Night snakes are typically found from southern Mexico in the state of Guerrero (including Sinaloa, Nayarit, Jalisco, Colima, Michoacan, Guerrero, West Puebla, Morelos, and Aguascalientes) north through much of the western United States (northeastern Baja, California, Arizona, western Colorado, Utah, Nevada, eastern California, southern Idaho, Oregon and Washington) and into south central British Columbia, Canada. They have also been found in Texas, Kansas, and Oklahoma. Though widely distributed, night snakes are considered rare in many parts of their geographic range.
Biogeographic Regions: nearctic (Native )
Distribution: Mexico (Sinaloa, Nayarit, Jalisco, Colima, Michoacan, Guerrero, W Puebla, Morelos) tortugensis: Isla Tortuga
Night snakes are small, usually less than 66 centimeters in length. They have vertical pupils and bronze-copper colored eyes. Dorsal coloration consists of a tan ground color with darker brown saddle-shaped spots and lateral spots. The head is also dark brown, with the color stretching from the eyes to the base of the head where it forms a dark blotch, contrasting with the cream colored labial area. Ventral areas are pearly white (often iridescent). They are rear fanged and only mildly venomous. There is no seasonal variation in this species, but they do exhibit sexual dimorphism, with females up to three times longer than males. Night snakes are geographically widespread, with 17 sub-species currently recognized. Each may differ slightly in the above morphological characters and original type description, particularly with regards to patterns of nuchal color blotches, dorsal spots, and scale counts.
Range length: 30 to 66 cm.
Other Physical Features: venomous
Sexual Dimorphism: female larger
Great Basin Shrub Steppe Habitat
The Great Basin shrub steppe is one of the ecoregions inhabited by the Utah prairie dog. The Great Basin shrub steppe ecoregion is situated in the most northerly of the four American deserts. Unlike the other three, which have almost exclusive ties to warm-temperate and tropical/subtropical vegetation types, the Great Basin has affinities with cold-temperate vegetation.
Dominant plant species in the region include such distinctly cold-temperate species as sagebrushes (Artemisia), saltbrushes (Atriplex), and Winter-fat (Ceratoides lanata). These scrub species are much-branched, non-sprouting, aromatic semi-shrubs with soft wood and evergreen leaves. The Great Basin also contains species with evolutionary ties to warmer climates, such as rabbitbrush (Chrysothamnus), blackbrush (Coleogyne), hopsage (grayia) and horsebrush (Tetradymia). The region, however, contains few cacti species, either in numbers of individuals or species, and also lacks most characteristic desert plants in minor drainages.
Some other notable mammals found in the Great Basin ecoregion are: Belding's ground squirrel (Spermophilus beldingi); Yellow-bellied marmot (Marmota flaviventris); Bighorn sheep (Ovis canadensis); Bushy-tailed woodrat (Neotoma cinerea); Canada lynx (Lynx canadensis); Canyon mouse (Peromyscus crinitus); Cliff chipmunk (Tamias dorsalis); Coyote (Canis latrans); Desert cottontail (Crotaphytus insularis); North American porcupine (Erethizon dorsatum).
Anuran taxa found in the Great Basin scrub steppe are eight in number: the Black toad (Anaxyrus exsul VU); Great Basin spadefoot toad (Spea intermontana); Northern leopard frog (Lithobates pipiens); Pacific treefrog (Pseudacris regilla); Northern red-legged frog (Rana aurora); Columbia spotted frog (Rana luteiventris); Southwestern toad (Anaxyrus microscaphus); and Woodhouse's toad (Anaxyrus woodhousii). The Tiger salamander (Ambystoma tigrinis) is the sole salamander found in this ecoregion.
