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Overview

Distribution

National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Global Range: (200,000 to >2,500,000 square km (about 80,000 to >1,000,000 square miles)) The range extends from extreme southwestern Missouri and central Kansas to southeastern Colorado, and south and west throughout most of Oklahoma and Texas (including coastal barrier islands), eastern and southern New Mexico, and southeastern Arizona to northeastern Sonora, Chihuahua and Durango east of Sierra Madre Occidental, Coahuila, Nuevo Leon, Tamaulipas, San Luis Potosi, and Zacatecas (Price 1990). Native eastern limit is uncertain; records for Missouri and Arkansas have been questioned (now extirpated from Arkansas; Trauth et al. 2004), and possibly the species is not native to Louisiana (Price 1990). This species has been introduced and is established in several areas in the southeastern United States, including North Carolina (Herpetol. Rev. 20:12), Florida (Jensen, 1994, Herpetol. Rev. 25:165), and elsewhere (see Price 1990 for references).

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Range Description

The range extends from extreme southwestern Missouri and central Kansas to southeastern Colorado, and south and west throughout most of Oklahoma and Texas (including coastal barrier islands), eastern and southern New Mexico, and southeastern Arizona to northeastern Sonora, Chihuahua and Durango east of Sierra Madre Occidental, Coahuila, Nuevo Leon, Tamaulipas, San Luis Potosi, and Zacatecas (Price 1990). Native eastern limit is uncertain; records for Missouri and Arkansas have been questioned (now extirpated from Arkansas; Trauth et al. 2004), and possibly the species is not native to Louisiana (Price 1990). This species has been introduced and is established in several areas in the southeastern United States, including North Carolina), Florida (Jensen 1994), and elsewhere (see Price 1990 for references).
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Geographic Range

The distribution of the Texas Horned Lizard ranges from Kansas to Northern Mexico and from Arizona to Louisiana (Bockstanz 1998).

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Continent: Middle-America North-America
Distribution: USA (SE Colorado, Kansas, New Mexico, SE Arizona, Texas, NW Louisiana, Oklahoma, introduced to Florida), Mexico (Chihuahua, Coahuila, Durango, Nuevo Leon, , San Luis Potosí, Sonora, Tamaulipas), Canada (British Columbia [fide BOULENGER 1887])  
Type locality: Great Plains east of the Rocky Mountains. Restricted to Fort Riley, Geary County, Kansas.
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Physical Description

Morphology

Physical Description

The Texas Horned Lizard has a dorsolaterally flattened, toad-like body (Seymour and Royo 1996). Due to their unusual body shape body and short legs, they have been mistaken for an amphibian, hence the name "Texas Horned Toad."

 There are spines located on the head, along the sides of the body and down the tail (Bockstanz 1998). These spines are modified epidermal scales. At the back of the head, there are two elongated spines that look like horns (Seymour and Royo 1996). There are also spines located along the dorsal surface of the lizard (Bockstanz 1998).

The ventral surface of the lizard is either gray or tan (Seymour and Royo 1996). The dorsal surface of the lizard is tan or gray with white and red or yellow highlights (Bockstanz 1998). There is a pattern of dark spots on the dorsal surface of the lizard, which correspond to the location of the dorsal spines (Bockstanz 1998).

The length of an average Texas Horned Lizard is 69mm snout-vent length (Munger 1986), however the upper boundary for males is 94mm and for females it is 114mm (Munger 1984).

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Size

Length: 18 cm

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Diagnostic Description

Differs from P. SOLARE in lacking four large horns with bases that touch at the back of the head. Differs from P. CORONATUM in having one (vs. 2-3) rows of enlarged scales on each side of the throat. Differs from P. PLATYRHINOS in having a double row rather than a single row of pointed fringe scales on each side of the body. Other horned lizards have either much smaller horns or a dark middorsal stripe rather than a pale one. See Stebbins (1985).

