Horned lizard

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Template:Short description Script error: No such module "about". Template:Automatic taxobox Phrynosoma, whose members are known as the horned lizards, horny toads, or horntoads, is a genus of North American lizards and the type genus of the family Phrynosomatidae. Their common names refer directly to their horns or to their flattened, rounded bodies (squat bodied), and blunt snouts.

The generic name Phrynosoma means "toad-bodied". In common with true toads (amphibians of the family Bufonidae), horned lizards tend to move sluggishly, often remain motionless, and rely on their remarkable camouflage to avoid detection by predators. They are adapted to arid or semiarid areas. The spines on the lizard's back and sides are modified reptile scales, which prevent water loss through the skin, whereas the horns on the head are true horns (i.e., they have a bony core). A urinary bladder is absent.[1] Of the 21 species of horned lizards, 15 are native to the US. The largest-bodied and most widely distributed of the American species is the Texas horned lizard.

Biology

Rain-harvesting

Like the unrelated thorny devil (Moloch horridus) which also lives in arid environments, some species of horned lizards exhibit a behaviour known as "rain-harvesting". As rain falls on the scales of a lizard's back, water is passively transported through channels to its mouth by capillary action.[2] The extent of this ability varies between species of horned lizards.[3]

Defenses

Template:Easy CSS image crop Horned lizards use a variety of means to avoid predation. Their coloration generally serves as camouflage. When threatened, their first defense is to remain motionless to avoid detection. If approached too closely, they generally run in short bursts and stop abruptly to confuse the predator's visual acuity. If this fails, they puff up their bodies to cause them to appear more horned and larger so that they are more difficult to swallow.[4]

To avoid being picked up by the head or neck, a horned lizard ducks or elevates its head and orients its cranial horns straight up, or back. If a predator tries to take it by the body, the lizard drives that side of its body down into the ground so the predator cannot easily get its lower jaw underneath.Script error: No such module "Unsubst".

Blood-squirting

At least eight species (P. asio, P. cornutum, P. coronatum, P. ditmarsi, P. hernandesi, P. orbiculare, P. solare, and P. taurus) are also able to squirt an aimed stream of blood from the corners of the eyes for a distance up to Script error: No such module "convert"..[5][6][7][8] They do this by restricting the blood flow leaving the head, thereby increasing blood pressure and rupturing tiny vessels around the eyelids. The blood not only confuses predators but also tastes foul to canine and feline predators. It appears to have no effect against predatory birds. Only three closely related species (P. mcallii, P. modestum, and P. platyrhinos) are certainly known to either be unable to squirt blood or only do it extremely rarely.[6]

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While previous thought held that compounds were added to the blood from glands in the ocular sinus cavity, current research has shown that the chemical compounds that make up the defense are already in the circulating blood.[6][7] It is possible that their diet of large quantities of venomous harvester ants could be a factor; however, the origin and structure of the chemicals responsible are still unknown. The blood-squirting mechanism increases survival after contact with canine predators;[7] the trait may provide an evolutionary advantage. Ocular autohemorrhaging has also been documented in other lizards,[9] which suggests blood-squirting could have evolved from a less extreme defense in the ancestral branch of the genus. Recent phylogenic research supports this claim, so the species incapable of squirting blood apparently have lost the adaptation for reasons yet unstudied.[10]

Population decline

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A University of Texas publication notes that horned lizard populations continue to disappear throughout their distribution despite protective legislation. Population declines are attributed to a number of factors, including the fragmentation and loss of habitat from real estate development and road construction, the planting of non-native grasses (both suburban and rural), conversion of native land to pastureland and agricultural uses, and pesticides. Additionally predation by domestic dogs and cats place continued pressure upon horned lizards.[11]

Fire ants (Solenopsis invicta), introduced from South America via the nursery industry's potted plants, pose a significant threat to all wildlife including horned lizards. Phrynosoma species do not eat fire ants. Fire ants kill many species of wildlife, and are fierce competitors against the native ants, which horned lizards require for food (with their specialized nutritional content). Fire ants have given all ants a bad reputation, and human attempts to eradicate ants, including invasive species and the native species on which the lizards prey, contribute to the continued displacement of native ant species and the decline of horned lizards.[11]

File:Horned lizards.jpg
Comparison of P. modestum and P. platyrhinos

The Texas horned lizard (Phrynosoma cornutum) has disappeared from almost half of its geographic range. Their popularity in the early to mid-20th-century pet trade, where collectors took thousands from the wild populations to sell to pet distributors, without provision for their highly specialized nutritional needs (primarily formic acid from harvester ants), resulted in certain death for almost all the collected lizards. In 1967, the state of Texas passed protective legislation preventing the collection, exportation, and sale of Phrynosoma, and by the early 1970s, most states enacted similar laws to protect and conserve horned lizards in the US. As recently as the early 2000s, though, the state of Nevada still allowed commercial sale of Phrynosoma species. Despite limited federal protection in Mexico, horned lizards are still offered in Mexican "pet" markets throughout the country.[11]

