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Sceloporus olivaceusTexas Spiny Lizard

By Kalina Theo

Geographic Range

Texas spiny lizards (Sceloporus olivaceus) are native to the Nearctic region. Their range extends from southern Tampico, through the Mexican states of Tamaulipas, San Luis Potosi, central Nuevo Leon, and southeastern Coahuila. Their range continues into the United States, through central and Eastern Texas to the Texas-Oklahoma border. There have been rare sightings of Texas spiny lizards in Oklahoma and New Mexico, but no studies have confirmed permanent populations there. (Fink, 2015; Hammerson and Frost, 2007; Kennedy, 1973; Kerster, 1964; Smith, 1934)

Habitat

Texas spiny lizards inhabit subtropical forests and shrublands, often in areas with enough vertical structure to remain arboreal. They are often associated with mesquite trees (genus Prosopis) or oaks (genus Quercus), but they also make use of anthropogenic structures like fences, abandoned houses, and bridges. The forest and scrub habitats that Texas spiny lizards prefer are often located along arid floodplains. Although they typically avoid entering water, they may do so to avoid predation. Texas spiny lizards also occupy peat bogs in some parts of Texas. There are no known reports of elevation ranges for Texas spiny lizards.

Texas spiny lizards are commonly called fence lizards, rusty lizards, or tree lizards, in part due to their choice of basking locations; they are often seen basking on fences, rocks, or high up in trees. During their breeding season, Texas spiny lizards move to areas with loose soil and significant levels of leaf litter, and then dig themselves underground. Females lay eggs on the ground in areas with adequate sun exposure and dry soil. (Cole, 1969; Dutton, et al., 1975; Fink, 2015; Hammerson and Frost, 2007; Kennedy, 1973; Kerster, 1964)

Physical Description

Texas spiny lizards have dorsal scales that are tan or brown with an olive tint, and wavy, axial bands of black or dark grey that repeat down their backs. They typically have distinctive rows of lighter scales extending longitudinally along either side of their backs. These alternating patterns of white, black, and brownish-green scales act as a form of crypsis, breaking up their outline and camouflaging them with their environment. Their ventral scales are lighter than their dorsal scales, and the ventral scales on their tails are often lighter than the scales on their bellies. Texas spiny lizards have smooth scales on their heads and spiny scales along their backs and tails. They have long toes with sharp claws, which help them climb among trees.

Upon hatching, Texas spiny lizards measure 22 to 28 mm in snout-vent length (SVL). Hatchlings have tails that are an average of 1.3 times longer than their SVL. Both sexes have similar SVLs at birth, but adult females are larger, on average, than adult males. Females reach a maximum SVL of 121 mm, whereas males reach a maximum SVL of 102mm. Texas spiny lizards can reach total lengths (TL) of 190 to 280 mm (average: 235 mm). Adults have tails that average 127 mm in length, or an average of 1.6 times greater than their SVL.

In addition to differences in size, males and females exhibit sexual dimorphism in scale characteristics. For example, males have narrow, longitudinal rows of blue scales along either side of their bellies, which females lack. Males also have two enlarged post-anal scales that are absent in females. (Chong, et al., 2022; Dutton, et al., 1975; Kennedy, 1973; Smith, 1934; Underwood, 1985)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • male more colorful
  • Range length
    190 to 280 mm
    7.48 to 11.02 in

Development

Texas spiny lizards have clutches ranging in size from 2 to 20 eggs (average: 11 eggs) and lay up to 4 clutches per breeding season. Females gestate eggs for 90 to 100 days prior to laying them.

Although they are primarily arboreal, Texas spiny lizards lay their eggs on the ground, often in dry soil. Females dig nests that are an average of 101 mm wide and between 101 and 152 mm deep. Female fill in these holes once they lay their eggs, and they do not return to their nests once they are buried.

Eggs incubate for 45 to 83 days (average: 60 days) prior to hatching. A study from southern Texas reported hatchlings measuring 22 to 28 mm in snout-vent length (SVL). Other studies have reported lengths of 30 to 40 mm, but these are likely measures of total length (TL). Male hatchlings have a longitudinal blue stripe along each side of their bellies. These blue stripes fade over time, but are still visible in adult males. Texas spiny lizards exhibit indeterminate growth. They have a slow growth rate, especially after they reach maturity. Compared to males, females typically take longer to reach maturity and are larger as adults. (Dutton, et al., 1975; Fink, 2015; Hammerson and Frost, 2007; Kennedy, 1973; Pianka and Parker, 1975)

Reproduction

Texas spiny lizards are polygynandrous. Males defend mating territories and display competitive behaviors towards other males. For example, males perform "push-ups" when they observe other males in their territory, and they may compete physically if visual displays do not deter competitors. Males also display aggressive behaviors during copulation, biting or otherwise restraining females if they try to retreat. Copulation often takes less than a minute, but there are still many cases of incomplete copulation. (Carman, et al., 2000; Fink, 2015; Robinson, 2014)

Texas spiny lizards breed seasonally from April through June. Males and females both have multiple mates within a single breeding season. Fertilization occurs internally and the gestation period for eggs is 90 to 100 days. Females lay clutches of 2 to 20 eggs (average: 11 eggs). They often lay only one clutch in their first year of maturity, but they may lay up to four clutches in subsequent years.

