CaliforniaHerps.com

A Guide to the Amphibians
and Reptiles of California


Colorado River Tree Lizard -
Urosaurus ornatus symmetricus

(Baird, 1859 “1858”)
Click on a picture for a larger view



Colorado River Tree Lizard Range Map Range in California: Red

Dot-locality Range Map




observation link





Colorado River Tree Lizard Colorado River Tree Lizard Colorado River Tree Lizard
These apparent Colorado Tree Lizards were found in Barstow, San Bernardino County, in what must be an introduced location. © Jeff & lynda Mintz Adult female, Colorado River,Yuma County, Arizona
Colorado River Tree Lizard Colorado River Tree Lizard Colorado River Tree Lizard
Adult female, Colorado River,Yuma County, Arizona Adult female, Colorado River,Yuma County, Arizona Adult female, Colorado River,Yuma County, Arizona
Colorado River Tree Lizard Colorado River Tree Lizard Colorado River Tree Lizard
Adult female, Colorado River, Yuma County, Arizona Adult, Colorado River, Imperial County
© William Flaxington
Adult, Colorado River, Imperial County
© William Flaxington
Colorado River Tree Lizard Colorado River Tree Lizard Colorado River Tree Lizard
Adult, with unshed tail, Yuma County, Arizona © Matt Dagrosa Adult, introduced into San Bernardino County. © William Flaxington Adult, introduced into San Bernardino County. © William Flaxington
Colorado River Tree Lizard Colorado River Tree Lizard Colorado River Tree Lizard
Adult, introduced into San Bernardino County. © Jonathan Hakkim Adult, introduced into San Bernardino County. © Jonathan Hakkim Adult, introduced into San Bernardino County. © Jonathan Hakkim
Colorado River Tree Lizard Colorado River Tree Lizard Colorado River Tree Lizard
Adult, El Centro, Imperial County © May 2013, Daniel Seung
Colorado River Tree Lizard Great Basin Collared Lizard  
Back scales of adult, introduced into San Bernardino County. © Jonathan Hakkim The Tree Lizard has a mixture of small
granular scales and larger weekly-keeled scales on the dorsal surface.
 
     
Habitat
Colorado River Tree Lizard Habitat Colorado River Tree Lizard Habitat Colorado River Tree Lizard Habitat
Habitat next to Colorado River,
Imperial County
Habitat along Colorado River,
Yuma County, Arizona
Habitat along Colorado River,
Yuma County, Arizona
Colorado River Tree Lizard Habitat Colorado River Tree Lizard Habitat Colorado River Tree Lizard Habitat
Colorado River, Imperial County Desert oasis habitat at Corn Springs, Riverside County Habitat near Colorado River,
Imperial County
  Colorado River Tree Lizard Habitat  
  Habitat next to Colorado River,
Yuma County, Arizona
 
     
Comparison with Similar Sympatric Species
There is one other similar species of lizard found in California that shares the range of the Colorado River Tree Lizard - the Western Long-tailed Brush Lizard. It has a longer tail, but since the tail is easily lost and re-grown that characteristic is not always reliable. The two species can be separated best by looking at the wide band of enlarged scales on the middle of the back that is found on each species.

Colorado River Tree Lizard Colorado River Tree Lizard Long-tailed Brush Lizard
Tree Lizard - Urosaurus ornatus

This tree lizard appears to be U. o. symmetricus. It was found in Barstow, outside of the known range of this subspecies, but the scales on the back show wide scales on the back that are split in the center by a larger band of smaller scales than is present on the tree lizard subspecies shown on the right.

Another example can be seen here: H.E.R.P. Database
Tree Lizard - Urosaurus ornatus

The band of wide scales on the back of a tree lizard is split in the center by a band of smaller scales.

The tree lizard shown above is U. o. schottii, which is different from the subspecies found in California - U. o. symmetricus, which has a wider band of small scales splitting the band of wide scales on the back.

Western Long-tailed Brush Lizard - Urosaurus graciosus

The band of wide scales on the back of the Western Long-tailed Brush Lizard is not split in the center by a band of smaller scales.
Baja California Brush Lizard Western Side-blotched Lizard Great Basin Collared Lizard
Small-Scaled Lizard - Urosaurus microscutatus

The Small-scaled Lizard has a band of slightly-enlarged scales on the middle of the back that are not split in the center by a band of smaller scales.

These enlarged scales are smaller than those of the Western Long-tailed Brush Lizard.
Western Side-blotched Lizard

The Western Side-blotched Lizard - Uta stansburiana elegans - has small scales on the back with no band of enlarged scales in the middle, and typically has a large dark blotch on the sides behind the front legs.
   
