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Show 266 THE PRINCIPLES OF PART II. same results as would follow from an actual inequality in the number of the sexes ; for if each male secures two or more females, many males will not be able to pair; and the latter assuredly will be the weaker or less attractive individuals. Many mammals and some few birds are polygamous, but with animals belo~ging ~o the lower classes I have found no evidence of tb1s habit. The intellectual powers of such animals· are, perhaps, not sufficient to lead them to collect and guard a harem of females. That some relation exists between polygamy and the development of second~ry sexual characters, appears nearly certain; and th1s supports the view that a numerical preponderance of males woulcl be eminently favourable to the action of sexual selection. Nevertheless many animals, especially birds, which are strictly monogamous, display strongly-marked secondary sexual characters; whilst some few animals, which are polygamous, are not thus characterised. We will first briefly run through the class of mammals, and then turn to birds. The gorilla seems to be a polygamist, and the male differs considerably from the female; so it is with some baboons which live in herds containing twice as many adult females as males. In South America the Mycetes caraya presents wellmarked sexual differences in colour, beard, and vocal organs, and the male generally lives with two or three wives: the male of the Oebus captwinus differs somewhat from the female, and appears to be polygamous.:» Little is known on this head with respect to most other monkeys, but some species are strictly monogamous. The ruminants are eminently polygamofls, and they 5 On the Gorilla, Savage and Wyman,' Boston Journal ofNat. Hist.' vol. v. 1845-4:7, p. 4:23. On Cynocephalus, Brehm, 'lllust. Thierleben,' B. i. 1864:, s. 77. On Mycetes, Rengger, 'Nutill'gesch.: Saugethiere von Paragun.y,' 1830, s. 14:, 20. On Ce1us, Brehm, ibid. s. 108. CH.Al'. VIII. SEXUAL SELECTION. 2G7 more frequently present sexual differences than almost any other group of mammals, especially in their weapons, but likewise in other characters. Most deer, cattle, and sheep are polygamous; as are most antelopes, though some of the latter are monogamous. Sir Andrew Smith, in speaking of the antelopes of South Africa, says that in herds of about a dozen there was· rarely more than one mature male. The Asiatic Antilope saiga appears to be the most inordinate polygamist in the world ; for Pallas 6 states that the male drives away all rivals, and collects a herd of about a hundred, consisting of females and kids : the female is hornless and has softer hair, but does not otherwise differ much from the male. The horse is polygamous, but, except in his greater size and in the proportions of his body, differs but little from the mare. The wild boar, in his great tusks and some other characters, presents wellmarked sexual characters ; in Europe and in India he lea~s a solitary life, except during the breeding-season; but at this season he consorts in India with several females, as Sir vV. Elliot, who has had large experience in observing this animal, believes: whether this holds good in Europe is doubtful, but is supported by some statements. The adult male Indian elephant, like the boar, passes much of his time in solitude; but when associating with others, "it is rare to find," as Dr. Campbell states, "more than one male with a whole " herd of females." The larger males expel or kill the smaller and weaker ones. The male differs from the female by his immense tusks and greater size strenoth ' 0 ' and endurance ; so great is the difference in these latter 6 Pallas, ' Spicilegia Zoolog.' Fuse. xii. 1777, p. 29. Sir Andrew Smith, 'Illustrations of the Zoology of S. Africa,' 184:9, pl. 29, on the ~obus. Owe.n, ~n his' Anato~y of Vertebrates' (vol. iii. 1868, p. 633) g1ves a table mmdentally showmg which species of Antelopes pair and which are gregarious. , |
