improbable that all should have partaken of the poison, and impossible
that all should have been caught in a trap. They must learn caution by
seeing their brethren caught or poisoned. In North America, where the
fur-bearing animals have long been pursued, they exhibit, according to
the unanimous testimony of all observers, an almost incredible amount
of sagacity, caution and cunning; but trapping has been there so long
carried on, that inheritance may possibly have come into play. I have
received several accounts that when telegraphs are first set up in any
district, many birds kill themselves by flying against the wires, but
that in the course of a very few years they learn to avoid this danger,
by seeing, as it would appear, their comrades killed. (32. For
additional evidence, with details, see M. Houzeau, Etudes sur les
Facultes Mentales des Animaux, tom. ii. 1872, p. 147.)
If we look to successive generations, or to the race, there is no doubt
that birds and other animals gradually both acquire and lose caution in
relation to man or other enemies (33. See, with respect to birds on
oceanic islands, my Journal of Researches during the Voyage of the
Beagle, 1845, p. 398. Origin of Species, 5th ed. p. 260.); and
this caution is certainly in chief part an inherited habit or instinct,
but in part the result of individual experience. A good observer, Leroy
(34. Lettres Phil. sur l Intelligence des Animaux, nouvelle edit.,
1802, p. 86.), states, that in districts where foxes are much hunted,
the young, on first leaving their burrows, are incontestably much more
wary than the old ones in districts where they are not much disturbed.
Our domestic dogs are descended from wolves and jackals (35. See the
evidence on this head in chap. i. vol. i., On the Variation of Animals
and Plants under Domestication. ), and though they may not have gained
in cunning, and may have lost in wariness and suspicion, yet they have
progressed in certain moral qualities, such as in affection,
trust-worthiness, temper, and probably in general intelligence. The
common rat has conquered and beaten several other species throughout
Europe, in parts of North America, New Zealand, and recently in
Formosa, as well as on the mainland of China. Mr. Swinhoe (36.
Proceedings Zoological Society, 1864, p. 186.), who describes these
two latter cases, attributes the victory of the common rat over the
large Mus coninga to its superior cunning; and this latter quality may
probably be attributed to the habitual exercise of all its faculties in
avoiding extirpation by man, as well as to nearly all the less cunning
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