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Barefoot Gecko (Coleonyx switaki)

Legal Status

State: Threatened

Federal: Bureau of Land

Management Sensitive

Critical Habitat: N/A

Recovery Planning: N/A

Taxonomy

The barefoot gecko (Coleonyx switaki) was originally described and

included the genus Anarbylus by Murphy (1974), but it is now

assigned to the genus Coleonyx (banded geckos) following Grismer

(Crother 2008). There is one recognized subspecies C. s. switaki

(Peninsular banded gecko) (Murphy 1974; Crother 2008), but the

state listing is for the full species. A description of the species’ physical

characteristics can be found in Stebbins (2003) and the California

Department of Fish and Game species account (CDFG 2005).

Distribution

General

The barefoot gecko has a small geographic range in the United States,

apparently limited to the eastern face of the Peninsular Ranges in

eastern San Diego County and extreme western Imperial County

(Zeiner et al. 1988). The species’ range extends south into Baja

California, Mexico, to about Bahia de los Angeles, San Ignacio, and

Santa Rosalia, and also occurs on San Marcos Island (Stebbins 2003;

CDFG 2005) (Figure SP-R2). The species’ range in California

encompasses about 370,120 acres.

The California Natural Diversity Database (CNDDB) includes 9

occurrences for the barefoot gecko, all of which were documented

between 1976 and 1988 (CDFG 2012). Due to the vulnerability of the

species to collectors, the locations of the occurrences are suppressed

Photo courtesy of John H. Tashjian, California Academy of Sciences.

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in the CNDDB report, but the U.S. Geological Survey (USGS) 7.5-

minute quadrangles in which the observations were made are

included in the report. The nine “historic” (pre-1990) occurrences

were documented in the following quadrangles: In-Ko-Pah Gorge

(three occurrences in 1976 and one in 1978) and Painted Gorge (one

occurrence in 1978) quadrangles in Imperial County; and the Tubb

Canyon (one record each in 1978 and 1988), Borrego Sink (one

record in 1979), and Agua Caliente Springs (one occurrence in 1985)

in San Diego County (CDFG 2012). The species also has been

reported as far north as the Palms to Pine Highway (State Highway

74) in Riverside County (Stebbins 2003). An isolated population is

reported from the Coyote Mountains in Imperial County, which is in

the Carrizo Mountain quadrangle, but no additional information for

this population is provided (CaliforniaHerps 2011). It is unknown

whether this is the same occurrence reported in the CNDDB for the

Carrizo Mountain quadrangle.

The North American Field Herping Association (NAFHA) maintains a

Herpetological Education and Research Project (HERP) database that

contains 11 records for San Diego County, collected between 2000

and 2010 (NAFHA 2010). The reports in the database do not include

more specific locations, but the habitats are reported to be rocky

areas, and are consistent with other records for the species. Due to the

general nature of the reported occurrences, it is unknown what

occurrences are on private land and public lands.

Distribution and Occurrences within the Plan Area

Historical

The western edge of the Desert Renewable Energy Conservation Plan

(DRECP) Area overlaps the eastern edge of the barefoot gecko

documented range and totals about 3,800 acres or about 10% of the

species’ range in California. Of the 3,800 acres, about 3,660 acres

(96%) are on public land. There are two historic (i.e., pre-1990)

CNDDB occurrences in the Plan Area, one on private land (at the time

the species was observed) and one in Anza-Borrego State Park.

HerpNet, a collaborative effort by natural history museums to

establish a global network of herpetological collections data involving

64 institutions, includes 14 museum records in California, 6 in

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Imperial County and 8 in San Diego County. These records range from

1965 to 1987 (HerpNet 2010). In Imperial and San Diego counties,

record localities include a dirt road 23.3 miles west of Calexico and 2.2

miles west of Highway 98, 3 kilometers (1.8 miles) east of Mountain

Springs on Old Highway 80, Highway 78, Palm Canyon Drive, and

Painted Gorge (HerpNet 2010).

Recent

There are no recent occurrence records for the barefoot gecko in the

Plan Area. However, because the species inhabits extremely rugged

and formidable terrain (see Habitat Requirements below), suitable

habitat is not subject to widespread development and loss. In the pre-

1990 CNDDB occurrence reports, the only threats identified for two of

the sites were over-collecting and recreation (camping, hiking, and

rock-hounding). It is assumed therefore that the pre-1990 CNDDB

occurrences are still extant and represent the current known range of

the species in California and within the Plan Area.

Natural History

Habitat Requirements

The barefoot gecko occurs in rock- and boulder-strewn and rock

outcrop habitats, often at the heads of canyons (Zeiner et al. 1988;

Stebbins 2003; CDFG 2005). It spends most of its time in deep rock

crevices and subterranean chambers where humidity is higher than at

the surface (CDFG 2005). It occurs from sea level to about 2,000 feet

(Stebbins 2003).

