126 



Fishery Bulletin 88(1), 1990 



Figure 10 



Urogenital color patterns of Dall's porpoise specimens; (a-c) females (TAJ 1(35, 104; SMB 060), (d-e) male.s (TA,1 172; WAA 053). 



1973). Morejohn and his colleagfues illustrated one 

 female and two male patterns, but failed to recognize 

 the large degree of individual variation exhibited by 

 Ball's porpoises in this respect. Figure 10 shows only 

 a few of the many observed patterns. Although most 

 of the patterns can be recognized as more similar to 

 the male or female type, the high degree of variability 

 in this aspect of the color pattern makes sexing in- 

 dividuals by this characteristic alone somewhat risky. 



Dorsal fin and fluke frosting A quantitative study 

 of Ball's porpoise coloration may reveal significant 

 sexual differences, but there seem to be no obvious 

 differences between the sexes in any component of the 

 pigmentation pattern, other than urogenital coloration. 

 Analysis of photographs showed that there is, however, 

 a high degree of developmental variation (Table 3). 

 Newborn Ball's porpoises have a muted color pattern 

 of gray tones with no frosting on the flukes or dorsal 

 fin. As the animal ages, the colors apparently inten- 



