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Show 1886.] MR. R. COLLETT ON BAL/ENOPTERA BOREALIS. 263 food; but Capt. Bull, from West Finmark, asserts that not only this summer, but in the previous ones, he found that the stomach contained the so-called " Kril," which forms the chief nourishment of the B. sibbaldi. This "Kril" is Euphausia inermis, a Thysanopod Crustacean, about 11 inch in length and semi-transparent. It is therefore certain that the B. borealis is not confined to the Copepoda for its nourishment, although the unusually fine and curly, almost woolly bristles on the inner side of the baleen-plates clearly show that their food consists of minute animals, and hardly ever of fish. XIV. Habits. B. borealis appeared off the coast sometimes singly, but as a rule in schools of different size, which might number as many as 50 individuals. Towards the end of the fishing-season they appeared to be more broken up, after having been terrified and scattered by the whaling-boats for months. Concerning their method of swimming, the whalers have noticed some small peculiarities. During their wanderings, or when they are not amongst the " Aate" (i. e. the shoals of crustaceans on which they feed), they swim fast, and do not require to blow so often as the other species. As a rule they blow only once or twice, whilst the other kinds blow as often as five or six times during each visit to the surface, and they swim for a considerable distance before they again appear. Their course under the water can be traced by the bubbles of air which appear on the surface. When in amongst a shoal of Calanus finmarchicus, and on the feed, they swim quite slowly, with their snout and half of their back above water. The B. musculus and the B. sibbaldi under such circumstances often turn on their side whilst swimming, with their mouths open to take the crustaceans. In its temper B. borealis is inoffensive and avoids the boats. But it has sometimes happened that in its death-agonies it has struck the boats, and on several occasions has injured their sides or propellers. Such conduct has, however, probably been unintentional, or committed in its agony, and cannot be considered, as it has often been called, natural ferocity. All the whalers are unanimous in opinion that B. borealis (as well as B. musculus and B. sibbaldi) can remain under water for a far greater time than is generally supposed. The duration of this time is estimated to be from 8 to 12 hours. Such periods of rest often occur at particular hours of the day. These animals are never heard to make any sound. XV. Value. The quantity of blubber as a rule is but little in this species. average-sized individual yields from 15 to 20 Norw. barrels (17 to 23 hectolitres) of oil; they appear this year to have been as a rule |
