262 § ANNUAL REPORT SMITHSONIAN INSTITUTION, 1949 
actions of animals in the light of the lives they normally lead in the 
wild. If we are well enough informed as to the conditions under 
which they live and their mode of life, we can often understand actions 
that would otherwise be incomprehensible or aimless to us. I do not 
believe that animals do any more aimless things than humans. On 
the contrary, I am often impressed by the direct and efficient 
manner in which they carry on the work of their lives. 
The habits of animals are so intimately associated with and gov- 
erned by their structure that one who is somewhat familiar with either 
the habits or the structure can often make rather close deductions 
from one regarding the other. 
Every habit or type of behavior that has been developed because it 
helps the animal in its life is, of course, a special trait. Some are so 
little known that attention might be focused upon them and con- 
sideration given to the manner in which they benefit the animal. 
To understand the animals best, we must realize that merely because 
we cannot perform a given act does not mean that an animal cannot 
do it. For example, the sense of smell in most humans is so unde- 
veloped that we cannot trail another animal by scent, as we know many 
animals do. Also, our hearing is so dull we cannot detect sounds that 
we know many other animals hear. Likewise, other senses of animals 
are probably so much more keenly developed than ours that they re- 
celve impressions or information of which we know little or nothing. 
For example, some animals give off vibrations that other animals are 
able to detect; the presence of a warm live body can be detected by 
certain snakes at distances of several feet even though their eyes and 
nostrils are not functioning; and apparently impressions are received 
by insects through their antennae and by fish through their lateral 
lines. 
How individual animals acquire their behavior patterns is a fas- 
cinating field for study. Some actions are apparently taught to the 
young by the parents; some are learned by the young by observing 
others of their kind; some are learned by the trial and error system, or 
as we know it, “by bitter experience”’; and some come to the animal 
by instinct; that is, the animal reacts in a certain way (usually the 
right way) under certain circumstances without previously having 
had an opportunity to learn consciously to act in that manner under 
those circumstances. How such reactions develop is explained by 
various theories and is a separate study. 
ECOLOGY, STRUCTURE, AND HABITS 
Ecologists refer to an animal as occupying an ecological niche, that 
is, the main activities of the animal take place within a certain type 
of habitat. It may live entirely within the water, on or under the 
ground, or almost entirely on trees, or combinations of any of these, 