The Great Basin holds numerous reptilian taxa: Bluntnose leopard lizard (Gambelia sila EN); Common kingsnake (Lampropeltis getula); Sierra gartersnake (Thamnophis couchii); Black-collared lizard (Crotaphytus insularis); Desert horned lizard (Phrynosoma platyrhinos); Desert spiny lizard (Sceloporus magister); Western gopher snake (Pituophis catenifer); Ground snake (Sonora semiannulata); Long-nosed leopard lizard (Gambelia wislizenii); Long-nosed snake (Rhinocheilus lecontei); Milk snake (Lampropeltis triangulum); Panamint alligator lizard (Elgaria panamintina), a California endemic found only in the following desert mountains: Panamint, Inyo, Nelson, White, Cosos and Argus; Yellow-bellied racer (Coluber constrictor); Ringneck snake (Diadophis punctatus); Sagebrush lizard (Sceloporus graciosus); Pygmy short-horned lizard (Phrynosoma douglasii); Side-blotched lizard (Uta stansburiana); Striped whipsnake (Masticophis taeniatus); Western banded gecko (Coleonyx variegatus); Western patch-nosed snake (Salvadora hexalepis); Western pond turtle (Emys marmorata); Western terrestrial garter snake (Thamnophis elegans); Tiger whiptail (Cnemidophorus tigris); Zebra-tailed lizard (Callisaurus draconoides); Rubber boa (Charina bottae); and Night snake (Hypsiglena torquata).
A large number of bird species occur within the Great Basin, either as resident or migratory taxa. Example avian species found here are: Lewis's woodpecker (Melanerpes lewis); Phainopepla (Phainopepla nitans); Pinyon jay (Phainopepla nitans VU), a specialist found in pinyon-juniper woodlands; Greater sage grouse (Centrocercus urophasianus NT); Sandhill crane (Grus canadensis).
Palouse Grasslands Habitat
This taxon is found in the Palouse grasslands, among other North American ecoregions. The Palouse ecoregion extends over eastern Washington, northwestern Idaho and northeastern Oregon. Grasslands and savannas once covered extensive areas of the inter-mountain west, from southwest Canada into western Montana in the USA. Today, areas like the great Palouse prairie of eastern are virtually eliminated as natural areas due to conversion to rangeland. The Palouse, formerly a vast expanse of native wheatgrasses (Agropyron spp), Idaho Fescue (Festuca idahoensis), and other grasses, has been mostly plowed and converted to wheat fields or is covered by Drooping Brome (Bromus tectorum) and other alien plant species.
the Palouse historically resembled the mixed-grass vegetation of the Central grasslands, except for the absence of short grasses. Such species as Bluebunch Wheatgrass (Elymus spicatus), Idaho Fescue (Festuca idahoensis) and Giant Wildrye (Elymus condensatus) and the associated species Lassen County Bluegrass (Poa limosa), Crested Hairgrass (Koeleria pyramidata), Bottlebrush Squirrel-tail (Sitanion hystrix), Needle-and-thread (Stipa comata) and Western Wheatgrass (Agropyron smithii) historically dominated the Palouse prairie grassland.
Representative mammals found in the Palouse grasslands include the Yellow-bellied Marmot (Marmota flaviventris), found burrowing in grasslands or beneath rocky scree; American Black Bear (Ursus americanus); American Pika (Ochotona princeps); Coast Mole (Scapanus orarius), who consumes chiefly earthworms and insects; Golden-mantled Ground Squirrel (Spermophilus lateralis); Gray Wolf (Canis lupus); Great Basin Pocket Mouse (Perognathus parvus); Northern River Otter (Lontra canadensis); the Near Threatened Washington Ground Squirrel (Spermophilus washingtoni), a taxon who prefers habitat with dense grass cover and deep soils; and the Northern Flying Squirrel (Glaucomys sabrinus), a mammal that can be either arboreal or fossorial.
There are not a large number of amphibians in this ecoregion. The species present are the Great Basin Spadefoot Toad (Spea intermontana), a fossorial toad that sometimes filches the burrows of small mammals; Long-toed Salamander (Ambystoma macrodactylum); Northern Leopard Frog (Glaucomys sabrinus), typically found near permanent water bodies or marsh; Columbia Spotted Frog (Rana luteiventris), usually found near permanent lotic water; Pacific Treefrog (Pseudacris regilla), who deposits eggs on submerged plant stems or the bottom of water bodies; Tiger Salamander (Ambystoma tigrinum), fossorial species found in burrows or under rocks; Woodhouse's Toad (Anaxyrus woodhousii), found in arid grasslands with deep friable soils; Western Toad (Anaxyrus boreas), who uses woody debris or submerged vegetation to protect its egg-masses.
