EXTERNAL CHARACTERS 247 



Throat Grooves 



Longitudinal grooves in the throat region (Plate I, fig. 2) were present in all the whales (seventeen males 

 and eleven females) examined for this character. It seems that, rarely, throat grooves may be absent 

 in the sperm whale, for Matthews mentions one negative record in his southern sample. Those of the 

 Azores whales exhibited great variation in number and arrangement: the examples reproduced in 

 Fig. 3, selected from sketches made on the flensing platform, show a series of increasing complexity 

 from one to as many as thirty-three grooves. The frequencies of their numbers, which are mere 

 counts irrespective of depth, definition and size of groove, are shown in Table 7. It can only be said 

 that most whales have fewer than about seven or eight grooves. But examination of their patterns 



Table 7. Frequencies of the numbers of throat grooves in 

 whales examined at Horta in 1949 



No. of whales 



No. of grooves Males Females 



1 1 1 



2 4 I 



3 ' — 



4 23 



5 3 — 



6 — 1 



7 — 2 



8 — — 



suggests an underlying plan. Four of the twenty-eight whales had only a pair of grooves, deep with 

 well-defined limits, lying about the middle line. Another four had some shallow accessory grooves 

 in addition to the two deep ones. Two whales had each three deep grooves and an accessory groove 

 arranged more or less symmetrically, and a further two had regular sets of four deep grooves each. 

 Seven others had sets of relatively shallow grooves in bilateral symmetry, each side comprising two 

 to seven grooves, arranged in a diminishing series with the longer grooves nearest the middle line. 

 The remaining seven whales had median sets of from five to thirty-three grooves. In any whale where 

 the grooves were numerous these might be dissected and anastomosed, giving a cracked appearance 

 to the throat. These patterns of bilateral and of median symmetry could all spring from the arrange- 

 ment with two grooves, and this arrangement, rather than that (found in two whales) of a single 

 median groove, would appear to be the primitive one. It is a condition which has been retained in 

 most representatives of that other group of toothed whales, the Ziphiidae. Pouchet & Chaves (1890) 

 have earlier compared the two deep throat grooves of Hyperoodon with a similar arrangement in a 

 sperm whale they examined at San Miguel. 



At Horta in 1949 a foetus 3-53 m. long had a pair of throat grooves, and Matthews has recorded 

 them from a southern foetus of 3-0 m. But Table 5 shows that they can appear earlier, when the 

 foetus is as small as 0-24 m., although possibly not at a younger age. There must be variation in the 

 foetal age at which they appear, for Beddard (1915, 191 9) found that they were absent not only in 

 foetuses of 0-114 and 0-241 m., but also in one of 0-5 m., and they are not shown in Kukenthal's figure 

 of a 0-74 m. foetus (1914, Plate 36, fig. 35). 



It might be supposed that numerous throat grooves are a sign of ageing, akin to the wrinkling of the 

 neck in man, but their numbers show no correlation with age in the post-natal whales examined at 

 Horta. Beddard (1900, p. 183) and Boschma (1938, p. 157) may be correct in suggesting that the 

 grooves allow distension of the throat when swallowing large prey. 