Foraging Requirements

Because the barefoot banded gecko inhabits areas with very difficult

access, little is known about its foraging requirements or other life

history traits discussed below. It is presumed to forage for insects, but

otherwise its diet is unknown (Zeiner et al. 1988). The diets of

congeners, including western banded gecko (C. variegatus), and Texas

banded gecko (C. brevis) are better known. The western banded gecko

preys on insect larvae, beetles, termites, grasshoppers, spiders, and

isopods (a crustacean group that includes pill or sow bugs) (Zeiner et

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al. 1988), and the Texas banded gecko preys on insects, spiders,

centipedes, millipedes, and isopods (Stebbins 2003).

Reproduction

Species-specific reproduction information for the barefoot gecko is

not available, but data are available for the related western banded

gecko and Texas banded gecko. The western banded gecko lays one to

three clutches (fertilized by stored sperm) of two eggs each in the

ground or under rocks annually, from about May through September

(Zeiner et al. 1988; Stebbins 2003). The Texas banded gecko lays one

or two clutches annually of about two eggs (range of one to four) in

April to June. Based on information for these congeners, it is expected

that the barefoot gecko has a similar pattern of possibly laying small

clutches, with possibly more than one clutch per year during a several

month window. However, life histories studies on the species are

needed to confirm this type of reproductive pattern.

Spatial Behavior

No information is available for the spatial behavior of the species,

including territories, home ranges, or dispersal. Like the other

Coleonyx species, the barefoot gecko is nocturnal and likely active in

the spring and summer, and possibly during warm periods in the fall

and winter (Zeiner et al. 1988). Activity on the surface is low (Dugan

2010). Its spatial behavior is probably limited by the availability of

suitable rock- and boulder-strewn and rock outcrop habitats. Because

of its close association with these site-specific habitats,

generalizations about its spatial behavior based on information about

western and Texas banded gecko probably is not appropriate.

Ecological Relationships

There are no species-specific data for ecological relationships.

However, it is probably prey for larger carnivorous lizards

(Crotaphytus, Gambelia, and Sceloporus), snakes, and birds (Zeiner et

al. 1988). Access to refugia where humidity is higher may be

important (CDFG 2010). Access to free water probably is not required

(CDFG 2010).

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Population Status and Trends

Global: Apparently secure (NatureServe 2010)

State: Critically imperiled (NatureServe 2010)

Within Plan Area: Critically imperiled (NatureServe 2010)

Very little is known about the status and population trends of this

species. It has a limited range in California, but is more widespread in

Baja California, Mexico, which accounts for its apparently stable status

globally but critically imperiled status in California. Although it is

considered critically imperiled in California and was state listed as

threatened in 1980, there are no identified major threats to the

species that would indicate an imminent severe population decline

(see the following Threats and Environmental Stressors section). The

total population size within its entire range is expected to be at least

several thousand individuals (NatureServe 2010). Although there are

only 10 CNDDB occurrence records for the period of 1976 through

2004 (CDFG 2011), the NAFHA database contains 11 records for San

Diego County, collected between 2000 and 2010 (NAFHA 2010).

Because this species has low surface activity and occurs in relatively

inaccessible habitats, it is difficult to detect (Dugan 2010) and

population studies are difficult to carry out (Zeiner et al. 1988).

Threats and Environmental Stressors

Potential threats that could cause large-scale destruction and

degradation of habitat for the barefoot gecko include highway

construction and mining (NatureServe 2010). Potential threats to

local populations include illegal collecting by hobbyists and

commercial collectors; habitat destruction by collectors is one of the

main threats to the species (CDFG 2005). Other threats include

impacts related to recreation, including camping, hiking, and rock-

hounding (CDFG 2011).

Conservation and Management Activities

Habitat for the barefoot gecko is protected in the Anza-Borrego Desert

State Park (CDFG 2005). In 2004, the 3,339-acre Vallecito Ranch,

which includes habitat for the barefoot gecko, was purchased with

funds provided through the Resources Legacy Fund Foundation’s

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Preserving Wild California program, The Nature Conservancy, and

state and federal programs to become part of the State Park (Anza-

Borrego Foundation 2011).

Data Characterization

The general geographic range of the barefoot gecko in the United

States is probably reasonably well known, with reported occurrences

from the Palms to Pines Highway (State Highway 74) in the north to

the U.S.–Mexico border in the south (Stebbins 2003). However, due to

the species’ low level of surface activity (Dugan 2010; SDG&E 2010)

and occurrence in rugged and relatively inaccessible habitat (rocky

canyons, washes, and rock outcrops), there are relatively few

documented occurrences considering there are 10 total CNDDB

records and 14 total records in HerpNet, a collaborative resource that

includes museum records (CDFG 2011; HerpNet 2010). It may only be

rarely observed even under ideal survey conditions (Dugan 2010). In

addition, because the species in highly vulnerable to illegal collecting,

the CNDDB suppresses site-specific information in the data available

to the public and only reports the USGS 7.5-minute quadrangles in

which the species has been documented.