There are a limited number of reptiles found in the Palouse grasslands, namely only: the Northern Alligator Lizard (Elgaria coerulea), often found in screes, rock outcrops as well as riparian vicinity; the Painted Turtle (Chrysemys picta), who prefers lentic freshwater habitat with a thick mud layer; Yellow-bellied Racer (Chrysemys picta); Ringneck Snake (Diadophis punctatus), often found under loose stones in this ecoregion; Pygmy Short-horned Lizard (Phrynosoma douglasii), a fossorial taxon often found in bunchgrass habitats; Side-blotched Lizard (Uta stansburiana), frequently found in sandy washes with scattered rocks; Southern Alligator Lizard (Elgaria multicarinata), an essentially terrestrial species that prefers riparian areas and other moist habitats; Pacific Pond Turtle (Emys marmorata), a species that usually overwinters in upland habitat; Western Rattlesnake (Crotalus viridis), who, when inactive, may hide under rocks or in animal burrows; Night Snake (Hypsiglena torquata); Western Skink (Plestiodon skiltonianus), who prefers grasslands with rocky areas; Western Terrestrial Garter Snake (Thamnophis elegans), found in rocky grasslands, especially near water; Rubber Boa (Charina bottae).
Night snakes are found in a variety of habitats (some more commonly than others), including rocky canyons (talus and scree), oak woodlands, savannahs, brushy flatlands, prairies, grasslands, croplands, and occasionally moist mountain meadows. They may be found hiding under surface debris or rocks and in crevices. Night snakes may be found from sea level up to 2650 meters above sea level and prefer arid or semi-arid habitats.
Range elevation: 0 to 2650 m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral ; forest ; scrub forest ; mountains
Habitat and Ecology
Night snakes use mild venom to subdue small prey. They are nocturnal hunters and prey items include scorpions, lizards (Bipes biporus, Cnemidophorus tigris, Coleonyx variegatus, Dipsosaurus dorsalis, Elgaria multicarinata, Sceloporus graciosus, Uta stansburiana, Xantusia vigilis) and their eggs (particularly of Uta stansburiana), salamanders (Batrachoseps sp.), frogs (Pseudacris sp.), toads (Incilius alvarius, Scaphiopus couchii, Spea hammondii), other snakes (Crotalus viridis), and insects. They are also known to occasionally eat carrion and may eat animals that wander into their daytime hiding places.
Animal Foods: amphibians; reptiles; eggs; carrion ; insects; terrestrial non-insect arthropods
Primary Diet: carnivore (Eats terrestrial vertebrates, Eats eggs, Insectivore )
Night snakes prey on multiple small vertebrate and invertebrate species, helping to control the populations of these animals. They also serve as prey to other vertebrate species such as birds and reptiles.
These snakes hide during the day, avoiding predation by many species. Night snakes are likely preyed upon by owls, noctural mammals, and other snakes. They are a known prey item of red-tailed hawks.
- Red-tailed hawk (Buteo jamaicensis)
Life History and Behavior
Night snakes have cat-like eyes with vertical pupils and larger cornea and lens apertures than diurnal snakes. Snakes mainly use their olfactory and vomeronasal systems to sense their environments. They use their forked tongues to draw air into pits in the roofs of their mouths, where neuroreceptors detect chemicals and other elements of their environments. They have well-developed senses of hearing, picking up sounds as vibrations along their bodies. They also have highly developed tactile receptors.
Communication Channels: tactile ; chemical
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical
Little is known about the development of night snake specifically, but it is likely that they follow the development pattern of other small snake species. After fertilization, females lay a clutch of 2-6 eggs, often in sandy soil. Young develop inside the egg, nourished by yolk, for 50-60 days, depending on temperature. When they hatch, young are independent and resemble small adults.
Development - Life Cycle: indeterminate growth
There is no data regarding the lifespan of night snakes in the wild, but they have been known to survive over 12 years in captivity.
Status: captivity: 12.2 (high) years.
Lifespan, longevity, and ageing
There is no information currently available regarding specific mating behaviors of night snakes. However, it is possible that males compete for mates, as seen in a related species, Imantodes cenchoa. It is likely that females produce only one clutch of eggs in a breeding season and therefore that this species is polygnous, or possibly monogamous.
