The Sharp-tailed Snake (Contia tenuis) is one of two species in the genus Contia, both of which are endemic to western North America. The Sharp-tailed Snake occurs along the west coast of North America from the northern parts of California to the southern parts of British Columbia. In BC, the species is known from the southern tip of Vancouver Island and the Gulf Islands. There is one confirmed site on the mainland, from the Pemberton area (see map below). There is an old, unconfirmed record from near Chase, the validity of which is questionable.
The Sharp-tailed Snake spends much of its life underground and is rarely seen. Its elusive behaviour makes it difficult to study, and as a result little is known about its habitat, biology and distribution. This snake is rarely found basking out in the open away from cover objects during the day, but it can occasionally be spotted on the surface during hot summer nights, based on information from Washington, where it has been seen crossing roads. The snakes' diet is thought to consist mainly of slugs, both introduced and native.
In BC, the peak seasons when the snakes can be found on the surface are in spring (March to early June) and in late September - October. The fall season is dependent on weather, and in years with warm and dry fall weather there might not be any activity near the surface.
Complexity of the substrate is important to the Sharp-tailed Snake as it lives most of the year underground. Talus patches with layers of rocks, including pebbles and gravelly substrates, is provides preferred 3-dimensional habitat. The snakes use piles of decaying wood and in residential areas compost piles. The Sharp-tailed Snake can be frequently found under cover objects such as flat rocks, woody debris, or pieces of plastic that are heated by the sun.
Female Sharp-tailed Snakes lay an average of 3-5 eggs, and in BC egg-laying may occur sometime in early summer. Only a few nests have been unearthed, and none have been found in BC. However, hatchlings (about 10 - 12 mm in snout vent length) have been found in the fall, suggesting that the eggs hatch the same year they are laid.
The distribution of Sharp-tailed Snakes is notoriously uneven across the landscape and even within sites where they do occur. There is some evidence from BC that they congregate in "hot-spots". These tend to be south to southwestern sloping talus areas with some protection from prevailing winds. Sharp-tailed Snakes appear to have small home ranges, as shown by tracking a few individuals; most relocations of individuals were within 15 m of each other. One snake moved 127 m from a southwest facing forest edge through a forest to a talus patch. More typically, slight seasonal shifts in habitats are likely to occur as the snakes disperse from their overwintering sites to the surrounding landscape.
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Status in Canada
The Sharp-tailed Snake is listed as Endangered in Canada (COSEWIC 2009) and is on Schedule 1, the official list of species at risk in Canada, under the federal Species at Risk Act. It is Red-listed in British Columbia (2012) and has the highest priority in the BC Ministry of Environment Conservation Framework. The global rating considers the species secure (G5, NatureServe 2010), based mainly on its core distribution in northern California and southern Oregon where it remains fairly common.
The main threat to the Sharp-tailed Snake in BC is from habitat loss, degradation and fragmentation associated with residential development and roads. Most known populations are within highly developed areas of BC, with growing rural and urban areas and accompanying infrastructure.
How to Identify the Sharp-tailed Snake
The Sharp-tailed Snake is a small snake, with adults usually less than 30 cm in total length, with females are larger than males; they may occasionally reaches a total length of 40 cm. The underside of the Sharp-tailed Snake has distinctive black and white barring, which is diagnostic. The dorsal (upper side) colour of an adult Sharp-tailed Snake is generally brick red with a faint lateral (along the side) line. Juvenile Sharp-tailed Snakes are brighter red-brown, often with an orange lateral line. The body scales do not have a keel, which all the garter snakes in BC have, and as a result the skin appears smooth. The tip of the tail has a thorn-like spine that is different from any of the other snakes in BC; in contrast, garter snakes have long tails that gradually taper to a point but lack the thorn-like tip.
An identification sheet that separates the Sharp-tailed Snake and the garter snakes in south-western BC can be found here:: http://hat.bc.ca/attachments/008_STS_IDkey.pdf
More information about the Sharp-tailed Snake
Sharp-tailed Snakes can co-exist with humans if their habitat requirements are met and important habitat features and patches are protected. This can be done by incorporating natural habitat areas into landscape or garden design. In new developments, natural habitats patches should be set aside and not be altered. Habitat can also be restored in gardens of existing developments by planting native plants and creating refuges for the snakes. A few attempts to restore habitat have been conducted by constructing articificial talus (layers of rock) and free-stack rock walls, but their effectiveness for enhancing habitat for snakes is undocumented.
Habitat Restoration and Enhancement
Before habitat restoration is attempted, it is important to conduct surveys to determine if the Sharp-tailed Snake is present. The snakes do not travel large distances, and it is unlikely that you can attract them if they are not already in your neighbourhood. Restoring or enhancing Sharp-tailed Snake habitat generally includes re-establishing complexity of the substrate, allowing the snakes to move up and down vertically. This can be done by crating rock piles, composed of different sizes of rocks, free-stack rock walls, or by heavy mulching with compost or leaves. Care should be taken to avoid introducing non-native species; source the materials as locally as possible. Piles of about one to two cubic meters of smaller rocks or decaying wood should be positioned in the open, so the sun can reach them, thus creating small south to south-west facing slopes.
Keep your lawn short to avoid dense grass mats because the Sharp-tailed Snake has been known to inhabit these mats. There are examples of Sharp-tailed Snakes being killed by weed-whackers during clean-up of long-grassed lawns. If the lawn has grown out of control, early winter (Nov and Dec) is the time to cut it because all the snakes will have moved to hibernation areas.
In gardens with known Sharp-tailed Snake populations, it is important to leave "messy" areas where the snakes can hide. This means that you should leave pieces of wood, flat rocks or piles of debris. Garter snakes and Sharp-tailed Snakes both readily inhabit areas with long grass, so leave a few strips along the edge of the lawn to attract these useful slug eaters to your garden.
Research and Survey Methods
Best Management Guidelines