Plants and Animals

Alasmidonta marginata Elktoe

species photo
David Stagliano

Key Characteristics

The elktoe is a relatively small (to 4 inches), elongate, thin-shelled mussel. The beak is large and centrally located above the hinge line; beak sculpture is heavy and consists of three to four double-looped ridges. Lateral teeth are generally absent and one, occasionally two, thin, elongate cardinal teeth are present. The shell has a prominent posterior ridge and is yellowish green with broad dark green rays and dots. The nacre is generally white and the foot is bright orange.

Status and Rank

US Status: No Status/Not Listed
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G4 - Apparently secure
State Rank: S3? - Vulnerable (inexact or uncertain)


CountyNumber of OccurrencesYear Last Observed
Allegan 8 2019
Barry 2 2010
Bay 1 1908
Berrien 6 2009
Calhoun 14 2019
Cheboygan 1 1913
Clare 1 2002
Clinton 8 2021
Dickinson 7 2017
Eaton 5 2002
Genesee 1 Historical
Gladwin 3 1981
Gratiot 7 2015
Hillsdale 5 2003
Ingham 9 2015
Ionia 39 2021
Iron 3 2019
Isabella 2 2015
Jackson 4 2012
Kalamazoo 14 2019
Kent 16 2021
Lenawee 13 2005
Livingston 4 2016
Mackinac 1 1941
Macomb 9 2012
Manistee 1 2011
Mecosta 1 1934
Menominee 10 2011
Midland 4 2020
Missaukee 2 2002
Monroe 11 2020
Montcalm 2 2015
Newaygo 2 1934
Oakland 6 2019
Osceola 3 2002
Ottawa 1 Historical
Presque Isle 2 1952
Roscommon 1 Historical
Saginaw 4 2011
Sanilac 10 2019
Schoolcraft 1 2019
Shiawassee 5 2001
St. Clair 13 2019
St. Joseph 17 2019
Tuscola 8 2015
Van Buren 1 Historical
Washtenaw 13 2018
Wayne 9 2020

Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.


The Elktoe is found in small to large sized streams and small to medium rivers. It is a riffle species, preferring swifter currents over packed sand and gravel substrates. The Elktoe is typically only found in clean, clear water (Cummings and Mayer 1992).

Specific Habitat Needs

Rocky substrates needed in: Mainstem stream (3rd-4th order), run; Mainstem stream (3rd-4th order), riffle.

Natural Community Types

  • Mainstem stream (3rd-4th order), run
  • Mainstem stream (3rd-4th order), riffle

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management Recommendations

The elktoe needs clean, fast-flowing water to survive. Therefore, changes to its habitat, such as river impoundment, siltation and channel disturbances, including dredging, negatively affect this species. Pollution from point (industrial and residential discharge) and non-point (siltation, herbicide and surface run-off) sources is also a threat to mussels and should be limited and monitored to insure compliance with the Clean Water Act. Control of zebra mussels is critical to preserving native mussels. It is essential to protect not only the habitat of the elktoe, but also the white sucker, northern hog sucker, shorthead redhorse, rockbass and warmouth, as they serve as hosts for the glochidia.

Survey Methods

Glass-bottom bucket less than waist deep water

Survey Period: From first week of June to first week of October

SCUBA searches

Survey Period: From first week of June to first week of October

Snorkeling searches

Survey Period: From first week of June to first week of October


Survey References

  • Cummings, K.S. and C.A. Mayer. 1992. Field Guide to Freshwater Mussels of the Midwest. Illinois Natural History Survey Manual 5, Champaign. 194pp.
  • Strayer, D.L. and D.R. Smith. 2003. A Guide to Sampling Freshwater Mussel Populations. American Fisheries Society Monograph 8, Bethesda. 103pp.

Technical References

  • Carman, S.M. 2002. Special animal abstract for Alasmidonta marginata (Elktoe). Michigan Natural Features Inventory, Lansing, MI. 3pp.
  • Cummings, K.S. and C.A. Mayer. 1992. Field Guide to Freshwater Mussels of the Midwest. Illinois Natural History Survey Manual 5, Champaign. 194pp.
  • Dillon, R.T. Jr. 2000. The Ecology of Freshwater Molluscs. Cambridge University Press, Cambridge, UK. 509pp.
  • Watters, G.T. 1993. A guide to the freshwater mussels of Ohio. Revised Edition. The Ohio Department of Natural Resources, Columbus. 106 pages.