It is scarcely possible to imagine a greater change in habits than that which the members of the ostrich family must suffer, when cooped up in small enclosures under a temperate climate, after freely roaming over desert and tropical plains or entangled forests; yet almost all the kinds have frequently produced young in the various European menageries, even the mooruk (Casuarius bennetii) from New Ireland. The African ostrich, though perfectly healthy and living long in the South of France, never lays more than from twelve to fifteen eggs, though in its native country it lays from twenty-five to thirty. (18/54. Marcel de Serres 'Annales des Sc. Nat.' 2nd series Zoolog. tome 13 page 175.) Here we have another instance of fertility impaired, but not lost, under confinement, as with the flying squirrel, the hen-pheasant, and two species of American pigeons.
Most Waders can be tamed, as the Rev. E.S. Dixon informs me, with remarkable facility; but several of them are short-lived under confinement, so that their sterility in this state is not surprising. The cranes breed more readily than other genera: Grus montigresia has bred several times in Paris and in the Zoological Gardens, as has G. cinerea at the latter place, and G. antigone at Calcutta. Of other members of this great order, Tetrapteryx paradisea has bred at Knowsley, a Porphyrio in Sicily, and the Gallinula chloropus in the Zoological Gardens. On the other hand, several birds belonging to this order will not breed in their native country, Jamaica; and the Psophia, though often kept by the Indians of Guiana about their houses, "is seldom or never known to breed." (18/55. Dr. Hancock in 'Charlesworth's Mag. of Nat. Hist.' volume 2 1838 page 491; R. Hill 'A Week at Port Royal' page 8; 'Guide to the Zoological Gardens' by P.L. Sclater 1859 pages 11, 12; 'The Knowsley Menagerie' by D. Gray 1846 p1. 14; E. Blyth 'Report Asiatic Soc. of Bengal' May 1855.)
The members of the great Duck family breed as readily in confinement as do the Columbae and Gallinae and this, considering their aquatic and wandering habits, and the nature of their food, could not have been anticipated. Even some time ago above two dozen species had bred in the Zoological Gardens; and M. Selys-Longchamps has recorded the production of hybrids from forty-four different members of the family; and to these Professor Newton has added a few more cases. (18/56. Prof. Newton in 'Proc. Zoolog. Soc.' 1860 page 336.) "There is not," says Mr. Dixon (18/57. 'The Dovecote and Aviary' page 428.), "in the wide world, a goose which is not in the strict sense of the word domesticable;" that is, capable of breeding under confinement; but this statement is probably too bold. The capacity to breed sometimes varies in individuals of the same species; thus Audubon (18/58. 'Ornithological Biography' volume 3 page 9.) kept for more than eight years some wild geese (Anser canadensis), but they would not mate; whilst other individuals of the same species produced young during the second year. I know of but one instance in the whole family of a species which absolutely refuses to breed in captivity, namely, the Dendrocygna viduata, although, according to Sir R. Schomburgk (18/59. 'Geograph. Journal' volume 13 1844 page 32.), it is easily tamed, and is frequently kept by the Indians of Guiana. Lastly, with respect to Gulls, though many have been kept in the Zoological Gardens and in the old Surrey Gardens, no instance was known before the year 1848 of their coupling or breeding; but since that period the herring gull (Larus argentatus) has bred many times in the Zoological Gardens and at Knowsley.
There is reason to believe that insects are affected by confinement like the higher animals. It is well known that the Sphingidae rarely breed when thus treated. An entomologist (18/60. Loudon's 'Mag. of Nat. Hist.' volume 5 1832 page 153.) in Paris kept twenty-five specimens of Saturnia pyri, but did not succeed in getting a single fertile egg. A number of females of Orthosia munda and of Mamestra suasa reared in confinement were unattractive to the males. (18/61. 'Zoologist' volumes 5-6 1847-48 page 1660.) Mr. Newport kept nearly a hundred individuals of two species of Vanessa, but not one paired; this, however, might have been due to their habit of coupling on the wing. (18/62. 'Transact. Entomolog. Soc.' volume 4 1845 page 60.) Mr. Atkinson could never succeed in India in making the Tarroo silk-moth breed in confinement. (18/63. 'Transact. Linn. Soc.' volume 7 page 40.) It appears that a number of moths, especially the Sphingidae, when hatched in the autumn out of their proper season, are completely barren; but this latter case is still involved in some obscurity. (18/64. See an interesting paper by Mr. Newman in the 'Zoologist' 1857 page 5764; and Dr. Wallace in 'Proc. Entomolog. Soc.' June 4, 1860 page 119.)]