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Type Information

Syntype for Phrynosoma cornutum
Catalog Number: USNM 143
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Locality: Western Texas, Locality In Multiple Counties, Texas, United States, North America
  • Syntype: Hallowell, E. 1852. Proc. Acad. Nat. Sci. Philadelphia. 6 (5): 178.
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Ecology

Habitat

Chihuahuan Desert Habitat

This taxon is found in the Chihuahuan Desert, which is one of the most biologically diverse arid regions on Earth. This ecoregion extends from within the United States south into Mexico. This desert is sheltered from the influence of other arid regions such as the Sonoran Desert by the large mountain ranges of the Sierra Madres. This isolation has allowed the evolution of many endemic species; most notable is the high number of endemic plants; in fact, there are a total of 653 vertebrate taxa recorded in the Chihuahuan Desert.  Moreover, this ecoregion also sustains some of the last extant populations of Mexican Prairie Dog, wild American Bison and Pronghorn Antelope.

The dominant plant species throughout the Chihuahuan Desert is Creosote Bush (Larrea tridentata). Depending on diverse factors such as type of soil, altitude, and degree of slope, L. tridentata can occur in association with other species. More generally, an association between L. tridentata, American Tarbush (Flourensia cernua) and Viscid Acacia (Acacia neovernicosa) dominates the northernmost portion of the Chihuahuan Desert. The meridional portion is abundant in Yucca and Opuntia, and the southernmost portion is inhabited by Mexican Fire-barrel Cactus (Ferocactus pilosus) and Mojave Mound Cactus (Echinocereus polyacanthus). Herbaceous elements such as Gypsum Grama (Chondrosum ramosa), Blue Grama (Bouteloua gracilis) and Hairy Grama (Chondrosum hirsuta), among others, become dominant near the Sierra Madre Occidental. In western Coahuila State, Lecheguilla Agave (Agave lechuguilla), Honey Mesquite (Prosopis glandulosa), Purple Prickly-pear (Opuntia macrocentra) and Rainbow Cactus (Echinocereus pectinatus) are the dominant vascular plants.

Because of its recent origin, few warm-blooded vertebrates are restricted to the Chihuahuan Desert scrub. However, the Chihuahuan Desert supports a large number of wide-ranging mammals, such as the Pronghorn Antelope (Antilocapra americana), Robust Cottontail (Sylvilagus robustus EN); Mule Deer (Odocoileus hemionus), Grey Fox (Unocyon cineroargentinus), Jaguar (Panthera onca), Collared Peccary or Javelina (Pecari tajacu), Desert Cottontail (Sylvilagus auduboni), Black-tailed Jackrabbit (Lepus californicus), Kangaroo Rats (Dipodomys sp.), pocket mice (Perognathus spp.), Woodrats (Neotoma spp.) and Deer Mice (Peromyscus spp). With only 24 individuals recorded in the state of Chihuahua Antilocapra americana is one of the most highly endangered taxa that inhabits this desert. The ecoregion also contains a small wild population of the highly endangered American Bison (Bison bison) and scattered populations of the highly endangered Mexican Prairie Dog (Cynomys mexicanus), as well as the Black-tailed Prairie Dog (Cynomys ludovicianus).

The Chihuahuan Desert herpetofauna typifies this ecoregion.Several lizard species are centered in the Chihuahuan Desert, and include the Texas Horned Lizard (Phrynosoma cornutum); Texas Banded Gecko (Coleonyx brevis), often found under rocks in limestone foothills; Reticulate Gecko (C. reticulatus); Greater Earless Lizard (Cophosaurus texanus); several species of spiny lizards (Scelopoprus spp.); and the Western Marbled Whiptail (Cnemidophorus tigris marmoratus). Two other whiptails, the New Mexico Whiptail (C. neomexicanus) and the Common Checkered Whiptail (C. tesselatus) occur as all-female parthenogenic clone populations in select disturbed habitats.

Representative snakes include the Trans-Pecos Rat Snake (Bogertophis subocularis), Texas Blackhead Snake (Tantilla atriceps), and Sr (Masticophis taeniatus) and Neotropical Whipsnake (M. flagellum lineatus). Endemic turtles include the Bolsón Tortoise (Gopherus flavomarginatus), Coahuilan Box Turtle (Terrapene coahuila) and several species of softshell turtles. Some reptiles and amphibians restricted to the Madrean sky island habitats include the Ridgenose Rattlesnake (Crotalus willardi), Twin-spotted Rattlesnake (C. pricei), Northern Cat-eyed Snake (Leptodeira septentrionalis), Yarrow’s Spiny Lizard (Sceloporus jarrovii), and Canyon Spotted Whiptail (Cnemidophorus burti).

