Hypsiglena torquataNight Snake

Geographic Range

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. (Uetz and Hallermann, 2012; Weaver, 2008)


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. (Goldberg, 2001; Hammerson, et al., 2012; Weaver, 2008)

  • Range elevation
    0 to 2650 m
    0.00 to 8694.23 ft

Physical Description

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. (Diller and Wallace, 1986; Gregory, 1996)

  • Sexual Dimorphism
  • female larger
  • Range length
    30 to 66 cm
    11.81 to 25.98 in


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. (Goldberg, 2001; Pizzato, et al., 2008)


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. (Goldberg, 2001; Pizzato, et al., 2008)

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. (Diller and Wallace, 1986; Dundee, 1950; Goldberg, 2001; Lieb and Clark, 1973; Pizzato, et al., 2008)

  • 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
  • Range gestation period
    50 to 60 days

This species is not known to exhibit any parental investment after eggs are laid. (Lieb and Clark, 1973)

  • Parental Investment
  • no parental involvement


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. ("Hypsiglena torquata: Night Snake", 2012; Weaver, 2009)

  • Range lifespan
    Status: captivity
    12.2 (high) years


Night snake are crepuscular and nocturnal, and are found in burrows or rocky crevices during the day. They are solitary animals outside of breeding, though any particular area may have multiple night snakes as residents. (Diller and Wallace, 1986)

Home Range

There is no evidence that night snakes have specified home ranges or defend territories. (Diller and Wallace, 1986)

Communication and Perception

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. (Mulcahy, 2007; Roots, 2006)

Food Habits

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. (Diller and Wallace, 1986; Rodriguez-Robles, et al., 1999)

  • Animal Foods
  • amphibians
  • reptiles
  • eggs
  • carrion
  • insects
  • terrestrial non-insect arthropods


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. (Diller and Wallace, 1986; "Night Snake: Hypsiglena torquata", 2012)

Ecosystem Roles

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. (Diller and Wallace, 1986; Weaver, 2008)

Economic Importance for Humans: Positive

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. (Weaver, 2008)

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

Texas night snakes (Hypsiglena torquata texana), a subspecies of night snake, has venom known to cause pain and possible hemorrhage in humans. (Vest, 1988)

  • Negative Impacts
  • injures humans

Conservation Status

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. (Hammerson, et al., 2012)


Samuel Burrell (author), Hobart & William Smith Colleges, Jim Ryan (editor), Hobart & William Smith Colleges, Jeremy Wright (editor), University of Michigan-Ann Arbor.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


uses sound to communicate


an animal that mainly eats meat


flesh of dead animals.


Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.


uses smells or other chemicals to communicate


active at dawn and dusk

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.


An animal that eats mainly insects or spiders.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


having more than one female as a mate at one time

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).


movements of a hard surface that are produced by animals as signals to others


uses sight to communicate


2012. "Hypsiglena torquata: Night Snake" (On-line). Encyclopedia of Life. Accessed February 25, 2013 at http://eol.org/pages/963474/overview.

Walter Feller. 2012. "Night Snake: Hypsiglena torquata" (On-line). Digital Desert. Accessed February 25, 2013 at http://digital-desert.com/wildlife/snakes/night-snake.html.

Diller, L., R. Wallace. 1986. Aspects of the life history and ecology of the desert night snake, Hypsiglena torquata deserticola: Colubridae, in southwestern Idaho. Southwestern Naturalist, 31: 55-64. Accessed February 20, 2012 at http://www.jstor.org/stable/3670960?seq=1.

Dundee, H. 1950. Additional Records of Hypsiglena from Oklahoma, with Notes on the Behavior and the Eggs. Herpetologica, 6/2: 28-30. Accessed February 20, 2012 at http://www.jstor.org/stable/10.2307/3889887.

Goldberg, S. 2001. Reproduction in the night snake, Hypsiglena torquata (Serpentes: Colubridae), from Arizona. The Texas Journal of Science, 53/2: 210. Accessed February 20, 2012 at http://www.freepatentsonline.com/article/Texas-Journal-Science/78359396.html.

Gregory, P. 1996. The occurrence of the night snake, Hypsiglena torquata, in British Columbia, with comments on its body size and diet. Canadian Field Naturalist, 110/4: 620-625. Accessed February 20, 2012 at http://apps.webofknowledge.com/full_record.do?product=UA&search_mode=GeneralSearch&qid=1&SID=3AmN75Jgj6fF7b7mnci&page=1&doc=1.

Hammerson, G., D. Frost, G. Santos-Barrera, J. Vasquez Díaz, G. Quintero Díaz. 2012. "Hypsiglena torquata" (On-line). The IUCN Red List of Threatened Species. Accessed February 23, 2013 at http://www.iucnredlist.org/details/full/63823/0.

Lieb, C., D. Clark. 1973. Notes on reproduction in the night snake (Hypsiglena torquata). The Southwestern Naturalist, 18: 248-252. Accessed February 20, 2012 at http://www.jstor.org/stable/10.2307/3670427.

Mulcahy, D. 2007. Molecular systematics of neotropical cat-eyed snakes: a test of the monophyly of Leptodeirini (Colubridae: Dipsadinae) with implications for character evolution and biogeography. Biological Journal of the Linnean Society, 92/3: 483-500. Accessed February 20, 2012 at http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8312.2007.00855.x/full.

Pizzato, L., M. Cantor, J. de Oliveira, O. Marques, V. Capovilla, M. Martins. 2008. Reproductive ecology of dipsadine snakes, with emphasis on South American species. Herpetologist's League Journals, 64/2: 168-179. Accessed February 20, 2012 at http://www.hljournals.org/doi/abs/10.1655/07-031.1.

Rodriguez-Robles, J., D. Mulcahy, H. Greene. 1999. Feeding ecology of the desert nightsnake, Hypsiglena torquata (Colubridae). Copeia, 1: 93-100. Accessed February 25, 2013 at http://faculty.unlv.edu/jrodriguez/15.pdf.

Roots, C. 2006. Nocturnal Animals. Westport, CT: Greenwood Press. Accessed February 25, 2013 at http://books.google.com/books?id=YlUQPtK8J9kC&pg=PA38&lpg=PA38&dq=hypsiglena+torquata+vision&source=bl&ots=NYO9rntM0y&sig=eqAetmo3mY9CNbXUFe-CJAv-uPs&hl=en&sa=X&ei=nZYrUce9N4i60QHFhoGYCQ&ved=0CCYQ6AEwBA#v=onepage&q&f=false.

Uetz, P., J. Hallermann. 2012. "Hypsiglena torquata (GÜNTHER, 1860)" (On-line). The Reptile Database. Accessed February 23, 2013 at http://reptile-database.reptarium.cz/species?genus=Hypsiglena&species=torquata.

Vest, D. 1988. Some effects and properties of Duvernoy's gland secretion from Hypsiglena torquata texana (Texas night snake). Toxicon, 26/4: 417-419. Accessed February 20, 2012 at http://www.sciencedirect.com/science/article/pii/0041010188900128.

Weaver, R. 2008. Distribution, abundance, and habitat associations of the night snake (Hypsiglena torquata) in Washington state. Northwestern Naturalist, 89: 164-170. Accessed February 20, 2012 at http://www.academia.edu/378705/Distribution_abundance_and_habitat_associations_of_Hypsiglena_chlorophaea_in_Washington_State.

Weaver, R. 2009. Microhabitat and prey odor selection in Hypsiglena chlorophaea. Copeia, 2009/3: 475-482. Accessed February 20, 2012 at http://www.asihcopeiaonline.org/doi/abs/10.1643/CE-08-094.