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| Adult, San Diego County |
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| Adult 1, coastal San Diego County |
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| Adult 2, coastal San Diego County |
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Threadsnakes will sometimes enter homes. Jerry McMurry discovered this snake in his home one summer night in coastal San Diego County.
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Adult, San Bernardino County
© Patrick Briggs |
Hatchling, Inyo County
© Adam G. Clause |
Pink adult, Inyo County
© Adam G. Clause |
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| Juvenile, Orange County © Ivan Vershynin |
Adult, Mono County
© Adam G. Clause |
Subadult, Mono County
© Adam G. Clause |
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| Adult, San Diego County © Paul Maier |
Adult, Orange County © Ivan Vershynin |
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| This adult threadsnake was observed just after dark in Los Angeles County at the mouth of an anthill where it was swarmed by ants as it burrowed into the nest, presumably to feed on the eggs and larvae. There's a link to a short video of this below. © William Mason |
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| Habitat |
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| Habitat, 1500 ft., San Gabriel Mountains, Los Angeles County |
San Diego County coastal sage habitat |
Habitat, San Diego County |
Habitat, Riverside County
riparian canyon |
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Habitat, San Diego County
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Habitat, Riverside County
riparian canyon
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Habitat, Orange County
© Ivan Vershynin |
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| Short Video |
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| A Southwestern Threadsnake discovered on a cool spring morning races across it's coastal San Diego County habitat with amazing speed. |
This adult threadsnake was observed just after dark in Los Angeles County at the mouth of an anthill where it burrowed into the nest, presumably to feed on the eggs and larvae. Ants can be seen swarming around the snake but it does not appear to be concerned about them.
© William Mason |
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Description |
Not Dangerous - This snake does not have venom that can cause death or serious illness or injury in most humans.
Commonly described as "harmless" or "not poisonous" to indicate that its bite is not dangerous, but "not venomous" is more accurate. (A poisonous snake can hurt you if you eat it. A venomous snake can hurt you if it bites you.)
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| Size |
Adults 7 - 16 inches long (18-41 cm). Hatchlings are around 4 - 5 inches long (10 - 12.7 cm).
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| Appearance |
A very thin snake with a blunt head and tail.
The tail is tipped with a small spine.
Eyes are nonfunctional dark spots visible under translucent plates.
The scales are shiny and cycloid.
Belly plates are not enlarged.
The lower jaw is countersunk.
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| Color and Pattern |
Coloring is brown, purple, or pink. This snake can be mistaken for a large worm.
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| Similar Snakes in California |
There are two subspecies of Western Treadsnake in California. There is also a very similar non-native blindsnake that has been introduced into Southern California and is gradually increasing its range in the state - the Brahminy Blindsnake.
Go to this page to see more information about comparing the Western Threadsnake with the Brahminy Blindsnake, and suggestions about what to do if you think you have found a Brahminy Blindsnake in California.
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| Life History and Behavior |
Activity |
Nocturnal. Occasionally found crawling exposed on surface at night. Sometimes seen crawling on paved roads at night. Hides in cracks and under surface debris in daytime. Sometimes found under rocks, boards, or other surface debris where the soil is slightly moist.
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| Defense |
| When threatened, this snake often writhes around, forming a tight coil while releasing pungent fluids from the cloaca. These fluids serve to repel defensive attacks by the ants and termites on which it feeds. May also play dead. |
| Diet and Feeding |
Eats ants and termites and their larvae and pupae, and occasionally other small insects.
When hunting for food, burrows under roots, rocks, and into ants nests.
Slender body allows them to forage in their ant and termite prey's burrow systems. |
| Reproduction |
Mates in the spring.
Females are oviparous - laying eggs sometime between July - August, and tending to them.
They may use communal nests.
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| Habitat |
Inhabits areas where the soil is suitable for burrowing: brushy mountain slopes, deserts, rocky hillsides, washes near streams, beach sand.
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| Geographical Range |
This subspecies, Rena humilis humilis - Southwestern Threadsnake, occurs along the Southern California coast - east, north of the range of R.h.cahuilae, into southern Nevada and western Arizona, - south along the west coast of Baja California, - and north, on the east side of the Sierra Nevada mountains, with isolated records from the Sierra Nevada/Tehachapi Mountains region at 9 mile canyon and Jawbone canyon.
The first Mono County record and the northernmost records for this species were documented from the southeastern Chalfant Valley in 2016.
Herpetological Review 47(2), 2016
Finding information about the ranges of the subspecies of Rena humilis is difficult, because they are not recognized by many herpetologists. Some field guides show no subspecies. Some show the range of R. h. humilis extending as far north of Needles, while others show it ranging to just north of the Riverside County border at the Colorado River, as I have decided to show on my map, although I am not certain that it is accurate.There is almost no information about the other subspecies found in Mexico so I have not tried to show them on my map.
The species Rena humilis - Western Threadsnake, is found from Southern California east through southern Arizona and New Mexico, into southwestern Texas, and south into Mexico and Baja California, Mexico.
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(Several subspecies are sometimes recognized, but I don't know their exact ranges outside of California.) |
| Notes on Taxonomy |
Some herpetologists do not recognize subspecies of Rena humilis. Those who do recognize four subspecies in the United States, and five in Mexico.
