E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Contia tenuis (Baird & Girard, 1852)
Sharp-Tailed Snake
Family: Dipsadidae

Species account author: Kristiina Ovaska

Photo of species

© Kristiina Ovaska  Email the photographer   (Photo ID #2639)

E-Fauna BC Static Map
Distribution of Contia tenuis in British Columbia
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Species Information

The Sharp-tailed Snake is a small, slender snake about the thickness of a pencil. Adults reach a length of about 40 cm but are more commonly under 30 cm long (COSEWIC 2009). Young snakes are only 8 – 10 cm in body (snout-vent) length at hatching. The back and sides are reddish, brownish, or sometimes slate grey; juveniles are often more brightly coloured than are adults. The last scale at the tip of the tail is modified into a thorn-like spike, from which the species gets its common name. This species can be distinguished from sympatric garter snakes by the following features: solid colour and lack of a stripe along the mid-back; smooth rather than rough appearance due to body scales that lack keels; short tail that ends in a thorn-like spike rather than a long, gradually tapering tail; and distinct black and white barring on the underside.

Biology

Reproduction

The Sharp-tailed Snake is oviparous and lays eggs. The clutch size is 3–5 eggs (Storm and Leonard 1995). Eggs of this species are rarely found, and only one case has been documented in nature: Brodie et al. (1968) found an egg-laying aggregation of 5 species of reptiles, including the Sharp-tailed Snake, in Oregon; 43 eggs of the Sharp-tailed Snake were found, representing several clutches. The young grow rapidly during their first year, but growth slows down as the snakes mature. The snakes probably reach sexual maturity at a body size (snout-vent length) of about 200 mm (COSEWIC 2009). The age at sexual maturity is poorly known but probably occurs between 3 and 6 years. Females are often larger and may mature later than do males. Recapture studies in British Columbia have shown that at least some individuals can reach an age of 9 years or more under natural conditions (Ovaska and Engelstoft 2008).
Diet

The Sharp-tailed Snake is thought to feed largely on slugs and will devour both introduced and native species of slugs (Leonard and Ovaska 1998). Their elongated, recurved teeth are considered an adaptation for feeding on these slippery prey items (Zweifel 1954).
Behaviour

The Sharp-tailed Snake is secretive and, unlike many other snakes, is seldom found out in the open. These snakes spend much of their time below the surface, probably in underground crevices or buried in the substrate. When on the surface, the snakes often hide under rocks, coarse woody debris, or other cover-objects.
Seasonal Charactertistics

In British Columbia, mating probably takes place in the spring, as aggregations containing pairs of adult males and females are often encountered at this time (Ovaska and Engelstoft 2008). Eggs are probably laid in the early summer, and the young hatch in the autumn. Very small snakes have been found in September and March on the Gulf Islands. Observations of the Sharp-tailed Snake have been documented in all months of the year, except in December in British Columbia. The snakes are most frequently found from March to early June during their peak activity period; a second, smaller peak of activity occurs in the fall, in September – October (Ovaska and Engelstoft 2008). The snakes hibernate during cold periods in the winter, and are also inactive during warm, dry periods in the summer. The timing of activities varies somewhat among years, reflecting weather conditions in particular years.

Habitat


In British Columbia, the Sharp-tailed Snake occurs in low-elevation woodland habitats dominated by Douglas-fir, arbutus and/or Garry oak. All records are from the Coastal Douglas-Fir Biogeoclimatic Zone. The snakes are often found in small openings on rocky outcrops and on warm hillsides (Engelstoft and Ovaska 1999, Wilkinson et al. 2007, COSEWIC 2009). The snakes require suitable cover for shelter, such as rocks or downed wood. Three-dimensional substrate allowing access to underground cracks and crevices is probably important, but few details are available. Patches of stable talus, especially with a southern exposure, provide important habitat for a number of reptiles, including the Sharp-tailed Snake.

Distribution


The Sharp-tailed Snake occurs from southwestern British Columbia through Washington and Oregon to southern Sierra Nevada and to the central coast of California. Its distribution is very patchy throughout the northern portion of the range in Washington and British Columbia. The species exists at the northern limits of its range in British Columbia, where it is known only from a few localities on southern Vancouver Island and the Gulf Islands. The Gulf Island localities are on North Pender, South Pender, Saltspring, and Galiano Islands (COSEWIC 2009). There are no recent records (since 1981) from Galiano. There is an additional record from the southern interior of British Columbia (near Chase; Tanner 1967), but it is probably in error (Leonard and Ovaska 1998).

Conservation


The Sharp-tailed Snake in British Columbia is at risk due to its small range, few localities, and threats to its habitats mainly from expanding urbanization and other human activities. Several localities are on federal lands or within parks (regional and national), where the habitat is protected from development; however, most sites are on unprotected private lands. The species is listed as nationally endangered and is on Schedule 1 (highest priority) of the Canada Species At Risk Act. In principle it requires protection on federal lands. On private lands, stewardship by local governments and landowners is required to protect populations of the snake. Options for local governments include incorporating the needs of the species into land use, community, and development area plans, as well as providing incentives for landowners to set aside important areas as conservation covenants. Private land owners can protect snake habitat on their lands, use snake friendly landscaping and gardening practices (Ovaska and Engelstoft 2003), and formalize their commitment with stewardship agreements with conservation organizations or establish conservation covenants, as appropriate for their particular situation.

Taxonomy


This species is currently the only representative of the genus Contia. However, genetic (Feldman and Spicer 2002) and morphological (Hoyer 2001) evidence have revealed the presence of two different forms within the nominal species C. Tenuis: a long-tailed form in coastal California and parts of southern Oregon, and a shorter-tailed form in the interior of California, most of Oregon, Washington, and British Columbia. The second, southern species has not been described formally. The Sharp-tailed Snake was formerly placed in the large cosmopolitan family Colubridae, which recently has been split. Its placement in the family Dipsadidae follows standard nomenclature as listed by Collins and Taggard (2009).

Comments


This snake is totally harmless – except for slugs, its main prey – but should not be handled unnecessarily. A photo taken from above usually provides sufficient information to document presence and confirm identification.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS1S2RedE (Nov 2009)
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2022-08-13 8:25:15 PM]
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