WHAT IS A MAMMAL? 



well worth the solving, with their mastery of flight, their 

 possession (?) of a sixth sense, and their super-organization of 

 the nervous system. The great waves of rodent increase which 

 come in cycles in Rabbits and Meadow Mice or Lemmings 

 present unusual opportunities for observation. 



Hunters and sportsmen learn many facts of life-history in 

 looking for game and because of this we know more today 

 about some of the large mammals than we do of the much more 

 abundant, small mammals. It can not be too strongly recom- 

 mended that persons who are out-of-doors, with opportunities 

 for observation, keep a journal or record of what they see of 

 mammal behavior. Not only will this practice give direction 

 and purpose to what may otherwise be random study, but it 

 will make natural history all the more fascinating and may 

 supj)ly some new and valuable data. 



Life Zones 



It will be noted that there are frequent references to "Life 

 Zones" in the geographical ranges in this field book. These 

 are the "Zones" used so extensively by the U. S. Biological 

 Survey. They are based upon the studies of Dr. C. H. 

 Merriam and others of the Survey and were set forth in their 

 earliest form by Dr. J. A. Allen, in 1871. Lack of space 

 prevents more than a passing reference to this scheme, but a 

 colored map is bound into the inner cover of this book and 

 several titles are mentioned in the bibliography at the close 

 of the book for the readers who are unfamiliar with these 

 useful terms. 



The attention of the reader is directed to the legend under 

 the colored map which points out that the "Zones" which are 

 known as Alleghenian, Carolinian, and Austroriparian in the 

 east become the Transition, Upper Sonoran, and Lower 

 Sonoran west of the looth meridian. 



^;^^ 



XV 



