ANIMAL BEHAVIOR—ERNEST P. WALKER 201 
Plainly he had come to recognize the jardiniere as home and was glad 
to get back to it when it was made possible for him to do so. 
Remarkable developments of the trait of returning to the home 
range are shown by carrier pigeons (Columba), and birds, mammals, 
and fish that migrate. 
SELF-PRESERVATION 
Humans ordinarily give little thought to the matter of self-preserva- 
tion, although it becomes a vital subject during wartime. Among 
other animals it is ever foremost. In its broadest aspects self-preserva- 
tion involves not only active and passive resistance to enemies, but 
also the ability to obtain food and shelter. Humans have recently 
had brought to their attention the fact that they, like other animals, 
must either be prepared to defend themselves or run away when an 
ageressor attacks or threatens. If there is no place to which they can 
escape, or if they cannot successfully fight off their enemy, they have 
only the alternatives of being subjugated and made slaves, as some- 
times happens among humans, or of being destroyed, which in the 
case of animals may mean being devoured. 
There are very few animals that are aggressive to the extent of 
trying to drive away or subjugate their neighbors merely for the 
pleasure of the victory. Ordinarily, they will start a fight only when 
it is necessary to obtain food, shelter, or a mate. 
The methods used by animals to avoid, escape, or defeat an enemy 
are almost as numerous as the species of animals, for the individuals 
of every species employ one or more methods. All are interesting 
and some are very remarkable. 
The seeking of shelter is the most common of passive defensive 
measures and is practiced to a greater or less degree by all animals. 
Some go into burrows in the ground, crevices in rocks, or holes in 
trees, while some of the larger ones retreat into dense jungles or 
forests. 
“Freezing,” the act of remaining motionless, is extensively employed, 
as at the first intimation of danger almost every animal ceases prac- 
tically all movement. Since an object which is very conspicuous 
when moving is readily overlooked when stationary, “‘freezing’’ is a 
highly successful means of avoiding detection by enemies. Even 
those that depend mainly on their ability to scent their prey may 
have difficulty locating it if they cannot see it. 
Rabbits and hares (Leporidae), quail (Colinus), and grouse (Tetra- 
onidae), when perfectly still in their native haunts, are very difficult 
to see, and often will not move unless one almost steps on them. 
This method of escape is applicable in almost any type of surrounding, 
even on seemingly barren plains or expanses of snow. It is most 
effective, of course, if the color pattern of the animal is such that it 