Female dig shallow holes in the ground, where they lay their eggs and cover them in loose dirt. Hatchlings are fully independent and disperse from nest sites within 3 or 4 days. There are no records of birth masses for Texas spiny lizards, but hatchlings measure 22 to 28 mm in snout-vent length (SVL). Females mature more slowly than males, but both sexes typically reach maturity within 2 years of hatching. (Fink, 2015; Kennedy, 1973; Kerster, 1964; Méndez-de la Cruz, et al., 1998; Pianka and Parker, 1975)

  • Breeding interval
    Texas spiny lizards breed multiple times in a breeding season
  • Breeding season
    April to June
  • Range number of offspring
    2 to 20
  • Range gestation period
    90 to 100 days
  • Average time to independence
    0 minutes
  • Range age at sexual or reproductive maturity (female)
    1 to 2 years
  • Range age at sexual or reproductive maturity (male)
    1 to 2 years

Texas spiny lizards provide very little parental investment in their offspring. Females dig shallow nests that provide protection and proper conditions for incubation, but they do not stay near nest sites to provide further protection. Females also invest energy in egg yolk, which facilitates embryonic growth. Males provide no parental investment beyond the act of mating. (Ballinger and Clark Jr, 1973; Fink, 2015; Kennedy, 1973)

  • Parental Investment
  • no parental involvement
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Texas spiny lizards are estimated to live 2 to 5 years in their natural habitats, but other species in the genus Sceloporus are reported to have lifespans of 6.7 years. In captivity, Texas spiny lizards can live up to 7 years. (Fink, 2015; Kennedy, 1973; Tacutu, et al., 2018)

  • Typical lifespan
    Status: wild
    2 to 5 years
  • Typical lifespan
    Status: captivity
    7 (high) years

Behavior

Texas spiny lizards are arboreal and scansorial, with long toes and sharp claws adapted to climbing trees. They are ectothermic and primarily diurnal, often basking in the beginning of the day and foraging or searching for mates once they have warmed up. Texas spiny lizards are solitary outside of breeding season, although they occasionally bask in groups. During the breeding season, males aggressively defend territories and exhibit complex social interactions when competing for mates.

Texas spiny lizards are motile, but they are fairly sedentary and do not migrate. At the northern end of their range, Texas spiny lizards brumate for several weeks during winter. Farther south, they will burrow underground and reduce their activity to avoid cold temperatures.

Texas spiny lizards are highly vigilant and capable of rapid movement if they sense predators. When threatened, they seek shelter in trees or under leaf litter. If captured or provoked, Texas spiny lizards can selectively detach their tails, which provides a distraction and gives them a chance to escape danger. (Dutton, et al., 1975; Gehlbach, 2010; Kennedy, 1973; Smith, 1934; Underwood, 1985)

  • Range territory size
    50 to 500 m^2

Home Range

Texas spiny lizards have home range sizes of 50 to 500 m^2 (average: 275 m^2). Exact home range size depends on several factors, including age (older individual = larger range), food availability (less food = larger range), and habitat quality (poor habitat = larger range). Texas spiny lizards usually select home ranges that include one or more large trees. Males typically have larger home ranges than females and will defend their territories aggressively during the breeding season. Adult Texas spiny lizards will maintain the same home range for several years. (Fink, 2015; Gehlbach, 2010; Kerster, 1964; Smith, 1934)

Communication and Perception

Texas spiny lizards communicate through visual signals, chemical pheromones, and tactile interactions. Males use visual displays, such as head-bobbing and push-ups, to defend their territories from competitors. Males also communicate their fitness to potential mates through visual displays, including push-ups, extensions of their dewlap (a fleshy fold on the throat), tail curls, and dorsoventral flattening. Males use dorsoventral flattening to show off the blue lateral lines on each side of their bellies. Females may also judge the spiny appearance of male scales as a measure of fitness.

Texas spiny lizards also use pheromones to communicate with nearby conspecifics. They spread pheromone secretions from their hindlimbs or cloacae onto substrates in their environment. Other Texas spiny lizards detect these pheromones using their vomeronasal organs.

