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Montana Animal Field Guide

Montana Field Guides

New Zealand Mudsnail - Potamopyrgus antipodarum

Exotic Species (not native to Montana)

Global Rank: G5
State Rank: SNA

Agency Status


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General Description
This is an introduced species to MT with an expanding distribution in the Missouri, Yellowstone, and Bighorn Rivers. It is not known in Montana west of divide. In Montana this species was first discovered in the Madison River above Hebgen Reservoir in 1995 (Gustafson 2001). However, the very large population present at that time indicataes that the introduction was a few years earlier. It is a native of New Zealand, but long established in Australia and Europe. This species has been known in North America since 1987 in the Snake River basin of Idaho

Diagnostic Characteristics
Taxonomically, New Zealand mud snails are in the snail family Hydrobiidae. Hydrobiids can be distinguished from other aquatic snail families by having dextral (opening to the right with the spire pointing away from you) shells with an operculum (a hard calcareous flat that can seal the opening of the shell). New Zealand mud snails are small (~ 1-2 mm) and generally dark colored

Summary of Observations Submitted for Montana
Number of Observations: 5

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Relative Density



(Observations spanning multiple months or years are excluded from time charts)

New Zealand mud snails appear to prefer flowing water habitats with stable flows. Springs, spring creeks, and river sections downstream from dams are all places that they thrive in. They are most typically found on larger cobble substrates or on pieces of wood.

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Citation for data on this website:
New Zealand Mudsnail — Potamopyrgus antipodarum.  Montana Field Guide.  .  Retrieved on , from