BC Conservation Data Centre: Species Summary
Hypsiglena chlorophaea
Desert Nightsnake
| Scientific Name: | Hypsiglena chlorophaea Cope, 1860 | ||||||||||
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| Scientific Name Synonyms: |
Hypsiglena torquata
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| English Name: | Desert Nightsnake | ||||||||||
| Classification / Taxonomy | |||||||||||
| Scientific Name - Concept Reference: | Mulcahy, D.G. 2008. Phylogeography and species boundaries of the western North American Nightsnake (Hypsiglena torquata): revisiting the subspecies concept. Molecular Phylogenetics and Evolution 46:1095-1115. | ||||||||||
| Classification Level: | Species | ||||||||||
| Taxonomy Comments: | SName changed from Hypsiglena torquata to Hypsiglena chlorophaea to align with NatureServe (May 5, 2009 - DW). English name changed to Desert Night Snake to align with Collins and Taggart 2009 and closer align with NatureServe (2010 LRR). Mulcahy (2008) identified six species of nightsnakes (H. torquata, H. affinis, H. jani, H. chlorophaea, H. ochrorhyncha, and an undescribed form from AZ and NM) all from within what was previously considered to be one 'H. torquata.' As a result, H. torquata is now restricted to MX and BC now has H. chlorophaea. (From NS, May 2009). |
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| Species Group: | Vertebrate Animal | ||||||||||
| Species Code: | R-HYCH | ||||||||||
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| Conservation Status / Legal Designation | |||||||||||
| Global Status: | G5 (Aug 2016) | ||||||||||
| Provincial Status: | S2 (Mar 2025) | ||||||||||
| BC List: | Red | ||||||||||
| Provincial FRPA list: | |||||||||||
| Provincial Wildlife Act: | |||||||||||
| COSEWIC Status: | Endangered (May 2011) | ||||||||||
| SARA Schedule: | 1 - Endangered (Jun 2003) | ||||||||||
| General Status Canada: | 1 - At Risk (2005) | ||||||||||
| Ecology & Life History | |||||||||||
| General Description: | |||||||||||
| Subspecies Comments: | The subspecies occurring in British Columbia is currently recognized as H. t. deserticola (Gregory in press), although it has been proposed as being lumped with two other subspecies, resulting in H. t. ochrorhyncha (Collins 1997). | ||||||||||
| Identification Comments: | This is a small colubrid snake with vertical eye pupils. Unlike other patterned snakes in BC, the dorsal markings are paired and offset. A dark, irregular marking occurs on the back of the neck. The dorsal background is cinnamon-coloured and the belly is light with a pearly sheen. | ||||||||||
| Global Reproduction Comments: |
In Idaho, adult females deposit a clutch of several eggs in June; males possibly are sexually mature in 1 year (Diller and Wallace 1986). | ||||||||||
| Provincial Reproduction Comments: | There is no reproduction data for BC. Reproductive data is very scarce for this species throughout its range. Males, and probably females can mate anytime during the active season, suggesting that there may be large variations depending on local environmental conditions or that eggs and/or sperm are retained until conditions are appropriate (Goldberg 2001; Diller and Wallace 1986). This also suggests that adult females may not be able to reproduce annually. Clutch sizes are known to range from 3 to 9 with smaller sizes being most common (Gregory in press). Oviposition probably occurs most often in June (Diller and Wallace 1986) . This (or earlier) should be the case as eggs in laboratory conditions take more than 50 days to hatching. | ||||||||||
| Provincial Ecology Comments: | The Night Snake is restricted to the extremely hot and rugged slopes of the south Okanagan and lower Similkameen valleys. It feeds primarily on other reptiles and their eggs which it encounters under rocks. It is thought that during summer, they are deep under rock debris to escape the extreme heat of the rocks but work their way up as the evening cools when they are active hunters of diurnal lizards. In turn, Night Snakes are probably food for other snakes, such as the Racer (Coluber constrictor), as well as bears and other mammal predators. They may occasionally be taken by owls when they are travelling on the surface. Predation by diurnal raptors does occur, probably when snakes are basking during spring and fall (Diller and Wallace 1986). Their reproductive behaviour is virtually unknown. | ||||||||||
