IOWA ACADEMY OF SCIENCES. 97 



ofteu met with among the Herbivora. The term polygamy, in its strict 

 sense, Cfin properly apply only to those species in which a single male habit- 

 ually copulates with several females, and jealously and persistently defends 

 them from the approach of other males. 



The most typical examples of this state of affairs are met with among the 

 Pinnipedia. and ultra polygamy is exemplified by the northern fur seal 

 ( Callorhinus ursimis). 



Two striking facts at once arrest the attention of even the most cursory 

 observer of this species: 



1st, The astonishing extent to which polygamy is carried. Mr. Elliott 

 thinks "that it will be nearly correct to assign to each male from twelve to 

 fifteen females, occupying the stations nearest the water, and those back iu 

 the rear from five to nine. I have counted forty-five cows all under one 

 bull. "2 



2nd, The no less astonishing disparity in size between the sexes. The 

 average length of the male is 7^ feet, while that of the female is 4 feet. The 

 male weighs 4.50 lbs., while the female weighs only 8.") lbs. It will thus be 

 seen that the male weighs nearly six times as much as the female. 



Two questions arise in view of the above facts: 



1st, Is there any relation between polygamy and sexual disparity in size? 

 2nd, If so, what is that relation? 



The Pinnipedia are fortunately sufKcieutly numerous in species and indi- 

 viduals to furnish an ample field for the study of both of the above questions. 

 They are all eminently gregarious in habit, a condition favorable to polyg- 

 amy. The order furnishes examples of both monogamous and polygamous 

 species, and almost every degree of sexual disparity in size to be found in 

 the Mammalia. We can easily construct a series of species, ascending from 

 those exhibiting the least sexual disparity to those exhibiting the greatest. 

 We can then see what, if any, relation exists between sexual disparity and 

 polygamy. We shall presently see that pugnacity on the part of the males 

 plays a not unmiportant role in our discussion, and for that reason the 

 fighting proclivities of the males will also be noted. 



The following arrangement, then, illustrates what might be termed the 

 ascending series of sexual disparity. The relation of the sexes (monogamy, 

 promiscuity, or polygamy) and the relative pugnacity of the males in rela- 

 tion to other males of the same species will also be noted in each case. 



Odoba'mis rosmarus (Walrus), (a) Sexes neaiiy equal iu size, the female 

 not being notably smaller than the male. (6) Monogamous, according to 

 the only information at the disposition of the writer. ^ (c) Disposition not 

 at all quarrelsome, the animals of both sexes being singularly good-natured 

 and peaceable, " huddling together like so many swine," although they will 

 tight fiercely in defense of their young. 



(Jlistophoro rristata (Hooded Seal;, (a) Considerable sexual disparity. The 

 male is 8 feet long, and the female 7 feet. Weight of male, 450 lbs.; female, 

 200 lbs. [b] Probably monogamous, although there is no direct evidence at 

 hand. There is at least nothing to indicate that they are polygamous in the- 



2. Quoted from '• Monograph of North American Pinnipeds " (Allen). Nearly all tho 

 material used in the above article has been talien from tliat work. 

 3 Monograph of North American Pinnipeds, p. 107. 



