Biology ETDs

Publication Date



Two species of cotton rats, Sigmodon minimus Mearns (least cotton rat) and S. hispidus Baird (hispid cotton rat), occur in the Rio Grande Valley of New Mexico. The northernmost published record-station for S. hispidus is near Scorro, Scorro County ( Bailey, 1931: 167), and that S. minimus is near Isleta, Bernalillo County (Ivey, 1947: 498 and map). When recent field work by the author revealed the presence of both species in the Rio Grande Valley north of these published record-stations the problem arose whether the range extensions were the result of a recent northward extension of the range of the genus or whether the animals have been present for some time and are now revealed by more intensive collecting. To solve the problem a study was made to determine the northernmost limits of the geographic ranges of these two species in New Mexico, their habitat preferences, and the factor or factors limiting their distribution throughout the state.



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Department Name

UNM Biology Department

First Committee Member (Chair)

James Findley

Second Committee Member

Lauren D. Potter

Third Committee Member

C. Clayton Holt