Independently of the fact of many animals under confinement not coupling, or, if they couple, not producing young, there is evidence of another kind that their sexual functions are disturbed. For many cases have been recorded of the loss by male birds when confined of their characteristic plumage. Thus the common linnet (Linota cannabina) when caged does not acquire the fine crimson colour on its breast, and one of the buntings (Emberiza passerina) loses the black on its head. A Pyrrhula and an Oriolus have been observed to assume the quiet plumage of the hen-bird; and the Falco albidus returned to the dress of an earlier age. (18/65. Yarrell 'British Birds' volume 1 page 506; Bechstein 'Stubenvogel' s. 185; 'Philosoph. Transact.' 1772 page 271. Bronn 'Geschichte der Natur' b. 2 s. 96 has collected a number of cases. For the case of the deer see 'Penny Cyclop.' volume 8 page 350.) Mr. Thompson, the superintendent of the Knowsley menagerie, informed me that he had often observed analogous facts. The horns of a male deer (Cervus canadensis) during the voyage from America were badly developed; but subsequently in Paris perfect horns were produced.
When conception takes place under confinement, the young are often born dead, or die soon, or are ill-formed. This frequently occurs in the Zoological Gardens, and, according to Rengger, with native animals confined in Paraguay. The mother's milk often fails. We may also attribute to the disturbance of the sexual functions the frequent occurrence of that monstrous instinct which leads the mother to devour her own offspring,—a mysterious case of perversion, as it at first appears.
Sufficient evidence has now been advanced to prove that animals when first confined are eminently liable to suffer in their reproductive systems. We feel at first naturally inclined to attribute the result to loss of health, or at least to loss of vigour; but this view can hardly be admitted when we reflect how healthy, long-lived, and vigorous many animals are under captivity, such as parrots, and hawks when used for hawking, cheetahs when used for hunting, and elephants. The reproductive organs themselves are not diseased; and the diseases, from which animals in menageries usually perish, are not those which in any way affect their fertility. No domestic animal is more subject to disease than the sheep, yet it is remarkably prolific. The failure of animals to breed under confinement has been sometimes attributed exclusively to a failure in their sexual instincts: this may occasionally come into play, but there is no obvious reason why this instinct should be especially liable to be affected with perfectly tamed animals, except, indeed, indirectly through the reproductive system itself being disturbed. Moreover, numerous cases have been given of various animals which couple freely under confinement, but never conceive; or, if they conceive and produce young, these are fewer in number than is natural to the species. In the vegetable kingdom instinct of course can play no part; and we shall presently see that plants when removed from their natural conditions are affected in nearly the same manner as animals. Change of climate cannot be the cause of the loss of fertility, for, whilst many animals imported into Europe from extremely different climates breed freely, many others when confined in their native land are completely sterile. Change of food cannot be the chief cause; for ostriches, ducks, and many other animals, which must have undergone a great change in this respect, breed freely. Carnivorous birds when confined are extremely sterile, whilst most carnivorous mammals, except plantigrades, are moderately fertile. Nor can the amount of food be the cause; for a sufficient supply will certainly be given to valuable animals; and there is no reason to suppose that much more food would be given to them than to our choice domestic productions which retain their full fertility. Lastly, we may infer from the case of the elephant, cheetah, various hawks, and of many animals which are allowed to lead an almost free life in their native land, that want of exercise is not the sole cause.
