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Morro Shoulderband Snail

Morro Shoulderband Snail


The Morro Shoulderband Snail (Helminthoglypta walkeriana) is an endangered species endemic to San Luis Obispo County. It was first identified in 1911 living in areas south of Cayucos. Since then its range has decreased considerably, due largely to habitat destruction and degradation. According to the U.S. Fish and Wildlife Service “The Morro shoulderband snail is threatened principally by habitat destruction and degradation due to increasing development, invasion of non-native plant species (i.e. veldt grass), senescence of dune vegetation, and recreational use (e.g. off-road vehicle activity). Competition with the brown garden snail (Helix aspersa), molluscicides, and increased likelihood of extinction due to the small size and isolation of populations are potential threats.”

Unlike the brown garden snail (European garden snail), the Morro shoulderband is not a garden pest. It feeds on decaying vegetation and is usually found in moist areas under bushes or vegetative duff. Recently, park staff discovered the snail even under the duff of such non-native species as veldt and European beachgrass. It is also commonly found under iceplant, another invasive non-native. Presumably, the native vegetation with which the species evolved would provide better habitat, at least when compared to veldt and beachgrass.

The snail was listed as endangered in 1994, and critical habitat was designated for it in February of 2001. Much of that habitat lies within Montana de Oro, and in several places it coincides with veldt grass removal projects. Because of this, State Parks, in cooperation with Fish and Wildlife, has begun surveying these areas for snails and also setting up semi-permanent plots in an attempt to track the population. It is hoped that restoring these areas to a more native condition will in the long run provide increased habitat for the snail.

One other significant discovery has been made with regard to this species. It had been thought until recently that the population was restricted to areas south of Morro Bay. In 2001, however, a population was discovered at Morro Strand State Beach near the highschool and near the Cloisters development. The extent and density of this population is not yet known, but its presence could be significant given the small numbers of Morro shoulderband snails left in existence.

Below is a picture of three snails found in the San Luis Obispo area. The Morro shoulderband and the Big Sur shoulderband have a similar appearance but can be distinguished by size, shape, and by the fact that the Morro has incised grooves which run roughly parallel to the dark band that characterizes both species.

snails of the area
From left to right: Morro Shoulderband Snail, European Garden Snail, Big Sur Shoulderband Snail


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