as
spontaneous amputation, technically termed autotomy. The lizard, for
example, when captured, will abruptly break loose his tail in order to
escape; and certain wood rats, when caught, loosen the skin on their
tails and deliberately slip away. Autotomy not only permits flight, but
also defends the animal against the most adverse conditions. Nearest
akin to this--defence by means of amputation--is the practice of bears
and raccoons of amputating their limbs when caught in steel traps.

Mimicry, which is treated under another chapter, comes under the head of
passive defence, and form and colour play an important part in it.
Strangely enough, animals which have never resorted to mimicry as a
means of protection, when associated with others who practice it, take
on the habit themselves. This may possibly be due to the fact that new
enemies are constantly arising.

As human sharpshooters dress in garments of the same colour as the woods
in which they hunt, so many animals use this principle of imitation. The
colour of most animals is very similar to their surroundings. This
enables them to lie in wait for prey, a practice as old as the hillsides
with animals. They have learned the extreme value of silence, and that
they must remain at times motionless. This is especially noticeable with
crocodiles, which wait for whole days without moving, concealed in the
water or deep grass, until their prey comes within striking distance,
when they pounce upon it. The same is true of the python snake, which
hangs from a tree so immovable that he appears like a vine or a branch
of the tree. If an animal attempts to pass, he drops upon it.

Perhaps the most unique and successful method of passive defence is the
feigning of death, or "playing 'possum" met with in several animals,
such as the red fox, the opossum, occasionally the elephant, and several
of the snakes. On many occasions I have been 'possum hunting in the
South and found my dog barking at an apparently dead 'possum. As soon as
these animals are approached by larger and stronger enemies, they drop
absolutely motionless on the ground and close their eyes as though they
were dead. Here they remain until the enemy either destroys them,
carries them away, or leaves them alone. If left alone for a few
moments, they immediately spring to their feet and make their escape.

Elephants often feign death when captured, in order to gain their
liberty. Animal catchers tell many interesti