| Migration Characteristics: (Global / Provincial) | |||||||||||
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Nonmigrant: Local Migrant: Distant Migrant: Within Borders Migrant: |
Y / Y N / Y N / N na / N |
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| Provincial Mobility & Migration Comments: | Very little is known about the movement patterns of the Night Snake. It is presumed that individuals demonstrate den site fidelity and the greatest distance that a Night Snake has been observed from a den is about 400 metres (Sarell 2005b), although individuals are probably capable of seasonal movements up to one kilometre. | ||||||||||
| Habitats: (Type / Subtype / Dependence) |
Forest / Conifer Forest - Dry / Unknown
Grassland/Shrub / Antelope-brush Steppe / Facultative - frequent use Grassland/Shrub / Grassland / Facultative - frequent use Grassland/Shrub / Meadow / Facultative - frequent use Grassland/Shrub / Sagebrush Steppe / Facultative - frequent use Rock/Sparsely Vegetated Rock / Rock/Sparsely Vegetated Rock / Facultative - frequent use Rock/Sparsely Vegetated Rock / Talus / Unknown Stream/River / Stream/River / Unknown |
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| Global Habitat Comments: | This snake generally inhabits arid and semiarid plains, canyons, and hillsides, usually in rocky, dissected or hilly terrain with sandy or gravelly soils, including areas dominated by desert, grassland, shrubland, savanna, or woodland (Hammerson 1999, Stebbins 2003). Periods of inactivity are spend under rocks or other surface cover, in crevices, or underground. In Idaho, individuals can be found under surface rocks in spring, but generally not in summer (Diller and Wallace 1986). | ||||||||||
| Provincial Habitat Comments: | In BC, Night Snakes are known to den in talus slopes and crevices in rock outcroppings. Most of their active time is thought to be spent in rugged areas where thermal gradients occur and prey (e.g. Western Skink) is abundant. There is some evidence that they also use creek corridors and the margins of lakes where amphibians and cooler temperatures are available. Egg laying in the wild has not been documented anywhere. | ||||||||||
| Food Habits: |
Carnivore: Adult, Immature
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| Global Food Habits Comments: | This snake eats mainly lizards and lizard eggs, sometimes small snakes, frogs, insects, and salamanders (Stebbins 1985, Diller and Wallace 1986). | ||||||||||
| Provincial Food Habits Comments: | There is only one feeding record of Night Snake in the wild (Lacey et al. 1996). This was a neonate Western Rattlesnake (Crotalus oreganus). Elsewhere they are known to eat primarily lizards, reptile eggs, snakes, amphibians, and young may eat insects (Gregory in press). Western Skinks (Eumeces skiltonianus) are abundant where Night Snakes live and probably make up most of their diet. | ||||||||||
| Global Phenology: |
Crepuscular: Adult, Immature
Hibernates/aestivates: Adult, Immature Nocturnal: Adult, Immature |
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| Provincial Phenology: (1st half of month/ 2nd half of month) |
Jan: Present / Present
Feb: Present / Present Mar: Present / Active Apr: Active / Reproducing May: Reproducing / Reproducing June: Reproducing / Reproducing July: Eggs present outside adult / Eggs present outside adult Aug: Active / Active Sept: Active / Active Oct: Present / Present Nov: Present / Present Dec: Present / Present |
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| Provincial Phenology Comments: | The earliest observation of a Night Snake in BC is 01 April. These were three adult females that were already 10 metres from their suspected den. Mating likely occurs in May, as this was when most males were active in Idaho and were thought to be seeking females (Diller and Wallace 1986). Night Snakes probably return to hibernacula starting in early September. One individual was captured in a drift fence on its way back to a den on 01 September. This coincides with activities observed in Idaho (Diller and Wallace 1986). The latest observation is of an individual that was further than 100 metres of any likely den on 12 October. The next latest record is 28 September of an individual near a den. | ||||||||||
| Colonial Breeder: | N | ||||||||||
| Length(cm)/width(cm)/Weight(g): | / / | ||||||||||
| Elevation (m) (min / max): |
Global:
Provincial: 340 / 1060 |