In 2009, Adalsteinsson, Branch, Trape, Vitt & Hedges (Molecular Phylogeny, Classification, and Biogeograpy of Snakes of the Family Leptotyphlopidae (Reptilia, Squamata). Zootaxa. 2240: pp. 1 - 50) placed this species in the genus Rena, making it Rena cahuilae.
Alternate and Previous Names (Synonyms)
Rena humilis humilis - Southwestern Threadsnake
Leptotyphlps humilis - Western Blind Snake (Stebbins 1966, 1985, 2003, Stebbins & Mcginnis 2012)
Leptotyphlps humilis humilis - Western Worm Snake (Stebbins 1954)
Leptotyphlps humilis humilis - Western worm snake (Van Denburgh 1922)
Leptotyphlops humilis - Worm Snake (Ophisaurus ventralis; Glauconia humilis; Stenostoma humile; Siagonodon humilis. California Rena, California Blind Snake; Glass Snake; Sheep-nosed Snake) (Grinnell and Camp 1917)
Worm snake (Stejneger 1891)
Humble sheep snake (Cronise 1868)
Blind snake
Brown blind snake
California worm snake
Cedros island worm snake
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| Conservation Issues (Conservation Status) |
| None |
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| Taxonomy |
| Family |
Leptotyphlopidae |
Threadsnakes (Blind Snakes) |
Stejneger, 1892 |
| Genus |
Rena |
Threadsnakes |
Baird & Girard, 1853 |
| Species |
humilis |
Western Threadsnake |
Baird & Girard, 1853 |
Subspecies
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humilis |
Southwestern Threadsnake |
(Baird & Girard, 1853) |
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Original Description |
Leptotyphlops - Stejneger, 1892
Leptotyphlops humilis - (Baird and Girard, 1853) - Cat. N. Amer. Rept., Pt. 1, p. 143
from Original Description Citations for the Reptiles and Amphibians of North America © Ellin Beltz
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Meaning of the Scientific Name |
Rena = either Latin - Reborn, or Greek - Peace
humilis - Latin - small or ground dwelling -- no specific reason in original description.
from Scientific and Common Names of the Reptiles and Amphibians of North America - Explained © Ellin Beltz
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Related or Similar California Snakes |
R. h. cahuilae - Desert Threadsnake
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More Information and References |
California Department of Fish and Wildlife
Stebbins, Robert C., and McGinnis, Samuel M. Field Guide to Amphibians and Reptiles of California: Revised Edition (California Natural History Guides) University of California Press, 2012.
Stebbins, Robert C. California Amphibians and Reptiles. The University of California Press, 1972.
Flaxington, William C. Amphibians and Reptiles of California: Field Observations, Distribution, and Natural History. Fieldnotes Press, Anaheim, California, 2021.
Samuel M. McGinnis and Robert C. Stebbins. Peterson Field Guide to Western Reptiles & Amphibians. 4th Edition. Houghton Mifflin Harcourt Publishing Company, 2018.
Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. 3rd Edition. Houghton Mifflin Company, 2003.
Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. Alfred A. Knopf, 1992.
Powell, Robert., Joseph T. Collins, and Errol D. Hooper Jr. A Key to Amphibians and Reptiles of the Continental United States and Canada. The University Press of Kansas, 1998.
Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Snakes of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009.
Bartlett, R. D. & Alan Tennant. Snakes of North America - Western Region. Gulf Publishing Co., 2000.
Brown, Philip R. A Field Guide to Snakes of California. Gulf Publishing Co., 1997.
Ernst, Carl H., Evelyn M. Ernst, & Robert M. Corker. Snakes of the United States and Canada. Smithsonian Institution Press, 2003.
Wright, Albert Hazen & Anna Allen Wright. Handbook of Snakes of the United States and Canada. Cornell University Press, 1957.
Joseph Grinnell and Charles Lewis Camp. A Distributional List of the Amphibians and Reptiles of California. University of California Publications in Zoology Vol. 17, No. 10, pp. 127-208. July 11, 1917.
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The following conservation status listings for this animal are taken from the January 2024 State of California Special Animals List and the January 2024 Federally Listed Endangered and Threatened Animals of California list (unless indicated otherwise below.) Both lists are produced by multiple agencies every year, and sometimes more than once per year, so the conservation status listing information found below might not be from the most recent lists. To make sure you are seeing the most recent listings, go to this California Department of Fish and Wildlife web page where you can search for and download both lists:
https://www.wildlife.ca.gov/Data/CNDDB/Plants-and-Animals.
A detailed explanation of the meaning of the status listing symbols can be found at the beginning of the two lists. For quick reference, I have included them on my Special Status Information page.
If no status is listed here, the animal is not included on either list. This most likely indicates that there are no serious conservation concerns for the animal. To find out more about an animal's status you can also go to the NatureServe and IUCN websites to check their rankings.
This snake is not included on the Special Animals List, which indicates that there are no significant conservation concerns for it in California.
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| NatureServe Global Ranking |
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| NatureServe State Ranking |
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| U.S. Endangered Species Act (ESA) |
None |
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| California Endangered Species Act (CESA) |
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| California Department of Fish and Wildlife |
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| Bureau of Land Management |
None |
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| USDA Forest Service |
None |
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| IUCN |
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