Be MISC. PUBLICATION 86, U. S. DEPT. OF AGRICULTURE 
and life-history studies are necessary for sound guidance. Effective 
conservation of the beneficial and the control of the harmful kinds of 
mammals depend on adequate knowledge of their habits. 
To the student the benefits of intimate acquaintance with the liv- 
ing things about him can scarcely be overestimated. Moreover, a 
widespread appreciation of nature, with the resulting inspiration 
to rugged and healthful thinking and living, has an important bear- 
ing on our national welfare. 
RELATION OF FIELD AND LABORATORY METHODS 
In the study of mammalian life histories, the use of both field 
and laboratory methods is abundantly justified. The possibility 
of a complete control of certain environmental factors under labora- 
tory conditions sometimes leads to undue enthusiasm for this type 
of research. The value of laboratory investigations, however, may 
often be lessened by a loss of the normal response of the mammal. 
With some mammals, which are of such size, number, and tem- 
perament that laboratory work with them is possible, studies like 
that of Yerkes (2/) with the dancing mouse may be counted on to 
yield results of the highest importance in respect to such problems 
as sense development and discrimination, habit formation, learning 
ability, and modifiability of behavior. The work of Sumner (/8), 
although largely concerned with problems of genetics, has afforded 
much information of value in studies of life history. Many mam- 
mals, however, can not be so easily brought into the laboratory or 
successfully kept in captivity. The ideal method is for a student 
of mammalian life histories in the field to carry his investigations 
into the laboratory whenever possible. The two fields are so vast 
and specialized, however, that this is rarely practicable. If adequate 
conclusions as to behavior under actual living conditions are to be 
reached, it is necessary to associate work in the laboratory with 
direct observations of the animal in the natural state; and many of 
the most important details of animal life histories can never be 
learned in the laboratory. 
Two authorities on this subject may be quoted here: Ritter (72, p. 
403) says, “the future’s progress in the biological sciences will he 
accomplished by a far closer, more vital interdependence between 
researches out in nature and researches in the laboratory.” Roose- 
velt (13, p. 11) states, “ it is essential to recognize that the best scien- 
tific men must largely work in the great out-of-doors laboratory of 
nature. It is only such outdoors work which will give us the chance 
to interpret aright the laboratory observations.” 
EQUIPMENT 
Equipment needed for field investigations of habits of mammals 
varies all the way from tools that are available almost everywhere 
to the complicated and expensive instruments necessary to the solu- 
tion of more difficult problems (7). Pick, shovel, ax or large 
hatchet, trowel or large spoon, brush cutter, grasscutter, tapeline, 
sketch pad, coordinate paper, and writing materials usually suffice 
for beginning studies. . 
Less refined modes of inquiry should give way as rapidly as prac- 
ticable to intensive investigations of a quantitative character. There 