Management and Monitoring Considerations

The main threat to the species has been illegal collection and

concomitant habitat destruction (CDFG 2005). Habitat loss or

degradation related to highway construction and mining is also a

potential threat to the species (Hollingsworth and Hammerson 2007).

Management of the species should focus on protecting species habitat

from both legal and illegal human activities. Too little is currently

known about the species’ life history and ecology to develop more

specific management recommendations.

Predicted Species Distribution in Plan Area

There are 890 acres of modeled suitable habitat for barefoot gecko

in the Plan Area. Modeled suitable habitat occurs in the Borrego

Valley-West Mesa ecoregion subsection up to 2,000 feet in elevation.

Suitable habitat includes canyons and open slopes with the following

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surface geology parent materials: granitic, granitic and

metamorphic, igneous and metamorphic, metavolcanic, mixed Rock,

plutonic rock, and volcanic.

Literature Cited

Anza-Borrego Foundation. 2011. “Protected Land.” Borrego Springs,

California: Anza-Borrego Foundation. Accessed May 2011.

http://theabf.org/what_we_do/saving_land/protected_land.

CaliforniaHerps. 2011. “Coleonyx switaki – Barefoot Gecko.” Accessed April

2011. http://www.californiaherps.com/lizards/pages/c.switaki.html.

CDFG (California Department of Fish and Game). 2005. “The Status of

Rare, Threatened, and Endangered Plants and Animals of

California 2000–2004.” Accessed March 2011.

http://www.dfg.ca.gov/wildlife/nongame/t_e_spp/new_te_rpt.html.

CDFG. 2012. RareFind, Version 4. Sacramento, California: California

Natural Diversity Database. Accessed February 2012.

Crother, B.I. (Chair). 2008. Scientific and Standard English Names of

Amphibians and Reptiles of North America North of Mexico, with

Comments Regarding Confidence in Our Understanding. 6th

Edition. By the Committee on Standard English and Scientific

Names. Society for the Study of Amphibians and Reptiles

Herpetological Circular 37: iii + 86p.

Dugan, E.A. 2010. “Protocol Barefoot Banded Gecko (Coleonyx switaki)

Survey Report – SDG&E – East County Substation.” Prepared

for San Diego Gas & Electric. September 14, 2010.

HerpNet. 2010.

Data for Coleonyx switaki obtained from the Arctos – MVZ Herp

Catalog, California Academy of Sciences (CAS) – CAS

Herpetology Collection Catalog, and the San Diego Natural

History Museum – Herp Specimens. Updated August 13, 2010.

Accessed July 1, 2011, through the HerpNet2 Portal.

www.herpnet2.org.

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Hollingsworth, B., and G.A. Hammerson. 2007. “Coleonyx switaki.” The

IUCN Red List of Threatened Species. Version 2011.1. Accessed

July 2, 2011. http://www.iucnredlist.org/apps/redlist/

details/64038/0.

Murphy, R.W. 1974. “A New Genus and Species of Eublepharine Gecko

(Sauria: Gekkonidae) from Baja California, Mexico.” In

Proceedings of the California Academy of Sciences 40:87–92.

Accessed April 5, 2011. http://www.biodiversitylibrary.org/

item/53704.

NAFHA (North American Field Herping Association). 2010.

Herpetological Education and Research Project (HERP), Online

database. Accessed March 2010. http://www.naherp.com.

NatureServe. 2010. “Barefoot Gecko.” “NatureServe Explorer: An

online encyclopedia of life” [web application]. Version 7.1.

Arlington, Virginia: NatureServe. Accessed March 30, 2011.

http://www.natureserve.org/explorer.

SDG&E (San Diego Gas and Electric). 2010. “Protocol Barefoot Banded

Gecko (Coleonyx switaki) Survey Report – SDG&E – East County

Substation.” September 14, 2010. Accessed July 1, 2011.

http://www.cpuc.ca.gov/environment/info/dudek/ECOSUB/T

echStudies/ECO_BBG-Report.pdf.

Stebbins, R.C. 2003. A Field Guide to Western Reptiles and Amphibians.

Peterson Field Guide, 3rd ed. New York, New York: Houghton

Mifflin Company. March 27, 2003.

Zeiner, D.C., W.F. Laudenslayer Jr., and K.E. Mayer. 1988. California’s

Wildlife: Volume I. Amphibians and Reptiles. Sacramento,

California: California Statewide Wildlife Habitat Relationships

System, California Department of Fish and Game.

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FIGURE SP-R2Barefoot Gecko Occurrences in the Plan Area (N=2)

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Note: Occurrence point size graphically represents the precision level code for the data point but is not scaled geographically.

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Species Range in California