There are thirty anuran species occurring in the Chihuahuan Desert: Chiricahua Leopard Frog (Rana chircahuaensis); Red Spotted Toad (Anaxyrus punctatus); American Bullfrog (Lithobates catesbeianus); Canyon Treefrog (Hyla arenicolor); Northern Cricket Frog (Acris crepitans); Rio Grande Chirping Frog (Eleutherodactylus cystignathoides); Cliff Chirping Frog (Eleutherodactylus marnockii); Spotted Chirping Frog (Eleutherodactylus guttilatus); Tarahumara Barking Frog (Craugastor tarahumaraensis); Mexican Treefrog (Smilisca baudinii); Madrean Treefrog (Hyla eximia); Montezuma Leopard Frog (Lithobates montezumae); Brown's Leopard Frog (Lithobates brownorum); Yavapai Leopard Frog (Lithobates yavapaiensis); Western Barking Frog (Craugastor augusti); Mexican Cascade Frog (Lithobates pustulosus); Lowland Burrowing Frog (Smilisca fodiens); New Mexico Spadefoot (Spea multiplicata); Plains Spadefoot (Spea bombifrons); Pine Toad (Incilius occidentalis); Woodhouse's Toad (Anaxyrus woodhousii); Couch's Spadefoot Toad (Scaphiopus couchii); Plateau Toad (Anaxyrus compactilis); Texas Toad (Anaxyrus speciosus); Dwarf Toad (Incilius canaliferus); Great Plains Narrowmouth Toad (Gastrophryne olivacea); Great Plains Toad (Anaxyrus cognatus); Eastern Green Toad (Anaxyrus debilis); Gulf Coast Toad (Incilius valliceps); and Longfoot Chirping Toad (Eleutherodactylus longipes VU). The sole salamander occurring in the Chihuahuan Desert is the Tiger Salamander (Ambystoma tigrinum).

Common bird species include the Greater Roadrunner (Geococcyx californianus), Burrowing Owl (Athene cunicularia), Merlin (Falco columbarius), Red-tailed Hawk (Buteo jamaicensis), and the rare Zone-tailed Hawk (Buteo albonotatus). Geococcyx californianus), Curve-billed Thrasher (Toxostoma curvirostra), Scaled Quail (Callipepla squamata), Scott’s Oriole (Icterus parisorum), Black-throated Sparrow (Amphispiza bilineata), Phainopepla (Phainopepla nitens), Worthen’s Sparrow (Spizella wortheni), and Cactus Wren (Campylorhynchus brunneicapillus). In addition, numerous raptors inhabit the Chihuahuan Desert and include the Great Horned Owl (Bubo virginianus) and the Elf Owl (Micrathene whitneyi).

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Comments: This lizard inhabits open arid and semiarid regions with sparse vegetation (deserts, prairies, playa edges, bajadas, dunes, foothills) with grass, cactus, or scattered brush or scrubby trees (Degenhardt et al. 1996, Bartlett and Bartlett 1999, Hammerson 1999, Stebbins 2003). Soil may vary in texture from sandy to rocky. When inactive, individuals burrow into the soil, enter rodent burrows, or hide under rocks. Sheffield and Carter (1994, Herpetol. Rev. 25:67-68) reported individuals that climbed 1-2 m up tree trunks when soils were wet after heavy rains. Eggs are laid in nests dug in soil or under rocks (Collins 1982).

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Habitat and Ecology

Habitat and Ecology
This lizard inhabits open arid and semi-arid regions with sparse vegetation (deserts, prairies, playa edges, bajadas, dunes, foothills) with grass, cactus, or scattered brush or scrubby trees (Degenhardt et al. 1996, Bartlett and Bartlett 1999, Hammerson 1999, Stebbins 2003). Soil may vary in texture from sandy to rocky. When inactive, individuals burrow into the soil, enter rodent burrows, or hide under rocks. Sheffield and Carter (1994) reported individuals that climbed one to two m up tree trunks when soils were wet after heavy rains. Eggs are laid in nests dug in soil or under rocks (Collins 1982).

Systems
  • Terrestrial
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The Texas Horned Lizard lives mainly in sandy areas where it often inhabits abandoned animal burrows (Bockstanz 1998). The habitat of the Texas Horned Lizard is usually in close proximity to the nests of harvester ants (Seymour 1996).

