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									        Discriminating Species of Peromyscus in Baldwin County Georgia

                                            Gretchen DeBaun

   Department of Biological and Environmental Sciences, Georgia College, Milledgeville, Georgia 31061, USA


       The objective of this study is to determine species of Peromyscus with four cranial

measurements (greatest length of skull, nasal length, post-palatal length, and length of diastema)

and one external measurement (tail length). Specimens used in this study were unknown species

of Peromyscus. Specimens were collected in Baldwin County, Georgia between 2008 and 2009.

This study concluded that with the use of four cranial measurements and one external

measurement, it is possible to distinguish different species of Peromyscus.


       It has been noted in several works the need to understand and record species prevalence

through biodiversity surveys (Reed et al., 2004). In the United States different species of the

white-footed mouse (Peromyscus) can be found livening in sympatry (Reed et al., 2004).

White-footed mice are among the most widely distributed mammals in North America, (Learm,

1994; Boone, 2004) with any species of Peromyscus living in the southeast (See Fig.1; Linzey,

Brecht, 2002). This study attempts to distinguish adult species of Peromyscus based on a suit of

four cranial characters and one external character, a modified technique of Reed et al.. The skull

measurements recorded were greatest skull length, nasal length, post-palatal length, and length of

the diastema. The external character measured was the total tail length. Specimens looked at

include cotton mice (Peromyscus gossypinus) and white-footed mice (Peromyscus leucopus).

                                    Fig.1                                                 Fig.2

                                    Methods and Materials

Study Area: Specimens were collected in the woodlands surrounding Lake Laurel in Baldwin

County, Milledgeville. All specimens used throughout the study were kept in the biology

department of Georgia College and State University. Some specimens used were collected

between May of 2008 and August of 2008, the rest were collected between February of 2009 and

March of 2009.

Sampling Methods: 30 Sherman traps were then baited with peanut butter on cotton balls. Traps

were marked with red ribbon for identification. Traps were set up in a row, roughly two feet

from each other. Traps were checked for specimens every Wednesday and Thursday; re-baited

most Tuesdays. Traps were closed on Thursdays and re-opened every Tuesday.

Data Analysis: Skulls were removed and cleaned in the biology department of Georgia College

and State University. Measurements of skull, noted above, were recorded from every specimen

collected. A comparison of skull measurements to a study completed by Reed et al. was

completed to distinguish between species of Peromyscus.


                  Range of External and Cranial Measurements (mm) of two
                           Peromyscus Species in Baldwin County

                                                   P. gossypinus        P. leucopus
                         Skull Length               26.0 - 27.9          24.5 - 25.9
                         Nasal Length                8.8 - 10.8          7.6 - 10.0
                   Post - Palatal Length            12.6 - 13.8          11.5 -13.5
                   Length of Diastema                 6.8 - 8.3           6.2 - 7.6
                         Tail Length                  56 - 146             54 - 64

       Eight P. leucopus and 31 P. gossypinus were determined.


       Results indicated no overlap in greatest length of skull between P. gossypiuns and

P. leucopus. Some overlap was noted in the other three cranial measurements (nasal length, post-

palatal length and length of the diastema), as well as in the one external measurement (tail

length). Enough data showed accurate discrimination between the two specimens (P. gossypinus

and P. leucopus). Similar results were found in the analysis preformed by Reed et al.; an

analysis using four cranial characters (greatest length of skull, nasal length, post-palatal length

and length of diastema) and one external character (tail length) correctly classified 100% of all

specimens. In the future, for this study, statistical analyses would need to be performed to obtain

more accurate results.

Acknowledgements – I would like to thank Dr. Dennis Parmley for his assistance in the collection

and research for this study. I would also like to thank the biology department of Georgia College

and State University for allowing us to use the Lake Laurel facility to collect our specimens.

                                        Literature Cited

Learm, J., Boone, J. L., 1994. Mensural Discrimination of Four Species of Peromyscus

     (Rodentia: Muridae) in the Southeastern United States. Brimleyana. 21:107-123.

Linzey, D., and C. Brecht. “Peromyscus leucopus/Peromyscus gossypinus.” Discover Life.

       Nov. 2002. <>.

Reed, A.W., Kennedy P.K., Beck M.L., Kennedy, M.L., 2004. Using Morphological Characters

       To Identify Peromyscus in Sympatry. Am.Midl. Nat. 152:190-195.

                                           Appendix I

       Five specimens collected came from trapping at Lake Laurel. The other specimens used

were provided by the biology department of Georgia College and State University.

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