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Barefoot Gecko (Coleonyx switaki)
Barefoot Gecko
(Coleonyx switaki)
Legal Status
State: Threatened
Federal: Bureau of Land
Management Sensitive
Critical Habitat: N/A
Recovery Planning: N/A
Photo courtesy of John H. Tashjian, California
Academy of Sciences.
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 nine
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 in
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Barefoot Gecko (Coleonyx switaki)
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
Imperial County and 8 in San Diego County. These records range from
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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). In addition, Grismer and Ottley (1988)
list 45 museum specimens: 11 from San Diego County, 6 from
Imperial County, 5 from Baja North, and 23 from Baja South.
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 pre1990 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
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isopods (a crustacean group that includes pill or sow bugs) (Zeiner et
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 2011). Access to free water probably is not required
(Zeiner et al. 1988).
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Barefoot Gecko (Coleonyx switaki)
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 2012), 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 rockhounding (CDFG 2012).
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 (AnzaBorrego 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 2012; 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 9,581 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. Appendix C includes specific model parameters and a
figure showing the modeled suitable habitat in the Plan Area.
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. 2011. “Survey Protocol for Presence of or Negative Finding for
the Barefoot Banded Gecko (Coleonyx switaki).” California
Department of Fish and Game. August 2011. Accessed March 9,
2012. http://www.dfg.ca.gov/wildlife/nongame/
survey_monitor.html.
CDFG. 2012. “Coleonyx switaki.” Element Occurrence Query. California
Natural Diversity Database (CNDDB). Rarefind Version 4.0
(Commercial Subscription). Sacramento, California: CDFG,
Biogeographic Data Branch. Accessed February 2012.
http://www.dfg.ca.gov/biogeodata/cnddb/mapsanddata.asp.
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.
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Barefoot Gecko (Coleonyx switaki)
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.
Grismer, L.L., and J.R. Ottley. 1988. “A Preliminary Analysis of
Geographic Variation in Coleonyx switaki (Squamata:
Eublepharidae) with a Description of an Insular Subspecies.”
Herpetologica 44:143–154.
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/
TechStudies/ECO_BBG-Report.pdf.
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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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