Biomes: Desert, grasslands, prairies, scrubland (Bartlett and Bartlett 1999)

Terrestrial Biomes: desert or dune ; savanna or grassland

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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Home range size and movements seem quite variable. Munger (1984a) found that single-season home range size in southern Arizona averaged 1.3 ha in females and 2.4 ha in males. Home range length extended up to about 400 m but often was 100-300 m, and some individuals that were observed more than 30 times moved over an area less than 55 m across. Some individuals tended not to remain in a limited area. Overlap of home ranges occurred but was not extensive.

In southern New Mexico, home range size was about 1 ha or less (Worthington 1972). Whitford and Bryant (1979) recorded movements of 9-91 m per day (average 47 m) in New Mexico. Individuals followed a zig-zag course and rarely crossed their own path.

In Colorado, Montgomery and Mackessy (in Mackessy 1998) reported that a juvenile moved approximately 100 m in two days. Another juvenile was recaptured 480 m from its original capture location after 47 days.

In Texas, total area of use varied from 291 sq m (25 days) to 14,690 sq m (116 days); weekly home ranges appeared to be mobile (Fair and Henke 1999). Annual adult survival rate was between 9 and 54 percent.

In Oklahoma, average individual daily linear movements for all lizards was 45.0 m (range 10-220 m); males moved significantly farther than females in but not after May when their average daily movements were very similar; average individual daily activity area for all lizards was 232.8 square meters (range 1.7-3011.4 sq m); males covered drastically larger areas in a day during May than did females (Stark et al. 2005).

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Trophic Strategy

Comments: Eats mainly ants but also other small insects (Stebbins 1985).

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Food Habits

The Texas Horned Lizard eats mainly Harvester ants, Pogonomyrmex spp., but will also eat grasshoppers, isopods, beetles and beetle larvae. In order to obtain enough energy, adult Texas Horned Lizards must forage from several colonies of Harvester ants. The Texas Horned Lizards' daily activities are planned around the times of highest ant activity. (Donaldson, et al 1994)

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: This species is represented by hundreds of collection sites throughout the historical range in the United States and by well over 100 sites in Mexico (Prices 1990). Many historically occupied sites still support populations (e.g., Hammerson 1999).

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Global Abundance

10,000 to >1,000,000 individuals

Comments: Total adult population size is unknown but surely exceeds 10,000 and likely exceeds 100,000. This species can be locally abundant in undeveloped areas with appropriate habitat (Carpenter et al. 1993, Hammerson 1999).

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General Ecology

Desert populations cycle in abundance, possibly following similar cycles of their primary prey (POGONOMYRMEX harvester ants) (Price 1990).

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Life History and Behavior

Cyclicity

Comments: Active April to September in north (Collins 1982, Hammerson 1982). Sometimes found on warm roads at night (Hammerson 1982).

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Reproduction

Lays clutch of 14 to 60 eggs, May-July. Eggs hatch in about 6 weeks (Behler and King 1979).

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The breeding season begins in late April and continues into July (Seymour 1996). These lizards are oviparous, and will lay their eggs in moist, sandy areas (Bartlett 1999). The eggs have a flexible, white shell, which measures 1-and1/2 inches in diameter (Seymour 1996). The incubation period for the eggs is 45-55 days (Bartlett 1999). The hatchlings are approximately 1.25 inches long, and are relatively smooth. However, the hatchlings do have the spines around their heads. There is no evidence of parental care for the young, so they must find food and defend themselves against predators immediately after hatching. The age of reproductive maturity is not known, however they are full-grown adults at three years of age (Seymour 1996).

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Evolution and Systematics

Functional Adaptations

Functional adaptation

Stance and skin channels harvest rainwater: Texas horned lizard
 

The body of Texas horned lizards captures rainwater via splayed stance and interscalar channels on the skin.

