ii8 DISCOVERY REPORTS 



is thrown into an arc of small radius and moves high out of the water so that an unusual depth of 

 flank is momentarily visible (Fig. iw; Plate XXXIII, fig. 5). The amount of wheeling motion appears 

 to be curtailed and the downward sinking comes on sooner, sometimes with lateral splashing. The 

 fin and caudal peduncle are again the last to disappear (Fig. 1 0, p). 



Breaking surface without breathing 

 On various occasions whales have been seen to break surface without blowing. On 22 December, 

 the dorsal fins of two were seen above the water. The whales were leisurely, and on approach of the 

 ship the fins submerged slowly. On 1 1 January, while whales were feeding upon krill close to the 

 surface, tail flukes (either right or left) and flippers often broke surface, and the former waved in the 

 air as though in execution of swimming movements. The significance of this will be referred to in the 

 notes upon feeding (pp. 124 and 133). On 31 January a whale beneath the surface, a point or two off 

 the course, made straight for the ship's stem and only averted collision by a sudden dive beneath the 

 keel when a yard or two away. As he did so, the dorsal fin and the caudal peduncle were momentarily 

 thrust out of the water. On 7 February, two other whales broke surface in much the same way. One 

 showed the caudal periduncle as it dived ; the other seemed to be on the point of blowing but apparently 

 changed its mind, the head and neck broke surface in the act of dipping, but most of the back remained 



covered. 



Swimming 



A view of whales swimming close to the surface is usually distorted by waves and wavelets, and the 

 movements are hard to determine. As in their other activities, the larger rorquals look stately when 

 they swim because of a majestic ease of motion, even when they are keeping abreast of a ship steaming 

 at 10-12 knots. Seen from above, the flippers slope backwards but are spread out from the sides. 



An idea of the rhythm of the tail flukes could be formed if it were possible to measure the distance 

 between the ' oily patches '. It will be remembered that these are produced from the action of the 

 flukes through the upward gush of water. At speeds of 10-12 knots, these patches appeared to be 

 separated by 5-10 yards and as many as six or ten in series sometimes became visible when a whale 

 was near the surface. According to these data, which are very rough, the flukes beat once every i or 2 

 sec. When a fluke is waved from side to side above the surface of the water, its rhythm appears rather 

 faster but was not timed. 



No whale was seen to swim twice as fast as the ship at full speed. The Skua was not able to steam 

 faster than 12 knots, but the whales seemed, on occasion, to spurt half as fast again, and this would 

 bring their speed for short distances up to 16-18 knots. 



Frequency of blozving 



Data on respiratory rhythm have been collected by timing the blowing of whales with a stop-watch. 

 As often as opportunity offered, the observations were taken in unbroken series but often they had to 

 be curtailed and then they consisted of no m.ore than one or a few breathing intervals. Thus the ob- 

 servations may be looked upon as of two kinds, A and B. The first (A) at a distance from the ship 

 spread over longer periods and the second (B) of supplementary observations on individual whales 

 nearer the ship. 



In the serial observations A, the stop-watch was started at the first sign of blowing and stopped at 

 the next, and in order to secure continuity of record, was immediately re-set and restarted. While, 

 therefore, the first observation in each series represents the time from blow to blow, the succeeding 

 observations represent the same less the time taken to read the watch which was about 2-15 sec, and 

 the data as given in Table 3 (p. 137) have been suitably adjusted. 



