Abstract: External features of the tail and pelage, and quantitative cranial characteristics were used to discriminate Peromyscus leucopus from P. maniculatus (n = 204) from northeastern North America. Species assignments were based on the phenotype of salivary amylase. Characteristics of the pelage and tail yielded correct identification of 55% of adult specimens. A previously published discriminant-function equation based on 11 cranial measurements correctly classified 66% of adults and 56% of specimens of all age classes. Two new discriminant equations were generated based on 12 and 11 skull measurements, respectively. The first equation correctly classified 100% of skulls in two separate datasets (n = 164; n = 50), and the second correctly classified 94% in a single dataset (n = 195).
To assess the usefulness of morphologic characters in identifying deer mice (Peromyscus maniculatus), white-footed mice (P. leucopus) and cotton mice (P. gossypinus) in sympatry, cranial and external measurements were recorded for two groups of these rodents. Each group contained individuals of the three species. One assemblage represented known individuals (species identifications verified using electrophoretic techniques) and the other unknowns (species identification not verified; test group). With the known group, we developed a system of identification based on selected morphologic features. These features were used to determine the identification of individuals in the test group. Following identification, individuals identified in the test group were confirmed using electrophoretic procedures. Two characters (greatest length of skull and length of hindfoot) separated 100% and 91% of P. gossypinus in the known group and 94.6% and 98% in the test group, respectively. A single external metric (tail length/total length) correctly classified 95% of P. maniculatus in both the known and test groups. A suite of four cranial (greatest length of skull, length of nasal, post-palatal length and length of diastema) and one external character (length of tail) correctly classified all of the individuals in the initial group and 90%, 91% and 100% of P. maniculatus, P. leucopus and P. gossypinus, respectively, in the test group. We concluded that morphologic characters can be used to accurately detect species of Peromyscus in sympatry.