   
  "During rainstorms, Texas horned lizards in enclosures were observed to exhibit a stereotyped behavior termed 'rain-harvesting.' The behavior involves: (1) raising the abdomen in an arch; (2) splaying and extending the legs; (3) dorso-ventral flattening and lateral spreading of the body; (4) lowering the head and tail; (5) opening and closing the jaws; and (6) drinking water collected on the dorsal body surface. Ingestion of integumentally-derived water was verified by recovery of dyed water from the gut. SEM stereophotographs illustrate the interscalar channels through which water is carried, apparently by capillary action, over body surfaces to the jaws. During light rainfall water flow to the jaws occurs within interscalar channels, but during heavy rainfall gravitational sheet flow may increase the amount of water arriving at the jaws. This integumental rain-harvesting system is similar to reported interscalar water transport in two agamid lizards, Moloch horridus and Phrynocephalus helioscopus. Apparently, Phrynosoma and P. helioscopus have similar behaviors for rain-harvesting. This is the first report to provide observations of a lizard obtaining water from natural precipitation for drinking by integumental interception and transport." (Sherbrooke 1990:302)
  Learn more about this functional adaptation.
  • Sherbrooke, W. C. 1990. Rain-Harvesting in the Lizard, Phrynosoma cornutum: Behavior and Integumental Morphology. Journal of Herpetology. 24(3): 302-308.
  • Sherbrooke, W. C. 2004. Integumental water movement and rate of water ingestion during rain harvesting in the Texas horned lizard, Phrynosoma cornutum. Amphibia-Reptilia. 25(1): 29-39.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Phrynosoma cornutum

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: N4 - Apparently Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Widespread and still relatively common in some areas of the south-central U.S. and northern Mexico; declines have been noted in portions of the range, but doing well in many areas; apparently moderately threatened by fire ants, insecticides, loss of habitat, and overcollecting.

Intrinsic Vulnerability: Moderately vulnerable

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2007

Assessor/s
Hammerson, G.A.

Reviewer/s
Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)

Contributor/s

Justification
Listed as Least Concern because the extent of occurrence, area of occupancy, number of subpopulations, and population size remain relatively large, despite declines in some (mostly marginal) portions of the range.
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Phrynosoma cornutum is listed as a threatened species in Texas and Okalahoma. The numbers of the Texas Horned Lizard have declined for several reasons: the collection of the lizard as a pet, the invasion of the imported fire ant, Solenopsis invicta, and loss of habitat (Donaldson, et al 1994). The change in land use has taken away homes from the lizards, and the use of pesticides on the harvester ants has depleted their main food source (Donaldson, et al 1994). Texas Parks and Wildlife along with other conservation groups are studying aspects of the Texas Horned Lizard as to protect it from any further negative human impact.

IUCN Red List of Threatened Species: least concern

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Global Short Term Trend: Relatively stable to decline of 30%

Comments: This species apparently has declined in area of occupancy and population size near the northeastern margins of the range in Texas, Oklahoma, and Kansas, but it is doing well in most the range. According to Price (1990), the Texas horned lizard has virtually disappeared from Texas east of a line from Fort Worth through Austin and San Antonio to Corpus Cristi (formerly widespread and abundant in that area); it has also declined in range and/or abundance in areas where it was formerly common in parts of north-central Texas, the Texas Panhandle, and parts of Oklahoma. Price's conclusions are supported by more recent surveys in Texas, Oklahoma, and Kansas. A 1992 Texas survey found the greatest declines in east Texas (where no individuals were found) and apparent declines also in central Texas; the species appeared to be doing well in northern and western Texas (Donaldson et al. 1994). Bartlett and Bartlett (1999) stated that the decline may have halted in at least some parts of Texas; they found numerous individuals in areas where searches in several previous years yielded few. A 1999 survey in Texas was unable to determine if the decline has halted or if it continues today (Henke 2003). A 1992 Oklahoma survey found the species to be rapidly disappearing in eastern areas of Oklahoma where it was once known to be abundant (Carpenter et al. 1993). A 1993 survey of the northern Flint Hills of Kansas suggested that populations were possibly declining (Busby and Parmalee 1996), and local collectors reported declines in the southeastern portions of Kansas (Bill Busby, pers. comm., 1998). In Colorado no trend information is available, but recent surveys indicate that the species appears to be locally common and stable (Siemers, pers. comm., 1998; Hammerson 1999). According to Rosen (Herp Diversity Review 1996), populations are thriving and plentiful in extreme southeastern Arizona. New Mexico densities have not changed historically, and populations are considered stable (Charles Painter, pers. comm., 1998). Status is unknown in Sonora, Mexico (Andres Villareal Lizarraga, pers. comm., 1998).

