(A) Map shows the approximate range of forest (green) and prairie (brown) deer mouse ecotypes in North America. Collection sites of wild-caught forest (P. m. rubidus, green) and prairie (P. m. gambelii, brown) ecotypes from western and eastern Oregon, USA, respectively, are shown. Photos illustrate representative habitat; pink flags indicate trap lines. (B) Body length (left; not including the tail) and tail length (right) for wild-caught adult mice (n = 38 forest and 32 prairie). Lines connect body and tail measurements for the same individual. Means are shown in bold. (Inset) Image of a representative tail from each ecotype. Scale bar, 1 cm. (C) Coat color (hue) values for the dorsal and flank regions of wild-caught adult mice (n = 16 forest and 20 prairie). Boxplots indicate the median (center white line) and the 25th and 75th percentiles (box extents); whiskers show largest or smallest value within 1.5 times the interquartile range. Black dots show individual data points. (Inset) Dorsal (D), flank (F), and ventral (V) regions from a representative forest and prairie mouse. ns = P > 0.05; ***P < 0.001 (Welch’s t test, two-sided). Original photography in (B) and (C) is copyrighted by the President and Fellows of Harvard College (photo credit: Museum of Comparative Zoology, Harvard University).