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Page:Popular Science Monthly Volume 54.djvu/686

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POPULAR SCIENCE MONTHLY.
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