Global Long Term Trend: Relatively stable to decline of 50%

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Population

Population
This species is represented by hundreds of collection sites throughout the historical range in the United States and by well over 100 sites in Mexico (Price 1990). Many historically occupied sites still support populations (e.g., Hammerson 1999). Total adult population size is unknown but surely exceeds 10,000 and probably exceeds 100,000. This species can be locally abundant in undeveloped areas with appropriate habitat (Carpenter et al. 1993, Hammerson 1999). This species apparently has declined in area of occupancy and population size near the northeastern margins of the range in Texas, Oklahoma, and Kansas, but it is doing well in most the range. According to Price (1990), the Texas Horned Lizard has virtually disappeared from Texas east of a line from Fort Worth through Austin and San Antonio to Corpus Cristi (formerly widespread and abundant in that area); it has also declined in range and/or abundance in areas where it was formerly common in parts of north-central Texas, the Texas Panhandle, and parts of Oklahoma. Price's conclusions are supported by more recent surveys in Texas, Oklahoma, and Kansas. A 1992 Texas survey found the greatest declines in east Texas (where no individuals were found) and apparent declines also in central Texas; the species appeared to be doing well in northern and western Texas (Donaldson et al. 1994). Bartlett and Bartlett (1999) stated that the decline may have halted in at least some parts of Texas; they found numerous individuals in areas where searches in several previous years yielded few. A 1999 survey in Texas was unable to determine if the decline has halted or if it continues today (Henke 2003). A 1992 Oklahoma survey found the species to be rapidly disappearing in eastern areas of Oklahoma where it was once known to be abundant (Carpenter et al. 1993). A 1993 survey of the northern Flint Hills of Kansas suggested that populations were possibly declining (Busby and Parmalee 1996), and local collectors reported declines in the southeastern portions of Kansas (Bill Busby pers. comm. 1998). In Colorado no trend information is available, but recent surveys indicate that the species appears to be locally common and stable (Siemers pers. comm. 1998, Hammerson 1999). According to Rosen (Herp Diversity Review 1996), populations are thriving and plentiful in extreme southeastern Arizona. New Mexico densities have not changed historically, and populations are considered stable (C. Painter pers. comm. 1998). Status is unknown in Sonora, Mexico (A. Villareal Lizarraga pers. comm. 1998). It is considered to be a very common species in Mexico.

Population Trend
Stable
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Threats

Degree of Threat: Medium

Comments: Declines may be related to the spread of fire ants, use of insecticides to control fire ants, heavy agricultural use of land and/or other habitat alterations, and overcollecting for the pet and curio trade (Price 1990, Carpenter et al. 1993, Donaldson et al. 1994).

This species is extremely vulnerable to changes in habitat, especially the loss of harvester ants (Carpenter et al. 1993). Harvester ants comprise up to 69% of the diet (Pianka and Parker 1975), and fire ants are thought to out-compete native harvester ants for food and space (Henke and Fair 1998). This threat may be significant in parts of Texas but probably not elsewhere. Intensive agriculture (plowing) could destroy adults and their eggs (Carpenter et al. 1993, Donaldson et al. 1994) but, according to Henke and Fair (1998), reports of declines due to loss of habitat caused by urbanization, suburban sprawl, and conversion of native rangeland to agricultural crops are mostly unsubstantiated (Henke and Fair 1998).

The widespread use of broadcast insecticides is also thought to contribute to declines. Insecticides can be detrimental by directly causing illness or death or indirectly by severely reducing or eliminating harvester ants (Henke and Fair 1998).

In the past, this lizard was collected for the pet trade, by boy scout troops for trading at jamborees, for the curio trade, and by tourists (Donaldson et al. 1994, Henke and Fair 1998).

Mortality from road traffic is an important local threat in some areas. Males are particularly vulnerable during May-June in Arizona-New Mexico (Sherbrooke 2002). A high level of road mortality may lead to significant local declines.

