AGE-PHASES OF THE RORQUAL. 423 



23. Age-Phases of the Rorqiml. 

 By R. Lydekkkr. 



[Received December 20, 1910 ; Read March 7, 1911.] 



Some mouths ago I received a communication to the effect 

 that one of the captains at the Norwegian whahng-stations on 

 the Mayo coast was surprised to find that the true Rorquals of the 

 species commonly known to English naturalists as JJalcenoptera 

 onusculus found in the Irish seas differed from those he was 

 accustomed to take in Norwegian waters, not only in colour but 

 likewise in their food. This species is stated in text-books to 

 feed largely on fish, especially herrings and pilchards ; and those 

 taken in Norwegian waters by the captain above mentioned 

 appear to have been exclusively fish-eaters. On the other hand 

 those taken on the Mayo coast in summer wei-e feeding exclu- 

 sively on pelagic crustaceans. As to the nature of the colour- 

 diflerences between Norwegian and Irish examples, I was unable 

 in spite of special inquiries, to obtain definite information. 

 I find, however, that Professor R. Collett, in a paper on Ru- 

 dolphi's Rorqual, published in the (Society "s ' Proceedings' for 1886 

 states (p. 265) that in the True or Common Rorqual the whole of 

 the under surface of the flukes is white ; this statement beino- 

 doubtless based on Norwegian specimens. On the other hand 

 in the life-size model in the Natural History branch of the Biitish 

 Museum of a specimen taken in the Moray Firth in the sprino- 

 of 1880 the under side of the flukes is coloured black. This 

 colouring is doubtless based on notes or a sketch taken when the 

 specimen was in the flesh ; and, for what this is worth its 

 correctness is confirmed by the fact that in the flukes itself 

 which is preserved in the Museum, no diflerence in the colour of 

 the upper and lower surfaces is noticeable. In this connection it 

 is important to mention that specimens of this Rorqual have been 

 taken oft' Cornwall — in one instance in September — while feeding 

 on herrings and pilchards*. 



This was the extent of my information on the subject till a 

 few days ago, when Dr. S. F. Harmer put into my hands some 

 notes on Norwegian Roi-quals he had recently received from a 

 correspondent. From these notes, which are based on informa- 

 tion furnished by an experienced Norwegian whale-gunner it 

 appears that the whalers of Finmarken recognise three varieties 

 or phases, of True Rorqual — namely, a darker, a lighter, and a 

 yellowish. The dark phase is stated to be always met with in 

 company with shoals of herrings, upon which it doubtless feeds. 

 These Rorquals usually arrive off' the Faroes in the middle of 

 June, coming from the south-west and pi-oceeding in a north- 

 easterly direction ; the immigration lasting till about the middle 

 of July. Early in August the whales commence their return 

 joui-ney southwaiTls, when they keep principally to the south side 

 of the islands. By the end of the same month nearlj^ all have 



* See Gray, Cat. Seals and Whales Brit. Mus. p. 149 (1866). 



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