Mating System: polygynous
These snakes are capable of breeding from spring through early fall (April-September). Clutch size may range from 2-6 eggs (averaging 3) and there is no evidence that females produce more than one clutch of eggs in a breeding season. The smallest sexually mature male recorded measured about 237 millimeters SVL (snout-vent length), while the smallest sexually mature female recorded measured 310 mm SVL, suggesting that males reach sexual maturity earlier than females. Age at sexual maturity also likely varies depending on geographic location. Young are independent upon hatching.
Breeding interval: Female night snakes breed once during mating season.
Breeding season: Breeding takes place from the spring through early fall.
Range number of offspring: 2 to 6.
Average number of offspring: 3.
Range gestation period: 50 to 60 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; fertilization ; oviparous
This species is not known to exhibit any parental investment after eggs are laid.
Parental Investment: no parental involvement
Molecular Biology and Genetics
Barcode data: Hypsiglena torquata
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Hypsiglena torquata
Public Records: 2
Specimens with Barcodes: 2
Species With Barcodes: 1
Night snakes are classified as a species of "Least Concern" by the International Union for Conservation of Nature and Natural Resources due to their wide distribution and stable population size.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List Assessment
Red List Category
Red List Criteria
Relevance to Humans and Ecosystems
Texas night snakes (Hypsiglena torquata texana), a subspecies of night snake, has venom known to cause pain and possible hemorrhage in humans.
Negative Impacts: injures humans (bites or stings, venomous )
Night snakes are nocturnal and live in areas mostly uninhabited by humans; there is no known positive economic importance for humans outside of scientific research, where studies have been conducted to test venom concentration as well as to analyze the systematics of the Hypsiglena torquata species complex.
Positive Impacts: research and education
Hypsiglena torquata, commonly known as the night snake, is a species of rear-fanged colubrid. It is found throughout the southwestern and western United States, as well as in Mexico and British Columbia, Canada. The number of subspecies varies depending on the source, but it is generally accepted that there are 17.
- Hypsiglena torquata affinis Boulenger, 1894 - Boulenger's night snake
- Hypsiglena torquata baueri Zweifel, 1958 - Cedros Island night snake, Bauer's nightsnake
- Hypsiglena torquata catalinae W.W. Tanner, 1966 - Santa Catalina night snake
- Hypsiglena torquata chlorophaea (Cope, 1860) - Sonoran night snake
- Hypsiglena torquata deserticola W.W. Tanner, 1966 - desert night snake
- Hypsiglena torquata gularis W.W. Tanner, 1954 - Isla Partida night snake
- Hypsiglena torquata jani (Dugès, 1866) - Texas night snake
- Hypsiglena torquata klauberi W.W. Tanner, 1944 - San Diego night snake
- Hypsiglena torquata loreala W.W. Tanner, 1944 - Mesa Verde night snake
- Hypsiglena torquata martinensis W.W. Tanner & Banta 1962 - San Martín Island night snake
- Hypsiglena torquata nuchalata W.W. Tanner, 1943 - California night snake
- Hypsiglena torquata ochrorhyncha Cope, 1860 - spotted night snake
- Hypsiglena torquata tiburonensis W.W. Tanner, 1981 - Tiburón Island night snake
- Hypsiglena torquata torquata (Günther, 1860) - collared night snake
- Hypsiglena torquata tortugaensis W.W. Tanner, 1944 - Isla tortuga night snake
- Hypsiglena torquata unaocularis W.W. Tanner, 1944 - Clarion Island night snake
- Hypsiglena torquata venusta Mocquard, 1899 - central Baja night snake
Total length is 12–26 in (30–66 cm). It is pale gray, light brown, or beige in color, with dark grey or brown blotches on the back and sides. The night snake's head is rather flat and triangular-shaped and usually has a pair of dark brown blotches on the neck. It also has a black or dark brown bar behind the eyes that contrast against the white or pale gray upper labial scales, and the pupil of the eye is vertical. The belly is white or yellowish. Females are usually longer and heavier than males.
