Truncilla truncata
Image of Truncilla truncata



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

  • State Status: SC
  • State Rank: S2S3
  • Global Rank: G5


County NameNumber of OccurrencesYear Last Observed
St. Clair42011
Van Buren1
Distribution map for Truncilla truncata

Updated 5/15/2018. 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


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.


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).

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at [Accessed Aug 17, 2018]


Technical References

Facebook link