ands it.
Or when the old goose covers up her nest, or the rabbit covers her
young with a blanket of hair and grass of her own weaving, I do not
look upon these things as independent acts of intelligence: it is the
cunning of nature; it is a race instinct.

Animals, on the whole, know what is necessary for them to know--what
the conditions of life have taught their ancestors through countless
generations. It is very important, for instance, that amphibians shall
have some sense that shall guide them to the water; and they have such
a sense. It is said that young turtles and crocodiles put down
anywhere will turn instantly toward the nearest water. It is certain
that the beasts of the field have such a sense much more fully
developed than has man. It is of vital importance that birds should
know how to fly, how to build their nests, how to find their proper
food, and when and where to migrate, without instruction or example,
otherwise the race might become extinct.

Richard Jefferies says that most birds'-nests need a structure around
them like a cage to keep the young from falling out or from leaving
the nest prematurely. Now, if such a structure were needed, either the
race of birds would have failed, or the structure would have been
added. Since neither has happened, we are safe in concluding it is not
needed.

We are not warranted in attributing to any wild, untrained animal a
degree of intelligence that its forbears could not have possessed. The
animals for the most part act upon inherited knowledge, that is,
knowledge that does not depend upon instruction or experience. For
instance, the red squirrels near me seem to know that chestnut-burs
will open if cut from the tree and allowed to lie upon the ground. At
least, they act upon this theory. I do not suppose this fact or
knowledge lies in the squirrel's mind as it would in that of a man--as
a deduction from facts of experience or of observation. The squirrel
cuts off the chestnuts because he is hungry for them, and because his
ancestors for long generations have cut them off in the same way. That
the air or sun will cause the burs to open is a bit of knowledge that
I do not suppose he possesses in the sense in which we possess it: he
is in a hurry for the nuts, and does not by any means always wait for
the burs to open; he frequently chips them up and eats the pale nuts.

The same squirrel will bite into the limbs of a maple tree in spring
and suck the sap. Wh