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Major Threats
Within the US, declines may be related to the spread of fire ants, use of insecticides to control fire ants, heavy agricultural use of land and/or other habitat alterations, and overcollecting for the pet and curio trade (Price 1990, Carpenter et al. 1993, Donaldson et al. 1994). This species is extremely vulnerable to changes in habitat, especially the loss of harvester ants (Carpenter et al. 1993). Harvester ants comprise up to 69% of the diet (Pianka and Parker 1975), and fire ants are thought to out-compete native harvester ants for food and space (Henke and Fair 1998). This threat may be significant in parts of Texas but probably not elsewhere. Intensive agriculture (plowing) could destroy adults and their eggs (Carpenter et al. 1993, Donaldson et al. 1994) but, according to Henke and Fair (1998), reports of declines due to loss of habitat caused by urbanization, suburban sprawl, and conversion of native rangeland to agricultural crops are mostly unsubstantiated (Henke and Fair 1998). The widespread use of broadcast insecticides is also thought to contribute to declines. Insecticides can be detrimental by directly causing illness or death or indirectly by severely reducing or eliminating harvester ants (Henke and Fair 1998). In the past, this lizard was collected for the pet trade, by boy scout troops for trading at jamborees, for the curio trade, and by tourists (Donaldson et al. 1994, Henke and Fair 1998). Mortality from road traffic is an important local threat in some areas. Males are particularly vulnerable during May-June in Arizona-New Mexico (Sherbrooke 2002). A high level of road mortality may lead to significant local declines.

There appear to be no threats to this species in Mexico.
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Management

Management Requirements: Based on abundance of harvester ants, McIntyre (2003) found no evidence that Conservation Reserve Program plots planted in exotic grasses are significantly poorer habitat for P. cornutum than native grass plantings.

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Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: Extant populations exist in a fairly large number of areas with adequate protection.

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Conservation Actions

Conservation Actions
Extant populations exist in a fairly large number of areas with adequate protection.
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Wikipedia

Texas horned lizard

The Texas horned lizard (Phrynosoma cornutum) is one of about 14 North American species of spikey-bodied reptiles called horned lizards. P. cornutum ranges from Colorado and Kansas to northern Mexico (in the Sonoran desert), and from southeastern Arizona to Texas.[2] There are also isolated, introduced populations in the Carolinas, Georgia, and northern Florida.[3] Texas horned lizards may also be native to Louisiana[4] and Arkansas.[5]

Etymology[edit]

The horned lizard is popularly called a "horned toad", "horny toad", or "horned frog", but it is neither a toad nor a frog. The popular names come from the lizard's rounded body and blunt snout, which give it a decidedly batrachian appearance. Phrynosoma literally means "toad-bodied," and cornutum means "horned". The lizard's horns are extensions of its cranium and contain true bone.

Description[edit]

The Texas horned lizard is the largest-bodied and most widely distributed of the approximately 14 species of horned lizards in the western United States and Mexico. The length of an average Texas horned lizard is 69 mm (2.7 in) snout-vent length,[6] however the upper boundary for males is 94 mm (3.7 in) and for females it is 114 mm (4.5 in).[7]

Defensive behavior[edit]

Although its coloration generally serves as camouflage against predation, when threatened by a predator, a horned lizard will puff up and become very fat, which causes its body scales to protrude, making it difficult to swallow. The Texas horned lizard, along with at least three other species of the genus Phrynosoma, also has the ability to squirt an aimed stream of blood from the corners of the eyes and sometimes from its mouth for a distance of up to 5 ft (1.5 m). This not only confuses would-be predators, but also the blood is mixed with a chemical that is foul-tasting to canine predators such as wolves, coyotes, and domestic dogs. The blood can destroy habitats, and is very effective in defense.

Diet and decline[edit]

About 70% of the Texas horned lizard's diet is made up of harvester ants, though they supplement these with termites, beetles, and grasshoppers. In recent years, the Texas horned lizard has declined by about 30% of its range, though there is some indication it may be making a comeback. The decline is usually blamed on overuse of pesticides and the spread of nonnative, but highly aggressive and fiercely territorial, red imported fire ants. Both eradicate harvester ant colonies, destroying the horned lizard's principal source of food. The Texas horned lizard is now a protected species, and it is illegal to take, possess, transport or sell them without a special permit.

In Native American religion and art[edit]

Some Native American peoples regard horned lizards as sacred. The animal is a common motif in the art of many Native Americans in the Southwestern U.S. and in Mexico.

