ie the isolated heights of the La Sal Mountains,
and 70 miles away, the Abajo Mountains (see Fig. 1).

In the thirteenth century, harassed by nomadic tribes and beset by years
of drouth, village dwelling Indians left their great cliff dwellings in
the myriad canyons of the Mesa Verde, and thus ended a period of 1300
years of occupancy. The story of those 1300 years, unfolded through
excavation and study of the dwellings along the cliffs and earlier
dwellings on the top of the Mesa, is one of the most fascinating in
ancient America. To stop destructive commercial exploitation of the
ruins, to preserve them for future generations to study and enjoy, and
to make them accessible to the public, more than 51,000 acres, including
approximately half of the Mesa, have been set aside as Mesa Verde
National Park, established in 1906. The policies of the National Park
Service provide protection, not only for the features of major interest
in each park, but for other features as well. Thus the policy in Mesa
Verde National Park is not only to preserve the many ruins, but also the
wildlife and plants.

Five considerations prompted me to undertake a study of the mammals of
Mesa Verde National Park: First, the relative lack of disturbance;
second, the interesting position, zoogeographically, of the Mesa that
extends as a spur of higher land from the mountains of southwestern
Colorado and that is almost surrounded by arid country typical of much
of the Southwest; third, the discovery in the Park of _Microtus
mexicanus_, a species of the Southwest until then not known from
Colorado; fourth, the co-operative spirit of the personnel at the Park
when I visited there in 1955; and finally, the possibility of making a
contribution not only to our knowledge of mammals, but to the
interpretive program of the Park Service.

[Illustration: FIG. 1. Map of the "four corners" region showing the
position of Mesa Verde National Park (in black) relative to the mass of
the Southern Rocky Mountains above 8000 feet elevation (indicated by
stippled border) to the northeast in Colorado, and the positions of
other isolated mountains in the region.]

A Faculty Research Grant from The University of Kansas provided some
secretarial help and field expenses for August and early September,
1956, when my wife, Justine, and I spent our vacation enjoyably
collecting and studying animals in the Park. The co-operation of Dr. E.
Raymond Hall is greatly appreciated; a