of the most-studied lizards in North.
[49]
Female choice on male traits in eastern fence lizards, Sceloporus ...
We designed an experiment using eastern fence lizards (Sceloporus undulatus) to uncover if females select their partners based on specific traits. We conducted ...
[50]
Direct and Indirect Effects of Environmental Temperature on the ...
Thus, we conclude a decrease in environmental temperature increases egg size and clutch size of Sceloporus undulatus via an increase in maternal size.Missing: laying | Show results with:laying
[51]
https://www.journals.uchicago.edu/doi/full/10.1086/507880
[52]
Extreme plasticity in reproductive biology of an oviparous lizard - PMC
Even when females facultatively retain eggs in dry or cold conditions, such retention generally causes only a minor (<10%) decrease in subsequent incubation ...
[53]
NEST-SITE SELECTION IN RELATION TO TEMPERATURE AND ...
Dec 1, 2002 · These two females nested about 1 m apart from one another on a south-facing slope and finished covering their clutches at 1300 and 1415 h. Both ...
[54]
Convergent evolution of embryonic growth and development in the ...
We used a common garden experiment to detect parallel clines in rates of embryonic growth and development by eastern fence lizards (Sceloporus undulatus). Using ...
[55]
Rapid assimilation of yolk enhances growth and development of ...
Oct 1, 2007 · In S. undulatus, embryos from VA grew faster than embryos from SC by assimilating energy more rapidly. Rapid assimilation of yolk by embryos ...
[56]
The Dynamics of a Utah Population of Sceloporus undulatus - jstor
Hatchlings first appear in late July at a size of about 25 mm SVL. This body length is doubled by the following June, and by August the lizards have reached ...
[57]
Invasive ants influence native lizard populations - ESA Journals
Jan 6, 2017 · Ants comprise a large proportion of the fence lizard diet (approximately 80% in juveniles), though other invertebrates (e.g., Orthoptera) make a ...
[58]
Sceloporus undulatus (Eastern fence lizard). Diet. - ResearchGate
Aug 6, 2025 · Fence lizard diet is comprised primarily of ants (juveniles: 80%; adults: 50%), but does include other taxa, predominantly beetles and other ...
[59]
Prey Selection by an Ambush Predator, Sceloporus undulatus
Prey Selection by an Ambush Predator, Sceloporus undulatus. KATHERINE S. EBERHART. 1,2. AND DOUGLAS E. RUBY. 1,3. 1Department of Natural Sciences, University of ...
[60]
Comparative study of tongue protrusion in three iguanian lizards ...
Sep 15, 2000 · High-speed videography and nerve-transection techniques were used to study prey capture in the iguanid Sceloporus undulatus, the agamid ...
[61]
Eastern Fence Lizards (Sceloporus undulatus) display an ontogenetic shift in relative consumption of native and invasive prey
### Summary of Eastern Fence Lizard Diet and Foraging
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Does seasonal variation in the corticosterone response affect ... - NIH
Jan 30, 2025 · Despite the dominance of ants in the diet, we found seasonal differences in diet. Diversity of diet composition was highest in the late ...
[63]
Eastern Fence Lizard - Chesapeake Bay Program
Small image of Male eastern fence lizard with a broken tail. Quick Facts. Species type. Native. Size. 4-7½ inches. Habitat. Dry ...
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Behavior Under Risk: How Animals Avoid Becoming Dinner - Nature
Prey can also use behavior to signal to a predator that it would be a waste of time and energy attempting an attack. For example, pushups performed by lizards ...
[65]
Frog, Lizard, Salamander Added to New York's Endangered ...
Apr 18, 2025 · New York has added the Atlantic Coast leopard frog, eastern fence lizard and eastern tiger salamander to its protected threatened and endangered species lists.