In popular culture[edit]

The Texas horned lizard is the state reptile of Texas[8] and, as the "horned frog", is the mascot of Texas Christian University.[9]

Current research[edit]

Horned lizards are primarily studied by researchers at TCU and the nearby Fort Worth Zoo, with raw data and fieldwork done by state employees. Further research toward the preservation of horned lizards is funded by sale of horned lizard "Keep Texas Wild" license plates.[10]

Temperament[edit]

Despite its fierce appearance, Texas horned lizards are extremely docile creatures. Since they have very few natural predators, they are not at all aggressive, and will never bite. Captured horned lizards will lie completely limp in a human's hand or pocket, playing dead, so they made excellent pets before they were threatened. Today, it is illegal to disturb or keep a horned lizard without a state permit.

The Texas horned lizard is a sunbather, and requires bright sunlight to produce vitamin D. Deprived of sunlight, the animal will be unable to produce vitamin D and will suffer from vitamin deficiency. For this reason horned lizards are most often found along the side of roads or other open, rocky areas, where they can lounge and take in sunlight.

At night, the lizard buries itself in sand.[11]

Otherwise, horned lizards are most often found near harvester ant hills. Although they prefer to move very little, horned lizards can move quite fast if they feel there is a predator in the area, and will dart into thick grass and foliage to escape. Horned lizards are also excellent diggers, and can quickly burrow underground to escape threats.

Genetic biodiversity[edit]

Research aimed at preservation has revealed the Texas horned lizard is extremely genetically diverse, and isolated pockets of genetically distinct subspecies have been found throughout Texas. Though each of these subspecies is physically identical to all other subspecies, it is likely that they are specifically adapted for the region in which they are found. This makes it difficult to know how one subspecies would survive if it were reintroduced into a new area.

Federal horned toad pic crop.jpg

The most numerous and widespread subspecies of Texas horned lizard is found in the Panhandle region of Texas. Other distinct subspecies have been identified in East Texas, the Hill Country, and along the coastline. It is not known whether these subspecies can reproduce with one another over the long term, making preservation of all of the subspecies even more crucial to the animals' preservation. It is also unknown whether any of these subspecies will show a particular resistance to the pesticides and fire ants threatening them.

References[edit]

Texas horned lizard in Beeville, Texas
Notes
  1. ^ Hammerson, G.A. (2007). "''Phrynosoma cornutum''". IUCN Red List of Threatened Species. Version 2009.1. International Union for Conservation of Nature. Retrieved 8 December 2009. 
  2. ^ "Phrynosoma cornutum". Phrynosoma.org. Retrieved 2009-06-27. 
  3. ^ "Texas Horned Lizard". Lizards of Georgia and South Carolina. University of Georgia. Retrieved 2009-06-27. 
  4. ^ "Amphibians and Reptiles of Louisiana". Brad Glorioso. Retrieved 2009-06-27. 
  5. ^ "Texas Horned Lizard (Phrynosoma cornutum)". Herps of Arkansas. Retrieved 2009-06-27. 
  6. ^ Munger, James C. (1986). "Rate of Death Due to Predation for two Species of Horned Lizard, Phrynosoma cornutum and Phrynosoma modestum''". Copeia (American Society of Ichthyologists and Herpetologists) 3 (3): 820–824. JSTOR 1444970. 
  7. ^ Munger, James C. (1984). "Home ranges of horned lizards (Phrynosoma): circumscribed and exclusive?". Oecologia 62 (3): 351–360. doi:10.1007/BF00384267 . JSTOR 4217328. 
  8. ^ "Texas State Symbols". Texas States Library and Archives Commission. Retrieved 2009-06-27. 
  9. ^ Gibson Roach, Joyce (March 2001). "Horned Frog defined". TCU Magazine (Texas Christian University). 
  10. ^ https://rts.texasonline.state.tx.us/NASApp/txdotrts/SpecialPlateOrderServlet?grpid=60&pltid=108
  11. ^ John F Breen, "Encyclopedia of Reptiles and Amphibians." T.F.H.
Sources
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Names and Taxonomy

Taxonomy

Comments: Reeder and Montanucci (2001) examined phylogenetic relationships of horned lizards (Phrynosoma) based on mtDNA and morphology.

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