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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




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Colorado River Tree Lizard Colorado River Tree Lizard Colorado River Tree Lizard
  Adult female, Yuma County, Arizona  
Colorado River Tree Lizard Colorado River Tree Lizard Colorado River Tree Lizard
Adult female, Yuma County, Arizona Adult, Imperial County
© William Flaxington
Colorado River Tree Lizard Colorado River Tree Lizard Colorado River Tree Lizard
Adult, Imperial County
© William Flaxington
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  
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

 
Similar Sympatric Species
The tail of a tree lizard is much longer than the tail of most similar lizards except for the Long-tailed Brush Lizard, Urosaurus graciosus, which occurs throughout all of the range of the tree lizard in California and most of its range elsewhere. The two species are often very similar in appearance, but they can be separated by examining the wide band of enlarged scales on the middle of the back that is found on both species:

Colorado River Tree Lizard Long-tailed Brush Lizard
The band of wide scales on the back of a tree lizard is split in the center by smaller scales.

(The picture above is not the U. o. symmetricus subspecies which has a wider band of small scales than the subspecies illustrated here.)

The band of wide scales on the back of the Long-tailed Brush Lizard is not split in the center by smaller scales.
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.

Great Basin Collared Lizard






Western Side-blotched Lizard
Similar Tree Lizard Subspecies from Outside California
The pictures belowshow Urosaurus ornatus schottii - Schott's Tree Lizard, the subspecies found east of the range of the Colorado River Tree Lizard. Without a magnifying glass, the appearance is the same. Some researchers do not recognize any subspecies of this lizard or any important differences between 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 Lizard from 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.
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.

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.

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 the 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.) There is a gular fold across the throat and a fold of skin on each side of the body.
Behavior and Natural History
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. Escapes by climbing out of reach up a rock or tree and running to the other side. Shelters in vegetation, under rocks, and in crevices in rock.
Diet
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.
Range
Urosaurus ornatus symmetricus is found in the far southeast part of California 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 unconfirmed (to me) 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.

A December 2013 Herpetological ReviewGeographical 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 occuring in the Imperial Valley.

There is also an introduced population of U. ornatus in the city of San Bernardino of unknown origin. More information will be available after the publication of this distribution note:
Hakim, J. and J. Bass: Urosaurus ornatus symmetricus. Distribution note in Herpetological Review (in press December 2010)

Beyond California,Urosaurus ornatus is found in much of Arizona, New Mexico and Texas, as well as in extreme southern Nevada and Utah, extreme southwest Wyoming, western Colorado, and in extreme northeast Baja California and into the states of Sonora, Chihuahua, Sinaloa, Coahuila, and Tamaulipas, in Mexico.
Found at elevations from sea level to around 9,000 ft. (2,770 m). (Stebbins 2003)
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.
Taxonomic Notes
A number of subspecies of Urosaurus ornatus have been recognized, with 6 found in the U. S. A. Many researchers choose not to recognize any subspecies.
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

Alternate Names
Urosaurus ornatus - Ornate Tree Lizard (with no subspecies recognized)

Related or Similar California Lizards
Urosaurus nigricaudus - Baja California Brush Lizard
Urosaurus graciosus - Long-tailed Brush Lizard

More Information and References
Natureserve Explorer

California Dept. of Fish and Game

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.

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 status listings come from the Special Animals List and the Endangered and Threatened Animals List which are published by the California Department of Fish and Wildlife.


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
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

 

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