In 2014, the Center for Biological Diversity in Tucson petitioned the Oklahoma Department of Wildlife Conservation to have the Texas horned lizard put on the endangered species list due to the massive decline of its population in Oklahoma, where it was once plentiful. The center said it may later seek protection for the animal on a federal level; it also said that reptiles in general are dying off at up to 10,000 times their historic extinction rate, greatly due to human influences.[12]

Species and subspecies

The following 21 species (listed alphabetically by scientific name) are recognized as being valid by the Reptile Database, three species of which have recognized subspecies:[13]

Image Common name Scientific name Distribution
File:Phrynosoma asio 61552500.jpg Giant horned lizard Phrynosoma asio
Cope, 1864Script error: No such module "Check for unknown parameters".		 southern Mexico
Baur's short-horned lizard Phrynosoma bauri
Montanucci, 2015Script error: No such module "Check for unknown parameters".
(disputed, may be conspecific with P. hernandesi)		 United States (southern Wyoming and Nebraska south through eastern Colorado to northern New Mexico)
File:Blainville's Horned Lizard, California, US imported from iNaturalist photo 287121136 (cropped).jpg San Diego horned lizard,

Blainville's horned lizard

Phrynosoma blainvillii
Gray, 1839Script error: No such module "Check for unknown parameters".		 United States (southern and central California), Mexico (northern Baja California)
File:Phrynosoma braconnieri 6765654 (cropped).jpg Short-tailed horned lizard Phrynosoma braconnieri
A.H.A. Duméril, 1870Script error: No such module "Check for unknown parameters".		 Mexico (Puebla and Oaxaca)
File:Phrynosoma hernandesi - Flickr - aspidoscelis (11).jpg Great Plains short-horned lizard Phrynosoma brevirostris
(Girard, 1858)Script error: No such module "Check for unknown parameters".
(disputed, may be conspecific with P. hernandesi)		 Canada and the United States
File:Cedros Island Horned Lizard, 22952, Ensenada, BC , MX imported from iNaturalist photo 39734057 (cropped).jpg Cedros Island horned lizard Phrynosoma cerroense
Stejneger, 1893Script error: No such module "Check for unknown parameters".		 Mexico (Cedros Island)
File:Texas Horned Lizard, Texas, US imported from iNaturalist photo 1845460 (cropped).jpg Texas horned lizard Phrynosoma cornutum
(Harlan, 1825)Script error: No such module "Check for unknown parameters".		 United States (southeast Colorado, central and southern areas of Kansas, central and western areas of Oklahoma and Texas, southeast New Mexico, and extreme southeast Arizona), Mexico (eastern Sonora, most of Chihuahua, northeast Durango, northern Zacatecas and San Luis Potosí, and throughout most of Coahuila, Nuevo León, and Tamaulipas)
File:09-036 Horned Lizard (Phyrnosoma coronatum) (3481417849).jpg Coast horned lizard Phrynosoma coronatum
(Blainville, 1835)Script error: No such module "Check for unknown parameters".
  • Cape horned lizard, P. c. coronatum
    (Blainville, 1835)Script error: No such module "Check for unknown parameters".
  • California horned lizard, P. c. frontale
    Van Denburgh, 1894Script error: No such module "Check for unknown parameters".
  • Central peninsular horned lizard, P. c. jamesi
    Schmidt, 1922Script error: No such module "Check for unknown parameters".
 Mexico (Baja California Sur)
San Luis Valley short-horned lizard Phrynosoma diminutum
Montanucci, 2015Script error: No such module "Check for unknown parameters".
(disputed, may be conspecific with P. hernandesi)		 United States (Colorado)
File:Phrynosoma ditmarsi, cananea sonora imported from iNaturalist photo 590575456 (cropped).jpg Ditmars' horned lizard,

rock horned lizard

Phrynosoma ditmarsi
Stejneger, 1906Script error: No such module "Check for unknown parameters".		 Mexico (Sonora), United States (Arizona)
File:Phrynosoma douglasii 41603876 (rotate) (cropped).jpg Pygmy short-horned lizard Phrynosoma douglasii
(Bell, 1828)Script error: No such module "Check for unknown parameters".		 northwestern United States and adjacent southwestern Canada
Sonoran horned lizard,

