Range in California: Red
Green: San Nicolas Night Lizard
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Adult, Santa Barbara Island
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Adult, Santa Barbara Island |
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Adult, Santa Barbara Island
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Adult, Santa Barbara Island |
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Adult, Santa Barbara Island |
Adult, Santa Barbara Island |
Adult, Santa Barbara Island |
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Adult, striped form, San Clemente Island
© Bob Haase |
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Habitat |
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Santa Barbara Island |
Santa Barbara Island from sea |
Santa Barbara Island and Sutil Islet,
early Summer |
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Santa Barbara Island, early Summer |
Rocky cliff-edge and Sutil Islet, early Summer, Santa Barbara Island
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Small canyon in Spring, with blooming Giant CoreopsisSanta Barbara Island.
© Tim Burkhardt |
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Grassy plateau, top of Santa Barbara Island |
View looking down at Elephant Seal Beach, Santa Barbara Island |
Dormant Giant Coreopsis, Santa Barbara Island, early summer |
| Description |
| Size |
| 2.5 - 4.2 inches long from snout to vent (6.3 - 10.6 cm). (Stebbins 2003) The largest of the Xantusiids, growing from about 5 - 8 inches long including the tail. |
| Appearance |
A medium-sized lizard with granular scales, soft skin that appears loose around the neck and shoulders, large plates on the head, lidless eyes with vertical pupils, a gular fold, and a fold of skin low on each side of the body.Two rows of supraoculars and 16 lengthwise rows of squarish scales at the midbelly.
Color and pattern are variable - Brown, olive-brown, grayish, rusty, or yellowish-brown with dark brown or black spots or blotches, sometimes with full or broken light stripes edged with black along the sides of the back. Striped lizards occur on San Clemente Island, but rarely on Santa Barbara Island. The underside is slate bluish, cream or pale yellow. The undersides of the feet are sometimes yellowish. |
| Behavior and Natural History |
| Once considered nocturnal, but apparently diurnal but sedentary, secretive, and rarely seen. Spends most of its time under cover, but occasionally seen exposed on the surface in daylight. Active throughout the year. Grows and matures slowly, living to at least 12 years old |
| Diet |
| Eats small invertebrates including insects, spiders, scorpions, and marine isopods along with plant material (which can make up to one-third of its diet.) |
| Reproduction |
| Breeds in March and April. Viviporous, bearing 2-9 live young mostly in September.
Reproductive potential is low. Adults do not reach sexual maturity
until their 3rd or 4th year and only about half of all females reproduce each year. |
| Range |
| Endemic to California. Found only on islands off the southern California coast - Santa Barbara Island, Sutil Islet, and San Clemente Island. |
| Habitat |
Found in almost any island habitat that provides it protection and shade - maritime desert scrub, grassland, chaparral, oak savanna, cactus, dry streambeds, cliffs, rocky beaches, sparsely-vegetated areas. Takes shelter in cracks in rocks or in the ground, and under surface objects such as rocks, fallen vegetation and beach driftwood.
Santa Barbara Island is a flat tree-less plateau with grasses, small shrubs, introduced ice plant, prickly-pear cactus and Giant Coreopsis. There are a few small rocky canyons along the edge with dense vegetation. |
| Taxonomic Notes |
| Two subspecies of X. riversiana are still recognized by on the official lists of the SSAR and the CNAH, X. r. reticulata, and X. r. riversiana. These names are hardly used by anyone else, and I have found very little information regarding differences between these subspecies. |
| Conservation Issues (Conservation Status) |
Protected since 1967. This lizard's restricted habitat has been threatened by the grazing of introduced livestock and game, (most of which have now been removed) and by introduced predators such as feral cats and possibly rats. It is also preyed upon heavily by native birds and mammals. In 1990 the USFWS categorized the status of lizards on San Clemente Island as stable.
A 1991 study by Fellers and Drost determined that the population on Santa Barbara Island is not threatened.
The U.S. Navy administers San Clemente and San Nicolas Islands, and has petitioned to have lizards from those islands removed from the Endangered Species List. Santa Barbara Island and Sutil Islet are protected as National Park property. |
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Taxonomy |
| Family |
Xantusiidae |
Night Lizards |
| Genus |
Xantusia |
Night Lizards |
| Species |
riversiana |
Island Night Lizard |
Subspecies
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reticulata |
San Clemente Night Lizard |
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Original Description |
Xantusia riversiana - Cope, 1883 - Proc. Acad. Nat. Sci. Philadelphia, Vol. 35, p. 29
Xantusia riversiana reticulata - Smith, 1946 - Journ. Washington Acad. Sci., Vol. 36, p. 392
from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz
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Meaning of the Scientific Name |
Xantusia - honors Xantus, John
riversiana - honors Rivers, James, J.
reticulata - Latin - net-like - probably refers to the pattern.
from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
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Alternate Names |
Xantusia riversiana - Island Night Lizard (with no subspecies recognized)
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Related or Similar California Lizards |
X. henshawi - Granite Night Lizard
X. gracilis - Sandstone Night Lizard
X. vigilis - Yucca Night Lizard
X. sierrae - Sierra Night Lizard
X. r. riversiana - San Nicolas Night Lizard
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More Information and References |
Natureserve Explorer
California Dept. of Fish and Game
US Fish & Wildlife Service
IUCN Red List
Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.
Behler, John L., & F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.
Thelander, C. G., ed. Life on the Edge: A Guide to California's Endangered Natural Resources Volume I: Wildlife.
Biosystems Books, Santa Cruz, California. 1994.
Schoenherr, Allan A. Natural History of the Islands of California. The University of California Press. 2003.
Fellers, G.M. and Drost, C.A. 1991. Xantusia riversiana. Catalogue of American Amphibians and Reptiles 516: 1-4.
U.S. Fish and Wildlife Service (USFWS). 1990. Endangered and threatened species recovery program: report to Congress.
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. |
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The following status listings come from the Special Animals List which is published several times each year by the California Department of Fish and Game.
Listing is by species, not just this subspecies.
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Organization
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Status Listing
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| U.S. Endangered Species Act (ESA) |
FT |
Threatened |
| California Endangered Species Act (CESA) |
None |
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| California Department of Fish and Game |
None |
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| Bureau of Land Management |
None |
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| USDA Forest Service |
None |
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| Natureserve Global Conservation Status Ranks |
G1 S1 |
Critically Imperiled |
World Conservation Union - IUCN Red List
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IUCN:VU |
Vulnerable |
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