While walking along the South Beach Trail in Pacific Rim National Park Reserve, I paused to examine a small snail gliding across a decaying leaf. Its finely-hairy shell, ridged and glistening with moisture, caught my eye. I suspected I had found a Northwest Hesperian (Vespericola columbianus)—a terrestrial snail native to the Pacific Northwest.
Field Marks and Identification of the Northwest Hesperian
The Northwest Hesperian is a member of the family Polygyridae, a group of air-breathing land snails. It is relatively small, with adult shells typically ranging from 10 to 17 mm in diameter. The shell is yellowish-brown to dark brown and covered in tiny dense hairs. The umbilicus of this species is perforate and narrow, partially covered by the apertural lip.
The snail’s small size, flattened shell and periostracal hairs are good starting points to identification. My hesitation with a conclusive identification is based on the size of the opening of the umbilicus (center hole). The umbilicus of the snail I observed seems to be smaller than the opening of other photographs of this species. The aperture (shell opening) is oval, slightly oblique and somewhat ear-shaped. The peristome (outer apertural lip) is thin and has a flared lip.
The snail’s body has a noticeable texture and is tan in colour, darker and greyer on the body-stalk. When active, it extends well beyond the shell. Like other pulmonate snails and slugs, it has two pairs of tentacles. The upper pair bears eyes at the tips, which are used for sensing light and movement. The bottom pair of tentacles are used for touch and taste. Given all these features, I am fairly confident that this snail is indeed Vespericola columbianus.
The Challenges of Identifying Snails
Small snails are notoriously hard to identify. South Coast Conservation Program provides a simple identification sheet that can be a helpful starting point. In addition, the Oregon Department of Agriculture has a number of guides to help identify snails and slugs, including some very useful posters. Dan Nelson over at 10,000 Things of the Pacific Northwest also provides a detailed overview of the complications and field marks to look for with the Northwest Hesperian.
Naturalists in British Columbia (and the rest of Canada) should look for copies of the book Identifying Land Snails and Slugs in Canada by F Wayne Grimm, Robert G Forsyth, Frederick W Schueler and Aleta Karstad. This magnificent book is available as a free, downloadable pdf. When the book was first published, it was possible to get free copies of it!
Northern Hesperian: Natural History and Behaviour
The Northern Hesperian is a detritivore, feeding primarily on various plant leaves, and decaying organic matter. This diet plays a crucial role in nutrient cycling, helping decompose organic matter and enrich the soil. Vespericola columbianus is primarily a nocturnal species and typically aestivates during the day—sealing itself inside its shell with a mucus membrane called an epiphragm to conserve moisture.
Snails and slugs are hermaphroditic, possessing both male and female reproductive organs. Mating typically occurs in moist conditions. Eggs are laid in damp soil or under leaf litter, where humidity supports their development.
Where to Find the Northwest Hesperian: Habitat and Distribution
The Northwest Hesperian is found in the coastal temperate rainforests of the Pacific Northwest, including British Columbia, Washington, Oregon, and southeastern Alaska. It typically occurs on the west side of the Coast Range on Vancouver Island and the west side of the Cascade Range in British Columbia, Washington, and Oregon. The genus name of the snail is from the Latin Vespericola which means “dwelling in the west.” The species name columbianus refers to the Columbia River, where the type specimen was collected.
This tiny snail prefers moist, shaded environments such as deciduous and mixed woodlands. It is often under logs and in leaf litter. The Northwest Hesperian can also occur under driftwood in grassy areas close to the ocean. As decomposers, they play a quiet but critical role in the coastal forest ecosystem. Because it is so small, it is easily missed!
Slowly Writing Stories on the Forest Floor
There’s something meditative and worthwhile about slowing down enough to notice the tiny lives that coexist in the complex ecosystem of the coastal rain forest. If you’re exploring the Pacific Northwest and come across a small, dark snail with a finely-bristled shell in the leaf litter, take a closer look—you might be in the company of Vespericola columbianus. The Northwest Hesperian may not be flashy, but its role in the ecosystem and its quiet resilience makes it a subject worthy of admiration.Â
