THE HUMPBACK WHALE 13 



body length rather than on sex. There appears to be no significant difference between 

 the body proportions of South Georgian and South African Humpback whales. 



Tables V, VI, VII and VIII show the manner in which the body proportions vary 

 with the size of whale. In these tables the mean value of each measurement for each 

 metre of whale length is given, together with the number of measurements producing 

 each mean value, and the range of variation of each value. The figures are given as the 

 actual values in metres in roman type, and expressed as percentages of total length in 

 italic type. The figures expressed as percentages of total length are first discussed : those 

 of the actual values are dealt with in a later section of this report. They may be taken 

 as a basis for the comparison of measurements of Humpback whales from any other 

 part of the world. 



The variations of the body proportions according to the length of the whale are shown 

 graphically for measurements nos. 3, 4, 5, 8, 10, 11, 12, 13, 20 and 21 in Figs. 1-20, 

 in which the percentage value of the measurements is plotted against total length of the 

 whale. The curves for each sex are separated and represent the values from South 

 Georgian whales: the values from South African whales are shown for comparison as 

 unjoined points because they are based upon too few measurements to justify the 

 drawing of curves. 



Bearing in mind the limited numbers upon which these figures are based it appears 

 that there is no significant difference between the shapes of the curves for males and 

 females, nor between South Georgian and South African whales, except for measure- 

 ment no. 13, the genito-anal distance, already mentioned. The main point of interest 

 presented by these curves is the fact that those for measurements nos. 3, 4, 5 and 20 

 (Figs. 1-6, 17, 18) slope upwards from their origin, and those for nos. 10, 11, 12, 13 

 (Figs. 9-16) slope downwards from their origin, showing that as the whale increases in 

 length the relative size of the head region increases and of the tail region decreases. The 

 rate of growth of the body, therefore, decreases from the head region backwards, a con- 

 clusion that differs slightly from that drawn by Hinton (1925) who suggested, from a 

 consideration of the data relating to twenty male Humpbacks examined by Barrett- 

 Hamilton, that the thoracic region was the principal seat of growth. There is some 

 slight indication that at extreme lengths the relative sizes of the head and tail regions 

 become slightly less and greater respectively, an event that may be correlated with the 

 attainment of physical maturity. 



The variations that occur in each measurement are shown in Table IX, in which the 

 values of each measurement, expressed as percentages of the total length, are divided 

 into arbitrary groups and the number of values falling into each group is recorded. These 

 data are shown graphically in Figs. 21-37 in which the curves all approximate to normal 

 frequency curves, the least regular ones being those derived from few data, or from 

 measurements taken between ill-defined points and consequently difficult to take uni- 

 formly. Only the data from whales taken at South Georgia are included in these tables 

 and figures, and the range of variation in the measurements shown in them indicates a 

 homogeneous population, and no admixture of races with structural differences. 