Similar Tree Lizard Subspecies from Outside California
The pictures below show Urosaurus ornatus schottii - Schott's Tree Lizard, the subspecies found east of the range of the Colorado River Tree Lizard. Unless you examine them with a magnifying glass, the appearance is the same. Some researchers do not recognize any subspecies of tree lizard or any important differences between any these subspecies.
Schott's Tree Lizard Schott's Tree Lizard Schott's Tree Lizard
Adult, Pima County, Arizona
Adult male, Santa Cruz County, Arizona
Schott's Tree Lizard Schott's Tree Lizard Schott's Tree Lizard
Adult, Coconino County, Arizona Adult, Maricopa County, Arizona Adult male, Pima County, Arizona
Schott's Tree Lizard Schott's Tree Lizard  
Adult female, Cochise County, Arizona  
   
Short Videos
(of other subspecies of Tree Lizards found outside California)
Tree Lizard Tree Lizard Tree Lizard
Tree Lizards beside a creek in
Coconino County, Arizona.
Tree Lizards in Coconino County, Arizona, doing territorial push-up displays. Two tree lizards running around on buildings. The first in Coconino County, Arizona, the second in Pima County, Arizona.
     
Description
 
Size
1.5 - 2.25 inches long from snout to vent (3.8 - 5.7 cm). (Stebbins 2003)

Appearance
A small slim climbing lizard with a long thin tail, usually seen on rocks and trees.
There is a gular fold across the throat and a fold of skin on each side of the body.

The scales on the back are small and granular, with two bands of enlarged scales down the middle of the back with a band of smaller scales between them.

(On this subspecies U. o symmetricus, the band of narrow scales on the mid back is wider than the width of one of the bands of enlarged scales, and the belly patches are separated.)
Color and Pattern
Color is brown, tan, gray, rusty, or nearly black with dark blotches or irregular narrow crossbars on the upper surfaces.
The coloring usually matches the surrounding environment, and changes from a dark to a light phase.
Male / Female Differences
Males have a blue, green, orange, or yellow throat patch, blue or green patches on the sides of the belly which do not usually connect, and enlarged postanal pores.

Females have a white belly and a white, orange or yellow throat.

Life History and Behavior

Activity
Diurnal.
Active spring through fall when it becomes inactive during late fall and winter cold.
Tree lizards have been found overwintering in aggregations.
Often seen basking on rocks in the morning with the head pointing downward.
Despite the name, this lizard seems to prefer rocks as basking sites.
Shelters in vegetation, under rocks, and in crevices in rock.
Defense
Escapes by climbing out of reach up a rock or tree and running to the other side.
The tail is easily detached and when detached wriggles for several minutes which may distract a predator from the lizard long enough for it to escape.
Diet and Feeding
Eats small invertebrates including beetles, ants, flies, grasshoppers, and spiders. Typically sits on shrubs, trees, and rocks and waits for prey to approach.
Reproduction
Breeding occurs in spring, with 1 to 6 clutches of 2 - 16 eggs laid from March to August.

Habitat
Tree lizards are found in desert habitats with or without trees, which include mesquite, tamarisk, oaks and cottonwoods, and are often seen on buildings and fence posts. They are especially attracted to the edges of rivers, streams and washes.
This tree lizard subspecies is more often found on rocks than on trees due to the rugged and treeless mountainous terrain that makes up much of their range.

Geographical Range
California

The Colorado River Tree Lizard is found in the far southeast part of California continuously along the Colorado River.

Robert Stebbins in his 2003 field guide says this lizard "ranges inland to Corn Spring area on ne. slope of Chuckwalla Mts." but I have not yet found any museum record for this location, or any other location away from the Colorado River where this lizard occurs naturally. There are reports of tree lizards found in riparian vegetation along artificially-constructed irrigation canals in the Imperial Valley. I received pictures of one living on a house in El Centro, Imperial County, near farms and irrigation canals, in May 2013. The San Diego Natural History Museum also has several specimens of U. ornatus collected in El Centro in 2008.

There is an introduced population tree lizards of unknown origin in the city of San Bernardino that was documented in 2010.  (Jim Bass and Jonathan Hakim, Herpetological Review Volume 41, Number 4 December 2010.) The lizards have been found on residential fences and walls in a developed suburban neighborhood. The authors believe the population is established and reproducing. They suggest that the source of introduction might be lizards that were transported from the Colorado River where the species occurs naturally during boating trips, because many of the homeowners in the area own boats.

A December 2013 Herpetological Review Geographical Distribution Note (Tyler J. Grant, Herpetological Review 44(4), 2013) documented a population of tree lizards from the yard of a house and two other locations in El Centro where they were  thought to be common in artificial landscapes. Due to a lack of phylogeographic differentiation between them and specimens from Maricopa County, Arizona, the author determines that it seems likely that they are an introduced population rather than naturally occurring in the Imperial Valley.

