6 MISC. PUBLICATION 86, U. S. DEPT. OF AGRICULTURE 
SUGGESTED STUDIES 
The points incorporated in the outline that follows are some of 
those concerning which additional detailed information is desirable. 
No one person can hope to acquire full information on all the items 
listed. The suggestions serve as a guide to what should be sought in 
the course of field work. They should also serve to encourage the 
recording of many facts that gome to the notice of the observer, facts 
that are not ordinarily recorded because of their supposed unimpor- 
tance. In general, the main headings alone will adequately serve the 
purpose of the investigator. In particular instances, however, the 
details listed under each heading may be found useful. 
No attempt is made to present a complete catalogue. Several 
legitimate fields of inquiry to which contributions can be made by 
field workers are omitted entirely; for example, the relation of 
habits to bodily structure. Almost any one of the suggestions in- 
cluded can be followed up and expanded with pleasure and profit 
(5, 15), and will be found to possess a surprising degree of interest 
and often of practical importance. 
For information regarding habits of the various mammals, the 
student is referred to Seton’s Life-histories of Northern Animals 
(74), his Lives of Game Animals (76), to Nelson’s Wild Animals 
of North America (10), and to the results of many special studies, 
including those portrayed in the Journal of Mammalogy and other 
scientific periodicals. 
ENVIRONMENT 
A, Physical surroundings. 
(1) Soil—kind, composition, texture, color, depth: chemical reactions, 
temperature and moisture at different depths; topography of 
region; general suitability for mammalian occupation or use: sand 
dunes, rocks, cliffs, caves. 
(2) Water—nearness, depth, composition, chemical reactions, currents, 
light, temperature, snow, ice. 
(3) Atmosphere—pressure, movements, temperature, moisture, light. 
(4) Changes in physical surroundings—relation of age-long changes in 
topography and climate to the development, migration, establish- 
ment, isolation, and extinction of the mammalian community. 
(5) Physical environment in relation to daily and seasonal activity— 
effects of weather, climate, and daily and seasonal cycles on the 
activity of the mammal, on hibernation, estivation, or other 
periodic phenomena, on nocturnal and diurnal activities, and on 
migration (regular or irregular) ; effects of long days, very dark . 
days, full moon, dark of the moon, and similar phenomena on 
habits; hours of activity and rest on part of different mammals; 
times of appearance and disappearance, as of bats. 
B. Plant surroundings. 
(1) Plants of the land—above and below the surface; plants of the 
water. 
(2) Food and shelter relations between mammals and plants. 
(3) Mammals as disseminators of plants. 
(4) Mammals as ae on plant growth, as enemies of plants. 
(5) Plants inimical mammals—poisonous plants; infection and trans- 
mission of bacterial diseases to mammals and man; periodicity 
of contagious diseases in mammals; degree and rapidity of 
recovery; manner of recovery, natural medicines, healing sub- 
stances or activities. 
(6) Relation between development of plants and animals, 