It would appear that any change in the habits of life, whatever these habits may be, if great enough, tends to affect in an inexplicable manner the powers of reproduction. The result depends more on the constitution of the species than on the nature of the change; for certain whole groups are affected more than others; but exceptions always occur, for some species in the most fertile groups refuse to breed, and some in the most sterile groups breed freely. Those animals which usually breed freely under confinement, rarely breed, as I was assured, in the Zoological Gardens, within a year or two after their first importation. When an animal which is generally sterile under confinement happens to breed, the young apparently do not inherit this power: for had this been the case, various quadrupeds and birds, which are valuable for exhibition, would have become common. Dr. Broca even affirms (18/66. 'Journal de Physiologie' tome 2 page 347.) that many animals in the Jardin des Plantes, after having produced young for three or four successive generations, become sterile; but this may be the result of too close interbreeding. It is a remarkable circumstance that many mammals and birds have produced hybrids under confinement quite as readily as, or even more readily than, they have procreated their own kind. Of this fact many instances have been given (18/67. For additional evidence on this subject see F. Cuvier in 'Annales du Museum' tome 12 page 119.); and we are thus reminded of those plants which when cultivated refuse to be fertilised by their own pollen, but can easily be fertilised by that of a distinct species. Finally, we must conclude, limited as the conclusion is, that changed conditions of life have an especial power of acting injuriously on the reproductive system. The whole case is quite peculiar, for these organs, though not diseased, are thus rendered incapable of performing their proper functions, or perform them imperfectly.
[STERILITY OF DOMESTICATED ANIMALS FROM CHANGED CONDITIONS.
With respect to domesticated animals, as their domestication mainly depends on the accident of their breeding freely under captivity, we ought not to expect that their reproductive system would be affected by any moderate degree of change. Those orders of quadrupeds and birds, of which the wild species breed most readily in our menageries, have afforded us the greatest number of domesticated productions. Savages in most parts of the world are fond of taming animals (18/68. Numerous instances could be given. Thus Livingstone ('Travels' page 217) states that the King of the Barotse, an inland tribe which never had any communication with white men, was extremely fond of taming animals, and every young antelope was brought to him. Mr. Galton informs me that the Damaras are likewise fond of keeping pets. The Indians of South America follow the same habit. Capt. Wilkes states that the Polynesians of the Samoan Islands tamed pigeons; and the New Zealanders, as Mr. Mantell informs me, kept various kinds of birds.); and if any of these regularly produced young, and were at the same time useful, they would be at once domesticated. If, when their masters migrated into other countries, they were in addition found capable of withstanding various climates, they would be still more valuable; and it appears that the animals which breed readily in captivity can generally withstand different climates. Some few domesticated animals, such as the reindeer and camel, offer an exception to this rule. Many of our domesticated animals can bear with undiminished fertility the most unnatural conditions; for instance, rabbits, guinea-pigs, and ferrets breed in miserably confined hutches. Few European dogs of any kind withstand the climate of India without degenerating, but as long as they survive, they retain, as I hear from Dr. Falconer, their fertility; so it is, according to Dr. Daniell, with English dogs taken to Sierra Leone. The fowl, a native of the hot jungles of India, becomes more fertile than its parent-stock in every quarter of the world, until we advance as far north as Greenland and Northern Siberia, where this bird will not breed. Both fowls and pigeons, which I received during the autumn direct from Sierra Leone, were at once ready to couple. (18/69. For analogous cases with the fowl see Reaumur 'L'Art de faire Eclore' etc. 1749 page 243; and Col. Sykes in 'Proc. Zoolog. Soc.' 1832 etc. With respect to the fowl not breeding in northern regions see Latham 'Hist. of Birds' volume 8 1823 page 169.) I have, also, seen pigeons breeding as freely as the common kinds within a year after their importation from the upper Nile. The guinea- fowl, an aboriginal of the hot and dry deserts of Africa, whilst living under our damp and cool climate, produces a large supply of eggs.