Nevertheless, our domesticated animals under new conditions occasionally show
signs of lessened fertility. Roulin asserts that in the hot valleys of the
equatorial Cordillera sheep are not fully fecund (18/70. "Mem. par divers
Savans" 'Acad. des Sciences' tome 6 1835 page 347.); and according to Lord
Somerville (18/71. 'Youatt on Sheep' page 181.) the merino-sheep which he
imported from Spain were not at first perfectly fertile, it is said (18/72. J.
Mills 'Treatise on Cattle' 1776 page 72.) that mares brought up on dry food in
the stable, and turned out to grass, do not at first breed. The peahen, as we
have seen, is said not to lay so many eggs in England as in India. It was long
before the canary-bird was fully fertile, and even now first-rate breeding
birds are not common. (18/73. Bechstein 'Stubenvogel' s. 242.) In the hot and
dry province of Delhi, as I hear from Dr. Falconer, the eggs of the turkey,
though placed under a hen, are extremely liable to fail. According to Roulin,
geese taken to the lofty plateau of Bogota, at first laid seldom, and then
only a few eggs; of these scarcely a fourth were hatched, and half the young
birds died; in the second generation they were more fertile; and when Roulin
wrote they were becoming as fertile as our geese in Europe. With respect to
the valley of Quito, Mr. Orton says (18/74. 'The Andes and the Amazon' 1870
page 107.) "the only geese in the valley are a few imported from Europe, and
these refuse to propagate." In the Philippine Archipelago the goose, it is
asserted, will not breed or even lay eggs. (18/75. Crawford 'Descriptive Dict.
of the Indian Islands' 1856 page 145.) A more curious case is that of the
fowl, which, according to Roulin, when first introduced would not breed at
Cusco in Bolivia, but subsequently became quite fertile; and the English Game
fowl, lately introduced, had not as yet arrived at its full fertility, for to
raise two or three chickens from a nest of eggs was thought fortunate. In
Europe close confinement has a marked effect on the fertility of the fowl: it
has been found in France that with fowls allowed considerable freedom only
twenty per cent of the eggs failed; when allowed less freedom forty per cent
failed; and in close confinement sixty out of the hundred were not hatched.
(18/76. 'Bull. de la Soc. d'Acclimat.' tome 9 1862 pages 380, 384.) So we see
that unnatural and changed conditions of life produce some effect on the
fertility of our most thoroughly domesticated animals, in the same manner,
though in a far less degree, as with captive wild animals.
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