Iowa Small Mammal Project

Data compiled by John Bowles
Web site and data processing by John Bowles and David Dobson
© 2006-2009

We present a data set of approximately 12,000 records of small mammals collected in Iowa between 1972 and 1993. When possible, the records include species, coordinates of observation or capture, gender, reproductive status and data, standard measurements (Hall 1962) and other identifiable characteristics. We also include habitat information and GIS data and maps for download.

Recommended Citation
Bowles, J.B., D.M. Dobson, and R.P. Lampe, 2009.  Iowa small mammal database (online data archive),

Flora and fauna data collecting is sporadic and depends largely on the interests of local individuals and institutions. Our work in Iowa began in the 1970’s when Bowles joined the Central College faculty in Pella, Iowa. Lampe started his work in 1976 at Buena Vista College (now university).

Figure 1.  This figure shows all small mammals observed and identified by Bowles and Lampe (or their trained students) from 1972 to 1993.  Included are specimens given to us by others from Iowa for identification.

Our activity peaked in the late 1970s and early 1980s when general interest in the State’s natural history increased. That interest was fueled by generation of Federal and State Endangered Species lists, Earth Day I, formation of the Iowa Natural History Association and its sponsorship both of symposia at Iowa Academy of Science meetings and of annual forays to counties where data were minimal or lacking. The first foray was to Fremont County in 1977 (Bowles 1977, Roosa 1977). Perhaps the most significant factor increasing interest in Iowa’s natural history, however, was the leadership of Dean M. Roosa, then naturalist for the Iowa Preserves Board.

Figure 2.  Map of sampling sites for small mammals recorded by Bowles or Lampe (or their trained students) from 1972 to 1993.  Note: In order to show sampling density in heavily sampled areas of this map, locations of samples were randomly spread out by up to 10 km from their actual locations.

Our primary purposes for developing this website are to: 1) make our data available to anyone seeking biological and ecological information about Iowa’s small mammals, 2) provide our capture locality points in GIS format, useful for generating maps showing overall distribution when combined with other information (see cautionary note below) 3) provide information that any teacher can use in developing class exercises using real data. Cautionary note: Distribution maps generated with our data alone simply show where we collected. To gain a more complete understanding of past and present patterns of distribution, it is imperative that researchers both consult the literature for past records and conduct their own field studies. Furthermore, care must be exercised when using our data since collecting methods varied according to the needs of our particular studies (e.g., live-traps, pit traps, snap-traps). 
Additional information about collecting sites and methods is in John Bowles’ field notes housed in the Museum of Natural History, University of Iowa, Iowa City.

Sorting Keys
The dataset can be filtered based on a number of parameters, including:

Habitat type:

You may also download the entire data set in Excel format by clicking here.

Explanatory notes
Data are presented in table form with one animal per row.  For each record, a variety of data is presented.  The species are listed by codes with two letters for genus and two letters for species as listed in Table 1.  See Table 2 for descriptions of the data types (columns of the data set).  The abbreviation NR (No Record) indicates that the data type was not recorded, and NA indicates Not Applicable (e.g. male reproductive measurements on female specimens, forearm and metacarpal measurements for non-bat specimens).

Table 1. Species listing

Code Name Common names
EPFU Eptesicus fuscus Big brown bat
LABO Lasiurus borealis Red bat
LACI Lasiurus cinereus Hoary bat
LANO Lasionycterus noctivagans Silver-haired bat
MYLU Myotis lucifugus Little brown bat
MYSE Myotis septentrionalis Northern big-eared bat
MYSO Myotis sodalis Indiana bat
NYHU Nycticeius humeralis Evening bat
PISU Pipistrellus subflavus Eastern pipstrelle bat
BLBR Blarina brevicauda Northern short-tailed shrew
BLHY Blarina hylophaga Elliot's short-tailed shrew
CLGA Clethrionomys gapperi Red-backed vole
CRPA Cryptotis parva Least shrew
GEBU Geomys bursarius Plains pocket gopher
MIOC Microtus ochrogaster Prairie vole
MIPE Microtus pennsylvanicus Meadow vole
MIPI Microtus pinetorum Woodland vole
MUER Mustela erminea Ermine
MUMU Mus musculus House mouse
ONLE Onychomys leucogaster Northern grasshopper mouse
PEFL Perognathus flavescens Plains pocket mouse
PELE Peromyscus leucopus White-footed mouse
PEMA Peromyscus maniculatus Deer mouse
RANO Rattus norvegicus Norway rat
REME Reithrodontomys megalotis Western harvest mouse
SCAQ Scalopus aquaticus Eastern mole
SOCI Sorex cinereus and/or Sorex haydeni* Masked shrew and Hayden's shrew
SYCO Synaptomys cooperi Southern bald lemming
TAST Tamias striatus Eastern chipmunk
ZAHU Zapus hudsonius Meadow jumping mouse
* cannot distinguish without observation of skull (Whidden et al., 200?)