Texas spiny lizards also use tactile communication when competing, mating, laying eggs, and capturing food. For example, males may physically attack competitors if visual displays are unsuccessful. Males may also bite or grab females during copulation. (Cole, 1969; Dutton, et al., 1975; Robinson, 2014; Robinson, et al., 2015)

Food Habits

Texas spiny lizards are insectivores, consuming various kinds of invertebrates. In captivity, they will eat crickets and grasshoppers (order Orthoptera), small cockroaches (order Blattodea), beetles and beetle larvae (order Coleoptera), and woodlice (suborder Oniscidea). Texas spiny lizards have similar diets regardless of age or sex.

Texas spiny lizards often stay up high in trees and wait to eat prey moving near them. They rarely leave trees or shrubs when hunting. Texas spiny lizard activity is driven by ambient temperatures; lower temperatures correspond with lower foraging effort. (Dutton, et al., 1975; Kennedy, 1973; Pianka and Parker, 1975; Robinson, et al., 2015)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods

Predation

Texas spiny lizards are most susceptible to predators when they are juveniles or small adults. They serve as prey for snakes, birds, mammals, and larger lizards. Coachwhip snakes (Masticophis flagellum) and bullsnakes (Pituophis catenifer) are commonly observed eating Texas spiny lizards. Other snake predators include Chihuahuan night snakes (Hypsiglena ochrorhyncha texana), rock rattlesnakes (Crotalus lepidus), gray-banded kingsnakes (Lampropeltis blairi), and eastern massasaugas (Sistrurus catenatus). Some larger spiny lizard species (genus Sceloporus), such as desert spiny lizards (Sceloporus magister), will eat Texas spiny lizards.

Avian predators include gray hawks (Buteo plagiatus), red-shouldered hawks (Buteo lineatus), and greater roadrunners (Geococcyx californianus). Mammals such as kit foxes (Vulpes macrotis) also prey on Texas spiny lizards. Birds and mammals prey on juveniles more frequently, while snakes will eat mature adults.

Texas spiny lizards have cryptic coloration that helps them camouflage with their environment. They are highly vigilant and are capable of moving quickly to reach cover if they detect a threat. Texas spiny lizards are also capable of autotomy, detaching their tails to distract predators that do manage to capture them. (Dutton, et al., 1975; Kennedy, 1973; Smith, 1934)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Texas spiny lizards consume various insects and other invertebrates, so they likely have a role in managing invertebrate populations. They also serve as prey for snakes, lizards, hawks, and some large mammals.

Texas spiny lizards serve as hosts for ectoparasites such as chiggers (family Trombiculidae), including the species Neoschongastia scelopori and Eutrombicula alfreddugesi. Texas spiny lizards are also confirmed to carry saurian malaria, which is caused by protozoan parasites in the genus Plasmodium. (Dutton, et al., 1975; Kennedy, 1973)

Commensal/Parasitic Species
  • Mites (Neoschongastia scelopori)
  • Mites (Eutrombicula alfreddugesi)
  • Protozoans (genus Plasmodium)

Economic Importance for Humans: Positive

Texas spiny lizards have positive economic impacts, as they are part of the pet trade. They generally range in price from 25 to 40 USD, depending on size and age. However, Texas spiny lizards are uncommon pets because licensed breeders are rare. (Imperial Reptiles & Exotics, 2023)

Economic Importance for Humans: Negative

There are no known negative economic impacts of Texas spiny lizards on humans.

Conservation Status

Texas spiny lizards are listed as a species of “Least Concern” on the IUCN Red List. Mexican populations have been assigned a "medium" environmental vulnerability, but they currently have no special status on the conservation list maintained by Mexico's environmental ministry, SEMARNAT. They also have no special status on the U.S. federal list, CITES, or the state of Michigan list.

Texas spiny lizards are currently considered to have stable populations, but they are being affected by habitat fragmentation, especially due to urbanization. Habitat fragmentation increases isolation between populations, which in turn increases the risk of inbreeding depression, genetic drift, and local extinctions. Population stability may also be threatened by high predation rates on hatchlings and juveniles.

Although there are no current conservation measures in place for Texas spiny lizards specifically, they may benefit indirectly from large-scale conservation practices. For example, the creation of wildlife corridors to connect fragmented habitats may improve gene flow between populations of Texas spiny lizards. (Fink, 2015; Hammerson and Frost, 2007; Terán-Juárez, et al., 2016)

Contributors

Kalina Theo (author), Radford University, Candice Amick (editor), Radford University, Katherine Gorman (editor), Radford University, Karen Powers (editor), Radford University, Galen Burrell (editor), Special Projects.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

agricultural

living in landscapes dominated by human agriculture.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

References

Ballinger, R., D. Clark Jr. 1973. Energy content of lizard eggs and the measurement of reproductive effort. Journal of Herpetology, 7/2: 129-134. Accessed April 17, 2023 at https://doi.org/10.2307/1563210.

