neck and along the sides of the body. The back is 

 mottled with pale ash gray or beige and yellow 

 brown, darkened in varying amounts with black. 

 Occasional individuals have a pale gray dorso- 

 lateral stripe on each side, edged with brown and 

 black; a brown vertebral stripe may also be 

 present. It is pale gray below, sometimes with a 

 bluish cast suffused on the belly and often on the 

 tail with yellow. Underside of feet may be yellow- 

 ish (Stebbins 1966). A photograph is in the 

 Endangered Species Technical Bulletin (1977, 

 Vol. 2, No. 9). 



RANGE 



Island night lizards occur on Santa Barbara, 

 San Nicolas, and San Clemente Islands, in the 

 California Channel Islands group (Stebbins 1966, 

 Savage 1967). A small population has recently 

 been discovered on Sutil Island (J. M. Erode pers 

 comm). Stebbins (1954) indicated that X. river- 

 siana occurred on Santa Catalina Island, but this 

 record needs confirmation. 



RANGE MAP 



Arrows on the accompanying map indicate 

 islands where X. riversiana occurs. 



STATES /COUNTIES 



California: Los Angelos, Ventura. 



HABITAT 



The species inhabits grassland brushy areas, 

 clumps of cactus (Opuntia), cliffs, and rocky 

 beaches (Stebbins 1954, 1966). 



FOOD AND FORAGING BEHAVIOR 



X. riversiana is an omnivorous, opportunistic 

 feeder, eating a large variety of anthropods — 

 spiders, marine isopods, scorpians, centipedes, 

 mites, aphids, wasps, flies, moths, silverfish, etc 

 (Stebbins 1954). Brattstrom (1952) notes that 

 ants and beetles are the most important food 

 items for this species; 31% of the animals he 

 examined from San Clemente Island had also 

 ingested plant matter consisting of flowers, leaves, 

 stems, and seeds {Mesembryanthemum, etc). 

 These lizards are thought of as active mostly at 



night, but they have been seen foraging in the 

 daytime (Stebbins 1954). 



SHELTER REQUIREMENTS 



X. riversiana seeks shelter under rocks, drift- 

 wood, and fallen branches (Stebbins 1966). 



NESTING AND BEDDING 



No information is available concerning 

 nesting. 



RITUAL REQUIREMENTS 



Not known. 



OTHER CRITICAL ENVIRONMENTAL 

 REQUIREMENTS 



Not known. 



POPULATION NUMBERS AND TRENDS 



No data are available on absolute densities. 

 Bezy (1976) indicated that X. riversiana was 

 widespread on San Clemente Island, restricted but 

 locally common on San Nicolas Island, and 

 restricted by limited habitat but moderately 

 abundant on Santa Barbara Island. He notes seri- 

 ous threats to X. riversiana or to its habitat on all 

 islands due to populations of introduced animals 

 (See Management and Conservation). 



REPRODUCTION 



X. riversiana is viviparous. Spermiogenesis 

 begins in March and concludes in June; females 

 ovulate from late May to early June (Goldberg 

 and Bezy 1974). Breeding probably occurs from 

 May through June. Goldberg and Bezy (1974) 

 report a range of 3 to 9 young per breeding 

 female per year, with a mean of 3.76 for San 

 Clemente Island females. They estimate that 

 about half of the female population is reproduc- 

 tively active in a given year. Young are born in 

 September, following a 14-week gestation period. 

 Goldberg and Bezy (1974) estimate that sexual 

 maturity is attained in the spring of the third or 

 fourth year. They consider X. riversiana to be a 

 K-selected species, being relatively late-maturing, 

 long-lived, with single broods, large adult body 