Table 2.  Data types presented



Species Four-letter code for genus and species - See Table 1)
Year Year captured
Month Month captured
Day Day captured
Date Full date of capture
County County where captured (all in Iowa)
X-coordinate UTM Zone 15, in meters (eastings)
Y-coordinate UTM Zone 15, in meters (northings)
HabitatCode One-letter code for habitat type (see Table 3 below)
ReferenceCode Abbreviated reference code for study (see Table 4 below)
Age Developmental stage of specimen
Sex Gender (male, female, unknown)
CaptureMethod Method used for capture
Specimen Disposition of capured specimen (released, discarded, preserved, etc.)
Total Length Total length in mm
Tail Length Tail length in mm
Hind Foot Length Hind foot length in mm
Ear Length Ear length in mm
Weight Weight in grams
Molt Molt stage
Forearm Forearm length in mm (bats only)
MCIII Metacarpal III length (bats only)
MCV Metacarpal V length (bats only)
Male external External analysis of reproductive status
TestisLength Testis length in mm (male only)
TestisWidth Testis width in mm (male only)
Epididymus Convolution status of epididymus tubules (male only)
SemVesicles Development of seminal vesicles (male only)
Mammae Size and status of mammae (female only)
TotalEmbryos Total embryos counted (female only)
Embryo length Crown to rump in mm (female only)
Pregnant Pregnancy status (female only)

Table 3. Habitat codes used

Code Habitat Description
G Tallgrass prairie Native or reconstructed; includes pure or mixed stands of switchgrass, big and little bluestem, Indian grass, and forbes (native and/or introduced).
P Pasture or Grassy field Introduced grasses: chiefly bluegrass, brome, or Reed's canary grass; solid or mixed with clover and/or forbs/weeds; active or abandoned (oldfield); upland, bottomland, fencerow, creekside, or roadside ditch.
D Deciduous woods Forest, woodlot, riparian, edge
H Hayfield Alfalfa; usually with clover and/or sweet-clover
R Railroad Rights of Way Active or abandoned; at least some grasses (native or introduced, annual or perennial)
C Cropland Active or idle corn, unspecified
S Sand prairie Native grasses on sandy substrate, usually shorter than in other prairie types
L Lake shore Lake shore (chiefly Red Rock Lake, which is flood-controlled)
W Cattails Cattail patch
M Marsh Marsh or slough
K Marijuana patch Patch of wild marijuana plants
B Buildings In or under buildings or structures
F Coniferous forest Evergreen woods, often pine trees
U Cavern Underground space such as cave or mine (not merely a burrow)
E Bridge Wooden bridge bat roost
X Not recorded Not recorded, not classified, or impossible to determine from description

Maps and Interpretation

We hope that the data set provided will offer opportunities for a variety of different types of research.  Below is an example of a question that could be addressed - species breakdown between prairie and forested areas.

GIS Datasets

We plan to offer the data in GIS format in the future.

Sample Exercises for Biology Classes

Here are some sample activities that could be completed with the data provided.  Some proficiency with Excel or other database software might be helpful.

  • Compute size statistics - Compare mean tail length distribution of Peromyscus leucopus (PELE) with Peromyscus maniculatus (PEMA) and forearm length of Eptesicus fuscus (EPFU) with any of the Myotis species.  Students can use a T-test to show that the tail lengths are significantly different, and devise a classification scheme based on the means and standard deviations.

  • Determine likely mammal population for a given habitat, e.g. bluegrass field, using the habitat data provided.

  • Are jumping mice more likely to give birth in the summer or the winter?  Use the reproductive statistics to ascertain reproductive patterns.

  • What species are likely to be found along a recently flooded shoreline?  This would reflect which species are the first to invade a newly exposed lakeshore.

  • Compare testes sizes at different times of year (e.g. June vs. September) for any given species.  What percent of the population has reached sexual maturity at these times of year?  What does this indicate about the reproductive cycle?

  • Using techniques like those in previous exercises, compare reproductive cycles of different species.  Are there differences?  Can they be explained?

  • Are male Peromyscus leucopus (PELE) more likely to be caught in July or August?  This is trickier than it seems, because collecting rates were not necessarily identical during the year.  One technique would be to compare percentages of PELE of all organisms sampled, and examine changes in their relative proportion of the records.  This can be compared with the reproductive cycle and with the maturity of the captured animals.


John Bowles produced a detailed study of Iowa mammals for his dissertation.  This covers the period prior to 1971, when our data here begin.  This work includes detailed distributional records, which cannot be inferred from the data here, and a variety of other maps and data sets.  Please see:

Bowles, J.B., 1975.  Distribution and Biogeography of Mammals of Iowa, Special Publications of the Museum of Texas Tech University No. 9, Texas Tech Press, Lubbock, 184 pp.

The first attempt at a comprehensive study of Iowa mammals was Thomas G. Scott's work:

Scott, T.G., 1937.  Mammals of Iowa.  Iowa State College Journal of Science 12:43-97.