In November 2020 I learned that there is an apparently undocumented population of Tree Lizards that appear to be U. o. symmetricus in a park in Barstow, San Bernardino County. The lizards have been observed there for years, so it is likely that they have spread beyond the park.


Outside of California

The Colorado River Tree Lizard subspecies is also found in Arizona along the Colorado River.

Other subspecies of the Ornate Tree Lizard are found in Arizona, New Mexico, Utah, Texas, extreme southern Nevada, extreme southwest Wyoming, western Colorado, and in extreme northeast Baja California and in the states of Sonora, Chihuahua, Sinaloa, Coahuila, and Tamaulipas, in Mexico.

Full Species Range Map
Elevational Range
Found at elevations from sea level to around 9,000 ft. (2,770 m). (Stebbins 2003)

Notes on Taxonomy
A number of subspecies of Urosaurus ornatus have been recognized, with 6 found in the U. S. A. including
U. o. symmetricus.
Many researchers choose not to recognize any subspecies.


Alternate and Previous Names (Synonyms)

Urosaurus ornatus - Ornate Tree Lizard (Stebbins 2003)
Urosaurus ornatus
- Tree Lizard (Stebbins 1966, 1985)
Uta ornata symmetrica - (Tree Lizard) (Stebbins 1954)
Uta ornatus symmetricus - Symetrical Uta (Smith 1946)

Conservation Issues  (Conservation Status)
None
Taxonomy
Family Phrynosomatidae Zebra-tailed, Earless, Fringe-toed, Spiny, Tree, Side-blotched, and Horned Lizards Fitzinger, 1843
Genus Urosaurus Tree & Brush Lizards Hallowell, 1854
Species ornatus Ornate Tree Lizard (Baird and Girard, 1852)
Subspecies

symmetricus Colorado River Tree Lizard (Baird, 1859 “1858”)
Original Description
Urosaurus - Hallowell, 1854 - Proc. Acad. Nat. Sci. Philadelphia, Vol. 7, p. 92
Urosaurus ornatus - (Baird and Girard, 1852) - Proc. Acad. Nat. Sci. Philadelphia, Vol. 6, p. 126 (part)
Urosaurus ornatus symmetricus - (Baird, 1858) - Proc. Acad. Nat. Sci. Philadelphia, Vol. 10, p. 253

from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz

Meaning of the Scientific Name
Urosaurus - Greek - oura - tail and saurus - lizard
ornatus
- Latin - ornamented
symmetricus - Latin - balanced or equal - referring to the regular series of larger dorsal scales

from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz

Related or Similar California Lizards
Urosaurus microscutatus - Small-scaled Lizard
Urosaurus graciosus - Long-tailed Brush Lizard

More Information and References
California Department of Fish and Wildlife

Stebbins, Robert C., and McGinnis, Samuel M.  Field Guide to Amphibians and Reptiles of California: Revised Edition (California Natural History Guides) University of California Press, 2012.

Stebbins, Robert C. California Amphibians and Reptiles. The University of California Press, 1972.

Samuel M. McGinnis and Robert C. Stebbins. Peterson Field Guide to Western Reptiles & Amphibians. 4th Edition. Houghton Mifflin Harcourt Publishing Company, 2018.

Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.

Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.

Powell, Robert., Joseph T. Collins, and Errol D. Hooper Jr. A Key to Amphibians and Reptiles of the Continental United States and Canada. The University Press of Kansas, 1998.

Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Turtles and Lizards of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009.

Jones, Lawrence, Rob Lovich, editors. Lizards of the American Southwest: A Photographic Field Guide. Rio Nuevo Publishers, 2009.

Smith, Hobart M. Handbook of Lizards, Lizards of the United States and of Canada. Cornell University Press, 1946.

St. John, Alan D. Reptiles of the Northwest: Alaska to California; Rockies to the Coast. Lone Pine Publishing, 2002.

Brennan, Thomas C., and Andrew T. Holycross. Amphibians and Reptiles in Arizona. Arizona Game and Fish Department, 2006.


Conservation Status

The following conservation status listings for this animal are taken from the November 2020 California "Special Animals List" and the November 2020 "State and Federally Listed Endangered and Threatened Animals of California" list, both of which are produced by multiple agencies and available here: https://www.wildlife.ca.gov/Data/CNDDB/Plants-and-Animals. You can check the link to see if there are more recent lists.

If no status is listed here, the animal is not included on either list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status you can go to the NatureServe and IUCN websites to check their rankings.

This animal is not included on the Special Animals List, which indicates that there are no significant conservation concerns for it in California.


Organization Status Listing  Notes
NatureServe Global Ranking
NatureServe State Ranking
U.S. Endangered Species Act (ESA) None
California Endangered Species Act (CESA) None
California Department of Fish and Wildlife None
Bureau of Land Management None
USDA Forest Service None
IUCN

 

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