OCR Text |
Show ~GS 'l'HE PUINCIPLES OF P.t~.r::r II. respects, that the males when caught ·are valued at twentY per cent. above the females. 7 vVith other pachyderm~ tous animals the sexes differ very little or not at all, and they are not, as far as known, polygamists. Hardly a single species amongst the Cheiroptera and ]~dentata, or in the great Orders of the Rodents anJ Insectivora, presents well-developed secondary sex~al differences · and I can find no account of any species being poly~amous, excepting, perhaps, the common r_at, the males of which, as some rat-catchers affirm, hve with several females. The lion in South Africa, as I hear from Sir Andrew Smith, sometimes lives with a single female, but generally with more than one, and, in one case, was found with as many as five females, so that he is polygamous. He is, as far as I can discover, the sole polygamist in the whole group of the terrestrial Carnivora, and he alone presents well-marked sexual characters. If, however, we turn to the marine Carnivora, the case is widely different; for many species of seals offer, as we shall hereafter see, extraordinary sexual differences, and they are eminently polygamous. Thus the male sea-elephant of the Southern Ocean, always possesses, according to Peron, several females, and the sea-lion of Forster is said to be surrounded by from twenty to thirty females. In the North, the male sea-bear of Steller is accompanied by even a greater number of females. With respect to birds, many species, the sexes of which differ greatly from each other, are certainly monogamous. In Great Britain we see well-marked sexual differences in, for instance, the wild-duck which pairs with a single female, with the common blackbird, 7 Dr. Campbell, in 'Proc. Zoolog. Soc.' 1869, p. 138. See also an interesting paper, by Lieut. Johnstone, in' Proc. Asiatic Soc. of Bengal,' l\Iay, 1868. CHAP. VIII. SEXUAL SEI.ECTION. 2G9 and with the bullfinch which is said to pair for life. So it is, as I am informed by Mr. V\' allace, with the Chatterm ·s or Cotingidre of South America, and numerous other birds. In several groups I have not been able to discover whether the species are polygamous or monogamous. Lesson says that birds of paradise, so remarkable for their sexual differences, are polygamous, but Mr. vVallace doubts whether he had sufficient evidence. l\ir. Salvin informs me that he has been led to believe that humming-birds are polygamous. The male widow-bird, remarkable for his caudal plumes, certainly seems to be a polygamist.6 I have been assured by lVlr. Jenner vVeir and by others, that three starlings not rarely frequent the same nest; but whether this is a case of polygamy or polyandry has not been ascertained. The Gallinacere present almost as strongly marked sexual differences as birds of paradise or hummingbirds, and many of the species are, as is well know11, polygamous; others being strictly monogamous. What a contrast is presented between the sexes by the polygamous peacock or pheasant, and the monogamous guinea-fowl or partridge ! Many similar cases could be given, as in the grouse tribe, in which the males of the polygamous capercailzie and black-cock differ greatly from the females; whilst the sexes of the monogamous red grouse and ptarmigan differ very little. Amongst the Cm·sores, no great number of species offer strongly- marked sexual differences, except the bustards, and the great bustard (Otis tarda ), is said to 8 'The Ibis,' vol. iii. 1861, p. 133, on the Progne Widow-bird. See also on the Vidua axillaris, ibid. vol. ii. 1860, p. 211. On the polygamy of the Capercailzie and Great Bustard, see L. Lloyd, 'Game Birds of Sweden,' 1867, p. 19, and 182. Montagu and Selby speak of the Black Grouse as polygamous and of the Red Grouse as mono~mous. |