I20 DISCOVERY REPORTS 



the Tables give evidence that more than one whale was under observation in each of the series of 

 timing records made. This is most easily seen in the maximum numbers of whales blowing simul- 

 taneously, a datum which indicates with a high degree of probability the number of whales in the 

 school . 



Kemp and Bennett (1932, p. 174) have pointed out that 'If, as often happens, several whales are 

 in company, they will generally rise to the surface and blow simultaneously. When whales are not 

 plentiful it is possible to be reasonably certain that the same school is being kept under observation ; 

 but when they are abundant the difficulties are greatly increased.' 



If the tendency to blow together could be relied upon, and the whales could be timed as a school, 

 interpretation of these data (A) would be straightforward. Unfortunately, however, the appearances 

 of the whales at the surface show a good deal of overlap and though the school often does blow to- 

 gether, irregularity is frequent. In view of the likelihood of confusing the blowing of one whale with 

 that of another, the results would appear to lend themselves to almost any interpretation. But analysis 

 shows that this is not so. The data show certain features which cannot be regarded as fortuitous : and 

 some of these features are confirmed by the supplementary observations (B). These latter consist of 

 isolated observations of whales close to the ship and they are important because they are believed, with 

 a fair degree of certainty, to represent the behaviour of individual whales. The two classes of obser- 

 vations will therefore be considered together. 



In series B, whales were commonly observed to blow at intervals of about 24-28 sec. about five or 

 six times in succession, whereupon they sounded for a longer period. On 7 February, for example, 

 a whale blew five times at more or less regular intervals in the course of 100 sec. and then disappeared. 

 On 1 9 December, blowing went on at short intervals for 115 sec. in one instance and 140 sec. in another 

 before the animal sounded. On occasion, when larger schools have been watched, the school has 

 risen more often, but not every whale has come to the surface at every blowing. 



Parallel instances of such rhythm in series A occur among the tabulated data and selected examples 

 are shown in Table i. They are illustrated in Fig. 2. 



Table i . Comparing the lengths of the periods of sounding (/ mid IT) zvith the interim period 

 during which blowing intervals were noted 



The absence of this particular rhythm (of blowing and sounding) among others of the data listed 

 in Table 3 may be due to the fact that some or all of the whales were behaving differently. Evidence 

 of different rhythm is given by the whales timed on 27 December. They were first observed more than 

 a mile off; they were approached, passed, and finally left on the starboard quarter. The observations 

 nos. 189-200, while the whales were far off, have the rhythm illustrated in Fig. 2, but the subsequent 

 observations, nos. 201-261, show no trace of it. 



