STUDIES OF MAMMALIAN LIFE HISTORIES 3 
is great need for the development of the ecologic method of approach 
in the study of the animal and its environment. Field plot or quad- 
rat methods should be combined with observations on the behavior of 
animals under confinement, the whole based on a thorough knowl- 
edge of normal field conditions over wide areas. No attempt is here 
made more than to refer to the development of this important side 
of the work, with the permanent field stations, specially trained per- 
sonnel, and comparatively elaborate equipment that it implies. De- 
velopment of new methods of study is one of the most important 
and promising lines of work in the entire field. 
The increasing employment of the camera in the study of habits 
is peculiarly desirable. Chapman (3, p. 1) thus states the case for 
the scientific value of bird photography: 
There are certain matters, such as a bird’s song, its time of migration, etce., 
which must be set forth with the pen; there are others, such as its haunts, 
nesting site, nest, eggs, the appearance and development of its young, where the 
camera is so far ahead of the pen in its power of graphic representation that 
it is a waste of time to use the former when circumstances permit the utiliza- 
tion of the latter. 
Though much less used in connection with mammal study, perhaps 
because of the nocturnal habits of these animals and the lesser acces- 
sibility of their haunts and homes, the value of the camera in this 
province can scarcely be overestimated. Photographs should be ob- 
tained of living animals in characteristic attitudes, of specimens, 
especially those freshly killed, of animals in traps, of characteristic 
food plants or other vegetation, and of noteworthy features of topog- 
raphy or environment. Photographic record is desirable also of 
tracks of animals, their systems of runways, beds or shelters, nests, 
piles of stored food or “ hay,” feces, claw and tooth marks on trees, 
cropped vegetation, and general habitat. The animal-portrait work 
of the day is of such high character that ordinarily it will not be 
possible for the biologist in the field to attempt to equal it; but it is of 
such importance that wherever possible a professional animal 
photographer should be a member of a field party. 
IMPORTANT DATA 
PREPARATION FOR WORK 
The study of mammalian life histories opens a field of activity for 
any sincere student with an enthusiasm for closer acquaintance with 
wild life. No human being and no book, but nature herself, is the 
supreme authority in natural history. The beginner as well as the 
veteran investigator may make important observations, although the 
most adequate training in scientific method and technic and broad 
experience are desirable for work on habits. At best, one can read 
all too little in “ Nature’s infinite book of secrecy.” 
ENVIRONMENT AND HEREDITY 
In a very real sense the mammal is the product of its surroundings, 
which on every side influence the individual, the community, and 
the species. Although there have been prolonged, critical, and 
thorough-going studies of heredity, similar investigations of the 
environment are for the most part lacking, so that the exact role 
