There are two ways and two alone whereby killing by man affects the fur-seal herd—namely, killing on land and killing at sea. Land killing has been vindicated in paragraph 9. We have here the necessary condemnation of pelagic killing expressed in equally full and frank terms. Land killing takes only males and leaves an adequate supply of bulls for breeding purposes; pelagic killing takes males and females alike, the latter sex constituting 62 to 84 out of every 100 killed.
It is not a vital matter that the female sex should be found to predominate in the pelagic catch, except in so far as it proves the falsity of the returns made so persistently by the Canadian sealing captain that the sexes are taken in virtually equal proportion at sea. The essential thing is that females are killed at all. That three fourths of all the animals taken at sea (during one season 140,000 animals were so taken) are of this sex only emphasizes the destructive nature of this industry.
12. The large proportion of females in the pelagic catch includes not only adult females that are both nursing and pregnant, but also young seals that are not pregnant and others that have not yet brought forth young, with such also as have recently lost their young through the various causes of natural mortality.
This statement is put in the mildest possible form out of consideration for the old-time British contentions that the breeding females did not leave the islands while their young were dependent upon them, and that those taken at sea were "barren." The investigations of 1896 and 1897 proved conclusively that every female of two years old and over taken at sea was pregnant, and that those over two years of age when taken in Bering Sea were in addition nursing, having dependent pups on the islands. The manner of statement seems to imply an equality in importance between "young" seals and "adults." As females are never killed on land, they are naturally of all ages when found at sea, and the young animals (yearlings and two-year-olds) are necessarily vastly in the minority.
13. The polygamous habit of the animal, coupled with an equal birth rate of the two sexes, permits a large number of males to be removed with impunity from the herd, while, as with other animals, any similar abstraction of females checks or lessens the herd's increase, or, when carried further, brings about an actual diminution of the herd. It is equally plain that a certain number of females may be killed without involving the actual diminution of the herd, if the number killed does not exceed the annual increment of the breeding herd, taking into consideration the annual losses by death through old age and through incidents of the sea.
This paragraph is really supplementary to 9 and 11. Neither the methods nor yet the principle of land killing are at fault. The animal being polygamous, a part of its male life can be removed with impunity. On the other hand, the killing of females leads to disastrous results.
The concluding sentence is a concession to diplomacy. It is true that a certain number of females may be killed without producing actual diminution. If pelagic sealing were stopped to-day the herd would naturally begin to increase. The measure of its increase would be the difference between the natural loss of adult breeders through old age and incidents of the sea, on the one hand, and the yearly accession of young breeders to bear their first pups, on the other. We can closely estimate the latter factor. It was equal, for example, to the quota of 20,000 in 1897, or sixteen and two thirds per cent of the birth rate. The quota was composed of males of approximately three years, and we may assume that a like number of three-year-old females entered the rookeries for the first time in the same season. We have then a gross gain to the breeding herd of sixteen and two thirds per cent.
We have no means of exact estimate for the loss of adult females because we do not know the period of life in the female. If, however, we estimate it at thirteen years, which seems to be a conservative figure, the animal would have ten years of breeding life. Then, from old age alone, ten per cent of the adult breeding females must die annually. This leaves a net gain of six and two thirds per cent with accidental factors unaccounted for. The killing of females which does not produce actual diminution must come well within this margin of six and two thirds per cent. It only remains to be stated that the pelagic catch of 1897, which was the smallest on record since 1884, exceeded fourteen per cent.
14. While, whether from a consideration of the birth rate or from an inspection of the visible effects, it is manifest that the take of females in recent years has been so far in excess of the natural increment as to lead to the reduction of the herd in the degree related above, yet the ratio of the pelagic catch of one year to that of the following has fallen off more rapidly than the ratio of the breeding herd of one year to the breeding herd of the next.
This paragraph corrects possible erroneous implications which might be drawn from the truism in the preceding paragraph. A certain number of females may be taken, etc., but so many in excess of the safety limit have been taken that the herd has been reduced "in the degree related above"—that is, for 1896-'97, nine to twelve per cent, and for 1884-'97, fifty to eighty per cent.