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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 Abstract 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. Introduction 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 2 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 3 collected. A comparison of skull measurements to a study completed by Reed et al. was completed to distinguish between species of Peromyscus. Results 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. Discussion 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. 4 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. <www.discoverlife.org>. 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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