Plants and Animals

Truncilla truncata Deertoe

Key Characteristics

The deertoe is a small to medium-sized mussel (to 3.5 inches), with a sturdy, triangular shell, anteriorly off-centered beak and pointed posterior end. Shell coloration varies between pale yellow, yellow-orange, grayish-tan and green, with a pattern of dark green broken, continuous or smudged rays, sometimes displaying a distinct zig-zag pattern within the rays. Nacre is white or pink.

Status and Rank

US Status: No Status/Not Listed
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G5 - Secure
State Rank: S2S3 - Rank is uncertain, ranging from imperiled to vulnerable


CountyNumber of OccurrencesYear Last Observed
Allegan 12 2019
Berrien 10 2004
Genesee 1 2008
Ionia 2 2013
Jackson 1 2010
Kent 5 2018
Lenawee 1 Historical
Macomb 2 2012
Menominee 1 2011
Midland 2 2020
Monroe 8 2009
Muskegon 1 2004
Ottawa 5 2019
Saginaw 7 2011
St. Clair 5 2011
St. Joseph 1 2005
Van Buren 1 Historical
Wayne 12 2019

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 deertoe prefers habitats of firm sand or gravel substrates in rivers and lakes with a moderately swift current, but has been observed occasionally in smaller streams as well (Oesch 1995, Watters et al. 2009).

Natural Community Types

  • Great lake, littoral, benthic
  • Great lake, pelagic, benthic
  • Inland lake, littoral, benthic
  • Inland lake, pelagic, benthic
  • Mainstem stream (3rd-4th order), pool
  • Mainstem stream (3rd-4th order), run
  • Mainstem stream (3rd-4th order), riffle
  • River (5th-6th order), pool
  • River (5th-6th order), run
  • River (5th-6th 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 deertoe and other mussels of the unionid family are particularly vulnerable to mortality through absorption of chemical pollutants (Valenti et al. 2006, Wang et al. 2007) and heavy metals (Pip 1995,  Valenti et al. 2005, Wang et al 2007). To effectively manage for healthy populations, herbicide/pesticide spraying, agricultural and urban runoff, and the dumping of industrial waste must be controlled. Sedimentation of waterways through dredging, construction, and dam removal harms this and other aquatic species (Box and Mossa 1999). As healthy populations and distribution of host fist are necessary to deertoe glochidia, river impoundment and other such projects which alter habitat and inhibit movement, should be kept to a minimum. Preventing  the spread of zebra mussels is essential to the continued survival of all native mussels. Cleaning boat hulls and trailers, and scuba/fishing gear can help to accomplish this.

Active Period

Gravid from first week of April to first week of October

Survey Methods

Visual and tactile search using scuba or glass-bottom buckets. Tactile search (by hand) is especially important where water turbidity and pebbles/rocks make visual detection difficult. After identification, live mussels should be planted back into the substrate anterior end down. Surveys should not take place after heavy rains or during periods of high water as these conditions can make detection much more difficult. Methods of documenting survey effort include: searching a large measured area, e.g. 128m2; taking multiple quadrat samples; and recording search time (person hours). For all methods, at least some excavation of substrate (by hand, 5-10cm down) should be done to detect buried mussels. Searching a large measured area or timed searches are generally better for detecting rare species and generating a species list than quadrat sampling. These two methods allow more types of microhabitats and a larger area to be covered. Quadrat sampling is better suited for documenting changes in density and other statistical analyses at the site level (Strayer and Smith 2003).

Glass-bottom bucket less than waist deep water

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

Time of Day: Daytime
Water Level: Low Water Levels
Water Turbidity: Low Turbidity

SCUBA greater than waist deep water

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

Time of Day: Daytime


Survey References

  • Strayer, D.L. and D.R. Smith. 2003. A Guide to Sampling Freshwater Mussel Populations. American Fisheries Society Monograph 8, Bethesda. 103pp.

Technical References

  • Box, J.B. and J. Mossa. 1999. Sediment, land use, and freshwater mussels: prospects and problems. Journal of the North American Benthological Society 18:99-117.
  • Oesch, R.D. 1995. Missouri Naiades: A Guide to the Mussels of Missouri.
  • Pip, E. 1995. Cadmium, lead and copper in freshwater mussels from the Assiniboine River, Manitoba, Canada. Journal of Molluscan Studies 61:295-302.
  • Sethi, Suresh A., Andrew R. Selle, Martin W. Doyle, Emily H. Stanley, and Helen E. Kitchel. 2004. Response of unionid mussels to dam removal in Koshkonong Creek, Wisconsin (USA). Hydrobiologia 525:157-165.
  • Valenti, T.W., D.S. Cherry, R.J. Currie, R.J. Neeves, J.W. Jones, R. Mair, and C.M. Kane. 2006. Chlorine toxicity to early like stages of freshwater mussels (Bivalvia: Unionidae). Environmental Toxicology and Chemistry 25(9):2512-18.
  • Valenti, T.W., D.S. Cherry, R.J. Neves, and J. Schmerfeld. 2005. Acute and chronic toxicity of mercury to early life stages of the rainbow mussel, Villosa iris (Bivalvia: Unionidae). Environmental Toxicology and Chemistry 24(5):1242-6.
  • Wang, N., C.G. Ingersoll, I.E. Greer, D.K. Hardesty, C.D. Ivey, J.L. Kunz, W.G. Brumbaugh, F.J. Dwyer, A.D. Robers, T. Augspurger, C.M. Cane, R.J. Neves, and M.C. Barnhart. 2007. Assessing contaminant sensitivity of early life stages of freshwater mussels (Unionidae): Chronic toxicity testing of juvenile mussels with copper and ammonia. Environmental Toxicology and Chemistry. 35pp.
  • Watters, G. Thomas, Michael A. Hoggarth, and David H. Stansbery. 2009. The Freshwater Mussels of Ohio. The Ohio State University Press, Columbus. 421 pp.