AGE ATTAINED BY SEALS. 51 



in the spring and was prepared to bear anotlier in the spring of 1897. An old hair 

 seal, Phoca laryha, taken at Marunicben, was also fertile, and it may be said that so 

 far no female seal so old that she has ceased to breed has been taken. 



The age to which fur seals attain is still x)roblematical, and until careful experi- 

 ments have been made it can only be stated approximately. The females have a 

 complete dentition at the age of 2, but the canines of the males are not full-grown 

 until the age of 5. The moustache is black in the young and whitens with time. 

 Any female with moustache entirely white can safely be placed as older than 4 years, 

 and any male as older than 5. Beyond that it is difficult to say more than that a seal 

 is old or very old, so much may be affirmed from the condition of the true molars, but 

 as to the exact number of years there are no data. Mere size is no criterion, for the 

 variation in this respect is so great that a small animal may be much older than one 

 of greater bulk. Neither is the wear of the teeth a sure guide, unless checked by 

 some other character, for the younger of two animals may have the more abraded 

 teeth, although from the general appearance of the teeth, and especially the amount of 

 absorption they have undergone, it is safe to say that the individual is adult, middle- 

 aged, or old. The various parts of the skeleton must be used with caution, since 

 some portions seem much older than others, and unless a person has had experience, 

 he would be sure to think the humeri belonged to a much older animal than the ver- 

 tebrae. Although the larger size and slower maturity of the bulls incline one to the 

 belief that they reach a greater age than the females, it is fair to say that no skull of 

 a bull whose teeth would indicate an age so great as that of some females obtained 

 has come under my notice. But, coupled with this, is the fact that the procuring of 

 bodies from the pelagic sealers has made it possible to secure a much larger propor- 

 tion of adult females than of adult males, so that while something like 75 skulls of 

 females, mostly adult, were available, there were not more than 25 skulls of old males. 



There is, however, another possible reason for the lack of very old bulls. As 

 stated in the chapter on mortality, the death rate among females is probably very 

 high, but it is also probable that the causes by which the death rate is influenced act 

 evenly throughout life, and the struggle for existence ataong females is mainly with 

 natural conditions. The males not only fight against surrounding conditions, but 

 with one another, and this last factor must act more and more severely with advancing 

 age, until the time comes when an old bull is driven out by some younger, stronger rival, 

 and retires from the rookery grounds only to die. This, of course, is pure theory, but 

 it accounts for the fact that among the male skulls picked up in various localities 

 there were none that appearred so old as some of the females. This does not 

 necessarily mean that the males do not attain a greater age than the females, for as 

 these last, as shown by the dentition and age at which they are sexually mature, reach 

 maturity sooner than the males, they naturally grow old sooner as well. 



The question of the proper proportion of males to females is purely problematical, 

 and the only data obtainable for comparison are such as can be derived from 

 domesticated animals, and as these are living under more or less artificial conditions 

 such data must be used with caution. With sheep 1 ram is deemed sufficient for at 

 least 50 ewes, and with cattle 1 bull to 20 or 25 cows on a range, or 1 to 50 where they 

 do not run at large. When running at large a single stallion is sufficient for from 20 

 to 40 mares, but when under control the number may be much larger, well on toward 

 a hundred. Among fowls, of what may be called the more natural breeds, having an 



