California Reptiles & Amphibians

Xantusia riversiana reticulata - San Clemente Night Lizard

Click on a picture for a larger view

Range in California: Red

Green: San Nicolas Night Lizard

Adult, Santa Barbara Island

Adult, striped form, San Clemente Island
© Bob Haase

Adult, San Clemente Island
© Bob Haase

Santa Barbara Island

Santa Barbara Island from sea

Santa Barbara Island and Sutil Islet,
early Summer

Santa Barbara Island, early Summer

Rocky cliff-edge and Sutil Islet, early Summer, Santa Barbara Island

Small canyon in Spring, with blooming Giant CoreopsisSanta Barbara Island.
© Tim Burkhardt

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.

Taxonomy
Family	Xantusiidae	Night Lizards
Genus	Xantusia	Night Lizards
Species	riversiana	Island Night Lizard
Subspecies	reticulata	San Clemente Night Lizard
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
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
Alternate Names
Xantusia riversiana - Island Night Lizard (with no subspecies recognized)
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
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.

Conservation Status
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.
Organization	Status Listing
U.S. Endangered Species Act (ESA)	FT	Threatened
California Endangered Species Act (CESA)	None
California Department of Fish and Game	None
Bureau of Land Management	None
USDA Forest Service	None
Natureserve Global Conservation Status Ranks	G1	Critically Imperiled
World Conservation Union - IUCN Red List	IUCN:VU	Vulnerable