Goode's desert horned lizard

Phrynosoma goodei
Stejneger, 1893Script error: No such module "Check for unknown parameters".		 United States (Arizona) and Mexico (Sonora)
File:Greater Short-horned Lizard imported from iNaturalist photo 133449794 on 10 December 2025 (rotated).jpg Greater short-horned lizard Phrynosoma hernandesi
Girard, 1858Script error: No such module "Check for unknown parameters".		 southwestern United States and northwestern Mexico
File:Phrynosoma mcallii 1536974 (cropped).jpg Flat-tail horned lizard Phrynosoma mcallii
(Hallowell, 1852)Script error: No such module "Check for unknown parameters".		 United States and Mexico
File:Roundtail Horned Lizard, Eddy County, US-NM, US imported from iNaturalist photo 448984177 (cropped).jpg Roundtail horned lizard Phrynosoma modestum
Girard, 1852Script error: No such module "Check for unknown parameters".		 United States (Texas, New Mexico eastern Arizona, southeastern Colorado), northcentral Mexico
File:Phrynosoma orbiculare 306114722 (cropped).jpg Mexican Plateau horned lizard,

Chihuahua Desert horned lizard

Phrynosoma orbiculare
(Linnaeus, 1758)Script error: No such module "Check for unknown parameters".
  • P. o. bradti
    Horowitz, 1955Script error: No such module "Check for unknown parameters".
  • P. o. cortezii
    (A.H.A. Duméril & Bocourt, 1870)Script error: No such module "Check for unknown parameters".
  • P. o. dugesii
    (A.H.A. Duméril & Bocourt, 1870)Script error: No such module "Check for unknown parameters".
  • P. o. orbiculare
    (Linnaeus, 1758)Script error: No such module "Check for unknown parameters".
  • P. o. orientale
    Horowitz, 1955Script error: No such module "Check for unknown parameters".
 Mexico (Chihuahua, Durango, Morelos, Nuevo León, Puebla, and Veracruz)
File:Desert Short-horned Lizard, Valencia County, NM, USA imported from iNaturalist photo 99242699 (cropped).jpg Desert short-horned lizard Phrynosoma ornatissimum
(Girard, 1858)Script error: No such module "Check for unknown parameters".
(disputed, may be conspecific with P. hernandesi)		 Canada and the United States
File:Desert Horned Lizard, California City, CA, USA imported from iNaturalist photo 369890015 (rotated).jpg Desert horned lizard Phrynosoma platyrhinos
Girard, 1852Script error: No such module "Check for unknown parameters".
  • Southern desert horned lizard, P. p. calidiarum
    (Cope, 1896)Script error: No such module "Check for unknown parameters".
  • Northern desert horned lizard, P. p. platyrhinos
    Girard, 1852Script error: No such module "Check for unknown parameters".
 southern Idaho in the north to northern Mexico
Guerreran horned lizard Phrynosoma sherbrookei
Nieto-Montes de Oca, Arenas-Moreno, Beltrán-Sánchez & Leaché, 2014Script error: No such module "Check for unknown parameters".		 Mexico
File:Phrynosoma solare 399512817 (rotated).jpg Regal horned lizard Phrynosoma solare
Gray, 1845Script error: No such module "Check for unknown parameters".		 Arizona and Mexico
File:Phrynosoma taurus 234908236 (cropped).jpg Mexican horned lizard Phrynosoma taurus
Dugès, 1873Script error: No such module "Check for unknown parameters".		 Mexico (Guerrero and Puebla)


Note: In the above list, a binomial authority or trinomial authority in parentheses indicates that the species or subspecies was originally described in a genus other than Phrynosoma.

Gallery

Symbol

Texas designated the Texas horned lizard (Phrynosoma cornutum) as the official state reptile in 1993.[14] Wyoming’s state reptile is the “Horn Toad”, the greater short-horned lizard (Phrynosoma hernandesi).[15][16]

The "TCU Horned Frog" is the mascot of Texas Christian University in Fort Worth, Texas. The "Horned Toad" is also the mascot for Coalinga High School in Coalinga, California. This school is located in Western Central California and its arid region is home to the San Diego Horned Lizard, which is protected. The City of Coalinga hosts an annual "Horned Toad Derby" on Memorial day weekend which features horned toad races, a carnival and parade.

References

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  1. ↑ Mader's Reptile and Amphibian Medicine and Surgery
  2. ↑ Script error: No such module "citation/CS1".
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  8. ↑ Script error: No such module "Citation/CS1".
  9. ↑ Script error: No such module "Citation/CS1".
  10. ↑ Script error: No such module "Citation/CS1".
  11. ↑ a b c Script error: No such module "citation/CS1".
  12. ↑ Script error: No such module "citation/CS1".
  13. ↑ Genus Phrynosoma at The Reptile Database www.reptile-database.org.
  14. ↑ Texas Horned Lizard Template:Webarchive. State Symbols USA. Retrieved on 2016-10-25.
  15. ↑ Script error: No such module "citation/CS1".
  16. ↑ Mason Lee. 2022. Wyoming’s surprising state reptile has spikes, shoots blood from eyes—. Barnyards & Backyards. 6-7 pp. University of Wyoming.

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External links

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