Other articles referenced in the text above include:

Bowles, J.B., 1977.  Update of mammals of Fremont County, Iowa Bird Life, 47(4):138-147.

Bowles, J.B., 1992.  History of mammal study in Iowa, Jour. Iowa Acad. Sci 99(4):76-77.

Hall, E. R., 1962, Collecting and Preparing Study Specimens of Small Vertebrates, Mus. of Nat. Hist.

Lampe, R.P., and J.B. Bowles, 1985.  Annotated checklist of the mammals of the Loess Hills of western Iowa.  Proc. Iowa Acad. Sci. 92(5):176-179.

Roosa, D.M., 1977.  The first Iowa foray.  Iowa Bird Life, 47(4):119-123.

The following table shows the individual studies that are included in the database.  If they were published, the appropriate journal reference is given.

Table 4. Reference codes explained

Reference Code



Specimens collected by L.A. Braband in Story County in 1979.  Unpublished Iowa State University M.S. thesis: Braband, L.A. 1979, Railroad right-of-ways as wildlife habitat.


Specimens collected by John Bowles and Nixon Wilson in Webster County, 1978-1979.  Unpublished.


Specimens collected by Rick Lampe and Nixon Wilson in Webster County, 1978-1979.  Unpublished.


Specimens collected in western Iowa by Bryon Clark and John Bowles in Gleason-Hubel Wildlife Area and Turin Loess Hills Preserve, 1979.  Study funded by Iowa Department of Natural Resources.  Unpublished internal report to DNR.


Bat specimens collected by Byron K. Clark, John Bowles, and Brenda S. Clark in 1982.  Published in Clark, B.K., J.B. Bowles, and B.S. Clark, 1987, Summer status of the endangered Indiana Bat in Iowa, Am. Midl. Nat. 118:32-39, and Clark, B.S., J.B. Bowles, and B.K. Clark, 1987, Summer occurrence of the Indiana bat, Keen’s myotis, evening bat, silver –haired bat and eastern pipistrelle in Iowa, Proc. Iowa Acad. Sci 94:89-93.


Specimens collected by Janet Voight in or near Wilcox Wildlife Area, Marion County, and Hull Wildlife Refuge, Mahaska County in 1976.  Published in Voight, J., and D.C. Glenn-Lewin, 1979, Stripmining, Peromyscus and other small mammals in southern Iowa.  Proc. Iowa Acad. Sci. 86:133-136.


Annual foray, organized by Iowa Dept. of Natural Resources.  Fremont County.


Annual foray, organized by Iowa Dept. of Natural Resources.  Allamakee County.


Annual foray, organized by Iowa Dept. of Natural Resources. 


Annual foray, organized by Iowa Dept. of Natural Resources. 


Annual foray, organized by Iowa Dept. of Natural Resources. 


Annual foray, organized by Iowa Dept. of Natural Resources. 


Annual foray, organized by Iowa Dept. of Natural Resources. 


Annual foray, organized by Iowa Dept. of Natural Resources. 


Annual foray, organized by Iowa Dept. of Natural Resources. 


Annual foray, organized by Iowa Dept. of Natural Resources. 


Annual foray, organized by Iowa Dept. of Natural Resources. 


Specimens collected by Jerry Choate et al., in southwestern Iowa in 1979.  Unpublished.


1978 Department of Natural Resources study in western Iowa conducted by Neil Heiser.  Unpublished.






Specimens collected by Nixon Wilson and John Bowles in Linn County in 1981.  Unpublished.


Specimens collected by Pettinger family at Pettinger farm in Lucas County in 1977-78.  Unpublished.


Specimens collected by John Bowles and students near Pella, IA, 1979-1985.  Unpublished.


Specimens collected by John Bowles and students in Monona County, Pella, IA, 1978-1979.  Unpublished.


Specimens collected by John Bowles et al. at Ogrens Farm in Marion County, 1974-80.  Unpublished.


Specimens collected by Rick Lampe and others at Pilot Knob State Park, 1981-82.  Unpublished.

Rabies Specimens from the State Hygienic Lab in Coralville, IA.


Specimens collected by Iowa Department of Natural Resources near Lake Rathbun, 1978-82. Published in Bowles, J.B., and A.D. Copsey, 1992, Small mammal abundance as a function of herbaceous cover type in southcentral Iowa, Prairie Naturalist.


Specimens collected on shoreline at Lake Redrock by Paul Heideman, John Bowles, and Kieth Erickson, 1978.  Published in Heideman, P.D., J.B. Bowles, and K.R. Erickson, 1983, Habitat selection by small mammals on the shoreline of a flood control lake in south-central Iowa, Proc. Iowa Acad. Sci. 90:93-97.


Soil Conservation Service study by David Beck.  Unpublished.


Specimens collected by John Bowles and Jon Stravers in southeastern Iowa in 1984.  Unpublished.

Temp (Temporary category; samples still under review) Specimens collected by John Bowles, not yet categorized and referenced.


Individual specimens collected by a private individual not for a specific study, mostly captured in Northeast Iowa.  Unpublished.