Carman, E., G. Ferguson, W. Gehrmann, T. Chen, M. Holick. 2000. Photobiosynthetic opportunity and ability for UV-B generated vitamin D synthesis in free-living house geckos (Hemidactylus turcicus) and Texas spiny lizards (Sceloporus olivaceous). Copeia, 2000/1: 245-250.

Chong, B., T. Wang, E. Erickson, P. Bergmann, D. Goldman. 2022. Coordinating tiny limbs and long bodies: Geometric mechanics of lizard terrestrial swimming. Proceedings of the National Academy of Sciences of the United States of America, 119/27: e2118456119. Accessed February 01, 2023 at https://doi.org/10.1073/pnas.2118456119.

Cole, C. 1969. Karyotypes and Evolution of the Spinosus Group of Lizards in the Genus Sceloporus (Ph.D. Dissertation). Tucson, Arizona: The University of Arizona.

Dutton, R., L. Fitzpatrick, J. Hughes. 1975. Energetics of the rusty lizard Sceloporus olivaceus. Ecology, 56/6: 1378-1387.

Fink, A. 2015. Are Corridors Effective? A Genetic Study of Texas Spiny Lizard Populations in Urban Parks of San Antonio (Master's Thesis). San Antonio, Texas: Trinity University.

Gehlbach, F. 2010. Suburbanization of a central Texas herpetofauna. Reptiles and Amphibians, 17/2: 87-93.

Hammerson, G., D. Frost. 2007. "Sceloporus olivaceus" (On-line). The IUCN Red List of Threatened Species 2007: e.T64133A12748044. Accessed June 05, 2023 at https://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T64133A12748044.en.

Imperial Reptiles & Exotics, 2023. "Texas Spiny Lizard Adult" (On-line). Accessed March 23, 2023 at https://imperialreptiles.com/products/texas-spiny-lizard-for-sale.

Jaksic, F., H. Greene. 1984. Empirical evidence of non-correlation between tail loss frequency and predation intensity on lizards. Oikos, 42/3: 407-411.

Kennedy, J. 1973. Sceloporus olivaceus. Catalogue of American Amphibians and Reptiles, 413: 1-4.

Kerster, H. 1964. Neighborhood size in the rusty lizard, Sceloporus olivaceus. Evolution, 18/3: 445-457.

Méndez-de la Cruz, F., M. Villagrán-Santa Cruz, R. Andrews. 1998. Evolution of viviparity in the lizard genus Sceloporus. Herpetologica, 54/4: 521-532.

Pianka, E., W. Parker. 1975. Age-specific reproductive tactics. The American Naturalist, 109/968: 453-464.

Robinson, C. 2014. Convergence in communication behavior and brain morphology in lizards: An evolutionary approach (Honors Thesis). Digital Commons Trinity University, 16: 1-41.

Robinson, C., M. Patton, B. Andre, M. Johnson. 2015. Convergent evolution of brain morphology and communication modalities in lizards. Current Zoology, 61/2: 281-291.

Smith, H. 1934. Descriptions of new lizards of the genus Sceloporus from Mexico and Southern United States. Transactions of the Kansas Academy of Science, 37: 287-297.

Tacutu, R., D. Thorton, E. Johnson, A. Budovsky, D. Barardo, T. Craig, E. Diana, G. Lehmann, D. Toren, J. Wang, V. Fraifeld, J. Magalhaes. 2018. "Human Ageing Genomic Resources: New and updated databases" (On-line). AnAge. Accessed April 28, 2023 at https://genomics.senescence.info/species/query.php?search=sceloporus.

Terán-Juárez, S., V. Mata-Silva, E. García-Padilla, J. Johnson, L. Wilson. 2016. The herpetofauna of Tamaulipas, Mexico: Composition, distribution, and conservation status. Mesoamerican Herpetology, 3/1: 43-111.

Underwood, H. 1985. Extraretinal photoreception in the lizard Sceloporus occidentalis: Phase response curve. American Journal of Physiology: Regulatory, Integrative, and Comparative Physiology, 248/4: 407-414.

Wiens, J., T. Reeder. 1997. Phylogeny of the spiny lizards (Sceloporus) based on molecular and morphological evidence. Herpetological Monographs, 11: 1-101.

Williams, D., N. Rains, A. Hale. 2019. Population genetic structure of Texas horned lizards: Implications for reintroduction and captive breeding. PeerJ, 7: e7746. Accessed January 26, 2023 at https://doi.org/10.7717/peerj.7746.

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