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| Distribution | |||||||||||
| Endemic: | N | ||||||||||
| Global Range Comment: | Range extends from south-central British Columbia south through Washington, Oregon, southern Idaho, eastern California, Nevada, Utah, western Colorado, northern, western, and much of southernwestern Arizona, northeastern Baja California, and northwestern mainland Mexico (Mulcahy 2008). | ||||||||||
| Authors / Contributors | |||||||||||
| Global Information Author: | Hammerson, G. | ||||||||||
| Last Updated: | Aug 12, 2009 | ||||||||||
| Provincial Information Author: | Sarell, M.J. | ||||||||||
| Last Updated: | Feb 25, 2005 | ||||||||||
| References and Related Literature | |||||||||||
B.C. Ministry of Environment. Recovery Planning in BC. B.C. Minist. Environ. Victoria, BC. |
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Collins, J.T. 1997. Standard common and current scientific names for North American amphibians and reptiles. Society for the Study of Amphibians and Reptiles. Herpetol. Circular No. 25. |
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Diller, L.V., and R.L. Wallace. 1986. Aspects of the life history and ecology of the desert night snake, Hypsiglena torquata deserticola: Colubridae, in southwestern Idaho. Southwest. Nat. 31(1):55-64. |
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Forest Practices Code. 1997. Night Snake in Species and Plant Community Accounts for Identified Wildlife: Vol. 1. B.C. Minist. For. and B.C. Environ. 184pp. |
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Goldberg, S.R. 2001. Reproduction in the Night Snake, Hypsiglena torquata (Serpentes: Colubridae), from Arizona. Texas J. Sci. 53(2): 107-114. |
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Gregory, L. 2005. COSEWIC status report on the night snake Hypsiglena torquata in Canada. in COSEWIC assessment and status report on the night snake Hypsiglena torquata in Canada. Comm. on the Status of Endangered Wildl. in Can.. Ottawa. 25pp. In press. |
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Gregory, P.T., and R.W. Campbell. 1984. The Reptiles of British Columbia. Royal B.C. Mus. Handb. 102pp. |
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Lacey, H., C.H. Shewchuck, P.T. Gregory, M.J. Sarell, and L.P. Gregory. 1996. The occurrence of the Night Snake, Hypsiglena torquata, in British Columbia, with comments on its bodysize and diet. Can. Field-Nat. 110:620-625. |
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Orchard, S.A. 1988. Species Notes for Reptiles. Vol. 3 in A.P. Harcombe, tech. ed. 1988. B.C. Minist. Environ., Lands and Parks, Wildl. Branch. 44pp. |
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Ovaska, K, S. Lennart, C Engelstoft, L. Matthias, E. Wind and J. MacGarvie. 2004. Best Management Practices for Amphibians and Reptiles in Urban and Rural Environments in British Columbia. Ministry of Water Land and Air Protection, Ecosystems Standards and Planning, Biodiversity Branch |
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Sarell, M. 2005b. Unpublished georeferenced observations of the Desert Night Snake (Hypsiglena torquata deserticola) in British Columbia. Excel 2000 database. |
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Sarell, M. 2005c. In Progress. Night Snake (Hypsiglena torquata) in Standards for Managing Identified Wildlife: Accounts, Volume 3. Biodiversity Branch, B.C. Minist. Water, Land, and Air Prot., Victoria. |
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Southern Interior Reptile and Amphibian Recovery Team. 2008. Recovery strategy for the Night Snake (Hypsiglena torquata) in British Columbia. Prepared for the B.C. Ministry of Environment, Victoria, BC. 13 pp. |
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St. John, A. 2002. Reptiles of the northwest: British Columbia to California. Lone Pine Publishing, Washington, USA. |
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The Reptiles of British Columbia: Night Snake, Hypsiglena torquata deserticola. 2004. Univ. Coll of the Cariboo, and B.C. Minist. Water, Land and Air Prot. Online. Available: http://www.bcreptiles.ca/snakes/night.htm |
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Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.
Suggested Citation:
B.C. Conservation Data Centre. 2009. Species Summary: Hypsiglena chlorophaea. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 15, 2026).