The night snake has been found as far north as southern British Columbia, and as far south as Guerrero, Mexico. The eastern range of the night snake extends to Texas. Still, not much is known as far as population densities and exact range due to the highly cryptic nature of the night snake.
The night snake is found in many differing types of habitat including: grasslands, deserts, sagebrush flats, chaparral, woodlands, thorn scrub, thorn forest, and mountain meadows. Both rocky and sandy areas are inhabited by night snakes, and elevations over 8,500 ft (2,600 m) have been recorded. The night snake is also known to inhabit mammal burrows.
Night snakes are known to be both crepuscular (most active at dawn and dusk), and nocturnal. They are usually seen at night while crossing roads, but can be found under rocks, boards, dead branches and other surface litter during the day. Night snakes hibernate during the winter months, and are known to aestivate during periods of the summer. They are generally most active from April to October, with peaks of activity usually occurring in June.
Although the night snake poses no threat to humans, it is slightly venomous and uses this venom to subdue its prey.
Their main prey is lizards. A study in southwestern Idaho found that the night snake's diet consisted mostly of side-blotched lizards (Uta stansburiana) and their eggs. Other prey includes juvenile rattlesnakes and blind snakes, salamanders, frogs, and large insects.
If threatened, the night snake may coil up and thrust its coils at the threat, while flattening its head into a triangular defensive shape.
Night snakes are known to be docile and easily handled. Captive night snakes have lived over 12 years.
- The Reptile Database. www.reptile-database.org
- Beolens B, Watkins M, Grayson M. 2011. The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. xiii + 296 pp. ISBN 978-1-4214-0135-5. (Hypsiglena torquata baueri, p. 19).
- Behler JL, King FW. 1979. The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Alfred A. Knopf. 743 pp. ISBN 0-394-50824-6. (Hypsiglena torquata, pp. 616-617 + Plate 586).
- Boulenger GA. 1894. Catalogue of the Snakes in the British Museum (Natural History). Volume II., Containing the Conclusion of the Colubridæ Aglyphæ. London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xi + 382 pp. + Plates I- XX. (Hypsiglena torquata, p. 210; see also H. ochrorhynchus, pp. 209-210, and H. affinis, pp. 210-211 + Plate VIII, Figure 1).
- Conant R. 1975. A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Second Edition. Boston: Houghton Mifflin. xviii + 429 pp. ISBN 0-395-19979-4 (hardcover), ISBN 0-395-19977-8 (paperback). (Hypsiglena torquata, pp. 217-218 + Plate 33 + Map 170).
- Conant R, Bridges W. 1939. What Snake Is That? A Field Guide to the Snakes of the United States East of the Rocky Mountains. (With 108 drawings by Edmond Malnate). New York and London: D. Appleton-Century. Frontispiece map + viii + 163 pp. + Plates A-C, 1-32. (Leptodeira torquata ochrorhyncha, pp. 128-129 + Plate 25, Figure 74).
- Günther A. 1860. Description of Leptodeira torquata, a new Snake from Central America. Ann. Mag. Nat. Hist., Third Series 5: 168-170 + Plate X., Figure A.
- Schmidt KP, Davis DD. 1941. Field Book of Snakes of the United States and Canada. New York: G.P. Putnam's Sons. 365 pp. (Hypsiglena ochrorhyncha, pp. 259-260, Figure 84 + Plate 29, center, on p. 349).
- Smith HM, Brodie ED Jr. 1982. Reptiles of North America: A Guide to Field Identification. New York: Golden Press. 240 pp. ISBN 0-307-13666-3. (Hypsiglena torquata, pp. 176-177).
- Stebbins RC. 2003. A Field Guide to Western Reptiles and Amphibians, Third Edition. The Peterson Field Guide Series ®. Boston and New York: Houghton Mifflin. xiii + 533 pp. ISBN 0-395-98272-3. (Hypsiglena torquata, pp. 403-404 + Plate 46 + Map 180).
- Wright AH, Wright AA. 1957. Handbook of Snakes of the United States and Canada. Ithaca and London: Comstock. 1,105 pp. (in 2 volumes). (Genus Hypsiglena, pp. 314-317, Map 30; species Hypsiglena torquata, pp. 318-330, Figures 97-101).